A New Subspecies Of Dusky Salamander Genus Desmognathus From South Central Florida PDF Download

Salamanders are often the most abundant vertebrates in forest communities and perform important ecological functions by acting as both predators and prey. Their decline, extirpation, and potential extinction can have dramatic effects on the environment through disruption of predator-prey interactions and alteration of nutrient cycles. Salamanders are also sensitive to habitat encroachment, disease, chemical contamination, and climate change, and their declines serve as an indication that environmental health may be compromised. Unfortunately, salamander declines and extinctions have been reported around the world. Several causes contribute to the declines including land use change, chemical contamination, over exploitation, invasive species, climate change and emerging pathogens.In the Eastern US, salamanders have experienced precipitous declines since at least the 1950s. Some have identifiable causes, but many declines are enigmatic, and studies are needed to identify potential causes and assess population status before restoration is possible. In Florida, declines have been reported in populations of Frosted Flatwoods Salamanders (A. cingulatum), Reticulated Flatwoods Salamanders (Ambystoma bishopi), Striped Newts (Notophthalmus perstriatus) and presumed Spotted Dusky Salamanders (D. compare conanti). Two other salamanders in Florida may also be in decline: the Seal Salamander (Desmognathus monticola) and the Southern Dusky Salamander (D. auriculatus). Dusky Salamanders (Family: Plethodontidae, Genus: Desmognathus) represent an understudied clade of lungless amphibians which are difficult to distinguish due to morphological conservatism. However, modern genetic techniques are revealing a previously hidden abundance of diversity, suggesting that local extirpation of "populations" may in fact represent species level extinctions. The overarching goals of my dissertation was to evaluate the current status of D. monticola and D. auriculatus in Florida and attempt to identify possible agents of their decline. I also investigated the prevalence of amphibian chytrid pathogens in historic and contemporary salamander populations in Florida. To answer my first question, I established historic location distributions in Florida from museum preserved specimens and surveyed all possible historic sites with traditional field techniques. Desmognathus monticola was restricted to a small series of ravines forming an unnamed tributary of Canoe Creek, Escambia Company We were unable to locate any specimens in the field, and show the population declined after their initial discovery in 1969. Desmognathus monticola has not been seen in the state of Florida since 2002 and appears to have been extirpated by poor land use practices. For D. auriculatus, I developed a custom environmental DNA (eDNA) assay and field collection technique to assist with species detection. I tested the effect of lentic versus lotic water habitat and pH on the efficacy of detecting D. auriculatus eDNA at sites of known presence. Although I found no significant effect of pH on eDNA detection success, I was unable to detect eDNA in lentic systems. However, I achieved 100% detection success at lotic system sites. I also detected D. auriculatus eDNA at one site of previously unknown presence but was unable to locate any live specimens during traditional surveys. I recommend conducting additional surveys at the site to ensure the eDNA detection was not a false positive. Finally, I conducted extensive field surveys throughout Florida to locate populations of D. auriculatus. I surveyed most historic collection sites and many new sites but found an extreme reduction in their area of occupancy, with the decline occurring in the 1970s. The Southern Dusky Salamander is now restricted to a few fragmented pockets in North Florida and appears to be extinct in the Florida Peninsula. Although the amphibian chytrid pathogen Batrachochytrium dendrobatidis (Bd) is present in current and historic salamander populations, its prevalence is low and does not appear to be the agent of decline. However, it is possible that infected wild D. auriculatus die shortly after contracting Bd and went untested, biasing our results. I was unable to determine the agent of D. auriculatus' decline, but comment on potential causes. In conclusion, my research is the first formal survey of the status of D. monticola since its initial discovery in 1969. I cannot assign a cause to its disappearance, but the most likely candidate is habitat destruction from poor forestry management. My research is also the first formal survey of D. auriculatus' status throughout the state of Florida. I demonstrate the utility of eDNA in locating the species, identify remaining populations, and address several possible causes of the species' decline.