(1) Landscape Genetics/Genomics

For my postdoctoral research, I modeled population dynamics and landscape genomics of invasive American Bullfrogs (Lithobates catesbeianus) in southeast Arizona; as well as landscape genomics and disease dynamics of Mountain Lions (Puma concolor) and State-endangered Boreal Toads (Anaxyrus boreas) in Colorado, USA. For Mountain Lions in Colorado, we found that gene flow in the rapidly-urbanizing Front Range region (i.e., near Denver, Colorado) was more restricted, effective population sizes were smaller, and urbanization limited gene flow; compared to a more rural, less developed region on the Western Slope of Colorado. However, measures of genetic diversity did not vary across these regions, suggesting urbanization is not yet impacting these apex predators to the extent that is occurring in southern California and Florida, where Mountain Lions are experiencing more drastic impacts of inbreeding and disease outbreaks (e.g., Feline Leukemia Virus) due to fragmented habitat and small population sizes. Rather, recent and rapid urbanization on the Front Range of Colorado is having more subtle impacts on mountain lion gene flow, which can be detected using next generation sequencing techniques (e.g., ddRADseq) that allow researchers to utilize large datasets of tens of thousands of loci, giving us high power to detect these more subtle impacts.

I also collaborated on a conservation and landscape genetics study of an island-endemic lizard found on only three of the northernmost Channel Islands off the coast of southern California; the Channel Island Fence Lizard (Sceloporus occidentalis becki). We found that on Santa Cruz Island, fence lizard gene flow is strongly tied to habitats with intermediate maximum temperatures (i.e., 'Goldilocks' temperatures; not too hot, not too cold), and where there is dense oak forest and chaparral vegetation, which is used for cover to regulate body temperatures and avoid predation. We also found small effective population sizes (Ne) for island fence lizards, suggesting that this species deserves greater conservation considerations, similar to other Channel Islands endemics such as the Channel Island Night Lizard (Xantusia riversiana) and Island Fox (Urocyon littoralis). 

For my PhD, I explored landscape genomic patterns across the range of one of the world’s largest and most infamous amphibian invasions; the Cane Toad (Rhinella marina) in Australia. Our results revealed little population structure and very low genetic differentiation (FST) among populations, consistent with prior studies documenting their extremely effective dispersal abilities. Moreover, we identified loci showing evidence of selection in edge populations, suggesting Cane Toads may be rapidly evolving to challenging environmental conditions they’ve encountered in Australia. At other range edges, we found evidence for reduced effective population sizes and genetic diversity, suggesting cane toads may be prevented from adapting to edge conditions by isolation and lack of genetic diversity, consistent with the “Central-Marginal Hypothesis” of species range limit evolution.

I also investigated landscape genetic patterns of an endemic Pacific northwest salamander with limited dispersal abilities and a restricted geographic range occupying temperate rainforests of northwest Washington; the Cope’s Giant Salamander (Dicamptodon copei). We found that logging and lack of forest cover have more pronounced deleterious effects on gene flow near the southern edge of this species’ geographic range, which is likely exacerbated by the overall drier, more marginal habitats in the southern portion of the range. This study led to focused conservation recommendations that varied across the species’ range, as opposed to blanket recommendations that often result from landscape genetics studies performed in only one small portion of a species’ range. 

PhD Dissertation, Washington State University: Landscape Genomics and Species Range Limit Evolution of the Invasive Cane Toad (Rhinella marina) in Australia

(2) Species Distribution/Ecological Niche Modeling

For my Masters research, I used GIS data collected both in the field and from online biodiversity databases to predict species distributions for 9 pond-breeding amphibians (Frogs, Toads, & Salamanders) across the Ozark forests of eastern Missouri. We discovered that predictions were more accurate for populations near the edge of the species’ geographic range (i.e., Spring Peepers, Green Frogs, Wood Frogs, & Spotted Salamanders) compared to those closer to the core of their range (i.e., American Bullfrogs, Northern Cricket Frogs). Moreover, broad-scale macroclimate variables were more important for predicting 'edgy' species distributions, while microhabitat characteristics (e.g., breeding pond characteristics, surrounding terrestrial habitat) were more important for species nearer to their range core. This suggests edge populations living in challenging, marginal habitats may be more limited by broad-scale climate factors than core populations. This also has important implications for species’ ecological and evolutionary responses to climate change, as well as practical implications for designing future species distribution modeling efforts. 

In addition, I worked on an ecological niche modeling project for 11 stream fish species (i.e., Stonerollers, Minnows, Darters, Topminnows, Sunfishes, Shiners, & Chubs) using sub-meter accuracy, GIS-based microhabitat data. We found that niche breadth and overlap were important predictors of population densities, highlighting the need for habitat assessments at finer geographic scales in addition to broad scale studies. 

Masters Thesis, Saint Louis University: Using Geographic Information Systems and Field Surveys to Investigate the Biotic and Abiotic Factors Regulating Pond Breeding Amphibian Distributions in Eastern Missouri