Research

The aptly named violet-mouthed snails are parasites on corals.

The focal species of my PhD, the aptly named violet-mouthed snails, live as ectoparasites on Porites corals throughout the Indo-Pacific.

I am broadly interested in the interface between ecology, how organisms interact with each other and their environment, and evolution (e.g. population genetics, speciation, genomics). My masters thesis focused on using natural geochemical tags to estimate population connectivity in Kellet’s whelk, Kelletia kelletii. As a PhD student at UCLA I moved to studying the population genetics and genomics of coral-associated snails in the Coral Triangle.

Collecting coral eating snails for a reciprocal transplant experiment in the Philippines

Collecting coral-eating snails for a reciprocal transplant experiment in the Philippines.

PhD Dissertation Summary

P1010004

Coralliophila violacea, a coral-eating snail that specializes on Porites corals.

The paradigm of allopatry as the principal mode of speciation has been challenged by evidence of ecological speciation. Sympatric speciation via divergent selection in different environments may be much more common than previously thought. While studies of ecological speciation in the ocean are still in their infancy, there are several reasons to believe that this process may occur in the sea. First, absolute dispersal barriers are exceedingly rare. As a result, speciation must proceed with varying levels of gene flow and this process is aided by divergent selection. Secondly, strong interspecific interactions (e.g. host-parasite) believed to promote ecological speciation in terrestrial species, are ubiquitous in the marine realm. mtDNA sequence data from the parasitic snail Coralliophila violacea show that sympatric populations living on different coral host lineages are diverging. Reciprocal transplant experiments demonstrated that adult snails collected from the divergent clades have strong host preferences.

A closeup of Porites coral.

A closeup of a Porites coral. Each small segment measuring only 1-1.5 mm is an individual polyp fringed with tentacles.

Porites corals in different shapes and colors. Bunaken National Park, North Sulawesi, Indonesia.

Porites corals in different shapes and colors. Bunaken National Park, North Sulawesi, Indonesia.

A key piece of evidence in understanding speciation is being able to differentiate between neutral divergence that can come from divergence without gene flow (allopatry) and true sympatric divergence where speciation is promoted through divergent selection. However, this is nearly impossible to elucidate using traditional sequencing methods. Next generation sequencing allows surveys of both neutral loci and loci under selection, to differentiate the role of neutral and selective processes. I used a comparative genome scan of RAD-seq loci to detect outliers and a gene-mapping approach to examine patterns of population differentiation with respect to coral host. Seven-four loci were identified as outliers putatively under directional selection, including one involved in xenobiotic detoxification.

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