Water clarity, maternal behavior, and physiology combine to eliminate UV radiation risk to amphibians in a montane landscape
ABSTRACT Increasing UV-B radiation (UV-B; 290-320 nm) due to stratospheric ozone depletion has been a leading explanation for the decline in amphibians for nearly 2 decades. Yet, the likelihood that UV-B can influence amphibians at the large spatial scales relevant to population declines has not yet been evaluated. A key limitation has been in relating results from individual sites to the effect of UV-B for populations distributed across heterogeneous landscapes. We measured critical embryonic exposures to UV-B for two species of montane amphibians with contrasting physiological sensitivities, long-toed salamander (Ambystoma macrodactylum) and Cascades frog (Rana cascadae), at field sites spanning a gradient of UV-B attenuation in water. We then used these experimental results to estimate the proportion of embryos exposed to harmful UV-B across a large number of breeding sites. By combining surveys of the incubation timing, incident UV-B, optical transparency of water, and oviposition depth and light exposure of embryos at each site, we present a comprehensive assessment of the risk posed by UV-B for montane amphibians of the Pacific Northwest. We found that only 1.1% of A. macrodactylum and no R. cascadae embryos across a landscape of breeding sites are exposed to UV-B exceeding lethal levels. These results emphasize that accurately estimating the risk posed by environmental stressors requires placing experimental results in a broader ecological context that accounts for the heterogeneity experienced by populations distributed across natural landscapes.
SourceAvailable from: Constance M O'Connor[Show abstract] [Hide abstract]
ABSTRACT: Abstract Many animal populations are in decline as a result of human activity. Conservation practitioners are attempting to prevent further declines and loss of biodiversity as well as to facilitate recovery of endangered species, and they often rely on interdisciplinary approaches to generate conservation solutions. Two recent interfaces in conservation science involve animal behavior (i.e., conservation behavior) and physiology (i.e., conservation physiology). To date, these interfaces have been considered separate entities, but from both pragmatic and biological perspectives, there is merit in better integrating behavior and physiology to address applied conservation problems and to inform resource management. Although there are some institutional, conceptual, methodological, and communication-oriented challenges to integrating behavior and physiology to inform conservation actions, most of these barriers can be overcome. Through outlining several successful examples that integrate these disciplines, we conclude that physiology and behavior can together generate meaningful data to support animal conservation and management actions. Tangentially, applied conservation and management problems can, in turn, also help advance and reinvigorate the fundamental disciplines of animal physiology and behavior by providing advanced natural experiments that challenge traditional frameworks.Physiological and Biochemical Zoology 01/2014; 87(1):1-14. DOI:10.1086/671165 · 2.05 Impact Factor
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ABSTRACT: Amphibian species capable of optimizing trait response to environmental stressors may develop complex strategies for defending against rapid environmental change. Trait responses may differ between populations, particularly if stressor strength varies across spatial or temporal gradients. Ultraviolet-B (UV-B) radiation is one such stressor that poses a significant threat to amphibian species. We examined the ability of long-toed salamanders (Ambystoma macrodactylum) at high- and low-elevation breeding sites to cooperatively employ behavioral and physiological trait responses to mediate UV-B damage. We performed a microhabitat survey to examine differences in oviposition behavior and UV-B conditions among breeding populations at high- (n = 3; >1,500 m) and low-elevation (n = 3; <100 m) sites. We found significant differences in oviposition behavior across populations, with females at high-elevation sites selecting oviposition substrates in UV-B protected microhabitats. We also collected eggs (n = 633) from each of the breeding sites for analysis of photolyase activity, a photoreactivating enzyme that repairs UV-B damage to the DNA, using a photoproduct immunoassay. Our results revealed no significant differences in photolyase activity between long-toed salamander populations at high and low elevations. For high-elevation salamander populations, relatively low physiological repair capabilities in embryos appear to be buffered by extensive behavioral modifications to reduce UV-B exposure and standardize developmental temperatures. This study provides valuable insight into environmental stress responses via the assessment of multiple traits in allowing sensitive species to persist in rapidly changing landscapes.Oecologia 05/2014; 175(3). DOI:10.1007/s00442-014-2957-z · 3.25 Impact Factor
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ABSTRACT: Ultraviolet-B (UV-B) radiation exposure is one hypothesized mechanism explaining amphibian population declines and malformations, but it is rarely quantified in amphibian habitats. We measured spatial and temporal variations in northern vernal pools with UV-B attenuation through the water column, incident UV-B across pool surfaces and seasons, and cumulative UV-B dose. Atmospheric, local, and landscape effects were compared with variances across spatial and temporal scales, plus influence on exposure risk. Risk was evaluated using published reports on detrimental levels for amphibian survival and health, with life history and behavior of vernal pool breeding Rana sylvatica L. (wood frog). Pools were exposed to sufficiently high UV-B at or near the surface for developing amphibians to be at risk of reduced survival, altered growth, and malformation. Atmospheric conditions, vegetative cover, and water column properties significantly influenced UV-B levels, with oviposition and larval behavior controlling actual embryonic and larval exposure. UV-B risk to vernal pool species is greater than predicted in previous studies. Given changes in light regimes, climate change, and forest harvesting, amphibian UV-B exposure could reach levels of great concern.Canadian Journal of Fisheries and Aquatic Sciences 10/2013; 70(10). DOI:10.1139/cjfas-2013-0137 · 2.28 Impact Factor