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Abstract:
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Amphibian decline is a major concern worldwide , and a lack of basic ecological and life history information for many species significantly limits our ability to evaluate the degree and possible causes of such declines , and to develop effective conservation strategies for threatened and endangered species . Not only is there a shortage of adequate long -term datasets necessary for robust analyses of population variability , but the elusive nature and obscure microhabitats of many species make it difficult to collect even the most basic natural history data . In a series of observational and experimental studies , I employed both traditional and novel ecological methodologies to examine environmental correlates of temporal population variability , foraging ecology and anti -predator behavior in endangered Barton Springs Salamander (Eurycea sosorum ) from Austin (Travis County ) , Texas .
Though headwater springs are typically thought of as habitats with relatively stable environmental conditions , I discovered that E . sosorum population abundance was strongly influenced by periodic extremes of rainfall that affect cycles in spring flow rates , water temperature , and other physico -chemical variables . I also found that population dynamics in E . sosorum are highly consistent with those expected for organisms with a storage effect life -history strategy , in which a few long -lived females capable of high fecundity and prolonged survival in subterranean habitat during adverse environmental conditions may be sufficient for population persistence . In addition , juveniles may use subterranean habitat as a thermal refuge .
Using stable isotope analyses and macroinvertebrate prey censuses , I determined that at the population level , adult E . sosorum exhibits high electivity for planarian flatworms (Dugesia sp . ) . This would not have been detectable using traditional methods of dietary analysis such as stomach or fecal content analysis because Dugesia are soft -bodied animals . Additionally , stable isotope analyses revealed that adult E . sosorum exhibits inter -individual diet variation and is capable of diet switching .
Finally , I discovered that anti -predator behavior in E . sosorum is influenced more strongly by visual and bioelectric cues from potential predators , but not olfactory cues . This is the first known demonstration of anti -predatory response mediated only by bioelectric stimuli in an amphibian , and one of very few to observe this phenomenon among aquatic vertebrates . |