Session 14: Herpetology Ecology IRoom: Ballroom 111B2022-07-29 08:15 - 09:30 |
| Moderator: Natalie Claunch |
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1. 08:15 Climate Effects on Adult Occupancy Dynamics and Probability of Reproduction for Three Amphibians in the Sierra Nevada, California. Brian Halstead*, U.S. Geological Survey, Western Ecological Research Center; Patrick Kleeman, U.S. Geological Survey, Western Ecological Research Center; Jonathan Rose, U.S. Geological Survey, Western Ecological Research Center bhalstead@usgs.gov
Availability of water in wetlands and small streams is likely to be strongly affected by climate change. In California, some of the driest and wettest years on record have occurred in the last decade. We examined how site and annual variation in climate affected adult occupancy dynamics and probability of reproduction of three montane amphibians in the Sierra Nevada, California, 2007-2021, with multi-scale multi-state occupancy models. Despite wide variation in climatic conditions related to water supply, occupancy of adults of all three species was relatively stable throughout the study, with sierran treefrogs (Pseudacris sierra) occupying a higher proportion of sites than endangered Sierra Nevada yellow-legged frogs (Rana sierrae) or threatened Yosemite toads (Anaxyrus canorus). Annual probability of reproduction of sierran treefrogs was high, but that of Sierra Nevada yellow-legged frogs and Yosemite toads was much more variable. Species responded differently to different climatic variables depending on their life history strategies. Understanding how occupancy of these anurans has been affected by recent climate extremes is the first step in understanding the likely consequences of future climate change for high-elevation anurans. |
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2. 08:30 Climate Ecology as a Driver of Amphibian Breeding Phenology Evolution. Bryan Juarez*, Stanford University; Lauren O'Connell, Stanford University bhjuarez@stanford.edu
Climate can have profound effects on the evolution of animal behavior and physiology. In ectothermic animals and seasonal breeders, breeding phenology (behavior) is tied to climate through physiology. Unlike breeding start dates, breeding duration has received little attention despite its relevance to population-level fitness. Since amphibians generally reproduce in water, breeding duration in amphibians is directly tied to climate. Reproductive calling behavior and abundant natural history observations in anuran amphibians make them an ideal study system to understand how breeding duration evolves in response to climate. To answer this question, we use phylogenetic comparative methods to analyze a global dataset of breeding durations, climate, body size, and microhabitat for 497 frog species. Relevant climate variables include mean annual temperature, precipitation, potential evapotranspiration, the seasonality of each, and topographic wetness. We find support for the decades-old adage in herpetology: breeding durations are longer in the tropics and shorter in the temperate zone. However, this latitudinal gradient of breeding duration is more complex than previously envisioned – the effect of latitudinal climate differences on breeding durations depends on body size. Overall, our model describes 20% of variation in breeding durations and these results are robust to phylogenetic uncertainty. This study highlights the benefit of using future research on reproductive plasticity, behavior, and physiology to determine extinction risk and develop better conservation strategies to mitigate the impacts of climate change. |
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3. 08:45 Environmental unpredictability and stochasticity underlie dispersive movements of a terrestrial amphibian. Nathalie Jreidini*, McGill University; David M. Green, McGill University nathalie.jreidini@gmail.com
Dispersive patterns are often thought to be driven by individual body size, sex, and density, yet such proximal factors rarely account for most of the variation present among dispersive movements in nature. With a linear mixed-effects model, we explored the impact of dispersal predictors as well as environmental stochasticity using a 20-year empirical dataset of movements performed by Fowler’s Toads (Anaxyrus fowleri) on the northern shore of Lake Erie at Long Point, Ontario. If any intrinsic or extrinsic predictors are responsible for the dispersive movements made by these toads, then they should account for significant amounts of the variation seen in the toads’ movement distances. Alternatively, if the toads are nomadic, then environmental variation should be of greater significance than any potential proximal predictors, whether intrinsic or extrinsic. We found that all potential predictors of dispersive movements of these animals were, at best, weak predictors, as they accounted for virtually none of the variation observed among movement distances. However, when exploring the impact of environmental stochasticity on dispersive movements, we identified a strong positive correlation between the distribution of toad movement distances and variability in lake water level. We therefore conclude that deterministic proximal factors are not necessary to drive dispersive movements, and that variation in dispersive movements can be ascribed, instead, to stochastic environmental unpredictability, consistent with nomadic movement patterns. |
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4. 09:00 Complex Interactions Among Multiple Stressors: Effects of Climate Change, Invasion, and Conspecifics on Larval Pacific Chorus Frogs (Pseudacris regilla). Abby Dalke*, Gonzaga University; Allie Erickson, Gonzaga University; Bailey Tasker, Gonzaga University; Skylar Riley, Gonzaga University; Paul Hurst, Gonzaga University; Scott Griffith, Whitworth University; Betsy Bancroft, Gonzaga University bancroft@gonzaga.edu
Freshwater ecosystems are threatened by the effects of climate change and invasion. Amphibians are an ideal model organisms for understanding the effects of climate change in the context of other stressors due to their phenotypic plasticity. To understand the effects of climate change combined with other stressors on Pacific chorus frogs (Pseudacris regilla; PCF), a 2x2x2 factorial experiment was carried out using a climate treatment (future/historic), conspecific density (conspecific present/absent), and indirect effects of invasive brook stickleback (Culaea inconstans) fish (chemical cues present/absent). Both simulated climate change and competition with a conspecific had large effects on development, growth, and morphology of PCFs, while invasive stickleback cues had smaller, less frequent effects. Most stressor interactions were antagonistic, particularly when all three stressors were present. Our results illustrate that multiple stressors interact in complex ways and stressors in the larval stage may have effects on adult fitness. |
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5. 09:15 Varying Effects of Anthropogenic and Natural Disturbance Regimes on Amphibian Populations in an Unstable Wetland Landscape. Victoria Tawa*, McGill University; David Green, McGill University victoria.tawa@mail.mcgill.ca
Environmental disturbance may have important consequences for the maintenance of biological diversity. Diversity may rise owing to an increase in landscape heterogeneity that disturbance can produce but if the intensity or magnitude of disturbance is beyond what may be tolerable, there may be severe negative consequences for biota. At Long Point, Ontario, Canada, anuran amphibians have recently experienced a chance confluence of major disturbance events, both anthropogenic and natural. Marshes have been treated with herbicide to control the spread of invasive Phragmites australis reeds at the same time as high water levels and storms on Lake Erie have eroded and washed out shoreline sand dunes. We studied how these habitat modifications have affected the resident species of frogs and toads. Using a 3-replicate 2x2 factorial site design of disturbance regimes, we collected occurrence data using minnow traps, acoustic surveys, and visual surveys, before and after the disturbances. We found that the dune washouts, which resulted in the formation of open, sand-filled ponds, and the anti-Phragmites herbicide treatments both reduced the homogeny of previous landscapes. Post-disturbance, ranid frogs (Lithobates spp.) were significantly less abundant in sites affected by dune washouts and significantly tended to inhabit both treated and control sites where vegetation was more abundant. The natural washouts, however, produced improved breeding habitat for Fowler’s Toads (Anaxyrus fowleri), which successfully bred in any washout site, regardless of herbicide-treatment status. Our results indicate that disturbance is necessary for maintaining diversity in anuran communities at this, and similar, environments. |