KRUG LAB - EVOLUTIONARY AND LARVAL ECOLOGY OF MARINE INVERTEBRATES
Danielle Trathen, M.S. 2010
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Danielle studied population connectivity in four Caribbean sea slugs, although at the time of her work, we only recognized two species in the complex she studied: Elysia papillosa (called E. patina in her thesis, and other papers at that time; Krug et al. 2016) and E. zuleicae. These species were thought to have planktotrophic development and hence a high potential for larval dispersal via ocean currents. Danielle sequenced a portion of the mitochondrial cytochrome c oxidase I gene and the nuclear histone III gene from slugs collected at a dozen sites ranging from Panama to Bermuda. As expected, E. zuleicae showed little population structure, although the Florida Keys showed pronounced isolation from the rest of the Caribbean. She detected one highly divergent clade restricted to one Caribbean island which was later described as a new species, E. buonoi Krug, Vendetti & Valdes 2016.
Surprisingly, Danielle found (a) a high degree of phylogeographic structure in E. papillosa, and (b) two highly divergent clades with largely non-overlapping distributions. The latter suggested two cryptic species were present, one in the northern Caribbean and one in the lesser Antilles; central Caribbean sites with both mtDNA clades also showed a heterozygote deficiency at the nuclear locus, consistent with two cryptic species co-occurring but not interbreeding. The southern species was subsequently described as Elysia taino Krug, Vendetti & Valdes 2016 in honor of the indigenous people of the eastern Caribbean islands. Danielle's genetic data were consistent with subsequent findings that most populations of E. papillosa are lecithotrophic, explaining the high degree of genetic differentiation among sites, whereas E. taino was planktotrophic is sampled locations and less structured.
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Danielle presented her research in 2009 at meetings of the Southern California Academy of Sciences, Western Society of Malacologists, and Western Society of Naturalists. She received a Best Student Talk award at the 2009 SCAS meeting. She was an undergraduate research fellow in our NSF-funded UMEB program, and received a graduate fellowship through ImpactLA, an NSF-funded GK12 program which has graduate students work with an area high school teacher to improve science instruction.