TY - NEWS TI - Attraction and defense: the role of floral traits for scarlet gilia T2 - Rocky Mountain Biological Laboratory Newsletter PY - 2003/// ER - TY - JOUR TI - Linking pollinator visitation rate and pollen receipt AU - Cayenne Engel, E. AU - Irwin, Rebecca E. T2 - American Journal of Botany AB - The majority of flowering plants require animals for pollination, a critical ecosystem service in natural and agricultural systems. However, quantifying useful estimates of pollinator visitation rates can be nearly impossible when pollinator visitation is infrequent. We examined the utility of an indirect measure of pollinator visitation, namely pollen receipt by flowers, using the hummingbird-pollinated plant, Ipomopsis aggregata (Polemoniaceae). Our a priori hypothesis was that increased pollinator visitation should result in increased pollen receipt by stigmas. However, the relationship between pollinator visitation rate and pollen receipt may be misleading if pollen receipt is a function of both the number of pollinator visits and variation in pollinator efficiency at depositing pollen, especially in the context of variable floral morphology. Therefore, we measured floral and plant characters known to be important to pollinator visitation and/or pollen receipt in I. aggregata (corolla length and width and plant height) and used path analysis to dissect and compare the effect of pollinator visitation rate vs. pollinator efficiency on pollen receipt. Of the characters we measured, pollinator visitation rate (number of times plants were visited multiplied by the mean percentage of flowers probed per visit) had the strongest direct positive effect on pollen receipt, explaining 36% of the variation in pollen receipt. Plant height had a direct positive effect on pollinator visitation rate and an indirect positive effect on pollen receipt. Despite the supposition that floral characters would directly affect pollen receipt as a result of changes in pollinator efficiency, corolla length and width only weakly affected pollen receipt. These results suggest a direct positive link between pollinator visitation rate and pollen receipt across naturally varying floral morphology in I. aggregata. Understanding the relationship between pollinator visitation rate and pollen receipt may be of critical importance in systems where pollinator visitation is difficult to quantify. DA - 2003/11// PY - 2003/11// DO - 10.3732/ajb.90.11.1612 VL - 90 IS - 11 SP - 1612-1618 J2 - American J of Botany LA - en OP - SN - 0002-9122 1537-2197 UR - http://dx.doi.org/10.3732/ajb.90.11.1612 DB - Crossref ER - TY - JOUR TI - IMPACT OF NECTAR ROBBING ON ESTIMATES OF POLLEN FLOW: CONCEPTUAL PREDICTIONS AND EMPIRICAL OUTCOMES AU - Irwin, Rebecca E. T2 - Ecology AB - Pollen movement within and among plants affects levels of inbreeding and plant fitness as well as the spatial scale of genetic differentiation. Pollen movement has primarily been studied as a function of the direct relationships between plants and pollinators; however, nonpollinating floral visitors, such as some nectar robbers, may have indirect effects on pollen dispersal by altering plant–pollinator interactions. Theory predicts that nectar robbing should have indirect positive effects on plants by increasing pollen dispersal distance and reducing self-pollen transfer (geitonogamy) and inbreeding through changes in pollinator behavior associated with reduced nectar rewards. Here I experimentally tested the indirect effects of the nectar-robbing bumble bee, Bombus occidentalis, on the distance of pollen movement among plants and levels of pollen movement within plants (estimated using powdered fluorescent dyes as pollen analogues) using the self-incompatible, hummingbird-pollinated host, Ipomopsis aggregata. Empirical results did not fully support the theoretical predictions. Heavy levels of nectar (>80% of available flowers robbed) had no effect on the mean and mean-squared distance of dye dispersal within populations. However, hummingbird pollinators were 50% more likely to depart from a population after visiting a plant with low robbing relative to a plant with high robbing, suggesting that pollen dispersal among populations might be reduced in plants with high robbing relative to plants with low robbing. Heavy nectar robbing reduced levels of self-dye transfer by one-half. However, when I manipulated robbing levels and access to self-pollen, the costs associated with increased robbing and reduced pollinator visitation (e.g., reduced seed production) outweighed any advantages associated with reduced geitonogamy. Taken together, these results suggest that the negative indirect effects of robbing on plant reproduction through decreased pollinator visitation and changes in pollinator departure from plants far exceed any positive effects associated with decreased geitonogamy. Given the widespread nature of plant attack by nectar robbers, these indirect effects are likely common phenomena structuring natural plant populations. Corresponding Editor: T.-L. Ashman DA - 2003/2// PY - 2003/2// DO - 10.1890/0012-9658(2003)084[0485:ionroe]2.0.co;2 VL - 84 IS - 2 SP - 485-495 J2 - Ecology LA - en OP - SN - 0012-9658 UR - http://dx.doi.org/10.1890/0012-9658(2003)084[0485:ionroe]2.0.co;2 DB - Crossref ER - TY - JOUR TI - THE ROLE OF HERBIVORES IN THE MAINTENANCE OF A FLOWER COLOR POLYMORPHISM IN WILD RADISH AU - Irwin, Rebecca E. AU - Strauss, Sharon Y. AU - Storz, Shonna AU - Emerson, Aimee AU - Guibert, Genevieve T2 - Ecology AB - EcologyVolume 84, Issue 7 p. 1733-1743 Regular Article THE ROLE OF HERBIVORES IN THE MAINTENANCE OF A FLOWER COLOR POLYMORPHISM IN WILD RADISH Rebecca E. Irwin, Rebecca E. Irwin Center for Population Biology, University of California, Davis, California 95616 USA Present address: Institute of Ecology, Ecology Building, University of Georgia, Athens, Georgia 30602 USA. E-mail: rirwin@arches.uga.eduSearch for more papers by this authorSharon Y. Strauss, Sharon Y. Strauss Center for Population Biology, University of California, Davis, California 95616 USASearch for more papers by this authorShonna Storz, Shonna Storz Center for Population Biology, University of California, Davis, California 95616 USASearch for more papers by this authorAimee Emerson, Aimee Emerson Center for Population Biology, University of California, Davis, California 95616 USASearch for more papers by this authorGenevieve Guibert, Genevieve Guibert Center for Population Biology, University of California, Davis, California 95616 USASearch for more papers by this author Rebecca E. Irwin, Rebecca E. Irwin Center for Population Biology, University of California, Davis, California 95616 USA Present address: Institute of Ecology, Ecology Building, University of Georgia, Athens, Georgia 30602 USA. E-mail: rirwin@arches.uga.eduSearch for more papers by this authorSharon Y. Strauss, Sharon Y. Strauss Center for Population Biology, University of California, Davis, California 95616 USASearch for more papers by this authorShonna Storz, Shonna Storz Center for Population Biology, University of California, Davis, California 95616 USASearch for more papers by this authorAimee Emerson, Aimee Emerson Center for Population Biology, University of California, Davis, California 95616 USASearch for more papers by this authorGenevieve Guibert, Genevieve Guibert Center for Population Biology, University of California, Davis, California 95616 USASearch for more papers by this author First published: 01 July 2003 https://doi.org/10.1890/0012-9658(2003)084[1733:TROHIT]2.0.CO;2Citations: 146 Corresponding Editor: L. F. Delph Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Abstract Plant species exhibiting polymorphisms with respect to flower color are widespread. Our understanding of the selection pressures that may maintain these color polymorphisms has primarily been confined to one set of organisms—pollinators. Yet, selection on flower color may also be driven by other agents, such as herbivores, especially in cases where pollinators and herbivores are using the same or correlated traits to select plants. A wealth of studies have documented pollinator preference for anthocyanin-recessive color morphs (A−; yellow and white flowers) of wild radish, Raphanus sativus, over anthocyanin-dominant morphs (A+; pink and bronze flowers); yet, differences in pollination alone do not explain the maintenance of the flower color polymorphism. Here, we ask whether variation in flower color in R. sativus influences the preference and performance of herbivores for A− flower color morphs vs. A+ flower color morphs in four types of herbivores (generalist and specialist Lepidoptera, slugs, aphids, and thrips). We found that all herbivores except for aphids and thrips preferred flowering A− color morphs compared to A+ morphs of R. sativus. Furthermore, all herbivores except larvae of specialist and generalist Lepidoptera performed better on A− color morphs. Differences in plant secondary chemistry may play a role in differential herbivore preference and performance on the anthocyanin flower color morphs. Chemical analyses of leaf secondary compounds (indole glucosinolates) revealed that A+ color morphs produced higher concentrations of indole glucosinolates than A− morphs in the presence of herbivore damage. Therefore, herbivores may exhibit lower preference for A+ color morphs, and these morphs may support lower herbivore performance because they are heavily defended once damaged. This is the first study, to our knowledge, to document differential preference and performance of herbivores for different flower color morphs. Previous studies have shown that increased herbivore damage can have profound negative direct and indirect effects on the reproduction of R. sativus. The data presented here suggest that differential preference and performance of herbivores for R. sativus color morphs may counter selection on flower color exerted by pollinators. Citing Literature Volume84, Issue7July 2003Pages 1733-1743 RelatedInformation DA - 2003/7// PY - 2003/7// DO - 10.1890/0012-9658(2003)084[1733:trohit]2.0.co;2 VL - 84 IS - 7 SP - 1733-1743 J2 - Ecology LA - en OP - SN - 0012-9658 UR - http://dx.doi.org/10.1890/0012-9658(2003)084[1733:trohit]2.0.co;2 DB - Crossref ER - TY - CHAP TI - Measuring and interpreting changes in connectivity for mammals in coniferous forests AU - Mills, L. S. AU - Schwartz, M. K. AU - Tallmon, D. A. AU - Lair, K. P. T2 - Mammal community dynamics : management and conservation in the coniferous forests of western North America A2 - Cynthia J. Zabel, Robert G. Anthony AB - Western coniferous forests have a history of natural disturbance due to fire, disease, and other factors (Agee 1993), but during the past century late-seral forests have been increasingly fragmented due to logging and development. For example, in the Pacific Northwest, less than half of pre-settlement, old-growth Douglas-fir (Pseudotsuga menziesii) forest remains, often in relatively small remnants of 100 ha or less in a matrix of clear-cuts and regenerating forest (Booth 1991, Garmon et al. 1999, Jules et al. 1999). Road building has also impacted wildlife habitat, with an average of 3.4 miles of road per square mile on United States Forest Service roaded-lands and approximately twice that on private lands (Federal Budget Consulting Group and Price-Waterhouse LLP 1997, Coghlan and Sowa 1998, Federal Register 2001, USDA 2001). PY - 2003/// DO - 10.1017/cbo9780511615757.018 PB - New York, NY, USA : Cambridge University Press SN - 9780521810432 ER - TY - JOUR TI - Potential causes of population declines in forest fragments in an Amazonian frog AU - Funk, WC AU - Mills, LS T2 - BIOLOGICAL CONSERVATION AB - Forest fragmentation results in population declines and extinctions for many forest vertebrates, but little is known about the mechanisms causing declines in fragments. We investigated potential causes of declines in forest fragments for an Amazonian forest frog (Colostethus stepheni) at an experimental fragmentation study site in central Amazonian Brazil using field estimates of abundance and vital rates coupled with population simulations. Although adult male survival was not reduced by fragmentation, mean clutch size was reduced by 17%. Population simulations demonstrate that a reduction in clutch size of this magnitude is sufficient to cause the observed magnitude of population declines in fragments. Female snout-vent length was also reduced in fragments and may be related to the observed reduction in clutch size. DA - 2003/6// PY - 2003/6// DO - 10.1016/s0006-3207(02)00274-4 VL - 111 IS - 2 SP - 205-214 SN - 0006-3207 KW - forest fragmentation KW - Colostethus stepheni KW - Amazonian Brazil KW - population decline KW - survival probability KW - clutch size KW - population simulations ER - TY - JOUR TI - Of mice and men and trillium: Cascading effects of forest fragmentation AU - Tallmon, DA AU - Jules, ES AU - Radke, NJ AU - Mills, LS T2 - ECOLOGICAL APPLICATIONS AB - Cascading ecological effects of anthropogenic habitat fragmentation have been studied primarily in extreme cases (e.g., the isolation of habitat fragments in a novel habitat matrix such as suburban developments, reservoirs, or agricultural fields), with less attention to more subtle and widespread cases, such as habitat fragmentation due to timber harvest. Few studies have used rigorous demographic data to demonstrate the direct and indirect effects of habitat fragmentation. We trapped deer mice ( Peromyscus maniculatus ) at five sites over two years in southwest Oregon, USA, and used multi‐state capture–recapture models to estimate deer mouse survival and movement in clearcuts, forest‐fragment edges, forest‐fragment interiors, and contiguous forests. We also estimated deer mouse densities in fragmented and unfragmented forests and combined deer mouse demographic studies with trillium ( Trillium ovatum ) seed predation trials to link deer mouse changes to reduced trillium recruitment previously observed at the same study sites. Mouse survival was highest in clearcuts, intermediate in forest fragments, and lowest in unfragmented (control) forests. Mouse movement among clearcuts, forest edges, and forest interiors was common over short time intervals. Collectively, demographic rates led to mouse densities that were 3–4 times higher at forest‐fragment sites than at unfragmented sites. Trillium seeds were ∼3 times more likely to be depredated in areas of elevated relative mouse abundance than in areas of lower relative abundance. Forest fragmentation has favored mouse populations, resulting in increased seed predation that may decrease recruitment rates and increase local extinction risks for trillium. DA - 2003/10// PY - 2003/10// DO - 10.1890/02-5111 VL - 13 IS - 5 SP - 1193-1203 SN - 1051-0761 KW - demography KW - edge effects KW - habitat fragmentation KW - direct and indirect effects KW - landscape ecology KW - Pacific Northwest, USA KW - Peromyscus maniculatus KW - plant-animal interactions KW - population dynamics KW - trillium recruitment, southwest Oregon, USA ER - TY - JOUR TI - Landscape location affects genetic variation of Canada lynx (Lynx canadensis) AU - Schwartz, MK AU - Mills, LS AU - Ortega, Y AU - Ruggiero, LF AU - Allendorf, FW T2 - MOLECULAR ECOLOGY AB - The effect of a population's location on the landscape on genetic variation has been of interest to population genetics for more than half a century. However, most studies do not consider broadscale biogeography when interpreting genetic data. In this study, we propose an operational definition of a peripheral population, and then explore whether peripheral populations of Canada lynx (Lynx canadensis) have less genetic variation than core populations at nine microsatellite loci. We show that peripheral populations of lynx have fewer mean numbers of alleles per population and lower expected heterozygosity. This is surprising, given the lynx's capacity to move long distances, but can be explained by the fact that peripheral populations often have smaller population sizes, limited opportunities for genetic exchange and may be disproportionately affected by ebbs and flows of species' geographical range. DA - 2003/7// PY - 2003/7// DO - 10.1046/j.1365-294x.2003.01878.x VL - 12 IS - 7 SP - 1807-1816 SN - 1365-294X KW - biogeography KW - landscape ecology KW - landscape genetics KW - Lynx canadensis KW - microsatellite KW - population genetics ER - TY - JOUR TI - Identification of mustelids using mitochondrial DNA and non-invasive sampling AU - Riddle, AE AU - Pilgrim, KL AU - Mills, LS AU - McKelvey, KS AU - Ruggiero, LF T2 - CONSERVATION GENETICS DA - 2003/// PY - 2003/// DO - 10.1023/a:1023338622905 VL - 4 IS - 2 SP - 241-243 SN - 1566-0621 KW - fisher KW - Gulo gulo KW - hair snares KW - Martes KW - mitochondrial DNA KW - mtDNA KW - mustelids KW - non-invasive sampling KW - wolverine ER - TY - JOUR TI - Estimating pregnancy rates and litter size in snowshoe hares using ultrasound AU - Griffin, P. C. AU - Bienen, L. AU - Gillin, C. M. AU - Mills, L. S. T2 - Wildlife Society Bulletin DA - 2003/// PY - 2003/// VL - 31 IS - 4 SP - 1066-1072 ER - TY - JOUR TI - Corridor use by diverse taxa AU - Haddad, NM AU - Bowne, DR AU - Cunningham, A AU - Danielson, BJ AU - Levey, DJ AU - Sargent, S AU - Spira, T T2 - ECOLOGY AB - One of the most popular approaches for maintaining populations and conserving 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 mammals, 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. Corresponding Editor: F. W. Davis DA - 2003/3// PY - 2003/3// DO - 10.1890/0012-9658(2003)084[0609:cubdt]2.0.co;2 VL - 84 IS - 3 SP - 609-615 SN - 0012-9658 KW - biodiversity KW - bird KW - butterfly KW - conservation KW - corridors KW - dispersal KW - fragmentation KW - frugivory KW - landscape experiment KW - movement KW - pollination KW - small mammals ER - TY - JOUR TI - Spatial heterogeneity, not visitation bias, dominates variation in herbivory AU - Bradley, KL AU - Damschen, EI AU - Young, LM AU - Kuefler, D AU - Went, S AU - Wray, G AU - Haddad, NM AU - Knops, JMH AU - Louda, SM T2 - ECOLOGY AB - 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. DA - 2003/8// PY - 2003/8// DO - 10.1890/02-3082 VL - 84 IS - 8 SP - 2214-2221 SN - 0012-9658 KW - herbivory KW - herbivory uncertainty principle KW - observer effect KW - plant performance KW - spatial heterogeneity KW - visitation effect ER - TY - JOUR TI - Predicting which species will benefit from corridors in fragmented landscapes from population growth models AU - Hudgens, BR AU - Haddad, NM T2 - AMERICAN NATURALIST AB - 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? DA - 2003/5// PY - 2003/5// DO - 10.1086/374343 VL - 161 IS - 5 SP - 808-820 SN - 1537-5323 KW - conservation KW - corridor KW - model KW - metapopulation ER -