Amphibian Conservation in Working and Natural Landscapes: Investigating the Impacts of Disease, Bioacoustics, and Natural History
Amphibians are among the world’s most endangered vertebrates, especially in the tropics. Land-use change remains the most significant driver of amphibian declines worldwide; natural history information on most tropical species is severely lacking, rendering conservation strategies difficult. Human actions have become one of the dominant forces driving the outcomes of a classic question in ecology: Why are species found where they are? Some frog species are tolerant to habitat disturbance, inhabiting urban areas or various types of agriculture, while others are only found in relatively untouched habitats like primary forests. Still other species are so understudied that we are unable to assess their distributions. This dissertation investigates the role of natural history traits in disturbance tolerance, as well as in the discovery of undescribed frog species and behaviors in Ecuador. Chapter 1 introduces these concepts in more detail. Chapter 2 investigates the effect of land management and species traits on pathogen prevalence, specifically the aquatic fungus Batrachochytrium dendrobatidis (Bd)—another major driver of global amphibian loss. At the community level, body size and lifetime aquatic index (level of water dependence for breeding) were the strongest predictors of Bd infection. The results introduce nuance to the theory that amphibian populations experience higher disease risk in natural habitats. In Chapter 3, I investigate how land-use change influences sound propagation, which has direct implications for amphibian communication. If the change in vegetation causes a habitat to become acoustically inhospitable, frogs with certain call properties would be rendered unable to attract mates. I found that species with high-pitched calls in some families (Hylidae and Strabomantidae) were more likely to be found in disturbed habitats—as hypothesized—but, unexpectedly, species with high-pitched calls in Centrolenidae were more likely to be found in undisturbed habitats. This work highlights the need to consider the acoustic environment when assessing a species’ vulnerability to habitat disturbance. In Chapter 4, I describe the call and visual signaling behavior of Sachatamia orejuela, an elusive glassfrog species that occupies a noisy acoustic niche. Documenting these new natural history traits provides a fascinating example of behavioral convergent evolution and further evidence that signals are shaped by their environment. Finally, Chapter 5 describes two new glassfrog species that are phenotypically very similar to other glassfrog species but are genetically and acoustically distinct. We recommend that both be listed as Endangered, given the rate of deforestation in their only known habitat. Chapter 6 discusses conservation challenges in the Ecuadorian Andes, especially for amphibians.