Date of Graduation

8-2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Biology (PhD)

Degree Level

Graduate

Department

Biological Sciences

Advisor/Mentor

Willson, John D.

Committee Member

Beaupre, Steven J.

Second Committee Member

Siepielski, Adam M.

Third Committee Member

Greene, Daniel U.

Keywords

community ecology; herpetology; occupancy modeling; population ecology; reptile and amphibian; wildlife management

Abstract

The loss of open-canopy ecosystems throughout North America has precipitated declines in reptile and amphibian species associated with these habitat types. Current efforts to restore open-canopy ecosystems are underway in many areas, but the local distributions of, habitat characteristics required by and the effects of management actions on many herpetofauna species are poorly understood or entirely unknown. Research examining relationships among herpetofauna and their environments is often complicated by the extremely low detectability seen in many studies. We used landscape-scale, assemblage-level surveys to investigate the occupancy patterns and habitat associations of open-canopy-associated herpetofauna in two regions, as well as gain a broad understanding of the effects of management actions on these assemblages. We also used a long-term monitoring program to document the direct effects of prescribed burn management on a snake community in a restored prairie site. Finally, we used advanced statistical modeling techniques to examine spatial, methodological, and species-specific variation in the detection process that can skew our understanding of species’ distributions and habitat associations when ignored. In Chapter 1, we conducted seven rounds of herpetofauna surveys at 81 open-canopy pine savanna sites under a wide range of management regimes, including working forests and conservation areas, and featuring a variety of landscape and vegetation characteristics in Northwest Louisiana. Open-canopy-pine-associated species richness and occupancy were positively related to open vegetation structure in the canopy and understory, as well as the presence of sandy soils, regardless of overstory tree species. These results suggest that working pine forests are capable of supporting open- canopy-pine-associated herpetofauna if certain structural and landscape conditions are present. In Chapter 2, we used a similar study design to examine the status and associations of prairie-associated herpetofauna at 34 remnant, restored, or degraded tallgrass prairie sites in Western Arkansas. Prairie mound density, suggesting a lack of intense anthropogenic disturbance in a site’s land-use history, had a significant positive relationship with community and species-specific occupancy of prairie-association herpetofauna, while current vegetation conditions did not strongly influence occupancy. Our findings suggest that prairie-associated herpetofauna distributions in this fragmented landscape are driven more by historic land use than by current habitat conditions. In Chapter 3, we used a long-term monitoring program to track the direct effects of prescribed burn management on a tallgrass prairie snake community. We documented direct mortality from burns in six snake species over an eight-year period, but populations did not appear to suffer meaningful declines due to these mortalities in the long-term. Finally, we used data from Chapters 1 and 2 to investigate spatial and methodological sources of variation in species-specific detection probabilities of squamate reptiles in Chapter 4. We implemented occupancy models that produce method- and species-specific detection probabilities and highlighted variation in the detection process that should be accounted for in herpetofauna research in order to avoid inaccurate inference relating to occupancy, abundance, and habitat associations. In sum, this dissertation produced applicable management guidelines, tools for conservation work, and methodological insight that we believe will advance the state of herpetofauna research.

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