(1) Landscape Genetics & Genomics

For my postdocs, 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, 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 they are experiencing more drastic impacts of inbreeding and disease outbreaks (e.g., Feline leukemia virus). Rather, recent and rapid urbanization on the Front Range of Colorado is having more subtle impacts on Mountain lion gene flow and genomic diversity, which can be detected using next generation sequencing techniques (e.g., ddRAD) that allow researchers to utilize large datasets of tens of thousands of loci, giving us high power to detect more subtle genomic impacts. 2019 Paper, 2022 Paper, 2023 Paper, 2023 Paper

I also worked 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 consideration, similar to other Channel Islands endemics such as the Channel Island night lizard (Xantusia riversiana) and Channel Island fox (Urocyon littoralis). 2021 Paper

For my PhD, I investigated the landscape genomics across the range of one of the world’s largest and most infamous amphibian invaders; the Cane toad (Rhinella marina) invasion of Australia. Our results revealed low population structure, little genomic differentiation (FST), and low genomic diversity among populations, consistent with prior studies documenting their strong 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 diversity, suggesting Cane toads may be prevented from adapting to edge conditions by isolation and lack of genomic diversity, consistent with the “Central-Marginal Hypothesis” of species range limit evolution. 2016 Paper, 2018 Paper, 2024 Paper, 2026 Paper

I also led a landscape genetics study of an endemic Pacific northwestern salamander in Washington state that has limited dispersal abilities and a restricted geographic range; the Cope’s giant salamander (Dicamptodon copei). We found that logging and lack of forest cover have had 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 warmer southern portions of the species' range. This study led to more focused conservation recommendations that varied across the salamander's geographic range, as opposed to blanket recommendations that result from landscape genetics performed in only a small portion of a species’ range. 2013 Paper

PhD Dissertation, Washington State University: 2015 Landscape Genomics and Species Range Limit Evolution of the Invasive Cane Toad (Rhinella marina) in Australia

(2) Species Distributions & Ecological Niche Modeling

For my Masters research in St. Louis, I used GIS data from both field surveys and online biodiversity databases to predict species distributions for nine different pond-breeding amphibians (frogs, toads, & salamanders) across the Ozark deciduous forests of eastern Missouri. We found more accurate predictions for populations near the edge of their geographic ranges (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 macro-climate variables (e.g., temperature, precipitation) were more important for predicting 'edgy' species distributions, while micro-habitat characteristics (e.g., breeding ponds, water quality, surrounding terrestrial habitat) were more important for species nearer to the core of their ranges. This suggests edge populations living in challenging, marginal habitats may be more limited by broad-scale climate factors than core populations; which has important management implications for eastern Ozark amphibians. 2011 Paper, 2012 Paper

In addition, I worked on an ecological niche modeling project for eleven different fish species (i.e., Stonerollers, Minnows, Darters, Topminnows, Sunfishes, Shiners, & Chubs) in a natural Ozark-forested stream using sub-meter accuracy, GIS-based micro-habitat 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 broader-scale studies. 2011 Paper

Masters Thesis, Saint Louis University: 2009 Using Geographic Information Systems and Field Surveys to Investigate the Biotic and Abiotic Factors Regulating Pond Breeding Amphibian Distributions in Eastern Missouri