Research

As an organismal evolutionary biologist, I am captivated by how species’ traits mediated their responses to geological and climatological processes at ancient timescales, and how species will respond to the rapid environmental changes of the Anthropocene. I integrate field and museum collections with genomic and phenotypic data to: (1) investigate diversification, (2) study microevolutionary changes in declining populations, and (3) conduct integrative biodiversity discovery and taxonomy.

Elucidating mechanisms of diversification on Sumatra

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I quantified between and within-island diversification in parachuting frogs and bent-toed geckos on Sumatra, and found that the majority of species in both groups resulted from ancient in situ processes. These results suggest that diversification did not occur during periods of Pleistocene connectivity as previously thought, and that Sumatra was a source of diversity for the whole region.

Using a phylogenetic approach, I found that divergence among four lineages of parachuting frogs occurred synchronously on Sumatra. Furthermore, genome-wide SNP data suggested that stream-breeding species showed congruent population breaks in regions that had marine incursions, whereas structure in pond-breeding species did not correspond to marine incursions. Combined, these results suggest that marine barriers contributed to in situ diversification on Sumatra, and that differences in reproductive biology may underlie disparate species’ responses to shared geological events.

Microevolutionary changes in the Anthropocene in the face of rapid global change

Specimens from the National Museum

The Appalachian Range along the eastern United States harbors the highest salamander diversity in the world and much of this diversity, particularly the woodland salamanders (genus Plethodon), experienced severe declines during the 1980s. The underlying causes of population decline remain unknown, thus the primary focus of my postdoctoral research is to investigate the genomic consequences of these documented declines in woodland salamanders. I am using target capture of formalin-fixed, historical frozen, and contemporary samples to quantify changes to genetic diversity and demography in salamander communities at two sites. This system provides an ideal framework for investigating where in the genome changes occur in declining species, if genomic signatures of decline are assemblage-wide or species specific, and if immune genes have undergone strong positive selection due to increased disease prevalence.

Biodiversity discovery, integrative taxonomy, and species delimitation

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Species are fundamental units of biology, and thus, documenting, quantifying and delimiting species is central to evolutionary research. The field of species delimitation has faced many challenges in the genomic age including understanding the effects of sampling regime, missing data, and data types on delimitation outcomes. My research addresses these challenges by integrating genomic and phenotypic data in a taxonomic framework. In North American whipsnakes, I tested the influence of missing SNP data on species delimitation and found that missing data had little effect on delimitation outcomes. I also delimited and described several lineages of whipsnakes.

Species discovery and taxonomic revision is an important component of my research on Sumatra, where total species diversity is vastly underestimated, in part due to the large numbers of cryptic species complexes. My research on parachuting frogs revealed species-level divergence in one highland species complex, and I used genome-wide SNPs, internal and external morphological traits, and larval morphology to revise the taxonomy of this group. In addition, my ongoing project with bent-toed geckos is uncovering a host of new species in need of taxonomic description, and I think the morphological crypsis in this system will serve as a great testing ground for emerging machine learning methods that integrate both genomic and morphological data.

Finally, biodiversity surveys in poorly documented regions are essential to fully understand global patterns of diversity and to inform conservation policy. I recently led an expedition to Nepal where I collaborated with local universities, government agencies, and a private research lab to survey and document herpetological diversity in the Kathmandu Valley.