@article{vecchi_kossi adakpo_dunn_nichols_penick_sanders_rebecchi_guidetti_2021, title={The toughest animals of the Earth versus global warming: Effects of long-term experimental warming on tardigrade community structure of a temperate deciduous forest}, volume={6}, ISSN={["2045-7758"]}, url={https://doi.org/10.1002/ece3.7816}, DOI={10.1002/ece3.7816}, abstractNote={Abstract Understanding how different taxa respond to global warming is essential for predicting future changes and elaborating strategies to buffer them. Tardigrades are well known for their ability to survive environmental stressors, such as drying and freezing, by undergoing cryptobiosis and rapidly recovering their metabolic function after stressors cease. Determining the extent to which animals that undergo cryptobiosis are affected by environmental warming will help to understand the real magnitude climate change will have on these organisms. Here, we report on the responses of tardigrades within a five‐year‐long, field‐based artificial warming experiment, which consisted of 12 open‐top chambers heated to simulate the projected effects of global warming (ranging from 0 to 5.5°C above ambient temperature) in a temperate deciduous forest of North Carolina (USA). To elucidate the effects of warming on the tardigrade community inhabiting the soil litter, three community diversity indices (abundance, species richness, and Shannon diversity) and the abundance of the three most abundant species (Diphascon pingue, Adropion scoticum, and Mesobiotus sp.) were determined. Their relationships with air temperature, soil moisture, and the interaction between air temperature and soil moisture were tested using Bayesian generalized linear mixed models. Despite observed negative effects of warming on other ground invertebrates in previous studies at this site, long‐term warming did not affect the abundance, richness, or diversity of tardigrades in this experiment. These results are in line with previous experimental studies, indicating that tardigrades may not be directly affected by ongoing global warming, possibly due to their thermotolerance and cryptobiotic abilities to avoid negative effects of stressful temperatures, and the buffering effect on temperature of the soil litter substrate.}, journal={ECOLOGY AND EVOLUTION}, author={Vecchi, Matteo and Kossi Adakpo, Laurent and Dunn, Robert R. and Nichols, Lauren M. and Penick, Clint A. and Sanders, Nathan J. and Rebecchi, Lorena and Guidetti, Roberto}, year={2021}, month={Jun} }
 @article{lau_ellison_nguyen_penick_demarcos_gotelli_sanders_dunn_cahan_2019, title={Draft Aphaenogaster genomes expand our view of ant genome size variation across climate gradients}, volume={7}, ISSN={["2167-8359"]}, DOI={10.7717/peerj.6447}, abstractNote={Given the abundance, broad distribution, and diversity of roles that ants play in many ecosystems, they are an ideal group to serve as ecosystem indicators of climatic change. At present, only a few whole-genome sequences of ants are available (19 of >16,000 species), mostly from tropical and sub-tropical species. To address this limited sampling, we sequenced genomes of temperate-latitude species from the genus Aphaenogaster , a genus with important seed dispersers. In total, we sampled seven colonies of six species: Aphaenogaster ashmeadi , Aphaenogaster floridana , Aphaenogaster fulva , Aphaenogaster miamiana , Aphaenogaster picea , and Aphaenogaster rudis . The geographic ranges of these species collectively span eastern North America from southern Florida to southern Canada, which encompasses a latitudinal gradient in which many climatic variables are changing rapidly. For the six genomes, we assembled an average of 271,039 contigs into 47,337 scaffolds. The Aphaenogaster genomes displayed high levels of completeness with 96.1% to 97.6% of Hymenoptera BUSCOs completely represented, relative to currently sequenced ant genomes which ranged from 88.2% to 98.5%. Additionally, the mean genome size was 370.5 Mb, ranging from 310.3 to 429.7, which is comparable to that of other sequenced ant genomes (212.8–396.0 Mb) and flow cytometry estimates (210.7–690.4 Mb). In an analysis of currently sequenced ant genomes and the new Aphaenogaster sequences, we found that after controlling for both spatial autocorrelation and phylogenetics ant genome size was marginally correlated with sample site climate similarity. Of all examined climate variables, minimum temperature, and annual precipitation had the strongest correlations with genome size, with ants from locations with colder minimum temperatures and higher levels of precipitation having larger genomes. These results suggest that climate extremes could be a selective force acting on ant genomes and point to the need for more extensive sequencing of ant genomes.}, journal={PEERJ}, author={Lau, Matthew K. and Ellison, Aaron M. and Nguyen, Andrew and Penick, Clint and DeMarcos, Bernice and Gotelli, Nicholas J. and Sanders, Nathan J. and Dunn, Robert R. and Cahan, Sara Helms}, year={2019}, month={Mar} }
 @article{penick_liebig_2017, title={A larval 'princess pheromone' identifies future ant queens based on their juvenile hormone content}, volume={128}, journal={Animal Behaviour}, author={Penick, C. A. and Liebig, J.}, year={2017}, pages={33–40} }
 @article{penick_diamond_sanders_dunn_2017, title={Beyond thermal limits: comprehensive metrics of performance identify key axes of thermal adaptation in ants}, volume={31}, ISSN={["1365-2435"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85010641179&partnerID=MN8TOARS}, DOI={10.1111/1365-2435.12818}, abstractNote={Summary
How species respond to temperature change depends in large part on their physiology. Physiological traits, such as critical thermal limits (CTmax and CTmin), provide estimates of thermal performance but may not capture the full impacts of temperature on fitness. Rather, thermal performance likely depends on a combination of traits—including thermal limits—that vary among species.
Here we examine how thermal limits correlate with the main components that influence fitness in ants. First, we compare how temperature affected colony survival and growth in two ant species that differ in their responses to warming in the field—Aphaenogaster rudis (heat-intolerant) and Temnothorax curvispinosus (heat-tolerant). We then extended our study to compare CTmax, thermal requirements of brood, and yearly activity season among a broader set of ant species.
While thermal limits were higher for workers of T. curvispinosus than A. rudis, T. curvispinosus colonies also required higher temperatures for survival and colony growth. This pattern generalized across 17 ant species, such that species whose foragers had a high CTmax also required higher temperatures for brood development. Finally, species whose foragers had a high CTmax had relatively short activity seasons compared with less heat-tolerant species.
The relationships between CTmax, thermal requirements of brood, and seasonal activity suggest two main strategies for growth and development in changing thermal environments: one where ants forage at higher temperatures over a short activity season, and another where ants forage at lower temperatures for an extended activity season. Where species fall on this spectrum may influence a broad range of life-history characteristics and aid in explaining the current distributions of ants as well as their responses to future climate change.


This article is protected by copyright. All rights reserved.}, number={5}, journal={FUNCTIONAL ECOLOGY}, author={Penick, Clint A. and Diamond, Sarah E. and Sanders, Nathan J. and Dunn, Robert R.}, year={2017}, month={May}, pages={1091–1100} }
 @article{maclean_penick_dunn_diamond_2017, title={Experimental winter warming modifies thermal performance and primes acorn ants for warm weather}, volume={100}, ISSN={0022-1910}, url={http://dx.doi.org/10.1016/j.jinsphys.2017.05.010}, DOI={10.1016/j.jinsphys.2017.05.010}, abstractNote={The frequency of warm winter days is increasing under global climate change, but how organisms respond to warmer winters is not well understood. Most studies focus on growing season responses to warming. Locomotor performance is often highly sensitive to temperature, and can determine fitness outcomes through a variety of mechanisms including resource acquisition and predator escape. As a consequence, locomotor performance, and its impacts on fitness, may be strongly affected by winter warming in winter-active species. Here we use the acorn ant, Temnothorax curvispinosus, to explore how thermal performance (temperature-driven plasticity) in running speed is influenced by experimental winter warming of 3–5 °C above ambient in a field setting. We used running speed as a measure of performance as it is a common locomotor trait that influences acquisition of nest sites and food in acorn ants. Experimental winter warming significantly altered thermal performance for running speed at high (26 and 36 °C) but not low test temperatures (6 and 16 °C). Although we saw little differentiation in thermal performance at cooler test temperatures, we saw a marked increase in running speed at the hotter test temperatures for ants that experienced warmer winters compared with those that experienced cooler winters. Our results provide evidence that overwintering temperatures can substantially influence organismal performance, and suggest that we cannot ignore overwintering effects when forecasting organismal responses to environmental changes in temperature.}, journal={Journal of Insect Physiology}, publisher={Elsevier BV}, author={MacLean, Heidi J. and Penick, Clint A. and Dunn, Robert R. and Diamond, Sarah E.}, year={2017}, month={Jul}, pages={77–81} }
 @article{diamond_chick_penick_nichols_cahan_dunn_ellison_sandersk_gotelli_2017, title={Heat tolerance predicts the importance of species interaction effects as the climate changes}, volume={57}, ISSN={["1557-7023"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85029143849&partnerID=MN8TOARS}, DOI={10.1093/icb/icx008}, abstractNote={SYNOPSIS
Few studies have quantified the relative importance of direct effects of climate change on communities versus indirect effects that are mediated thorough species interactions, and the limited evidence is conflicting. Trait-based approaches have been popular in studies of climate change, but can they be used to estimate direct versus indirect effects? At the species level, thermal tolerance is a trait that is often used to predict winners and losers under scenarios of climate change. But thermal tolerance might also inform when species interactions are likely to be important because only subsets of species will be able to exploit the available warmer climatic niche space, and competition may intensify in the remaining, compressed cooler climatic niche space. Here, we explore the relative roles of the direct effects of temperature change and indirect effects of species interactions on forest ant communities that were heated as part of a large-scale climate manipulation at high- and low-latitude sites in eastern North America. Overall, we found mixed support for the importance of negative species interactions (competition), but found that the magnitude of these interaction effects was predictable based on the heat tolerance of the focal species. Forager abundance and nest site occupancy of heat-intolerant species were more often influenced by negative interactions with other species than by direct effects of temperature. Our findings suggest that measures of species-specific heat tolerance may roughly predict when species interactions will influence responses to global climate change.}, number={1}, journal={INTEGRATIVE AND COMPARATIVE BIOLOGY}, author={Diamond, Sarah E. and Chick, Lacy and Penick, Clint A. and Nichols, Lauren M. and Cahan, Sara Helms and Dunn, Robert R. and Ellison, Aaron M. and Sandersk, Nathan J. and Gotelli, Nicholas J.}, year={2017}, month={Jul}, pages={112–120} }
 @article{cahan_nguyen_stanton-geddes_penick_hernaiz-hernandez_demarco_gotelli_2017, title={Modulation of the heat shock response is associated with acclimation to novel temperatures but not adaptation to climatic variation in the ants Aphaenogaster picea and A. rudis}, volume={204}, journal={Comparative Biochemistry and Physiology. A, Molecular & Integrative Physiology}, author={Cahan, S. H. and Nguyen, A. D. and Stanton-Geddes, J. and Penick, C. A. and Hernaiz-Hernandez, Y. and DeMarco, B. B. and Gotelli, N. J.}, year={2017}, pages={113–120} }
 @article{gospocic_shields_glastad_lin_penick_yan_mikheyev_linksvayer_garcia_berger_et al._2017, title={The neuropeptide corazonin controls social behavior and caste identity in ants}, volume={170}, number={4}, journal={Cell}, author={Gospocic, J. and Shields, E. J. and Glastad, K. M. and Lin, Y. P. and Penick, C. A. and Yan, H. and Mikheyev, A. S. and Linksvayer, T. A. and Garcia, B. A. and Berger, S. L. and et al.}, year={2017}, pages={748-} }
 @article{sasaki_penick_shaffer_haight_pratt_liebig_2016, title={A simple behavioral model predicts the emergence of complex animal hierarchies}, volume={187}, number={6}, journal={American Naturalist}, author={Sasaki, T. and Penick, C. A. and Shaffer, Z. and Haight, K. L. and Pratt, S. C. and Liebig, J.}, year={2016}, pages={765–775} }
 @article{diamond_nichols_pelini_penick_barber_cahan_dunn_ellison_sanders_gotelli_2016, title={Climatic warming destabilizes forest ant communities}, volume={2}, ISSN={2375-2548}, url={http://dx.doi.org/10.1126/sciadv.1600842}, DOI={10.1126/sciadv.1600842}, abstractNote={A field-based climate warming experiment reveals a loss of dynamical community stability due to altered species interactions. How will ecological communities change in response to climate warming? Direct effects of temperature and indirect cascading effects of species interactions are already altering the structure of local communities, but the dynamics of community change are still poorly understood. We explore the cumulative effects of warming on the dynamics and turnover of forest ant communities that were warmed as part of a 5-year climate manipulation experiment at two sites in eastern North America. At the community level, warming consistently increased occupancy of nests and decreased extinction and nest abandonment. This consistency was largely driven by strong responses of a subset of thermophilic species at each site. As colonies of thermophilic species persisted in nests for longer periods of time under warmer temperatures, turnover was diminished, and species interactions were likely altered. We found that dynamical (Lyapunov) community stability decreased with warming both within and between sites. These results refute null expectations of simple temperature-driven increases in the activity and movement of thermophilic ectotherms. The reduction in stability under warming contrasts with the findings of previous studies that suggest resilience of species interactions to experimental and natural warming. In the face of warmer, no-analog climates, communities of the future may become increasingly fragile and unstable.}, number={10}, journal={Science Advances}, publisher={American Association for the Advancement of Science (AAAS)}, author={Diamond, Sarah E. and Nichols, Lauren M. and Pelini, Shannon L. and Penick, Clint A. and Barber, Grace W. and Cahan, Sara Helms and Dunn, Robert R. and Ellison, Aaron M. and Sanders, Nathan J. and Gotelli, Nicholas J.}, year={2016}, month={Oct}, pages={e1600842} }
 @article{brent_penick_trobaugh_moore_liebig_2016, title={Induction of a reproductive-specific cuticular hydrocarbon profile by a juvenile hormone analog in the termite Zootermopsis nevadensis}, volume={26}, number={5}, journal={Chemoecology}, author={Brent, C. S. and Penick, C. A. and Trobaugh, B. and Moore, D. and Liebig, J.}, year={2016}, pages={195–203} }
 @article{karlik_epps_dunn_penick_2016, title={Life Inside an Acorn: How Microclimate and Microbes Influence Nest Organization in Temnothorax Ants}, volume={122}, ISSN={["1439-0310"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84983511133&partnerID=MN8TOARS}, DOI={10.1111/eth.12525}, abstractNote={Nests provide a buffer against environmental variation, but conditions may also vary at different locations within a nest. Conditions can vary based on abiotic factors, such as moisture and temperature, as well as biotic factors, such as the presence of microbes and potential pathogens. Therefore, characterizing how animals adjust their position inside their nests to track microclimate preferences while at the same time preventing pathogen exposure is necessary to understand the benefits nests provide. Here we studied how colonies of the acorn-nesting ant Temnothorax curvispinosus responded to experimental manipulation of moisture, temperature, and microbial growth inside their nests. Colonies showed no response to differences in moisture and moved to the bottom of the acorn regardless of moisture treatment. When nests were heated from the top to simulate warming by the sun, workers preferentially moved brood to the warm, upper half of the acorn, which would stimulate brood development. Finally, the strongest factor that influenced colony position was the presence of microbes inside the nest—colonies avoided the bottom of the nest when it was inoculated with microbes, and colonies in new acorns shifted to the top of the acorn over time as mold and other microbes had time to grow. The relatively strong response of T. curvispinosus to microbial growth inside their nests suggests that pathogen pressures—in addition to microclimate—have a significant impact on how colonies use nest spaces. Social insects are known to invest heavily in antimicrobial compounds that kill or slow the growth of microbes, but avoidance may represent an additional line of defense to prevent pathogen exposure.}, number={10}, journal={ETHOLOGY}, author={Karlik, Joseph and Epps, Mary Jane and Dunn, Robert R. and Penick, Clint A.}, year={2016}, month={Oct}, pages={790–797} }
 @article{penick_savage_dunn_2015, title={Stable isotopes reveal links between human food inputs and urban ant diets}, volume={282}, ISSN={0962-8452 1471-2954}, url={http://dx.doi.org/10.1098/rspb.2014.2608}, DOI={10.1098/rspb.2014.2608}, abstractNote={The amount of energy consumed within an average city block is an order of magnitude higher than that consumed in any other ecosystem over a similar area. This is driven by human food inputs, but the consequence of these resources for urban animal populations is poorly understood. We investigated the role of human foods in ant diets across an urbanization gradient in Manhattan using carbon and nitrogen stable isotopes. We found that some—but not all—ant species living in Manhattan's most urbanized habitats had δ13C signatures associated with processed human foods. In particular, pavement ants (Tetramorium sp. E) had increased levels of δ13C similar to δ13C levels in human fast foods. The magnitude of this effect was positively correlated with urbanization. By contrast, we detected no differences in δ15N, suggesting Tetramorium feeds at the same trophic level despite shifting to human foods. This pattern persisted across the broader ant community; species in traffic islands used human resources more than park species. Our results demonstrate that the degree urban ants exploit human resources changes across the city and among species, and this variation could play a key role in community structure and ecosystem processes where human and animal food webs intersect.}, number={1806}, journal={Proceedings of the Royal Society B: Biological Sciences}, publisher={The Royal Society}, author={Penick, Clint A. and Savage, Amy M. and Dunn, Robert R.}, year={2015}, month={May}, pages={20142608} }
 @article{penick_ebie_moore_2014, title={A non-destructive method for identifying the sex of ant larvae}, volume={61}, number={1}, journal={Insectes Sociaux}, author={Penick, C. A. and Ebie, J. and Moore, D.}, year={2014}, pages={51–55} }
 @article{penick_brent_dolezal_liebig_2014, title={Neurohormonal changes associated with ritualized combat and the formation of a reproductive hierarchy in the ant Harpegnathos saltator}, volume={217}, number={9}, journal={Journal of Experimental Biology}, author={Penick, C. A. and Brent, C. S. and Dolezal, K. and Liebig, J.}, year={2014}, pages={1496–1503} }
 @article{diamond_penick_pelini_ellison_gotelli_sanders_dunn_2013, title={Using Physiology to Predict the Responses of Ants to Climatic Warming}, volume={53}, ISSN={["1557-7023"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84893732452&partnerID=MN8TOARS}, DOI={10.1093/icb/ict085}, abstractNote={Physiological intolerance of high temperatures places limits on organismal responses to the temperature increases associated with global climatic change. Because ants are geographically widespread, ecologically diverse, and thermophilic, they are an ideal system for exploring the extent to which physiological tolerance can predict responses to environmental change. Here, we expand on simple models that use thermal tolerance to predict the responses of ants to climatic warming. We investigated the degree to which changes in the abundance of ants under warming reflect reductions in the thermal niche space for their foraging. In an eastern deciduous forest system in the United States with approximately 40 ant species, we found that for some species, the loss of thermal niche space for foraging was related to decreases in abundance with increasing experimental climatic warming. However, many ant species exhibited no loss of thermal niche space. For one well-studied species, Temnothorax curvispinosus, we examined both survival of workers and growth of colonies (a correlate of reproductive output) as functions of temperature in the laboratory, and found that the range of thermal tolerances for colony growth was much narrower than for survival of workers. We evaluated these functions in the context of experimental climatic warming and found that the difference in the responses of these two attributes to temperature generates differences in the means and especially the variances of expected fitness under warming. The expected mean growth of colonies was optimized at intermediate levels of warming (2-4°C above ambient); yet, the expected variance monotonically increased with warming. In contrast, the expected mean and variance of the survival of workers decreased when warming exceeded 4°C above ambient. Together, these results for T. curvispinosus emphasize the importance of measuring reproduction (colony growth) in the context of climatic change: indeed, our examination of the loss of thermal niche space with the larger species pool could be missing much of the warming impact due to these analyses being based on survival rather than reproduction. We suggest that while physiological tolerance of temperature can be a useful predictive tool for modeling responses to climatic change, future efforts should be devoted to understanding the causes and consequences of variability in models of tolerance calibrated with different metrics of performance and fitness.}, number={6}, journal={INTEGRATIVE AND COMPARATIVE BIOLOGY}, author={Diamond, Sarah E. and Penick, Clint A. and Pelini, Shannon L. and Ellison, Aaron M. and Gotelli, Nicholas J. and Sanders, Nathan J. and Dunn, Robert R.}, year={2013}, month={Dec}, pages={965–974} }