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Novak M. High variation in handling times confers 35-year stability to predator feeding rates despite community change. Ecology 2023; 104:e3954. [PMID: 36495236 DOI: 10.1002/ecy.3954] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 09/15/2022] [Accepted: 11/07/2022] [Indexed: 12/14/2022]
Abstract
Historical resurveys of ecological communities are important for placing the structure of modern ecosystems in context. Rarely, however, are snapshot surveys alone sufficient for providing direct insight into the rates of the ecological processes underlying community functioning, either now or in the past. In this study, I used a statistically reasoned observational approach to estimate the feeding rates of a New Zealand intertidal predator, Haustrum haustorium, using diet surveys performed at several sites by Robert Paine in 1968-1969 and by me in 2004. Comparisons between time periods reveal a remarkable consistency in the predator's prey-specific feeding rates, which contrasts with the changes I observed in prey abundances, the predator's body-size distribution, and the prey's proportional contributions to the predator's apparent diet. Although these and additional changes in the predator's per-capita attack rates seem to show adaptive changes in its prey preferences, they do not. Rather, feeding-rate stability is an inherently statistical consequence of the predator's high among-prey variation in handling times which determine the length of time that feeding events will remain detectable to observers performing diet surveys. Though understudied, similarly high among-prey variation in handling (or digestion) times is evident in many predator species throughout the animal kingdom. The resultant disconnect between a predator's apparent diet and its actual feeding rates suggests that much of the temporal, biogeographic, and seemingly context-dependent variation that is often perceived in community structure, predator diets, and food-web topology may be of less functional consequence than assumed. Qualitative changes in ecological pattern need not represent qualitative changes in ecological process.
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Affiliation(s)
- Mark Novak
- Department of Integrative Biology, Oregon State University, Corvallis, Oregon, USA
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Taylor D, deJesus EJ, Novak M, Terry RC. The effects of formalin fixation and fluid storage on stable isotopes in rodent hair. J Mammal 2021. [DOI: 10.1093/jmammal/gyab102] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
Stable isotopes are increasingly being used to unlock the wealth of information contained in specimens preserved in museum collections. However, preservation methods that employ formalin may confound ecological interpretations. To quantify the effects of formalin fixation and subsequent fluid storage in ethanol on the isotopic signatures of small mammal hair, we analyzed δ 13C and δ 15N values from specimens of seven rodent species that were sampled repeatedly both before and after varying lengths of formalin fixation (1–11 days) and ethanol storage (1–6 years). We supplemented these data with a 2-week fixation experiment using deer mice (Peromyscus maniculatus) in which no ethanol storage was employed. As expected, preservation in formalin and ethanol had no discernable effect on δ 15N values. In contrast, specimen δ 13C values decreased in a saturating fashion during formalin fixation and over subsequent years of fluid storage in ethanol. On the basis of models that we fit to these time series, we estimate the long-term effect of fixation and storage on δ 13C values to be −0.92‰ after 4 years. This biologically relevant shift in δ 13C values should be accounted for when inferring the diets of species from fluid-stored museum collections and when comparing across specimens with different preservation histories.
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Affiliation(s)
- David Taylor
- Department of Integrative Biology, Oregon State University, 3029 Cordley Hall, Corvallis, OR 97331, USA
| | - Elia J deJesus
- Department of Integrative Biology, Oregon State University, 3029 Cordley Hall, Corvallis, OR 97331, USA
| | - Mark Novak
- Department of Integrative Biology, Oregon State University, 3029 Cordley Hall, Corvallis, OR 97331, USA
| | - Rebecca C Terry
- Department of Integrative Biology, Oregon State University, 3029 Cordley Hall, Corvallis, OR 97331, USA
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Pardi MI, Terry RC, Rickart EA, Rowe RJ. Testing climate tracking of montane rodent distributions over the past century within the Great Basin ecoregion. Glob Ecol Conserv 2020. [DOI: 10.1016/j.gecco.2020.e01238] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Teitelbaum CS, Altizer S, Hall RJ. Movement rules determine nomadic species' responses to resource supplementation and degradation. J Anim Ecol 2020; 89:2644-2656. [PMID: 32783225 DOI: 10.1111/1365-2656.13318] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 07/27/2020] [Indexed: 11/29/2022]
Abstract
In environments that vary unpredictably, many animals are nomadic, moving in an irregular pattern that differs from year to year. Exploring the mechanisms of nomadic movement is needed to understand how animals survive in highly variable environments, and to predict behavioural and population responses to environmental change. We developed a network model to identify plausible mechanisms of nomadic animal movement by comparing the performance of multiple movement rules along a continuum from nomadism to residency. Using simulations and analytical results, we explored how different types of habitat modifications (that augment or decrease resource availability) might affect the abundance and movement rates of animals following each of these rules. Movement rules for which departure from patches depended on resource availability and/or competition performed almost equally well and better than residency or uninformed movement under most conditions, even though animals using each rule moved at substantially different rates. Habitat modifications that stabilized resources, either by resource supplementation or degradation, eroded the benefits of informed nomadic movements, particularly for movements based on resource availability alone. These results suggest that simple movement rules can explain nomadic animal movements and determine species' responses to environmental change. In particular, landscape stabilization and supplementation might be useful strategies for promoting populations of resident animals, but would be less beneficial for managing highly mobile species, many of which are threatened by habitat disruption and changes in climate.
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Affiliation(s)
| | - Sonia Altizer
- Odum School of Ecology, University of Georgia, Athens, GA, USA
| | - Richard J Hall
- Odum School of Ecology, University of Georgia, Athens, GA, USA.,Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, USA
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Shipway S, Rowe KMC, Rowe KC. Persistence of the broad-toothed rat (Mastacomys fuscus) across Victoria is correlated with climate and elevation. WILDLIFE RESEARCH 2020. [DOI: 10.1071/wr19077] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Abstract
ContextThe broad-toothed rat (Mastacomys fuscus; BTR) is distributed throughout south-eastern Australia, but its populations are restricted and dispersed. BTRs prefer cooler, wetter habitats and, as such, future climate change is projected to lead to further range reductions. However, recent changes in its distribution have not been well documented, and there is limited knowledge about the current occupancy and population size of the species in Victoria.
AimsTo evaluate recent historical changes in the distribution of BTRs in Victoria, and to test whether changes in distribution are correlated with climate and elevation.
MethodsWe obtained all documented records of BTRs in the state before 1990 and used field notes and verbal descriptions to geo-reference their historical localities. We then used a repeated sampling design to resurvey all historically occupied sites with a geographic coordinate uncertainty of 4km or less. We tested for the effects of climate and elevation on the persistence of BTRs.
Key resultsWe detected BTRs at 32 of 68 historical sites surveyed. Consistent with climate model predictions, site persistence was more likely to occur at sites of higher elevation and precipitation and less likely to occur at sites with a higher temperature. Minimum temperature of the coldest month was the single best predictor of persistence.
ConclusionsThese results demonstrated a substantial decline in the persistence of BTRs at historical sites across Victoria and provided a benchmark for future monitoring and management efforts.
ImplicationsThe decline of BTRs from historically occupied sites across Victoria is consistent with their listing as endangered in the state, and climate correlations suggest further declines, with projected climate change compounding other threats to the species such as introduced predators, feral herbivores, fire and land use. However, the status of BTRs in Victoria and understanding of the threats to their persistence are based on sparse data, highlighting the critical need for more effective monitoring of the species.
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Refsnider JM, Carter SE, Kramer GR, Siefker AD, Streby HM. Is dietary or microhabitat specialization associated with environmental heterogeneity in horned lizards ( Phrynosoma)? Ecol Evol 2019; 9:5542-5550. [PMID: 31160981 PMCID: PMC6540669 DOI: 10.1002/ece3.5109] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Revised: 03/04/2019] [Accepted: 03/05/2019] [Indexed: 01/03/2023] Open
Abstract
Niche breadth is predicted to correlate with environmental heterogeneity, such that generalists will evolve in heterogeneous environments and specialists will evolve in environments that vary less over space and time. We tested the hypothesis that lizards in a heterogeneous environment were generalists compared to lizards in a homogeneous environment. We compared niche breadths of greater short-horned lizards by quantifying resource selection in terms of two different niche axes, diet (prey items and trophic level), and microhabitat (ground cover and shade cover) between two populations occurring at different elevations. We assessed the heterogeneity of dietary and microhabitat resources within each population's environment by quantifying the availability of prey items, ground cover, and shade cover in each environment. Overall, our results demonstrate that despite differences in resource heterogeneity between elevations, resource selection did not consistently differ between populations. Moreover, environmental heterogeneity was not associated with generalization of resource use. The low-elevation site had a broader range of available prey items, yet lizards at the high-elevation site demonstrated more generalization in diet. In contrast, the high-elevation site had a broader range of available microhabitats, but the lizard populations at both sites were similarly generalized for shade cover selection and were similarly specialized for ground cover selection. Our results demonstrate that environmental heterogeneity of a particular resource does not necessarily predict the degree to which organisms specialize on that resource.
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Affiliation(s)
| | - Sarah E. Carter
- Department of Environmental SciencesUniversity of ToledoToledoOhio
| | - Gunnar R. Kramer
- Department of Environmental SciencesUniversity of ToledoToledoOhio
| | - Adam D. Siefker
- Department of Environmental SciencesUniversity of ToledoToledoOhio
| | - Henry M. Streby
- Department of Environmental SciencesUniversity of ToledoToledoOhio
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7
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Kohli BA, Rowe RJ. Beyond guilds: the promise of continuous traits for mammalian functional diversity. J Mammal 2019. [DOI: 10.1093/jmammal/gyz054] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Brooks A Kohli
- Natural Resources and the Environment, University of New Hampshire, Durham, NH, USA
| | - Rebecca J Rowe
- Natural Resources and the Environment, University of New Hampshire, Durham, NH, USA
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Summer behavior and diurnal activity of mountain vizcachas (Lagidium viscacia) in two colonies of Northwestern Patagonia. MAMMAL RES 2018. [DOI: 10.1007/s13364-018-0410-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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9
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Massey AL, Rickart EA, Rowe RJ. Habitat Use of the Piñon Mouse (Peromyscus truei) in the Toiyabe Range, Central Nevada. WEST N AM NATURALIST 2017. [DOI: 10.3398/064.077.0407] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Aimee L. Massey
- Department of Fisheries and Wildlife, Oregon State University, 104 Nash Hall, Corvallis, OR 97331
| | - Eric A. Rickart
- Natural History Museum of Utah, University of Utah, 301 Wakara Way, Salt Lake City, UT 84108
| | - Rebecca J. Rowe
- Department of Natural Resources and the Environment, University of New Hampshire, 56 College Road, Durham, NH 03824
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Jaworski KE, Lattanzio MS. Physiological Consequences of Food Limitation for a Color Polymorphic Lizard: Are Coping Responses Morph-Specific? COPEIA 2017. [DOI: 10.1643/cp-17-597] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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11
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Terry RC. Isotopic niche variation from the Holocene to today reveals minimal partitioning and individualistic dynamics among four sympatric desert mice. J Anim Ecol 2017; 87:173-186. [PMID: 29048750 DOI: 10.1111/1365-2656.12771] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 10/08/2017] [Indexed: 12/01/2022]
Abstract
Species interact with each other and their environment over a range of temporal scales, yet our understanding of resource partitioning and the mechanisms of species coexistence is largely restricted to modern time-scales of years to decades. Furthermore, the relative magnitudes of inter- vs. intraspecific variation in resource use are rarely considered, despite the potential for the latter to influence a species' ability to cope with changing environmental conditions. Modern desert rodent communities are thought to be strongly structured by competitive interactions, with niche partitioning of food resources hypothesized to explain the coexistence of multiple sympatric granivores. Yet the stability of niche dynamics over extended temporal scales within desert rodent communities is unknown. I examined the isotopic niche dynamics of four common sympatric desert mice (three granivores: Chaetodipus formosus, Perognathus longimembris and Reithrodontomys megalotis, and one omnivore: Peromyscus maniculatus) in the Smoke Creek Desert of northwestern Nevada using 13 C and 15 N isotopes obtained from "Modern" (2008-2013 CE), "Historical" (1989-2005 CE) and Holocene fossil specimens spanning the last c. 7,500 years. I found significant variation in niche position, niche breadth and interspecific niche overlap of these species through time. The niche breadth dynamics of the cricetids (P. maniculatus and R. megalotis) were positively correlated with one another, while the niche breadth dynamics of the heteromyid C. formosus were negatively correlated with those of all other species. Body size, dietary functional group, palaeoenvironmental trends and time-averaging provided little explanatory power. Importantly, Modern and Historical patterns of resource use and partitioning differed from Holocene baselines in terms of decreased niche overlap and in the absolute and relative position of each species' niche in at least one isotopic axis. These observations suggest that each species' resource use changed individualistically over the Holocene, hence niche dynamics are poorly explained by the hypothesis of temporally stable species interactions at millennial time-scales. Furthermore, changes to the resource base over the last century (likely due to the spread of invasive cheatgrass) may be increasing resource partitioning in the Modern, pushing species past their baseline ranges of resource use variation.
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Affiliation(s)
- Rebecca C Terry
- Department of Integrative Biology, Oregon State University, Corvallis, OR, USA
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Terry RC, Guerre ME, Taylor DS. How specialized is a diet specialist? Niche flexibility and local persistence through time of the Chisel‐toothed kangaroo rat. Funct Ecol 2017. [DOI: 10.1111/1365-2435.12892] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Rebecca C. Terry
- Department of Integrative Biology Oregon State University 3029 Cordley Hall Corvallis OR97331 USA
| | - Megan E. Guerre
- Department of Integrative Biology Oregon State University 3029 Cordley Hall Corvallis OR97331 USA
| | - David S. Taylor
- Department of Integrative Biology Oregon State University 3029 Cordley Hall Corvallis OR97331 USA
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Lowrey C, Longshore K, Riddle B, Mantooth S. Ecology, distribution, and predictive occurrence modeling of Palmer’s chipmunk (Tamias palmeri): a high-elevation small mammal endemic to the Spring Mountains in southern Nevada, USA. J Mammal 2016. [DOI: 10.1093/jmammal/gyw026] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Abstract
Although montane sky islands surrounded by desert scrub and shrub steppe comprise a large part of the biological diversity of the Basin and Range Province of southwestern North America, comprehensive ecological and population demographic studies for high-elevation small mammals within these areas are rare. Here, we examine the ecology and population parameters of the Palmer’s chipmunk (Tamias palmeri) in the Spring Mountains of southern Nevada, and present a predictive GIS-based distribution and probability of occurrence model at both home range and geographic spatial scales. Logistic regression analyses and Akaike Information Criterion model selection found variables of forest type, slope, and distance to water sources as predictive of chipmunk occurrence at the geographic scale. At the home range scale, increasing population density, decreasing overstory canopy cover, and decreasing understory canopy cover contributed to increased survival rates.
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McCain C, Szewczyk T, Bracy Knight K. Population variability complicates the accurate detection of climate change responses. GLOBAL CHANGE BIOLOGY 2016; 22:2081-2093. [PMID: 26725404 DOI: 10.1111/gcb.13211] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Revised: 10/08/2015] [Accepted: 12/07/2015] [Indexed: 06/05/2023]
Abstract
The rush to assess species' responses to anthropogenic climate change (CC) has underestimated the importance of interannual population variability (PV). Researchers assume sampling rigor alone will lead to an accurate detection of response regardless of the underlying population fluctuations of the species under consideration. Using population simulations across a realistic, empirically based gradient in PV, we show that moderate to high PV can lead to opposite and biased conclusions about CC responses. Between pre- and post-CC sampling bouts of modeled populations as in resurvey studies, there is: (i) A 50% probability of erroneously detecting the opposite trend in population abundance change and nearly zero probability of detecting no change. (ii) Across multiple years of sampling, it is nearly impossible to accurately detect any directional shift in population sizes with even moderate PV. (iii) There is up to 50% probability of detecting a population extirpation when the species is present, but in very low natural abundances. (iv) Under scenarios of moderate to high PV across a species' range or at the range edges, there is a bias toward erroneous detection of range shifts or contractions. Essentially, the frequency and magnitude of population peaks and troughs greatly impact the accuracy of our CC response measurements. Species with moderate to high PV (many small vertebrates, invertebrates, and annual plants) may be inaccurate 'canaries in the coal mine' for CC without pertinent demographic analyses and additional repeat sampling. Variation in PV may explain some idiosyncrasies in CC responses detected so far and urgently needs more careful consideration in design and analysis of CC responses.
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Affiliation(s)
- Christy McCain
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO, 80309, USA
- CU Museum of Natural History, University of Colorado, 265 UCB, Boulder, CO, 80309, USA
| | - Tim Szewczyk
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO, 80309, USA
| | - Kevin Bracy Knight
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO, 80309, USA
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Finarelli JA, Liow LH. Diversification histories for North American and Eurasian carnivorans. Biol J Linn Soc Lond 2016. [DOI: 10.1111/bij.12777] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- John A. Finarelli
- School of Biology and Environment Science; University of College Dublin; Belfield Dublin 4 Ireland
- UCD Earth Institute; University of College Dublin; Belfield Dublin 4 Ireland
| | - Lee Hsiang Liow
- Department of Biosciences; Centre for Ecological and Evolutionary Synthesis (CEES); University of Oslo; 0316 Oslo Norway
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Rowe KC, Rowe KMC, Tingley MW, Koo MS, Patton JL, Conroy CJ, Perrine JD, Beissinger SR, Moritz C. Spatially heterogeneous impact of climate change on small mammals of montane California. Proc Biol Sci 2015; 282:20141857. [PMID: 25621330 DOI: 10.1098/rspb.2014.1857] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Resurveys of historical collecting localities have revealed range shifts, primarily leading edge expansions, which have been attributed to global warming. However, there have been few spatially replicated community-scale resurveys testing whether species' responses are spatially consistent. Here we repeated early twentieth century surveys of small mammals along elevational gradients in northern, central and southern regions of montane California. Of the 34 species we analysed, 25 shifted their ranges upslope or downslope in at least one region. However, two-thirds of ranges in the three regions remained stable at one or both elevational limits and none of the 22 species found in all three regions shifted both their upper and lower limits in the same direction in all regions. When shifts occurred, high-elevation species typically contracted their lower limits upslope, whereas low-elevation species had heterogeneous responses. For high-elevation species, site-specific change in temperature better predicted the direction of shifts than change in precipitation, whereas the direction of shifts by low-elevation species was unpredictable by temperature or precipitation. While our results support previous findings of primarily upslope shifts in montane species, they also highlight the degree to which the responses of individual species vary across geographically replicated landscapes.
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Energy flow and functional compensation in Great Basin small mammals under natural and anthropogenic environmental change. Proc Natl Acad Sci U S A 2015; 112:9656-61. [PMID: 26170294 DOI: 10.1073/pnas.1424315112] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Research on the ecological impacts of environmental change has primarily focused at the species level, leaving the responses of ecosystem-level properties like energy flow poorly understood. This is especially so over millennial timescales inaccessible to direct observation. Here we examine how energy flow within a Great Basin small mammal community responded to climate-driven environmental change during the past 12,800 y, and use this baseline to evaluate responses observed during the past century. Our analyses reveal marked stability in energy flow during rapid climatic warming at the terminal Pleistocene despite dramatic turnover in the distribution of mammalian body sizes and habitat-associated functional groups. Functional group turnover was strongly correlated with climate-driven changes in regional vegetation, with climate and vegetation change preceding energetic shifts in the small mammal community. In contrast, the past century has witnessed a substantial reduction in energy flow caused by an increase in energetic dominance of small-bodied species with an affinity for closed grass habitats. This suggests that modern changes in land cover caused by anthropogenic activities--particularly the spread of nonnative annual grasslands--has led to a breakdown in the compensatory dynamics of energy flow. Human activities are thus modifying the small mammal community in ways that differ from climate-driven expectations, resulting in an energetically novel ecosystem. Our study illustrates the need to integrate across ecological and temporal scales to provide robust insights for long-term conservation and management.
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Stephens RB, Karau KH, Yahnke CJ, Wendt SR, Rowe RJ. Dead mice can grow – variation of standard external mammal measurements from live and three postmortem body states. J Mammal 2015. [DOI: 10.1093/jmammal/gyu022] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Perry JJ, Vanderduys EP, Kutt AS. More famine than feast: pattern and variation in a potentially degenerating mammal fauna on Cape York Peninsula. WILDLIFE RESEARCH 2015. [DOI: 10.1071/wr15050] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Context Global mammal populations continue to be threatened by environmental change, and recent decadal monitoring in northern Australia suggests a collapse in mammal abundance in key locations. Cape York Peninsula has globally significant natural values but there is very little published about the status and distribution of mammals in this region. Aims Following an extensive field survey we investigated two key questions: (i) what is the composition, spatial variation and change from previous regional surveys in the mid to late 1900s in the native terrestrial and arboreal mammal fauna recorded; and (ii) which landscape and site factors best predict mammal richness and abundance. Methods We sampled 202 one-hectare sites across seven locations from 2009 to 2012 in woodlands, closed forestand dune scrub and tussock grasslands. We collected landscape and site-based environmental data for each location, representing fire, weather and vegetation factors. We used generalised linear mixed models to examine the relationship between mammals and these factors. Key results Mammals were generally scarce across the sites and were more abundant and species rich in wet coastal grasslands or closed forests then tropical savanna woodlands. Fire frequency data and the surrounding vegetation complexity were consistent landscape-scale predictors of mammals; ground cover and woody complexity were significant at the site scale. Conclusions Notwithstanding interpretational constraints related to the limited evidence base of historic sampling, the mammal fauna recorded in this study for Cape York Peninsula was similar in composition to the mammal fauna described from 1948–1980 and surveys in 1985, with some species seemingly declining (e.g. Melomys burtoni, Dasyurus hallucatus, Sminthopsis virginiae) and others stable (e.g. Rattus sordidus) or more common (e.g. Rattus tunneyi); however, across all sites abundance was low, and many sites had few or no mammals. Implications In the absence of consistent long-term systematic monitoring it is difficult to determine if this survey and historical surveys represent pre-European patterns for mammals. The absence or low abundance of mammals in most sites suggest that cotemporary patterns may not represent an intact mammal fauna. Due to the equivocal nature of these findings a critical next step is to establish robust monitoring and experimental work to reveal the response of mammals to management interventions.
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Rowe RJ, Terry RC. Small mammal responses to environmental change: integrating past and present dynamics. J Mammal 2014. [DOI: 10.1644/13-mamm-s-079] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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21
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Badgley C, Smiley TM, Finarelli JA. Great Basin mammal diversity in relation to landscape history. J Mammal 2014. [DOI: 10.1644/13-mamm-s-088] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Varner J, Dearing MD. The importance of biologically relevant microclimates in habitat suitability assessments. PLoS One 2014; 9:e104648. [PMID: 25115894 PMCID: PMC4130583 DOI: 10.1371/journal.pone.0104648] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Accepted: 07/16/2014] [Indexed: 11/21/2022] Open
Abstract
Predicting habitat suitability under climate change is vital to conserving biodiversity. However, current species distribution models rely on coarse scale climate data, whereas fine scale microclimate data may be necessary to assess habitat suitability and generate predictive models. Here, we evaluate disparities between temperature data at the coarse scale from weather stations versus fine-scale data measured in microhabitats required for a climate-sensitive mammal, the American pika (Ochotona princeps). We collected two years of temperature data in occupied talus habitats predicted to be suitable (high elevation) and unsuitable (low elevation) by the bioclimatic envelope approach. At low elevations, talus surface and interstitial microclimates drastically differed from ambient temperatures measured on-site and at a nearby weather station. Interstitial talus temperatures were frequently decoupled from high ambient temperatures, resulting in instantaneous disparities of over 30°C between these two measurements. Microhabitat temperatures were also highly heterogeneous, such that temperature measurements within the same patch of talus were not more correlated than measurements at distant patches. An experimental manipulation revealed that vegetation cover may cool the talus surface by up to 10°C during the summer, which may contribute to this spatial heterogeneity. Finally, low elevation microclimates were milder and less variable than typical alpine habitat, suggesting that, counter to species distribution model predictions, these seemingly unsuitable habitats may actually be better refugia for this species under climate change. These results highlight the importance of fine-scale microhabitat data in habitat assessments and underscore the notion that some critical refugia may be counterintuitive.
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Affiliation(s)
- Johanna Varner
- Department of Biology, University of Utah, Salt Lake City, Utah, United States of America
- * E-mail:
| | - M. Denise Dearing
- Department of Biology, University of Utah, Salt Lake City, Utah, United States of America
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Varner J, Dearing MD. Dietary plasticity in pikas as a strategy for atypical resource landscapes. J Mammal 2014. [DOI: 10.1644/13-mamm-a-099.1] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Kurnath P, Dearing MD. Warmer ambient temperatures depress liver function in a mammalian herbivore. Biol Lett 2013; 9:20130562. [PMID: 24046878 DOI: 10.1098/rsbl.2013.0562] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Diet selection in mammalian herbivores is thought to be mainly influenced by intrinsic factors such as nutrients and plant secondary compounds, yet extrinsic factors like ambient temperature may also play a role. In particular, warmer ambient temperatures could enhance the toxicity of plant defence compounds through decreased liver metabolism of herbivores. Temperature-dependent toxicity has been documented in pharmacology and agriculture science but not in wild mammalian herbivores. Here, we investigated how ambient temperature affects liver metabolism in the desert woodrat, Neotoma lepida. Woodrats (n = 21) were acclimated for 30 days to two ambient temperatures (cool = 21°C, warm = 29°C). In a second experiment, the temperature exposure was reduced to 3.5 h. After temperature treatments, animals were given a hypnotic agent and clearance time of the agent was estimated from the duration of the hypnotic state. The average clearance time of the agent in the long acclimation experiment was 45% longer for animals acclimated to 29°C compared with 21°C. Similarly, after the short exposure experiment, woodrats at 29°C had clearance times 26% longer compared with 21°C. Our results are consistent with the hypothesis that liver function is reduced at warmer environmental temperatures and may provide a physiological mechanism through which climate change affects herbivorous mammals.
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Affiliation(s)
- Patrice Kurnath
- Department of Biology, University of Utah, Salt Lake City, UT 84112, USA.
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Morelli TL, Smith AB, Kastely CR, Mastroserio I, Moritz C, Beissinger SR. Anthropogenic refugia ameliorate the severe climate-related decline of a montane mammal along its trailing edge. Proc Biol Sci 2012; 279:4279-86. [PMID: 22896652 PMCID: PMC3441072 DOI: 10.1098/rspb.2012.1301] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
We conducted detailed resurveys of a montane mammal, Urocitellus beldingi, to examine the effects of climate change on persistence along the trailing edge of its range. Of 74 California sites where U. beldingi were historically recorded (1902–1966), 42 per cent were extirpated, with no evidence for colonization of previously unoccupied sites. Increases in both precipitation and temperature predicted site extirpations, potentially owing to snowcover loss. Surprisingly, human land-use change buffered climate change impacts, leading to increased persistence and abundance. Excluding human-modified sites, U. beldingi has shown an upslope range retraction of 255 m. Generalized additive models of past distribution were predictive of modern range contractions (AUC = 0.76) and projected extreme reductions (52% and 99%, respectively) of U. beldingi's southwestern range to 2080 climates (Hadley and CCCMA A2). Our study suggests the strong impacts of climate change on montane species at their trailing edge and how anthropogenic refugia may mitigate these effects.
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Affiliation(s)
- Toni Lyn Morelli
- Museum of Vertebrate Zoology, University of California, 3101 Valley Life Sciences, Berkeley, CA 94720, USA.
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Temperature-dependent toxicity in mammals with implications for herbivores: a review. J Comp Physiol B 2012; 183:43-50. [DOI: 10.1007/s00360-012-0670-y] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2011] [Revised: 04/16/2012] [Accepted: 04/18/2012] [Indexed: 11/26/2022]
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Valdivia N, Golléty C, Migné A, Davoult D, Molis M. Stressed but stable: canopy loss decreased species synchrony and metabolic variability in an intertidal hard-bottom community. PLoS One 2012; 7:e36541. [PMID: 22574181 PMCID: PMC3344890 DOI: 10.1371/journal.pone.0036541] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Accepted: 04/09/2012] [Indexed: 11/18/2022] Open
Abstract
The temporal stability of aggregate community properties depends on the dynamics of the component species. Since species growth can compensate for the decline of other species, synchronous species dynamics can maintain stability (i.e. invariability) in aggregate properties such as community abundance and metabolism. In field experiments we tested the separate and interactive effects of two stressors associated with storminess--loss of a canopy-forming species and mechanical disturbances--on species synchrony and community respiration of intertidal hard-bottom communities on Helgoland Island, NE Atlantic. Treatments consisted of regular removal of the canopy-forming seaweed Fucus serratus and a mechanical disturbance applied once at the onset of the experiment in March 2006. The level of synchrony in species abundances was assessed from estimates of species percentage cover every three months until September 2007. Experiments at two sites consistently showed that canopy loss significantly reduced species synchrony. Mechanical disturbance had neither separate nor interactive effects on species synchrony. Accordingly, in situ measurements of CO(2)-fluxes showed that canopy loss, but not mechanical disturbances, significantly reduced net primary productivity and temporal variation in community respiration during emersion periods. Our results support the idea that compensatory dynamics may stabilise aggregate properties. They further suggest that the ecological consequences of the loss of a single structurally important species may be stronger than those derived from smaller-scale mechanical disturbances in natural ecosystems.
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Affiliation(s)
- Nelson Valdivia
- Instituto de Ciencias Marinas y Limnológicas, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile.
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Miller BJ, Harlow HJ, Harlow TS, Biggins D, Ripple WJ. Trophic cascades linking wolves (Canis lupus), coyotes (Canis latrans), and small mammals. CAN J ZOOL 2012. [DOI: 10.1139/z11-115] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
When large carnivores are extirpated from ecosystems that evolved with apex predators, these systems can change at the herbivore and plant trophic levels. Such changes across trophic levels are called cascading effects and they are very important to conservation. Studies on the effects of reintroduced wolves in Yellowstone National Park have examined the interaction pathway of wolves ( Canis lupus L., 1758) to ungulates to plants. This study examines the interaction effects of wolves to coyotes to rodents (reversing mesopredator release in the absence of wolves). Coyotes ( Canis latrans Say, 1823) generally avoided areas near a wolf den. However, when in the proximity of a den, they used woody habitats (pine or sage) compared with herbaceous habitats (grass or forb or sedge)– when they were away from the wolf den. Our data suggested a significant increase in rodent numbers, particularly voles (genus Microtus Schrank, 1798), during the 3-year study on plots that were within 3 km of the wolf den, but we did not detect a significant change in rodent numbers over time for more distant plots. Predation by coyotes may have depressed numbers of small mammals in areas away from the wolf den. These factors indicate a top–down effect by wolves on coyotes and subsequently on the rodents of the area. Restoration of wolves could be a powerful tool for regulating predation at lower trophic levels.
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Affiliation(s)
- Brian J. Miller
- Wind River Ranch Foundation, P.O. Box 27, Watrous, NM 87753, USA; Denver Zoological Foundation, 2300 Steele Street, Denver, CO 80205, USA
| | - Henry J. Harlow
- University of Wyoming, Department of Zoology and Physiology, Box 3166, University Station, Laramie, WY 80271, USA
| | - Tyler S. Harlow
- University of Wyoming, Department of Zoology and Physiology, Box 3166, University Station, Laramie, WY 80271, USA
| | - Dean Biggins
- USGS, Fort Collins Science Center, 2150 Centre Avenue, Building C, Fort Collins, CO 80526, USA
| | - William J. Ripple
- Department of Forest Ecosystems and Society, Oregon State University, Corvallis, OR 97331, USA
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