Genetic Connectivity of Stream Salamanders in Urban, Suburban, and Rural Habitats
Ongoing human population growth and increased urban development around the world is inflicting new pressures and challenges for wildlife living within areas affected by urbanization. Habitat alteration can have severe consequences for native species that remain in previously undisturbed areas. Urban development has shown to reduce abundance and density of populations and create barriers to gene flow for stream salamanders in urban areas. Although they are still relatively common and abundant through the Northeast, Northern two-lined salamander (Eurycea bislineata) populations are declining in urban habitats including in New York City. In this study, I explored genetic structure of E. bislineata across an urban, suburban and rural habitat to better understand how urbanization is affecting genetic connectivity between headwater streams. Next, I investigated what environmental and/or urban features influence gene flow patterns in E. bislineata across these same three habitats using landscape genetic methods. Lastly, I used environmental DNA monitoring with metabarcoding techniques to explore stream salamander presence on an urban-to-rural gradient and to investigate overall vertebrate species richness differences to further understand how urban development may be affecting biodiversity in urban aquatic ecosystems. E. bislineata within the urban habitat had greater genetic structure, yet exhibited comparable genetic diversity levels to individuals in the suburban and rural habitat. A mixture of terrestrial variables influence gene flow in the urban habitat, percent canopy cover is most influential for gene flow in the suburban habitat, and variation in aquatic variables affects gene flow patterns for rural stream salamanders. Urbanization factors were identified as the second most important features affecting genetic variation for salamanders in the suburban and urban habitats. Finally, using eDNA from stream water, I found that E. bislineata is present in streams across a gradient of urban development, while another common stream salamander species, Desmognathus fuscus was only detected in more non-urban habitats. With this method, I also detected differences in species composition in urban versus non-urban habitats, mostly due to more non-native species eDNA detected in more urbanized streams. This dissertation provides further understanding of how urbanization affects the evolution of a native amphibian species and how urban development affects stream salamander distribution in the NYC metropolitan area. This information will inform conservation efforts and urban planning in cities that want to promote longevity of populations of this indicator species in our urban ecosystems.
Fusco, Nicole A, "Genetic Connectivity of Stream Salamanders in Urban, Suburban, and Rural Habitats" (2020). ETD Collection for Fordham University. AAI27958134.