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The Reticulated Flatwoods Salamander, Ambystoma bishopi, is an inhabitant of longleaf pine forests in the southeastern United States. Historically distributed across southern Alabama, Georgia, and the Florida panhandle west of the Apalachicola-Flint Rivers, the range of this species has been drastically reduced. It is currently listed as federally endangered under the Endangered Species Act (ESA). Population viability analyses (PVAs) represent a key component of many recovery plans for threatened and endangered species. Here we use 10 years of mark recapture data collected from two breeding populations of A. bishopi to construct a demographic model that can be used to evaluate future extinction risk. In chapter one, we quantify population sizes through time, and estimate the impact of annual variability in numbers on genetic viability. This species exists in small (< 500) breeding populations and exhibit annual fluctuations in abundance characteristic of pond-breeding amphibians. In chapter 2, we adopt a modified version of the von Bertalanffy equation to construct size-at-age curves for A. bishopi that include the metamorphic transition. Individuals exhibit rapid growth in the larval stage such that they emerge as metamorphs at 60% of their final body size. In chapter 3, we employ a Cormack-Jolly-Seber model, modified to include continuous covariates, to generate size-dependent survival curves. Survival of A bishopi exhibits dramatic annual and seasonal variability, but is always positively correlated with body size. Lastly, in chapter 4, we combine the elements of all previous chapters to construct an Integral Projection Model (IPM). Given the prevalence of complete recruitment failure in these populations, and their relatively small size, extinction probabilities under a business-as-usual model were high. Increasing the frequency of successful recruitment drastically reduces extinction risk; however, adult survival exerts the greatest influence on long-term population growth. To assure the recovery of A. bishopi, management must consider all elements of the life-history when allocating resources and effort. More generally, both aquatic and terrestrial habitats must be protected for amphibian conservation to be effective, making them ideal candidates for 'umbrella species' status. Amphibian conservation would also benefit from an increase in systematic, long-term data collection. / Doctor of Philosophy / The southeastern United States is the global salamander hotspot, representing a crucible for diversity. Longleaf pine forests, the predominant ecosystem in the southeast, have been reduced to 3% of their former range, with dire consequences for the animals that inhabit them. The Reticulated Flatwoods Salamander, Ambystoma bishopi, is endemic to the region, and currently listed as federally endangered owing to recent population declines. A recovery plan for the species therefore, is required by law, under the Endangered Species Act (ESA). A salient component of modern recovery plans are population forecasts that evaluate future extinction risk. Such forecasts can then be used to assess alternative management strategies proposed to improve the species' long-term prospects. By studying two of the last remaining populations of A. bishopi from 2010-2019, we were able to collect the data required to construct a demographic model that can be used to run population projections. In some regards, A. bishopi is a typical amphibian, in that their populations show dramatic fluctuations in numbers through time, and they exhibit rapid growth in the aquatic larval stage, achieving 60% of their maximum body size in the first three months of life. Flatwoods salamanders breed in ephemeral wetlands, that often dry before successful metamorphosis can occur. The frequency of pond-drying results in a high probability of extinction for a single population, but survival of breeding individuals was equally important when considering long-term persistence. To assure the recovery of A. bishopi, management must consider all elements of the life-history when allocating resources and effort. More generally, both aquatic and terrestrial habitats must be protected for amphibian conservation to be effective, making them ideal candidates for 'umbrella species' status.

Global amphibian declines have been attributed to numerous and often synergistic causes, such as invasive species, pathogens, and ultraviolet-B (UV-B) radiation. The effects of these stressors are context dependent and can vary with location, species, and populations. As sensitivity to UV-B has shown inconsistencies across amphibian taxa, it can be expected that variation also occurs between populations of a single species. High elevation populations of the long-toed salamander (Ambystoma macrodactylum) face exponentially higher UV-B radiation levels relative to low elevation populations and these levels are predicted to increase in conjunction with continued ozone depletion. We hypothesized that breeding long-toed salamander females at high elevations have modified oviposition behavior to better protect embryos from UV-B induced damage. In addition, we hypothesized that long-toed salamander embryos at high elevation would exhibit elevated photolyase activity, a photo-reactivating enzyme that repairs UV-B radiation-induced damage to DNA. We predicted that this behavioral defense strategy would be employed together with an elevated physiological response as a correlated defense response to increased levels of UV-B radiation in high elevation populations. We surveyed high and low elevation long-toed salamander breeding sites throughout Oregon to quantify oviposition site characteristics and associated UV-B profiles. We simultaneously collected embryos for quantification of photolyase activity in a bacterial transformation assay. We found significant differences in oviposition behavior across elevations, with high elevation breeding females ovipositing in deeper water and using UV-B protective refugia. Oviposition sites at low elevations, however, were most often found in UV-B exposed microhabitats located at the surface of the water. This population difference in oviposition behavior resulted in a standardization of UV-B and temperature conditions for long-toed salamander embryos across elevation. In contrast, we found no population differentiation in photolyase activity between high and low elevation breeding sites. This indicates that behavioral selection for UV-B protected oviposition substrates may either be negating the need for increased photolyase activity in long-toed salamander embryos, or that populations lack the capacity to adapt a heightened physiological response to UV-B at high elevations. Together, these results show how trade-offs in physiology and behavior are a unique adaptation to a significant environmental stressor. Further research into the susceptibility of amphibian species to changing environmental conditions may help to demonstrate the effectiveness of correlated trait responses and plasticity in behavior, and species persistence under changing climate regimes. / Graduation date: 2012

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 68-82). Also available on the World Wide Web.

My research explores the complex strategies animals adapt to cope with multiple selection pressures. I studied the behavioral and color response of two salamander sister species, Ambystoma barbouri and A. texanum, to temperature, predation risk and ultraviolet radiation (UVR, 280-320 nm). Ambystoma barbouri undergo development in streams, while A. texanum larvae inhabit ponds. Thus, A. barbouri are exposed to increased habitat ephemerality, enhanced predation risk, and UVR exposure. I show how A. barbouri have evolved alternate coping mechanisms in response to these environmental factors, relative to A. texanum. In this comparison study, I've quantified the affects of these selection pressures on larval color change, refuge use and depth choice.I found Ambystoma barbouri to have a significantly darker mean color than A. texanum. Additionally, both species significantly change color to match their background and in response to temperature. When exposed to warm temperatures, early-stage larvae of both species became lighter. Both species also changed color over ontogeny, with larvae becoming significantly lighter over development. Remarkably, A. texanum larvae mediated risk from predatory fish chemical cues by visually assessing the degree to which they cryptically match their background. If cryptic, A. texanum larvae remained on that background color rather than in refuge. A. barbouri larvae preferred to hide in refuge or on dark backgrounds regardless of crypticity, butquickly change color to match their new background. I found that both species darken in response to UVR. When given the choice of refuge, both species spent significantly more time in hiding when UVR was present. When given a choice of water depth, larvae preferred deep water in the presence of UVR radiation.Adapting multiple color and behavioral responses to individual selection pressures help organisms mediate conflicting demands from multiple selection pressures. For example, when predatory fish are present, larvae should move to shallow water to avoid predation. In the presence of UVR, however, larvae should prefer deeper water. I found A. barbouri larvae choose deep water to avoid high UVR exposure despite the risk of predation. Evolving multiple behavioral strategies allows A. barbouri larvae to avoid UVR damage and mediate predation risk.

In terrestrial habitats with a history of mining activity and previous or ongoing reclamation efforts, understanding the effects of acidification on the ecology of amphibians is an important part of the restoration process and the conservation of local amphibian populations. Pond-breeding amphibians spend much of their post metamorphic life history in direct contact with the soil in upland habitat adjacent to aquatic breeding sites. I reared recently metamorphosed marbled salamanders (Ambystoma opacum) to evaluate the role of soil acidity on determinants of fitness such as growth and survival. My results indicate that a substrate of pH 4 was lethal to recent A. opacum metamorphs. Among animals surviving the higher pH treatments, we found that individuals reared on a pH 5 substrate suffered a reduction in total length and snout vent length by the end of the experiment. The mechanisms of acidity are complex; both hydrogen ions and anions contribute to negative effects on amphibians. Sulfuric acid has larger negative effects than other acids and sulfates can cause reductions in growth without a change in pH. I reared larval spotted (Ambystoma maculatum) and Jefferson salamanders (Ambystoma jeffersonianum) to evaluate the effects of pH and sulfates on two species with differential acid resistances. My results indicate that a pH of 4 is lethal to larval salamanders of both species. In high sulfate treatments there was an early reduction in growth in the spotted salamander, but not in the Jefferson salamander showing that acid resistance applies to the effects of sulfates as well as hydrogen ions. Together, our results suggest that acid and sulfate deposition can affect the fitness of Ambystoma salamanders through direct mortality and a decrease the growth rate of salamanders both as larvae and subsequent to metamorphosis.

The Gray Fossil Site (GFS), a Mio-Pliocene (4.5–7 Ma) locality in the southern Appalachians, boasts the most diverse pre-Pleistocene salamander fauna in North America: Desmognathus sp., Plethodon sp., Notophthalmus sp., a Spelerpinae-type plethodontid, and Ambystoma sp. Because greater taxonomic resolution can result in more precise paleobiological interpretations, additional specimens were studied here. ETMNH 8045, a nearly complete articulated ambystomatid, appears most like Ambystoma maculatum in dentition and vertebral proportions. ETMNH 18219, an isolated vomer, is consistent with modern Pseudotriton and Gyrinophilus in possessing a postdentigerous process and a similar dentigerous row morphology. If these taxa, or species of similar ecological preferences, occurred around the GFS, it seems unlikely they co-inhabited the sinkhole lake. Aquatic stages of Pseudotriton and terrestrial Gyrinophilus last multiple years; their presence could further support a perennial lake interpretation. Modern A. maculatum preferentially breed in vernal pools; confirmed identification could suggest local seasonal wetlands.

The genetics of colonization is understudied in salamanders but has large conservation implications as new habitats are formed or restored to their previous condition. The 1980 eruption of Mount St. Helens provided a natural experiment to study the genetic effects of a large infrequent environmental disturbance on two species of salamander, Taricha granulosa (Rough-skinned newt) and Ambystoma gracile (Northwestern salamander). Both these species breed in ponds, and are thought to exhibit high breeding site fidelity and low vagility. I designated three treatments based on the effects of the eruption: new ponds (created by the eruption, immigrants only), recovery lakes (in blast zone, survivors plus immigrants), and reference lakes (unaffected by eruption, assumed to represent pre-eruption genetic diversity measures). Salamanders took at least nine years to colonize the new ponds. I studied the population genetics of colonization and recovery using microsatellites and AFLPs (amplified fragment length polymorphisms) to measure genetic diversity, gene flow, and population substructure at Mount St. Helens National Volcanic Monument. Based on population genetics theory and the life history characteristics of these pond-breeding amphibians, I predicted that genetic diversity would be lower in newly colonized ponds compared to recovery or reference sites. I also expected significant levels of population substructuring. Finally, I predicted that because of their lower vagility and large number of neotenes, that A. gracile would have less gene flow and a greater degree of population substructuring than T. granulosa. My predictions were not supported by my data. There was no loss of genetic diversity in new or recovery populations in either species. There was no strong evidence for population substructure by either AMOVA, isolation by distance or principal components analysis. Gene flow (Fst) was high in both species. Taricha granulosa and A. gracile were found to be resistant to a large infrequent environmental disturbance. Loss of genetic variability in new populations cannot automatically be assumed. Predicting dispersal and colonization ability based on the broad category of pond-breeding amphibian is not always reliable.

The long-toed salamander (Ambystoma macrodactylum) is the top vertebrate predator in fishless high-elevation lakes in North Cascades National Park Service Complex (NOCA), Washington. The purpose of this research was to determine the effects of physico-chemical factors and introduced trout on abundance and behavior of A. macrodactylum larvae. Although high-elevation lakes in NOCA were naturally fishless, trout were stocked in many lakes during this century to provide recreational angling opportunity. Twenty fishless lakes and 25 lakes with fish were sampled from 1990 to 1994. Larval salamander density and behavior were assessed by snorkeling lake perimeters and searching through nearshore substrate material and aquatic vegetation. In fishless lakes, larval salamander densities were positively related to total Kjeldahl-N concentration (TKN) and negatively related to lake elevation. Based on analysis of salamander stomach contents, crustacean zooplankton, especially cladocerans, were important food resources for larval A. macrodactylum. Total crustacean zooplankton, as well as cladoceran densities, were positively related to TKN concentration, suggesting that increased zooplankton food resources contributed to increased densities of A. macrodactylum. The effects of fish introductions on larval salamander densities depended on TKN concentration and whether or not trout had established reproducing populations. Mean larval salamander densities for fishless lakes with TKN<0.05 mg/l, generated from a linear regression equation with TKN and lake elevation as independent variables, were not significantly different from mean larval densities in lakes with either reproducing trout or in lakes with non-reproducing trout. However, in fishless lakes with TKN���0.05 mg/l, mean larval densities were significantly higher than in lakes with reproducing fish where trout reached high densities. In fishless lakes with TKN���0.095 mg/l, mean larval densities were significantly higher than in lakes with non-reproducing fish where trout fry were periodically stocked at low densities. Reduced larval salamander densities in lakes with trout likely was a consequence of trout predation. Although most larvae were associated with boulder, cobble, and woody debris substrates in nearshore areas of NOCA lakes, differences in the proportion of larvae hidden in benthic substrates between lakes with fish and without fish were not statistically significant. / Graduation date: 1997