@article{calvert_madden_nichols_haddad_lahne_dunn_mckenney_2021, title={A review of sourdough starters: ecology, practices, and sensory quality with applications for baking and recommendations for future research}, volume={5}, url={https://doi.org/10.7717/peerj.11389}, DOI={10.7717/peerj.11389}, abstractNote={The practice of sourdough bread-making is an ancient science that involves the development, maintenance, and use of a diverse and complex starter culture. The sourdough starter culture comes in many different forms and is used in bread-making at both artisanal and commercial scales, in countries all over the world. While there is ample scientific research related to sourdough, there is no standardized approach to using sourdough starters in science or the bread industry; and there are few recommendations on future directions for sourdough research. Our review highlights what is currently known about the microbial ecosystem of sourdough (including microbial succession within the starter culture), methods of maintaining sourdough (analogous to land management) on the path to bread production, and factors that influence the sensory qualities of the final baked product. We present new hypotheses for the successful management of sourdough starters and propose future directions for sourdough research and application to better support and engage the sourdough baking community.}, journal={PEERJ}, author={Calvert, Martha D. and Madden, Anne A. and Nichols, Lauren M. and Haddad, Nick M. and Lahne, Jacob and Dunn, Robert R. and McKenney, Erin A.}, year={2021}, month={May} }
 @article{costanza_watling_sutherland_belyea_dilkina_cayton_bucklin_romanach_haddad_2020, title={Preserving connectivity under climate and land-use change: No one-size-fits-all approach for focal species in similar habitats}, volume={248}, ISSN={["1873-2917"]}, DOI={10.1016/j.biocon.2020.108678}, abstractNote={Habitat connectivity is essential for maintaining populations of wildlife species, especially as climate changes. Knowledge about the fate of existing habitat networks in a changing climate and in light of land-use change is critical for determining which types of conservation actions must be taken to maintain those networks. However, information is lacking about how multiple focal species that use similar habitats overlap in the degree and geographic patterns of threats to linkages among currently suitable habitat patches. We sought to address that gap. We assessed climate change threat to existing linkages in the southeastern United States for three wildlife species that use similar habitats but differ in the degree to which their ranges are limited by climate, habitat specificity, and dispersal ability. Linkages for the specialist species (timber rattlesnake), whose range is climate-restricted, were more likely to serve as climate change refugia – that is, they were more likely to be climate-stable – by the middle of the 21st century. This contrasts with the two more generalist species (Rafinesque's big-eared bat and American black bear), whose linkages were threatened by climate change and thus required adaptation measures. Further incorporation of projected land-use change and current protection status for important linkages narrows down our recommended conservation actions for each species. Our results highlight the surprising ways in which even species that use similar habitats will experience differences in the degree and geographic patterns of threats to connectivity. Taking action before these projected changes occur will be critical for successful conservation.}, journal={BIOLOGICAL CONSERVATION}, author={Costanza, Jennifer K. and Watling, James and Sutherland, Ron and Belyea, Curtis and Dilkina, Bistra and Cayton, Heather and Bucklin, David and Romanach, Stephanie S. and Haddad, Nick M.}, year={2020}, month={Aug} }
 @article{henry_brammer-robbins_aschehoug_haddad_2019, title={Do substitute species help or hinder endangered species management?}, volume={232}, ISSN={0006-3207}, url={http://dx.doi.org/10.1016/J.BIOCON.2019.01.031}, DOI={10.1016/J.BIOCON.2019.01.031}, abstractNote={Substitute species (common species used to represent endangered species) are used to evaluate a range of conservation strategies globally. However, the effectiveness of this approach has not been empirically evaluated. We leveraged a large-scale habitat restoration experiment to test the validity of the substitute species concept. We selected a common butterfly, Satyrodes appalachia, that is on first inspection as near a substitute as possible - it is closely related to, overlaps in distribution, habitat requirements, host use, and life history with Neonympha mitchellii francisci, an endangered butterfly. We integrated small-scale measures of behavior, habitat preference, and demography of both species in our test, demonstrating that subtle differences between two species cause the substitute relationship to fail. Despite nearly identical habitat requirements, we found the endangered butterfly used different host plants, had higher larval survival in restored sites, and was found in more open habitat than the common butterfly. These differences added up to differences in abundances; the endangered species was more abundant than the common species in restored sites, the opposite was true in un-restored sites. Management decisions based on unvalidated substitute species run the risk of doing more harm than good for endangered species conservation. Instead, using experiments to evaluate a target species' response to management will result in effective recovery strategies.}, journal={Biological Conservation}, publisher={Elsevier BV}, author={Henry, Erica and Brammer-Robbins, Elizabeth and Aschehoug, Erik and Haddad, Nick}, year={2019}, month={Apr}, pages={127–130} }
 @article{caughlin_damschen_haddad_levey_warneke_brudvig_2019, title={Landscape heterogeneity is key to forecasting outcomes of plant reintroduction}, volume={29}, ISSN={1051-0761 1939-5582}, url={http://dx.doi.org/10.1002/EAP.1850}, DOI={10.1002/EAP.1850}, abstractNote={Abstract}, number={2}, journal={Ecological Applications}, publisher={Wiley}, author={Caughlin, T. Trevor and Damschen, Ellen I. and Haddad, Nick M. and Levey, Douglas J. and Warneke, Christopher and Brudvig, Lars A.}, year={2019}, month={Mar} }
 @article{schultz_haddad_henry_crone_2019, title={Movement and Demography of At-Risk Butterflies: Building Blocks for Conservation}, volume={64}, ISSN={["0066-4170"]}, DOI={10.1146/annurev-ento-011118-112204}, abstractNote={The number of insect species at risk of population decline and extinction is increasing rapidly. Yet we know almost nothing about the ecology of these species, except for at-risk butterflies. A growing body of literature shows how butterfly vital rates, including demography and movement, are essential for guiding conservation and recovery. History has shown us that without these data, conservation decisions often weaken, rather than enhance, population viability. This is especially true in changing landscapes. We review knowledge of vital rates across all at-risk butterflies. We have information on movement for 17 of 283 butterfly species and information on demography for 19 species. We find that habitat-specific movement behavior is key to understanding how to connect populations, and habitat-specific demography is central to managing habitats. Methods and analyses worked out for butterflies can provide a scaffold around which to build studies for the conservation of other at-risk insects.}, journal={ANNUAL REVIEW OF ENTOMOLOGY, VOL 64}, author={Schultz, Cheryl B. and Haddad, Nick M. and Henry, Erica H. and Crone, Elizabeth E.}, year={2019}, pages={167–184} }
 @article{fletcher_didham_banks-leite_barlow_ewers_rosindell_holt_gonzalez_pardini_damschen_et al._2018, title={Is habitat fragmentation good for biodiversity?}, volume={226}, ISSN={0006-3207}, url={http://dx.doi.org/10.1016/J.BIOCON.2018.07.022}, DOI={10.1016/J.BIOCON.2018.07.022}, abstractNote={Habitat loss is a primary threat to biodiversity across the planet, yet contentious debate has ensued on the importance of habitat fragmentation ‘per se’ (i.e., altered spatial configuration of habitat for a given amount of habitat loss). Based on a review of landscape-scale investigations, Fahrig (2017; Ecological responses to habitat fragmentation per se. Annual Review of Ecology, Evolution, and Systematics 48:1-23) reports that biodiversity responses to habitat fragmentation ‘per se’ are more often positive rather than negative and concludes that the widespread belief in negative fragmentation effects is a ‘zombie idea’. We show that Fahrig's conclusions are drawn from a narrow and potentially biased subset of available evidence, which ignore much of the observational, experimental and theoretical evidence for negative effects of altered habitat configuration. We therefore argue that Fahrig's conclusions should be interpreted cautiously as they could be misconstrued by policy makers and managers, and we provide six arguments why they should not be applied in conservation decision-making. Reconciling the scientific disagreement, and informing conservation more effectively, will require research that goes beyond statistical and correlative approaches. This includes a more prudent use of data and conceptual models that appropriately partition direct vs indirect influences of habitat loss and altered spatial configuration, and more clearly discriminate the mechanisms underpinning any changes. Incorporating these issues will deliver greater mechanistic understanding and more predictive power to address the conservation issues arising from habitat loss and fragmentation.}, journal={Biological Conservation}, publisher={Elsevier BV}, author={Fletcher, Robert J., Jr and Didham, Raphael K. and Banks-Leite, Cristina and Barlow, Jos and Ewers, Robert M. and Rosindell, James and Holt, Robert D. and Gonzalez, Andrew and Pardini, Renata and Damschen, Ellen I. and et al.}, year={2018}, month={Oct}, pages={9–15} }
 @article{haddad_holt_fletcher_loreau_clobert_2017, title={Connecting models, data, and concepts to understand fragmentation's ecosystem-wide effects}, volume={40}, ISSN={["1600-0587"]}, DOI={10.1111/ecog.02974}, abstractNote={at large spatial scales not attainable with experiments. Our Special Issue highlights some of the benefi ts of observational studies for advancing our understanding of fragmentation, including the use of observational studies to test hypotheses regarding conceptual models of habitat fragmentation (Brudvig et al. 2017), responses in fragmented agricultural landscapes (Carri é et al. 2017), models comparing patchmatrix with mosaic approaches (Leroux et al. 2017), and ecological responses in fragments created by people centuries ago (Reynolds et al. 2017). Our feature articles are followed in this same issue of Ecography by a number of others that accomplish objectives not possible in controlled experiments, for example understanding fragmentation ’ s eff ects over large geographic regions within continents. Indeed, one fruitful potential direction in research will be the integration of experimental landscape studies with analyses conducted at larger spatial scales, where experiments are well-nigh impossible.}, number={1}, journal={ECOGRAPHY}, author={Haddad, Nick M. and Holt, Robert D. and Fletcher, Robert J., Jr. and Loreau, Michel and Clobert, Jean}, year={2017}, month={Jan}, pages={1–8} }
 @article{haddad_gonzalez_brudvig_burt_levey_damschen_2017, title={Experimental evidence does not support the Habitat Amount Hypothesis}, volume={40}, ISSN={["1600-0587"]}, DOI={10.1111/ecog.02535}, abstractNote={For a half century, habitat configuration – the arrangement of habitat patches within a landscape – has been central to theories of landscape ecology, population dynamics, and community assembly, in addition to conservation strategies. A recent hypothesis advanced by Fahrig (2013) would, if supported, greatly diminish the relevance of habitat configuration as a predictor of diversity. The Habitat Amount Hypothesis posits that the sample area effect overrides patch size and patch isolation effects of habitat fragmentation on species richness. It predicts that the amount of habitat in a local landscape, regardless of configuration, is the main landscape‐level determinant of species richness. If habitat amount is indeed the major, landscape‐level driver of species richness, the slopes of the species–area relationship (SAR) for otherwise similar fragmented and unfragmented landscapes should be indistinguishable. We tested the Habitat Amount Hypothesis with data from two replicated and controlled habitat fragmentation experiments that disentangle the effects of habitat amount and configuration. One experiment provided time‐series data on plant species richness and the other on micro‐arthropod species richness. We found that, relative to less fragmented habitats, the SARs for fragmented habitats have significantly higher slopes and that the magnitude of the difference in slopes increased over time. Relatively more species were lost in smaller areas when fragments were more isolated. In both experiments, the proportion of species lost due to increased habitat fragmentation was nearly identical to the proportion lost due to reduced habitat amount. Our results provide a direct and experimentally derived refutation of the Habitat Amount Hypothesis, supporting the long‐held view that in addition to area, patch isolation and configuration are important determinants of species richness. Differences in species richness between fragmented and non‐fragmented habitats increase over time, demonstrating that long‐term studies are needed to understand the effects of fragmentation, above and beyond the amount of habitat lost.}, number={1}, journal={ECOGRAPHY}, author={Haddad, Nick M. and Gonzalez, Andrew and Brudvig, Lars A. and Burt, Melissa A. and Levey, Douglas J. and Damschen, Ellen I.}, year={2017}, month={Jan}, pages={48–55} }
 @article{herrmann_haddad_levey_2017, title={Testing the relative importance of local resources and landscape connectivity on Bombus impatiens (Hymenoptera, Apidae) colonies}, volume={48}, ISSN={["1297-9678"]}, DOI={10.1007/s13592-017-0499-1}, abstractNote={Bee populations are decreasing worldwide. The underlying causes are likely determined by factors at different scales. We tested the relative importance of local resources and landscape connectivity on 64 bumblebee (Bombus impatiens) colonies in experimentally isolated and connected habitat fragments. We used colony mass, no. of workers, and no. of gynes to estimate colony performance. Landscape connectivity did not significantly affect colony performance, but local floral resources had a significantly positive effect, especially in isolated fragments. These results suggest that bumblebee colonies encountered sufficient floral resources within the local 1.4 ha habitat fragments to support colony growth, making long-distance foraging trips to neighboring fragments unnecessary. From a conservation perspective, we suggest that efforts to improve colony performance should prioritize boosting local floral resources over manipulation of large-scale landscape features.}, number={4}, journal={APIDOLOGIE}, author={Herrmann, John D. and Haddad, Nick M. and Levey, Douglas J.}, year={2017}, month={Jul}, pages={545–555} }
 @article{resasco_bruna_haddad_banks-leite_margules_2017, title={The contribution of theory and experiments to conservation in fragmented landscapes}, volume={40}, ISSN={["1600-0587"]}, DOI={10.1111/ecog.02546}, abstractNote={The clearing and fragmentation of terrestrial ecosystems is commonly acknowledged as a major cause of the decline of biodiversity. These and other predicted responses to habitat fragmentation are derived from theory, which ecologists have tested with empirical approaches ranging from observations to experimental manipulations. These empirical approaches have also identified areas of theory in need of additional development. For example, experimental studies of fragmentation have provided insights such as the key role played by the matrix surrounding fragments, the importance of edge effects, and the impacts of corridors linking fragments with one another. Much less clear, however, is the extent to which these theoretical and empirical studies – while advancing our conceptual understanding of ecological responses to landscape change – help guide management and conservation practice. We review lessons learned from landscape‐scale fragmentation experiments and observational studies, present the results of a survey of fragmentation and conservation experts which probed for links and mismatches between fragmentation studies and conservation practice, and discuss how future studies can contribute to conservation practice. Our survey showed that respondents consider fragmentation theory and empirical studies and their findings important for guiding conservation and management practices. The survey also identified that there are disconnects between what is typically studied by fragmentation ecologists and factors that are central to the practice of biodiversity conservation, notably, community‐based human dimensions (e.g. economic, social, health issues), policy and governance, ecosystem services, eco‐evolutionary responses of species, and interaction of multiple threats to biodiversity and ecosystem processes. We discuss how these disconnects can present opportunities for experiments to continue to provide valuable recommendations for conservation practice in fragmented landscapes.}, number={1}, journal={ECOGRAPHY}, author={Resasco, Julian and Bruna, Emilio M. and Haddad, Nick M. and Banks-Leite, Cristina and Margules, Christopher R.}, year={2017}, month={Jan}, pages={109–118} }
 @article{herrmann_carlo_brudvig_damschen_haddad_levey_orrock_tewksbury_2016, title={Connectivity from a different perspective: comparing seed dispersal kernels in connected vs. unfragmented landscapes}, volume={97}, ISSN={["1939-9170"]}, DOI={10.1890/15-0734.1}, abstractNote={Abstract}, number={5}, journal={ECOLOGY}, author={Herrmann, John D. and Carlo, Tomas A. and Brudvig, Lars A. and Damschen, Ellen I. and Haddad, Nick M. and Levey, Douglas J. and Orrock, John L. and Tewksbury, Joshua J.}, year={2016}, month={May}, pages={1274–1282} }
 @article{levey_caughlin_brudvig_haddad_damschen_tewksbury_evans_2016, title={Disentangling fragmentation effects on herbivory in understory plants of longleaf pine savanna}, volume={97}, ISSN={["1939-9170"]}, DOI={10.1002/ecy.1466}, abstractNote={Abstract}, number={9}, journal={ECOLOGY}, author={Levey, Douglas J. and Caughlin, T. Trevor and Brudvig, Lars A. and Haddad, Nick M. and Damschen, Ellen I. and Tewksbury, Joshua J. and Evans, Daniel M.}, year={2016}, month={Sep}, pages={2248–2258} }
 @article{sivakoff_morris_aschehoug_hudgens_haddad_2016, title={Habitat restoration alters adult butterfly morphology and potential fecundity through effects on host plant quality}, volume={7}, ISSN={["2150-8925"]}, DOI={10.1002/ecs2.1522}, abstractNote={Abstract}, number={11}, journal={ECOSPHERE}, author={Sivakoff, Frances S. and Morris, William F. and Aschehoug, Erik T. and Hudgens, Brian R. and Haddad, Nick M.}, year={2016}, month={Nov} }
 @article{haddad_2015, title={Corridors for people, corridors for nature}, volume={350}, ISSN={["1095-9203"]}, DOI={10.1126/science.aad5072}, abstractNote={How can the environmental impacts of roads be reduced?}, number={6265}, journal={SCIENCE}, author={Haddad, Nick M.}, year={2015}, month={Dec}, pages={1166–1167} }
 @article{chaplin-kramer_ramler_sharp_haddad_gerber_west_mandle_engstrom_baccini_sim_et al._2015, title={Degradation in carbon stocks near tropical forest edges}, volume={6}, ISSN={["2041-1723"]}, DOI={10.1038/ncomms10158}, abstractNote={Abstract}, journal={NATURE COMMUNICATIONS}, author={Chaplin-Kramer, Rebecca and Ramler, Ivan and Sharp, Richard and Haddad, Nick M. and Gerber, James S. and West, Paul C. and Mandle, Lisa and Engstrom, Peder and Baccini, Alessandro and Sim, Sarah and et al.}, year={2015}, month={Dec} }
 @article{cayton_haddad_gross_diamond_ries_2015, title={Do growing degree days predict phenology across butterfly species?}, volume={96}, ISSN={["1939-9170"]}, DOI={10.1890/15-0131.1}, abstractNote={Global climate change is causing shifts in phenology across multiple species. We use a geographically and temporally extensive data set of butterfly abundance across the state of Ohio to ask whether phenological change can be predicted from climatological data. Our focus is on growing degree days (GDD), a commonly used measure of thermal accumulation, as the mechanistic link between climate change and species phenology. We used simple calculations of median absolute error associated with GDD and an alternative predictor of phenology, ordinal date, for both first emergence and peak abundance of 13 butterfly species. We show that GDD acts as a better predictor than date for first emergence in nearly all species, and for peak abundance in more than half of all species, especially univoltine species. Species with less ecological flexibility, in particular those with greater dietary specialization, had greater predictability with GDD. The new method we develop for predicting phenology using GDD offers a simple yet effective way to predict species' responses to climate change.}, number={6}, journal={ECOLOGY}, author={Cayton, Heather L. and Haddad, Nick M. and Gross, Kevin and Diamond, Sarah E. and Ries, Leslie}, year={2015}, month={Jun}, pages={1473–1479} }
 @article{aschehoug_sivakoff_cayton_morris_haddad_2015, title={Habitat restoration affects immature stages of a wetland butterfly through indirect effects on predation}, volume={96}, ISSN={["1939-9170"]}, DOI={10.1890/14-2403.1}, abstractNote={Habitat loss worldwide has led to the widespread use of restoration practices for the recovery of imperiled species. However, recovery success may be hampered by focusing on plant communities, rather than the complex suite of direct and indirect interactions among trophic levels that occur in natural systems. Through a factorial field experiment, we tested the effects of wetland restoration on egg and juvenile survival of a locally rare butterfly, Satyrodes appalachia, via tree removal and damming. Tree removal more than tripled S. appalachia host plant abundance, but neither restoration action directly affected S. appalachia egg and juvenile survival. Instead, we found strong indirect effects of habitat manipulation on S. appalachia egg and juvenile survival that were mediated through predation. The interaction of tree removal and damming significantly decreased predation of S. appalachia eggs relative to each treatment alone. Damming alone had a significant positive indirect effect on the survival of S. appalachia juveniles, likely because increases in standing water reduced predator access. Our results emphasize the need for experiments that evaluate the demographic responses of imperiled species to habitat restoration prior to management action and quantify potential indirect effects mediated through higher trophic levels.}, number={7}, journal={ECOLOGY}, author={Aschehoug, Erik T. and Sivakoff, F. S. and Cayton, H. L. and Morris, W. F. and Haddad, N. M.}, year={2015}, month={Jul}, pages={1761–1767} }
 @article{henry_haddad_wilson_hughes_gardner_2015, title={Point-count methods to monitor butterfly populations when traditional methods fail: a case study with Miami blue butterfly}, volume={19}, ISSN={["1572-9753"]}, DOI={10.1007/s10841-015-9773-6}, number={3}, journal={JOURNAL OF INSECT CONSERVATION}, author={Henry, Erica H. and Haddad, Nick M. and Wilson, John and Hughes, Phillip and Gardner, Beth}, year={2015}, month={Jun}, pages={519–529} }
 @article{diamond_dunn_frank_haddad_martin_2015, title={Shared and unique responses of insects to the interaction of urbanization and background climate}, volume={11}, ISSN={2214-5745}, url={http://dx.doi.org/10.1016/J.COIS.2015.10.001}, DOI={10.1016/J.COIS.2015.10.001}, abstractNote={Urbanization profoundly alters biological systems; yet the predictability of responses to urbanization based on key biological traits, the repeatability of these patterns among cities, and how the impact of urbanization on biological systems varies as a function of background climatic conditions remain unknown. We use insects as a focal system to review the major patterns of responses to urbanization, and develop a framework for exploring the shared and unique features that characterize insect responses to urbanization and how responses to urbanization might systematically vary along background environmental gradients in climate. We then illustrate this framework using established patterns in insect macrophysiology.}, journal={Current Opinion in Insect Science}, publisher={Elsevier BV}, author={Diamond, Sarah E and Dunn, Robert R and Frank, Steven D and Haddad, Nick M and Martin, Ryan A}, year={2015}, month={Oct}, pages={71–77} }
 @article{brudvig_damschen_haddad_levey_tewksbury_2015, title={The influence of habitat fragmentation on multiple plant-animal interactions and plant reproduction}, volume={96}, DOI={10.1890/14-2275.1}, abstractNote={Despite broad recognition that habitat loss represents the greatest threat to the world's biodiversity, a mechanistic understanding of how habitat loss and associated fragmentation affect ecological systems has proven remarkably challenging. The challenge stems from the multiple interdependent ways that landscapes change following fragmentation and the ensuing complex impacts on populations and communities of interacting species. We confronted these challenges by evaluating how fragmentation affects individual plants through interactions with animals, across five herbaceous species native to longleaf pine savannas. We created a replicated landscape experiment that provides controlled tests of three major fragmentation effects (patch isolation, patch shape [i.e., edge‐to‐area ratio], and distance to edge), established experimental founder populations of the five species to control for spatial distributions and densities of individual plants, and employed structural equation modeling to evaluate the effects of fragmentation on plant reproductive output and the degree to which these impacts are mediated through altered herbivory, pollination, or pre‐dispersal seed predation. Across species, the most consistent response to fragmentation was a reduction in herbivory. Herbivory, however, had little impact on plant reproductive output, and thus we found little evidence for any resulting benefit to plants in fragments. In contrast, fragmentation rarely impacted pollination or pre‐dispersal seed predation, but both of these interactions had strong and consistent impacts on plant reproductive output. As a result, our models robustly predicted plant reproductive output (r2 = 0.52–0.70), yet due to the weak effects of fragmentation on pollination and pre‐dispersal seed predation, coupled with the weak effect of herbivory on plant reproduction, the effects of fragmentation on reproductive output were generally small in magnitude and inconsistent. This work provides mechanistic insight into landscape‐scale variation in plant reproductive success, the relative importance of plant–animal interactions for structuring these dynamics, and the nuanced nature of how habitat fragmentation can affect populations and communities of interacting species.}, number={10}, journal={Ecology}, author={Brudvig, L. A. and Damschen, E. I. and Haddad, N. M. and Levey, D. J. and Tewksbury, J. J.}, year={2015}, pages={2669–2678} }
 @article{breckheimer_haddad_morris_trainor_fields_jobe_hudgens_moody_walters_2014, title={Defining and Evaluating the Umbrella Species Concept for Conserving and Restoring Landscape Connectivity}, volume={28}, ISSN={["1523-1739"]}, DOI={10.1111/cobi.12362}, abstractNote={Abstract}, number={6}, journal={CONSERVATION BIOLOGY}, author={Breckheimer, Ian and Haddad, Nick M. and Morris, William F. and Trainor, Anne M. and Fields, William R. and Jobe, R. Todd and Hudgens, Brian R. and Moody, Aaron and Walters, Jeffrey R.}, year={2014}, month={Dec}, pages={1584–1593} }
 @article{adrion_kousathanas_pascual_burrack_haddad_bergland_machado_sackton_schlenke_watada_et al._2014, title={Drosophila suzukii: The Genetic Footprint of a Recent, Worldwide Invasion}, volume={31}, ISSN={["1537-1719"]}, DOI={10.1093/molbev/msu246}, abstractNote={Native to Asia, the soft-skinned fruit pest Drosophila suzukii has recently invaded the United States and Europe. The eastern United States represents the most recent expansion of their range, and presents an opportunity to test alternative models of colonization history. Here, we investigate the genetic population structure of this invasive fruit fly, with a focus on the eastern United States. We sequenced six X-linked gene fragments from 246 individuals collected from a total of 12 populations. We examine patterns of genetic diversity within and between populations and explore alternative colonization scenarios using approximate Bayesian computation. Our results indicate high levels of nucleotide diversity in this species and suggest that the recent invasions of Europe and the continental United States are independent demographic events. More broadly speaking, our results highlight the importance of integrating population structure into demographic models, particularly when attempting to reconstruct invasion histories. Finally, our simulation results illustrate the general challenge in reconstructing invasion histories using genetic data and suggest that genome-level data are often required to distinguish among alternative demographic scenarios.}, number={12}, journal={MOLECULAR BIOLOGY AND EVOLUTION}, author={Adrion, Jeffrey R. and Kousathanas, Athanasios and Pascual, Marta and Burrack, Hannah J. and Haddad, Nick M. and Bergland, Alan O. and Machado, Heather and Sackton, Timothy B. and Schlenke, Todd A. and Watada, Masayoshi and et al.}, year={2014}, month={Dec}, pages={3148–3163} }
 @article{damschen_baker_bohrer_nathan_orrock_turner_brudvig_haddad_levey_tewksbury_2014, title={How fragmentation and corridors affect wind dynamics and seed dispersal in open habitats}, volume={111}, ISSN={["0027-8424"]}, DOI={10.1073/pnas.1308968111}, abstractNote={Significance}, number={9}, journal={PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, author={Damschen, Ellen I. and Baker, Dirk V. and Bohrer, Gil and Nathan, Ran and Orrock, John L. and Turner, Jay R. and Brudvig, Lars A. and Haddad, Nick M. and Levey, Douglas J. and Tewksbury, Joshua J.}, year={2014}, month={Mar}, pages={3484–3489} }
 @article{resasco_haddad_orrock_shoemaker_brudvig_damschen_tewksbury_levey_2014, title={Landscape corridors can increase invasion by an exotic species and reduce diversity of native species}, volume={95}, DOI={10.1890/14-0169.1}, abstractNote={Landscape corridors are commonly used to mitigate negative effects of habitat fragmentation, but concerns persist that they may facilitate the spread of invasive species. In a replicated landscape experiment of open habitat, we measured effects of corridors on the invasive fire ant, Solenopsis invicta, and native ants. Fire ants have two social forms: polygyne, which tend to disperse poorly but establish at high densities, and monogyne, which disperse widely but establish at lower densities. In landscapes dominated by polygyne fire ants, fire ant abundance was higher and native ant diversity was lower in habitat patches connected by corridors than in unconnected patches. Conversely, in landscapes dominated by monogyne fire ants, connectivity had no influence on fire ant abundance and native ant diversity. Polygyne fire ants dominated recently created landscapes, suggesting that these corridor effects may be transient. Our results suggest that corridors can facilitate invasion and they highlight the importance of considering species' traits when assessing corridor utility.}, number={8}, journal={Ecology}, author={Resasco, J. and Haddad, N. M. and Orrock, J. L. and Shoemaker, D. and Brudvig, T. A. and Damschen, E. I. and Tewksbury, J. J. and Levey, D. J.}, year={2014}, pages={2033–2039} }
 @misc{haddad_brudvig_damschen_evans_johnson_levey_orrock_resasco_sullivan_tewksbury_et al._2014, title={Potential Negative Ecological Effects of Corridors}, volume={28}, DOI={10.1111/cobi.12323}, abstractNote={Abstract}, number={5}, journal={Conservation Biology}, author={Haddad, N. M. and Brudvig, L. A. and Damschen, E. I. and Evans, D. M. and Johnson, B. L. and Levey, D. J. and Orrock, J. L. and Resasco, J. and Sullivan, L. L. and Tewksbury, J. J. and et al.}, year={2014}, pages={1178–1187} }
 @article{diamond_cayton_wepprich_jenkins_dunn_haddad_ries_2014, title={Unexpected phenological responses of butterflies to the interaction of urbanization and geographic temperature}, volume={95}, ISSN={["1939-9170"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84907211442&partnerID=MN8TOARS}, DOI={10.1890/13-1848.1}, abstractNote={Urbanization and global climate change can profoundly alter biological systems, yet scientists often analyze their effects separately. We test how the timing of life cycle events (phenology) is jointly influenced by these two components of global change. To do so, we use a long‐term phenological data set of 20 common butterfly species from 83 sites across the state of Ohio, USA, with sites that range from rural undeveloped areas to moderately sized cities. These sites span a latitudinal gradient in mean temperature of several °C, mimicking the range of projected global climate warming effects through the end of the century. Although shifts toward earlier phenology are typical of species' responses to either global climate change or urbanization, we found that their interaction delayed several Ohio butterfly species' first appearance and peak abundance phenology. Exploitative species exhibited smaller delays in first appearance and peak abundance phenology in areas that were urbanized and geographically warm. Our results show that phenological responses to urbanization are contingent upon geographic variation in temperature, and that the impacts of urbanization and global climate change should be considered simultaneously when developing forecasts of biological responses to environmental change.}, number={9}, journal={ECOLOGY}, author={Diamond, Sarah E. and Cayton, Heather and Wepprich, Tyson and Jenkins, Clinton N. and Dunn, Robert R. and Haddad, Nick M. and Ries, Leslie}, year={2014}, month={Sep}, pages={2613–2621} }
 @article{mata_haddad_holyoak_2013, title={How invader traits interact with resident communities and resource availability to determine invasion success}, volume={122}, ISSN={["1600-0706"]}, DOI={10.1111/j.1600-0706.2012.20401.x}, abstractNote={Competition for limited resources is considered a key factor controlling invasion success. Resource availability can be viewed in either the long or short‐term. Long‐term availability depends on the baseline nutrient availability in the ecosystem and how those conditions shape the ecological community. Short‐term resource availability fluctuates with disturbances that alter nutrient availability and/or the density and composition of the ecological community.}, number={1}, journal={OIKOS}, author={Mata, T. M. and Haddad, N. M. and Holyoak, M.}, year={2013}, month={Jan}, pages={149–160} }
 @article{wilson_sexton_jobe_haddad_2013, title={The relative contribution of terrain, land cover, and vegetation structure indices to species distribution models}, volume={164}, ISSN={["1873-2917"]}, DOI={10.1016/j.biocon.2013.04.021}, abstractNote={Habitat assessments for biodiversity conservation are often complicated by the lack of detailed knowledge of a study species’ distribution. As an alternative to resource-intensive field-based methods to obtain such information, remotely sensed products can be utilized in species distribution models to infer a species’ distribution and ecological needs. Here we demonstrate how to arbitrate among a variety of remotely sensed predictor variables to estimate the distribution and ecological needs of an endangered butterfly species occurring mainly in inaccessible areas. We classified 19 continuous environmental predictor variables into three conceptually independent predictor classes, terrain, land cover, and vertical vegetation structure, and compared the accuracy of competing Maxent habitat models consisting of different combinations of each class. Each class contributed, though disproportionately, to our most reliable model that considered all 19 variables. We confirm that variables obtained from remote sensors can effectively estimate the distribution and ecological needs of a relatively unknown imperiled species occurring in inaccessible locations. Importantly, increasing the variety of predictor classes through multi-sensor fusion resulted in greater model accuracy than increasing the absolute number of predictor variables.}, journal={BIOLOGICAL CONSERVATION}, author={Wilson, John W. and Sexton, Joseph O. and Jobe, R. Todd and Haddad, Nick M.}, year={2013}, month={Aug}, pages={170–176} }
 @article{haddad_2012, title={Connecting ecology and conservation through experiment}, volume={9}, ISSN={["1548-7105"]}, DOI={10.1038/nmeth.2107}, number={8}, journal={NATURE METHODS}, author={Haddad, Nick M.}, year={2012}, month={Aug}, pages={794–795} }
 @article{milko_haddad_lance_2012, title={Dispersal via stream corridors structures populations of the endangered St. Francis' satyr butterfly (Neonympha mitchellii francisci)}, volume={16}, ISSN={["1572-9753"]}, DOI={10.1007/s10841-011-9413-8}, number={2}, journal={JOURNAL OF INSECT CONSERVATION}, author={Milko, Laura V. and Haddad, Nick M. and Lance, Stacey L.}, year={2012}, month={Apr}, pages={263–273} }
 @article{dinnage_cadotte_haddad_crutsinger_tilman_2012, title={Diversity of plant evolutionary lineages promotes arthropod diversity}, volume={15}, ISSN={["1461-0248"]}, DOI={10.1111/j.1461-0248.2012.01854.x}, abstractNote={Abstract}, number={11}, journal={ECOLOGY LETTERS}, author={Dinnage, Russell and Cadotte, Marc W. and Haddad, Nick M. and Crutsinger, Gregory M. and Tilman, David}, year={2012}, month={Nov}, pages={1308–1317} }
 @article{hudgens_morris_haddad_fields_wilson_kuefler_jobe_2012, title={How complex do models need to be to predict dispersal of threatened species through matrix habitats?}, volume={22}, DOI={10.1890/11-1048.1}, abstractNote={Persistence of species in fragmented landscapes depends on dispersal among suitable breeding sites, and dispersal is often influenced by the “matrix” habitats that lie between breeding sites. However, measuring effects of different matrix habitats on movement and incorporating those differences into spatially explicit models to predict dispersal is costly in terms of time and financial resources. Hence a key question for conservation managers is: Do more costly, complex movement models yield more accurate dispersal predictions? We compared the abilities of a range of movement models, from simple to complex, to predict the dispersal of an endangered butterfly, the Saint Francis' satyr (Neonympha mitchellii francisci). The value of more complex models differed depending on how value was assessed. Although the most complex model, based on detailed movement behaviors, best predicted observed dispersal rates, it was only slightly better than the simplest model, which was based solely on distance between sites. Consequently, a parsimony approach using information criteria favors the simplest model we examined. However, when we applied the models to a larger landscape that included proposed habitat restoration sites, in which the composition of the matrix was different than the matrix surrounding extant breeding sites, the simplest model failed to identify a potentially important dispersal barrier, open habitat that butterflies rarely enter, which may completely isolate some of the proposed restoration sites from other breeding sites. Finally, we found that, although the gain in predicting dispersal with increasing model complexity was small, so was the increase in financial cost. Furthermore, a greater fit continued to accrue with greater financial cost, and more complex models made substantially different predictions than simple models when applied to a novel landscape in which butterflies are to be reintroduced to bolster their populations. This suggests that more complex models might be justifiable on financial grounds. Our results caution against a pure parsimony approach to deciding how complex movement models need to be to accurately predict dispersal through the matrix, especially if the models are to be applied to novel or modified landscapes.}, number={5}, journal={Ecological Applications}, author={Hudgens, B. R. and Morris, W. F. and Haddad, N. M. and Fields, W. R. and Wilson, J. W. and Kuefler, D. and Jobe, T.}, year={2012}, pages={1701–1710} }
 @article{sullivan_johnson_brudvig_haddad_2011, title={Can dispersal mode predict corridor effects on plant parasites?}, volume={92}, ISSN={["0012-9658"]}, DOI={10.1890/10-1116.1}, abstractNote={Habitat corridors, a common management strategy for increasing connectivity in fragmented landscapes, have experimentally validated positive influences on species movement and diversity. However, long-standing concerns that corridors could negatively impact native species by spreading antagonists, such as disease, remain largely untested. Using a large-scale, replicated experiment, we evaluated whether corridors increase the incidence of plant parasites. We found that corridor impacts varied with parasite dispersal mode. Connectivity provided by corridors increased incidence of biotically dispersed parasites (galls on Solidago odora) but not of abiotically dispersed parasites (foliar fungi on S. odora and three Lespedeza spp.). Both biotically and abiotically dispersed parasites responded to edge effects, but the direction of responses varied across species. Although our results require additional tests for generality to other species and landscapes, they suggest that, when establishing conservation corridors, managers should focus on mitigating two potential negative effects: the indirect effects of narrow corridors in creating edges and direct effects of corridors in enhancing connectivity of biotically dispersed parasites.}, number={8}, journal={ECOLOGY}, author={Sullivan, Lauren L. and Johnson, Brenda L. and Brudvig, Lars A. and Haddad, Nick M.}, year={2011}, month={Aug}, pages={1559–1564} }
 @article{leidner_haddad_2011, title={Combining Measures of Dispersal to Identify Conservation Strategies in Fragmented Landscapes}, volume={25}, ISSN={["0888-8892"]}, DOI={10.1111/j.1523-1739.2011.01720.x}, abstractNote={Abstract:  Understanding the way in which habitat fragmentation disrupts animal dispersal is key to identifying effective and efficient conservation strategies. To differentiate the potential effectiveness of 2 frequently used strategies for increasing the connectivity of populations in fragmented landscapes—corridors and stepping stones—we combined 3 complimentary methods: behavioral studies at habitat edges, mark‐recapture, and genetic analyses. Each of these methods addresses different steps in the dispersal process that a single intensive study could not address. We applied the 3 methods to the case study of Atrytonopsis new species 1, a rare butterfly endemic to a partially urbanized stretch of barrier islands in North Carolina (U.S.A.). Results of behavioral analyses showed the butterfly flew into urban and forested areas, but not over open beach; mark‐recapture showed that the butterfly dispersed successfully through short stretches of urban areas (<500 m); and genetic studies showed that longer stretches of forest (>5 km) were a dispersal barrier, but shorter stretches of urban areas (≤5 km) were not. Although results from all 3 methods indicated natural features in the landscape, not urbanization, were barriers to dispersal, when we combined the results we could determine where barriers might arise: forests restricted dispersal for the butterfly only when there were long stretches with no habitat. Therefore, urban areas have the potential to become a dispersal barrier if their extent increases, a finding that may have gone unnoticed if we had used a single approach. Protection of stepping stones should be sufficient to maintain connectivity for Atrytonopsis new species 1 at current levels of urbanization. Our research highlights how the use of complementary approaches for studying animal dispersal in fragmented landscapes can help identify conservation strategies.}, number={5}, journal={CONSERVATION BIOLOGY}, author={Leidner, Allison K. and Haddad, Nick M.}, year={2011}, month={Oct}, pages={1022–1031} }
 @article{johnson_haddad_2011, title={Edge effects, not connectivity, determine the incidence and development of a foliar fungal plant disease}, volume={92}, ISSN={["1939-9170"]}, DOI={10.1890/10-1072.1}, abstractNote={Using a model plant-pathogen system in a large-scale habitat corridor experiment, we found that corridors do not facilitate the movement of wind-dispersed plant pathogens, that connectivity of patches does not enhance levels of foliar fungal plant disease, and that edge effects are the key drivers of plant disease dynamics. Increased spread of infectious disease is often cited as a potential negative effect of habitat corridors used in conservation, but the impacts of corridors on pathogen movement have never been tested empirically. Using sweet corn (Zea mays) and southern corn leaf blight (Cochliobolus heterostrophus) as a model plant-pathogen system, we tested the impacts of connectivity and habitat fragmentation on pathogen movement and disease development at the Savannah River Site, South Carolina, USA. Over time, less edgy patches had higher proportions of diseased plants, and distance of host plants to habitat edges was the greatest determinant of disease development. Variation in average daytime temperatures provided a possible mechanism for these disease patterns. Our results show that worries over the potentially harmful effects of conservation corridors on disease dynamics are misplaced, and that, in a conservation context, many diseases can be better managed by mitigating edge effects.}, number={8}, journal={ECOLOGY}, author={Johnson, Brenda L. and Haddad, Nick M.}, year={2011}, month={Aug}, pages={1551–1558} }
 @article{haddad_crutsinger_gross_haarstad_tilman_2011, title={Plant diversity and the stability of foodwebs}, volume={14}, ISSN={["1461-0248"]}, DOI={10.1111/j.1461-0248.2010.01548.x}, abstractNote={Insect outbreaks in forest and agriculture monocultures led Charles Elton to propose, a half-century ago, that higher plant diversity stabilized animal foodweb dynamics in natural ecosystems. We tested this hypothesis by studying arthropod community dynamics in a long-term experimental manipulation of grassland plant species diversity. Over the course of a decade, we found that higher plant diversity increased the stability (i.e. lowered year-to-year variability) of a diverse (>700 species) arthropod community across trophic levels. As the number of plant species increased, the stability of both herbivore and predator species richness and of total herbivore abundance increased. The underlying mechanisms driving these diversity-stability relationships were plant diversity, via effects on primary productivity and plant community stability, and portfolio effects. Taken together, our results show that higher plant diversity provides more temporally consistent food and habitat resources to arthropod foodwebs. Consequently, actively managing for high plant diversity may have stronger than expected benefits for increasing animal diversity and controlling pest outbreaks.}, number={1}, journal={ECOLOGY LETTERS}, author={Haddad, Nick M. and Crutsinger, Gregory M. and Gross, Kevin and Haarstad, John and Tilman, David}, year={2011}, month={Jan}, pages={42–46} }
 @article{leidner_haddad_lovejoy_2010, title={Does Tropical Forest Fragmentation Increase Long-Term Variability of Butterfly Communities?}, volume={5}, ISSN={["1932-6203"]}, DOI={10.1371/journal.pone.0009534}, abstractNote={Habitat fragmentation is a major driver of biodiversity loss. Yet, the overall effects of fragmentation on biodiversity may be obscured by differences in responses among species. These opposing responses to fragmentation may be manifest in higher variability in species richness and abundance (termed hyperdynamism), and in predictable changes in community composition. We tested whether forest fragmentation causes long-term hyperdynamism in butterfly communities, a taxon that naturally displays large variations in species richness and community composition. Using a dataset from an experimentally fragmented landscape in the central Amazon that spanned 11 years, we evaluated the effect of fragmentation on changes in species richness and community composition through time. Overall, adjusted species richness (adjusted for survey duration) did not differ between fragmented forest and intact forest. However, spatial and temporal variation of adjusted species richness was significantly higher in fragmented forests relative to intact forest. This variation was associated with changes in butterfly community composition, specifically lower proportions of understory shade species and higher proportions of edge species in fragmented forest. Analysis of rarefied species richness, estimated using indices of butterfly abundance, showed no differences between fragmented and intact forest plots in spatial or temporal variation. These results do not contradict the results from adjusted species richness, but rather suggest that higher variability in butterfly adjusted species richness may be explained by changes in butterfly abundance. Combined, these results indicate that butterfly communities in fragmented tropical forests are more variable than in intact forest, and that the natural variability of butterflies was not a buffer against the effects of fragmentation on community dynamics.}, number={3}, journal={PLOS ONE}, author={Leidner, Allison K. and Haddad, Nick M. and Lovejoy, Thomas E.}, year={2010}, month={Mar} }
 @article{krosby_tewksbury_haddad_hoekstra_2010, title={Ecological Connectivity for a Changing Climate}, volume={24}, ISSN={["1523-1739"]}, DOI={10.1111/j.1523-1739.2010.01585.x}, abstractNote={A frequently proposed strategy to reduce the negative effects of climate change on biological diversity is to increase ecological connectivity (Heller & Zavaleta 2009)— the flow of organisms and ecological processes across landscapes (Taylor et al. 1993). Traditionally, conservation professionals have sought to maintain or restore connectivity to ensure gene flow among isolated populations and promote recolonization of vacant patches (Hanski 1998). Given the rapid emergence of connectivity enhancement as a climate-change adaptation strategy, we considered whether connectivity should be emphasized in conservation strategies as global or regional temperatures increase and what principles for connectivity enhancement could be applied to maximize the usefulness of the strategy. The best historical analogue for the ongoing rise in global temperatures occurred 55 million years ago at the Paleocene and Eocene boundary, when the average global temperature rose 5–6 ◦C in 10,000–20,000 years (Wing et al. 2005). At that time, species’ ranges shifted and subtropical cypress swamps, complete with alligators, existed on Ellesmere Island in the Arctic (Estes & Hutchison 1980). A similar rise in temperature has been projected within the next 100–200 years (IPCC 2007), two orders of magnitude faster than previous warming events. Movements of some species, however, are now restricted by human-caused fragmentation and other barriers. The primary rationale for increasing connectivity is that if the effects of land-cover fragmentation can be mitigated, this should enhance the ability of species to move into new regions as climate changes (Fig. 1), thereby decreasing the probability of extirpation or extinction. Here, increasing connectivity refers to management actions that facilitate dispersal of species among natural areas, for example, through the establishment of landscape corridors or stepping-stone reserves or through actions that increase matrix permeability. Because funds}, number={6}, journal={CONSERVATION BIOLOGY}, author={Krosby, Meade and Tewksbury, Joshua and Haddad, Nick M. and Hoekstra, Jonathan}, year={2010}, month={Dec}, pages={1686–1689} }
 @article{bartel_haddad_wright_2010, title={Ecosystem engineers maintain a rare species of butterfly and increase plant diversity}, volume={119}, ISSN={["1600-0706"]}, DOI={10.1111/j.1600-0706.2009.18080.x}, abstractNote={We evaluated whether ecosystem engineers can accomplish two conservation goals simultaneously: (1) indirectly maintain populations of an endangered animal through habitat modifi cation and (2) increase riparian plant diversity. We tested for eff ects of a prominent ecosystem engineer, the beaver Castor canadensis, on populations of St. Francis’ satyr butterfl y Neonympha mitchellii francisci and plant species richness and composition. We performed our test by surveying riparian vegetation communities in all stages of beaver-infl uenced wetland succession. We found that beavers created wetland habitats that supported plant species not found elsewhere in riparian zones and increased plant species diversity across the landscape by creating a novel combination of patch types. Our results confi rmed what others have found about engineering eff ects on plant diversity, but these results further demonstrated a case where ecosystem engineers indirectly maintain populations of rare animals by modifying the composition and diversity of plant communities within wetlands. Our research demonstrates how an ecosystem engineer can infl uence habitat availability and composition of plant communities important for an endangered insect, and maintain overall plant species diversity by increasing habitat heterogeneity.}, number={5}, journal={OIKOS}, author={Bartel, Rebecca A. and Haddad, Nick M. and Wright, Justin P.}, year={2010}, month={May}, pages={883–890} }
 @article{leidner_haddad_2010, title={Natural, not urban, barriers define population structure for a coastal endemic butterfly}, volume={11}, ISSN={["1572-9737"]}, DOI={10.1007/s10592-010-0117-5}, number={6}, journal={CONSERVATION GENETICS}, author={Leidner, Allison K. and Haddad, Nick M.}, year={2010}, month={Dec}, pages={2311–2320} }
 @article{kuefler_hudgens_haddad_morris_thurgate_2010, title={The conflicting role of matrix habitats as conduits and barriers for dispersal}, volume={91}, DOI={10.1890/09-0614.1}, abstractNote={Determining connectivity within complex landscapes is difficult if habitats that facilitate dispersal differ from habitats where animals normally are found or enter. We addressed the question of how landscape features affect dispersal by quantifying two critical aspects of animal movement behavior that determine dispersal rates across complex landscapes: conductivity of major habitat types and behavior at boundaries between habitat types. Our tests consisted of behavioral experiments and observational surveys of a wetland butterfly,Satyrodes appalachia. Displacement rates varied among habitats, with the longest moves and straightest paths leading to greater displacement rate in open habitat and shortest moves and most sinuous paths causing the slowest displacement rate in riparian forest habitat. We found a strong negative relationship between the probability of entering a habitat and the speed of moving through it. Recognizing this central conflict between entering and moving through habitat is important for assessing the connectivity of complex landscapes.}, number={4}, journal={Ecology (Brooklyn, New York, N.Y.)}, author={Kuefler, D. and Hudgens, B. and Haddad, N. M. and Morris, W. F. and Thurgate, N.}, year={2010}, pages={944–950} }
 @article{wells_williams_walker_haddad_2009, title={Effects of Corridors on Genetics of a Butterfly in a Landscape Experiment}, volume={8}, ISSN={["1938-5412"]}, DOI={10.1656/058.008.0412}, abstractNote={Abstract 
 To investigate the possible role of landscape connectivity on the genetic structure of isolated populations, we examined the effects of habitat corridors on the population genetics of a vagile butterfly species, Junonia coenia, within a large-scale, experimental system. Using allozyme electrophoresis, a total of nine loci were identified and scored, six of which exhibited polymorphism. Our data demonstrated consistently higher levels of expected (He) and observed (Ho) heterozygosity in butterflies sampled from patches connected by corridors compared to unconnected patches. A t-test comparing He and H0 in connected versus unconnected patches found a marginally significant difference in one locus, the glycolytic enzyme phosphoglucose isomerase (PGI). Connected patches exhibited overall lower F ST values compared to unconnected patches, indicating potentially increased levels of gene flow due to corridors. Our results support previous investigations on dispersal and population size for J. coenia, and show that higher dispersal through corridors promotes genetic variability at a locus (PGI) implicated in dispersal and fitness in butterflies.}, number={4}, journal={SOUTHEASTERN NATURALIST}, author={Wells, Carrie N. and Williams, Ray S. and Walker, Gary L. and Haddad, Nick M.}, year={2009}, pages={709–722} }
 @article{brudvig_damschen_tewksbury_haddad_levey_2009, title={Landscape connectivity promotes plant biodiversity spillover into non-target habitats}, volume={106}, ISSN={["0027-8424"]}, DOI={10.1073/pnas.0809658106}, abstractNote={Conservation efforts typically focus on maximizing biodiversity in protected areas. The space available for reserves is limited, however, and conservation efforts must increasingly consider how management of protected areas can promote biodiversity beyond reserve borders. Habitat corridors are considered an important feature of reserves because they facilitate movement of organisms between patches, thereby increasing species richness in those patches. Here we demonstrate that by increasing species richness inside target patches, corridors additionally benefit biodiversity in surrounding non-target habitat, a biodiversity “spillover” effect. Working in the world's largest corridor experiment, we show that increased richness extends for approximately 30% of the width of the 1-ha connected patches, resulting in 10–18% more vascular plant species around patches of target habitat connected by corridors than around unconnected but otherwise equivalent patches of habitat. Furthermore, corridor-enhanced spillover into non-target habitat can be predicted by a simple plant life-history trait: seed dispersal mode. Species richness of animal-dispersed plants in non-target habitat increased in response to connectivity provided by corridors, whereas species richness of wind-dispersed plants was unaffected by connectivity and increased in response to changes in patch shape—higher edge-to-interior ratio—created by corridors. Corridors promoted biodiversity spillover for native species of the threatened longleaf pine ecosystem being restored in our experiment, but not for exotic species. By extending economically driven spillover concepts from marine fisheries and crop pollination systems, we show how reconnecting landscapes amplifies biodiversity conservation both within and beyond reserve borders.}, number={23}, journal={PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, author={Brudvig, Lars A. and Damschen, Ellen I. and Tewksbury, Joshua J. and Haddad, Nick M. and Levey, Douglas J.}, year={2009}, month={Jun}, pages={9328–9332} }
 @article{haddad_crutsinger_gross_haarstad_knops_tilman_2009, title={Plant species loss decreases arthropod diversity and shifts trophic structure}, volume={12}, ISSN={["1461-0248"]}, DOI={10.1111/j.1461-0248.2009.01356.x}, abstractNote={Abstract}, number={10}, journal={ECOLOGY LETTERS}, author={Haddad, Nick M. and Crutsinger, Gregory M. and Gross, Kevin and Haarstad, John and Knops, Johannes M. H. and Tilman, David}, year={2009}, month={Oct}, pages={1029–1039} }
 @article{haddad_hudgens_damiani_gross_kuefler_pollock_2008, title={Determining optimal population monitoring for rare butterflies}, volume={22}, ISSN={["1523-1739"]}, DOI={10.1111/j.1523-1739.2008.00932.x}, abstractNote={Abstract: Determining population viability of rare insects depends on precise, unbiased estimates of population size and other demographic parameters. We used data on the endangered St. Francis' satyr butterfly (Neonympha mitchellii francisci) to evaluate 2 approaches (mark–recapture and transect counts) for population analysis of rare butterflies. Mark–recapture analysis provided by far the greatest amount of demographic information, including estimates (and standard errors) of population size, detection, survival, and recruitment probabilities. Mark–recapture analysis can also be used to estimate dispersal and temporal variation in rates, although we did not do this here. Models of seasonal flight phenologies derived from transect counts (Insect Count Analyzer) provided an index of population size and estimates of survival and statistical uncertainty. Pollard–Yates population indices derived from transect counts did not provide estimates of demographic parameters. This index may be highly biased if detection and survival probabilities vary spatially and temporally. In terms of statistical performance, mark–recapture and Pollard–Yates indices were least variable. Mark–recapture estimates were less likely to fail than Insect Count Analyzer, but mark–recapture estimates became less precise as sampling intensity decreased. In general, count‐based approaches are less costly and less likely to cause harm to rare insects than mark–recapture. The optimal monitoring approach must reconcile these trade‐offs. Thus, mark–recapture should be favored when demographic estimates are needed, when financial resources enable frequent sampling, and when marking does not harm the insect populations. The optimal sampling strategy may use 2 sampling methods together in 1 overall sampling plan: limited mark–recapture sampling to estimate survival and detection probabilities and frequent but less expensive transect counts.}, number={4}, journal={CONSERVATION BIOLOGY}, author={Haddad, Nick M. and Hudgens, Brian and Damiani, Chris and Gross, Kevin and Kuefler, Daniel and Pollock, Ken}, year={2008}, month={Aug}, pages={929–940} }
 @article{kuefler_haddad_hall_hudgens_bartel_hoffman_2008, title={Distribution, population structure and habitat use of the endangered Saint Francis Satyr butterfly, Neonympha mitchellii francisci}, volume={159}, ISSN={["1938-4238"]}, DOI={10.1674/0003-0031(2008)159[298:DPSAHU]2.0.CO;2}, abstractNote={ABSTRACT The endangered St. Francis Satyr (Neonympha mitchellii francisci) is a small sedentary butterfly and one of the rarest in North America. Our study examined various quantitative aspects of this butterfly's biology, including the distributional range, habitat associations, population size and trends, demographic parameters and spatial aspects of population structure. The range of N.m. francisci distribution is restricted to DoD lands at Ft. Bragg, North Carolina, where the butterfly utilizes wetland habitats, predominantly those that have previously been impounded by beaver. In situ habitat associations and captive rearing experiments indicate that multiple sedges in the genus Carex, particularly C. mitchelliana, may be important larval food plants. Subpopulation estimates range between 49–739 individuals at any one site, while cumulative population estimates range between 700–1400 individuals for all accessible areas on Ft. Bragg. Habitats occupied by N.m. francisci are frequently subject to burning or flooding and thus butterfly subpopulations are extremely dynamic, fluctuating in response to these disturbances. This regular disturbance regime dictates that dispersal is necessary for population persistence. Several inter-colony movements were measured during capture-recapture studies and we observed both subpopulation extinctions and colonization of new habitat through the period of our studies. Conservation of N.m. francisci depends on accommodating unique aspects of its populations, including its dependence on beaver and its multi-tiered metapopulation structure.}, number={2}, journal={AMERICAN MIDLAND NATURALIST}, author={Kuefler, Daniel and Haddad, Nick M. and Hall, Stephen and Hudgens, Brian and Bartel, Becky and Hoffman, Erich}, year={2008}, month={Apr}, pages={298–320} }
 @article{haddad_2008, title={Finding the corridor more traveled}, volume={105}, ISSN={["0027-8424"]}, DOI={10.1073/pnas.0810867106}, abstractNote={As wildlands give way to an expanding human footprint, scientists and land managers have struggled to develop land conservation strategies that protect biodiversity. A favored strategy is to connect large habitat areas with landscape corridors (1–3). Yet, the scientific question remains: Do corridors actually work to promote dispersal and conserve biodiversity? In this issue of PNAS, Gillies and St. Clair's (4) answer this question with a clever behavioral experiment that offers new insights into the circumstances under which corridors benefit species.}, number={50}, journal={PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, author={Haddad, Nick M.}, year={2008}, month={Dec}, pages={19569–19570} }
 @article{haddad_holyoak_mata_davies_melbourne_preston_2008, title={Species' traits predict the effects of disturbance and productivity on diversity}, volume={11}, ISSN={["1461-0248"]}, DOI={10.1111/j.1461-0248.2007.01149.x}, abstractNote={Abstract}, number={4}, journal={ECOLOGY LETTERS}, author={Haddad, Nick M. and Holyoak, Marcel and Mata, Tawny M. and Davies, Kendi F. and Melbourne, Brett A. and Preston, Kim}, year={2008}, month={Apr}, pages={348–356} }
 @article{damschen_brudvig_haddad_levey_orrock_tewksbury_2008, title={The movement ecology and dynamics of plant communities in fragmented landscapes}, volume={105}, ISSN={["0027-8424"]}, DOI={10.1073/pnas.0802037105}, abstractNote={A conceptual model of movement ecology has recently been advanced to explain all movement by considering the interaction of four elements: internal state, motion capacity, navigation capacities, and external factors. We modified this framework to generate predictions for species richness dynamics of fragmented plant communities and tested them in experimental landscapes across a 7-year time series. We found that two external factors, dispersal vectors and habitat features, affected species colonization and recolonization in habitat fragments and their effects varied and depended on motion capacity. Bird-dispersed species richness showed connectivity effects that reached an asymptote over time, but no edge effects, whereas wind-dispersed species richness showed steadily accumulating edge and connectivity effects, with no indication of an asymptote. Unassisted species also showed increasing differences caused by connectivity over time, whereas edges had no effect. Our limited use of proxies for movement ecology (e.g., dispersal mode as a proxy for motion capacity) resulted in moderate predictive power for communities and, in some cases, highlighted the importance of a more complete understanding of movement ecology for predicting how landscape conservation actions affect plant community dynamics.}, number={49}, journal={PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, author={Damschen, Ellen I. and Brudvig, Lars A. and Haddad, Nick M. and Levey, Douglas J. and Orrock, John L. and Tewksbury, Joshua J.}, year={2008}, month={Dec}, pages={19078–19083} }
 @article{gross_kalendra_hudgens_haddad_2007, title={Robustness and uncertainty in estimates of butterfly abundance from transect counts}, volume={49}, ISSN={["1438-390X"]}, DOI={10.1007/s10144-007-0034-8}, abstractNote={Abstract}, number={3}, journal={POPULATION ECOLOGY}, author={Gross, Kevin and Kalendra, Eric J. and Hudgens, Brian R. and Haddad, Nick M.}, year={2007}, month={Jul}, pages={191–200} }
 @article{damschen_haddad_orrock_tewksbury_levey_2006, title={Corridors increase plant species richness at large scales}, volume={313}, ISSN={["0036-8075"]}, DOI={10.1126/science.1130098}, abstractNote={Habitat fragmentation is one of the largest threats to biodiversity. Landscape corridors, which are hypothesized to reduce the negative consequences of fragmentation, have become common features of ecological management plans worldwide. Despite their popularity, there is little evidence documenting the effectiveness of corridors in preserving biodiversity at large scales. Using a large-scale replicated experiment, we showed that habitat patches connected by corridors retain more native plant species than do isolated patches, that this difference increases over time, and that corridors do not promote invasion by exotic species. Our results support the use of corridors in biodiversity conservation.}, number={5791}, journal={SCIENCE}, author={Damschen, Ellen I. and Haddad, Nick M. and Orrock, John L. and Tewksbury, Joshua J. and Levey, Douglas J.}, year={2006}, month={Sep}, pages={1284–1286} }
 @article{kuefler_haddad_2006, title={Local versus landscape determinants of butterfly movement behaviors}, volume={29}, ISSN={["1600-0587"]}, DOI={10.1111/j.0906-7590.2006.04574.x}, abstractNote={Large‐scale patterns of animal distributions and abundances may be determined by mechanisms that act at local or landscape scales. We studied the movement behaviors of four species of bottomland butterflies in a natural setting to examine the determinants of movement behavior across different scales. We tested the relative importance of three landscape attributes: drainage slope, boundary type, and stream proximity, and local habitat attributes related to food plants and plants that influence habitat structure. Across species, we tested the relative importance of organism size and habitat specificity to explain response variation. In general, butterfly responses to landscape features were more universal than responses to local features. Specifically, results from this study showed that drainage slope did not influence movement behaviors but boundary type, stream proximity, and host plant abundance all influenced movement patterns. Responses to local features varied by species and often complemented landscape effects on movement. Responses to all features were not related to butterfly size, but did vary in accordance with butterfly host plant specificity. These behaviors help to explain landscape‐level variation in population distribution among species.}, number={4}, journal={ECOGRAPHY}, author={Kuefler, Daniel and Haddad, Nick M.}, year={2006}, month={Aug}, pages={549–560} }
 @misc{damschen_rosenfeld_wyer_murphy-medley_wentworth_haddad_2006, title={Women in ecology - Authors reply}, volume={4}, number={1}, journal={Frontiers in Ecology and the Environment}, author={Damschen, E. I. and Rosenfeld, K. M. and Wyer, M. and Murphy-Medley, D. and Wentworth, T. R. and Haddad, N. M.}, year={2006}, pages={10} }
 @article{brinkerhoff_haddad_orrock_2005, title={Corridors and olfactory predator cues affect small mammal behavior}, volume={86}, ISSN={["1545-1542"]}, DOI={10.1644/1545-1542(2005)086[0662:CAOPCA]2.0.CO;2}, abstractNote={Abstract The behavior of prey individuals is influenced by a variety of factors including, but not limited to, habitat configuration, risk of predation, and availability of resources, and these habitat-dependent factors may have interactive effects. We studied the responses of mice to an increase in perceived predation risk in a patchy environment to understand how habitat corridors might affect interactions among species in a fragmented landscape. We used a replicated experiment to investigate corridor-mediated prey responses to predator cues in a network of open habitat patches surrounded by a matrix of planted pine forest. Some of the patches were connected by corridors. We used mark–recapture techniques and foraging trays to monitor the movement, behavior, and abundance of small mammals. Predation threat was manipulated in one-half of the replicates by applying an olfactory predator cue. Corridors synchronized small mammal foraging activity among connected patches. Foraging also was inhibited in the presence of an olfactory predator cue but apparently increased in adjacent connected patches. Small mammal abundance did not change as a result of the predator manipulation and was not influenced by the presence of corridors. This study is among the 1st to indicate combined effects of landscape configuration and predation risk on prey behavior. These changes in prey behavior may, in turn, have cascading effects on community dynamics where corridors and differential predation risk influence movement and patch use.}, number={4}, journal={JOURNAL OF MAMMALOGY}, author={Brinkerhoff, RJ and Haddad, NM and Orrock, JL}, year={2005}, month={Aug}, pages={662–669} }
 @article{levey_bolker_tewksbury_sargent_haddad_2005, title={Effects of landscape corridors on seed dispersal by birds}, volume={309}, ISSN={["1095-9203"]}, DOI={10.1126/science.1111479}, abstractNote={Habitat fragmentation threatens biodiversity by disrupting dispersal. The mechanisms and consequences of this disruption are controversial, primarily because most organisms are difficult to track. We examined the effect of habitat corridors on long-distance dispersal of seeds by birds, and tested whether small-scale (<20 meters) movements of birds could be scaled up to predict dispersal of seeds across hundreds of meters in eight experimentally fragmented landscapes. A simulation model accurately predicted the observed pattern of seed rain and revealed that corridors functioned through edge-following behavior of birds. Our study shows how models based on easily observed behaviors can be scaled up to predict landscape-level processes.}, number={5731}, journal={SCIENCE}, author={Levey, DJ and Bolker, BM and Tewksbury, JJ and Sargent, S and Haddad, NM}, year={2005}, month={Jul}, pages={146–148} }
 @misc{levey_bolker_tewksbury_sargent_haddad_2005, title={Landscape corridors: Possible dangers? Response}, volume={310}, number={5749}, journal={Science}, author={Levey, D. J. and Bolker, B. M. and Tewksbury, J. J. and Sargent, S. and Haddad, N. M.}, year={2005}, pages={781-} }
 @article{haddad_tewksbury_2005, title={Low-quality habitat corridors as movement conduits for two butterfly species}, volume={15}, ISSN={["1939-5582"]}, DOI={10.1890/03-5327}, abstractNote={Corridors are a primary conservation tool to increase connectivity, promote individual movement, and increase gene flow among populations in fragmented landscapes. The establishment of effective conservation corridors will depend on constructing or pre- serving connecting habitat that attracts dispersing individuals. Yet, it remains unclear wheth- er corridors must necessarily be composed of high-quality habitat to be effective and promote dispersal and gene flow. We address this issue with two mobile, open-habitat butterfly species, Junonia coeniaHubner andEuptoieta claudiaCramer. Using experimental landscapes created explicitly to examine the effects of corridors on dispersal rates, we show that open-habitat corridors can serve as dispersal conduits even when corridors do not support resident butterfly populations. Both butterfly species were rare near forest edges and equally rare in narrow corridors, yet both species dispersed more often between patches connected by these corridors than between isolated patches. At least for species that can traverse corridors within a generation, corridor habitat may be lower in quality than larger patches and still increase dispersal and gene flow. For these species, abundance surveys may not accurately represent the conservation value of corridors.}, number={1}, journal={ECOLOGICAL APPLICATIONS}, author={Haddad, NM and Tewksbury, JJ}, year={2005}, month={Feb}, pages={250–257} }
 @article{weldon_haddad_2005, title={The effects of patch shape on indigo buntings: Evidence for an ecological trap}, volume={86}, ISSN={["0012-9658"]}, DOI={10.1890/04-0913}, abstractNote={Habitat loss and fragmentation have led to a widespread increase in the proportion of edge habitat in the landscape. Disturbance-dependent bird species are widely assumed to benefit from these edges. However, anthropogenic edges may concentrate nest predators while retaining habitat cues that birds use to select breeding habitat. This may lead birds to mistakenly select dangerous habitat—a phenomenon known as an ''ecological trap.'' We experimentally demonstrated how habitat shape, and thus amount of edge, can adversely affect nest site selection and reproductive success of a disturbance-dependent bird species, the Indigo Bunting (Passerina cyanea). We did so within a landscape-scale experiment composed of equal-area habitat patches that differed in their amount of edge. Indigo Buntings preferentially selected edgy patches, which contained 50% more edge than more compact rectangular patches. Further, buntings fledged significantly fewer young per pair in edgy patches than in rectangular patches. These results provide the first experimental evidence that edges can function as ecological traps.}, number={6}, journal={ECOLOGY}, author={Weldon, AJ and Haddad, NM}, year={2005}, month={Jun}, pages={1422–1431} }
 @misc{damschen_rosenfeld_wyer_murphy-medley_wentworth_haddad_2005, title={Visibility matters: increasing knowledge of women's contributions to ecology}, volume={3}, ISSN={["1540-9309"]}, DOI={10.2307/3868465}, abstractNote={Recent scholarship about women and science is a good source of material for addressing the under-representation of women in science. This review is the result of an interdisciplinary fusion of science and women's studies to critically assess teaching tools in undergraduate ecology education. We examine: (1) the representation of women and the coverage of social and cultural context in introductory ecology textbooks, and (2) student learning about women's contributions to ecology. Discipline demographics reveal that women are presented in textbooks less often than expected, and that explicit discussions of the social and cultural context of science are rare. When course content is enriched with material about women's contributions, student's awareness of women scientists improves. Such knowledge can play a critical role in proactively challenging students' perceptions of ecology and ecologists, creating a more positive classroom climate for all students, and introducing novel avenues of questioning and discovery.}, number={4}, journal={FRONTIERS IN ECOLOGY AND THE ENVIRONMENT}, author={Damschen, EI and Rosenfeld, KM and Wyer, M and Murphy-Medley, D and Wentworth, TR and Haddad, NM}, year={2005}, month={May}, pages={212–219} }
 @article{haddad_bowne_cunningham_danielson_levey_sargent_spira_2003, title={Corridor use by diverse taxa}, volume={84}, ISSN={["0012-9658"]}, DOI={10.1890/0012-9658(2003)084[0609:cubdt]2.0.co;2}, abstractNote={One of the most popular approaches for maintaining populations and con- serving biodiversity in fragmented landscapes is to retain or create corridors that connect otherwise isolated habitat patches. Working in large-scale, experimental landscapes in which open-habitat patches and corridors were created by harvesting pine forest, we showed that corridors direct movements of different types of species, including butterflies, small mam- mals, and bird-dispersed plants, causing higher movement between connected than between unconnected patches. Corridors directed the movement of all 10 species studied, with all corridor effect sizes .68%. However, this corridor effect was significant for five species, not significant for one species, and inconclusive for four species because of small sample sizes. Although we found no evidence that corridors increase emigration from a patch, our results show that movements of disparate taxa with broadly different life histories and functional roles are directed by corridors.}, number={3}, journal={ECOLOGY}, author={Haddad, NM and Bowne, DR and Cunningham, A and Danielson, BJ and Levey, DJ and Sargent, S and Spira, T}, year={2003}, month={Mar}, pages={609–615} }
 @article{hudgens_haddad_2003, title={Predicting which species will benefit from corridors in fragmented landscapes from population growth models}, volume={161}, ISSN={["1537-5323"]}, DOI={10.1086/374343}, abstractNote={Connecting isolated patches of habitat in fragmented landscapes with corridors is a popular conservation strategy. This strategy is also controversial in large part because of uncertainty about what characteristics of a species and its environment promote corridor use. In this article we address the question, For what types of species will populations benefit from corridors? We asked this question using a model of two logistically growing populations connected by migration in which both emigration and migration success were determined by the presence or absence of a corridor. We found that in the short run (e.g., during recovery from disaster), corridors are most effective for species with fast‐growing populations that have low survivorship when dispersing through unsuitable (matrix) habitat. We also found that emigration rates and habitat‐specific mortality rates are key determinants of the effects of corridors on population size. In the long term, corridors are most likely to benefit species with slow‐growing populations that have low survivorship when dispersing through matrix habitat. Our results confirm the major conclusions from previous empirical studies of corridor benefits. However, most studies fail to consider the most appropriate questions to determine the potential benefits of habitat corridors. First, what is the time scale of the conservation goal? Corridors have positive effects on different suites of species in the short and long term. Second, is the major threat of local extinction due to sustained population decline or boom‐bust cycles? Third, what is the migration rate through the matrix? Fourth, what fraction of migrants dispersing through the matrix successfully immigrate to another patch?}, number={5}, journal={AMERICAN NATURALIST}, author={Hudgens, BR and Haddad, NM}, year={2003}, month={May}, pages={808–820} }
 @article{bradley_damschen_young_kuefler_went_wray_haddad_knops_louda_2003, title={Spatial heterogeneity, not visitation bias, dominates variation in herbivory}, volume={84}, ISSN={["0012-9658"]}, DOI={10.1890/02-3082}, abstractNote={Experiments in ecology can have unintended side effects. Recently, it has been suggested that the act of visiting a plant, inherent to studying herbivory, may alter plant performance and interactions. To evaluate the generality of this inference, we examined plant performance and herbivory on 14 plant species in three geographic regions. Visitation did not significantly affect any of the variables that we measured, including leaf damage, height, biomass, or survivorship, for any species. However, rates of herbivory varied significantly among sites and regions. Thus, our data do not support the generality of visitation impacting estimates of herbivory. We propose that future studies of herbivory will gain more by evaluating spatial heterogeneity in interaction outcomes than by quantifying possible experimenter-caused variation.}, number={8}, journal={ECOLOGY}, author={Bradley, KL and Damschen, EI and Young, LM and Kuefler, D and Went, S and Wray, G and Haddad, NM and Knops, JMH and Louda, SM}, year={2003}, month={Aug}, pages={2214–2221} }
 @article{tewksbury_levey_haddad_sargent_orrock_weldon_danielson_brinkerhoff_damschen_townsend_2002, title={Corridors affect plants, animals, and their interactions in fragmented landscapes}, volume={99}, ISSN={["0027-8424"]}, DOI={10.1073/pnas.202242699}, abstractNote={Among the most popular strategies for maintaining populations of both plants and animals in fragmented landscapes is to connect isolated patches with thin strips of habitat, called corridors. Corridors are thought to increase the exchange of individuals between habitat patches, promoting genetic exchange and reducing population fluctuations. Empirical studies addressing the effects of corridors have either been small in scale or have ignored confounding effects of increased habitat area created by the presence of a corridor. These methodological difficulties, coupled with a paucity of studies examining the effects of corridors on plants and plant–animal interactions, have sparked debate over the purported value of corridors in conservation planning. We report results of a large-scale experiment that directly address this debate. In eight large-scale experimental landscapes that control for patch area and test alternative mechanisms of corridor function, we demonstrate that corridors not only increase the exchange of animals between patches, but also facilitate two key plant–animal interactions: pollination and seed dispersal. Our results show that the beneficial effects of corridors extend beyond the area they add, and suggest that increased plant and animal movement through corridors will have positive impacts on plant populations and community interactions in fragmented landscapes.}, number={20}, journal={PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, author={Tewksbury, JJ and Levey, DJ and Haddad, NM and Sargent, S and Orrock, JL and Weldon, A and Danielson, BJ and Brinkerhoff, J and Damschen, EI and Townsend, P}, year={2002}, month={Oct}, pages={12923–12926} }
 @article{haddad_tilman_knops_2002, title={Long-term oscillations in grassland productivity induced by drought}, volume={5}, ISSN={["1461-0248"]}, DOI={10.1046/j.1461-0248.2002.00293.x}, abstractNote={Disturbances such as drought have immediate impacts on ecosystem functioning, but little is known about long‐term dynamic consequences of disturbance. Here, we show that a major drought perturbed prairie grassland from nearly constant average annual production, and induced 9 years of oscillations with a 2‐year period. This pattern occurred in unmanipulated plots in many widely separated fields that were part of two different long‐term studies. Using direct and indirect tests, we could reject the hypothesis that the oscillations were externally imposed by climate or herbivores. Weak evidence supported the hypothesis that oscillations were internally generated, caused by a litter and nitrogen dependent feedback on productivity. This hypothesis was supported by the results of two other long‐term studies, in which burning and, separately, nitrogen addition eliminated the 2‐year oscillations in plant production. However, more direct evidence failed to support the litter hypothesis. A final, but untested hypothesis was suggested by the observation that production tended to be synchronized amongst dominant plants. Drought may have synchronized production dynamics amongst plants with biennially greater allocation to above‐ground growth. Regardless of the specific mechanism, our results show that a single disturbance may have long‐lasting effects on the dynamics of plant production.}, number={1}, journal={ECOLOGY LETTERS}, author={Haddad, NM and Tilman, D and Knops, JMH}, year={2002}, month={Jan}, pages={110–120} }
 @article{haddad_tilman_haarstad_ritchie_knops_2001, title={Contrasting effects of plant richness and composition on insect communities: A field experiment}, volume={158}, ISSN={["0003-0147"]}, DOI={10.1086/320866}, abstractNote={We experimentally separated the effects of two components of plant diversity—plant species richness and plant functional group richness—on insect communities. Plant species richness and plant functional group richness had contrasting effects on insect abundances, a result we attributed to three factors. First, lower insect abundances at higher plant functional group richness were explained by a sampling effect, which was caused by the increasing likelihood that one low‐quality group, C4 grasses, would be present and reduce average insect abundances by 25%. Second, plant biomass, which was positively related to plant functional group richness, had a strong, positive effect on insect abundances. Third, a positive effect of plant species richness on insect abundances may have been caused by greater availability of alternate plant resources or greater vegetational structure. In addition, a greater diversity of insect species, whose individual abundances were often unaffected by changes in plant species richness, may have generated higher total community abundances. After controlling for the strong, positive influence of insect abundance on insect diversity through rarefaction, insect species richness increased as plant species richness and plant functional group richness increased. Although these variables did not explain a high proportion of variation individually, plant species richness and plant functional group richness had similar effects on insect diversity and opposing effects on insect abundances, and both factors may explain how the loss of plant diversity influences higher trophic levels.}, number={1}, journal={AMERICAN NATURALIST}, author={Haddad, NM and Tilman, D and Haarstad, J and Ritchie, M and Knops, JMH}, year={2001}, month={Jul}, pages={17–35} }
 @article{haddad_2000, title={Corridor length and patch colonization by a butterfly, Junonia coenia}, volume={14}, DOI={10.1046/j.1523-1739.2000.99041.x}, abstractNote={Abstract: Corridors have been proposed to reduce isolation and increase population persistence in fragmented landscapes, yet little research has evaluated the types of landscapes in which corridors will be most effective. I tested the hypothesis that corridors increase patch colonization by a butterfly, Junonia coenia, regardless of the butterfly's initial distance from a patch. I chose J. coenia because it has been shown to move between patches preferentially through corridors. Individuals were released 16–192 m away from open experimental patches into adjacent open corridors or forest. Neither corridors nor distance had a significant effect on patch colonization, but there was a significant interaction between the presence or absence of corridors and distance. At small distances (16–64 m), J. coenia was more likely to colonize open patches when released within forest than within open corridors, most likely because J. coenia used corridors as habitat. Nevertheless, patch colonization by butterflies released within forest decreased rapidly as distance from patches increased, as predicted by a null model of random movement. Colonization did not change with distance in the corridor, and at long distances (128–192 m), butterflies released in corridors were twice as likely to colonize open patches as those released in forest. These results suggest that one critical factor, interpatch distance, may determine the relative effectiveness of corridors and other landscape configurations, such as stepping stones, in reducing isolation in fragmented landscapes. When distances between patches are short compared to an animal's movement ability, a stepping stone approach may most effectively promote dispersal. Alternatively, the conservation value of corridors is highest relative to other habitat configurations when longer distances separate patches in fragmented landscapes.}, number={3}, journal={Conservation Biology}, author={Haddad, N. M.}, year={2000}, pages={738–745} }
 @article{haddad_2000, title={Corridor use predicted from behaviors at habitat boundaries (vol 153, pg 215, 1998)}, volume={155}, number={1}, journal={American Naturalist}, author={Haddad, N. M.}, year={2000}, pages={U7} }
 @article{haddad_hicks_2000, title={Host pubescence and the behavior and performance of the butterfly Papilio troilus (Lepidoptera : Papilionidae)}, volume={29}, ISSN={["0046-225X"]}, DOI={10.1603/0046-225X(2000)029[0299:HPATBA]2.0.CO;2}, abstractNote={Abstract We found that leaf pubescence in Sassafras albidum (Nuttall) Nees negatively influences the growth and survivorship of a lepidopteran herbivore, Papilio troilus (L.). S. albidum leaves varied greatly in pubescence among plants. In laboratory choice experiments, P. troilus larvae preferred to eat and adult females preferred to oviposit on nonpubescent S. albidum leaves. Larvae fed pubescent S. albidum had slower growth and higher mortality in early instars than larvae fed on nonpubescent leaves. These negative effects of pubescence on adult oviposition, larval growth rate, and larval survivorship suggest that the population size of P. troilus will reflect availability of nonpubescent hostplants. In field surveys, the frequency of pubescent S. albidum was significantly greater in open habitats created by harvesting pine forest than in hardwood forests, perhaps because of higher light and lower moisture in open areas. By changing the availability of quality food resources, forest management may have unintended negative impacts on this butterfly population.}, number={2}, journal={ENVIRONMENTAL ENTOMOLOGY}, author={Haddad, NM and Hicks, WM}, year={2000}, month={Apr}, pages={299–303} }
 @article{haddad_rosenberg_noon_2000, title={On experimentation and the study of corridors: Response to Beier and Noss}, volume={14}, ISSN={["1523-1739"]}, DOI={10.1046/j.1523-1739.2000.99572.x}, abstractNote={*Department of Zoology, Box 7617, North Carolina State University, Raleigh, NC 27695–7617, U.S.A., email nick haddad@ncsu.edu†Oregon Cooperative Fish and Wildlife Research Unit, Department of Fisheries and Wildlife, Oregon State University, Corvallis, OR 97333, U.S.A., email dan.rosenberg@orst.edu‡Department of Fisheries and Wildlife Biology, Colorado State University, Fort Collins, CO 80523–1474, U.S.A.,email brnoon@cnr.colostate.edu}, number={5}, journal={CONSERVATION BIOLOGY}, author={Haddad, NM and Rosenberg, DK and Noon, BR}, year={2000}, month={Oct}, pages={1543–1545} }
 @article{haddad_haarstad_tilman_2000, title={The effects of long-term nitrogen loading on grassland insect communities}, volume={124}, ISSN={["1432-1939"]}, DOI={10.1007/s004420050026}, abstractNote={Just as long-term nitrogen loading of grasslands decreases plant species richness and increases plant biomass, we have found that nitrogen loading decreases insect species richness and increases insect abundances. We sampled 54 plots that had been maintained at various rates of nitrogen addition for 14 years. Total insect species richness and effective insect diversity, as well as herbivore and predator species richness, were significantly, negatively related to the rate of nitrogen addition. However, there was variation in trophic responses to nitrogen. Detritivore species richness increased as nitrogen addition increased, and parasitoids showed no response. Insect abundances, measured as the number of insects and insect biovolume (an estimate of biomass), were significantly, positively related to the rate of nitrogen addition, as were the abundances of herbivores and detritivores. Parasitoid abundance was negatively related to the rate of nitrogen addition. Changes in the insect community were correlated with changes in the plant community. As rates of nitrogen addition increased, plant species richness decreased, plant productivity and plant tissue nitrogen increased, and plant composition shifted from C 4  to C 3  grass species. Along this gradient, total insect species richness and effective insect diversity were most strongly, positively correlated with plant species richness. Insect biovolume was negatively correlated with plant species richness. Responses of individual herbivores varied along the nitrogen gradient, but numbers of 13 of the 18 most abundant herbivores were positively correlated with their host plant biomass. Although insect communities did not respond as strongly as plant communities, insect species richness, abundance, and composition were impacted by nitrogen addition. This study demonstrates that long-term nitrogen loading affects the entire food chain, simplifying both plant and insect communities.}, number={1}, journal={OECOLOGIA}, author={Haddad, NM and Haarstad, J and Tilman, D}, year={2000}, month={Jul}, pages={73–84} }