Research Projects
Glacial recolonization of North America by the acorn barncle, Semibalanus balanoides
In the Northwest Atlantic fluctuating glaciation throughout the Pleistocene left its signature in the genomes of many organisms. Classical effects of glacial re-expansion include serial bottlenecking of genetic diversity along latitudinal clines. Populations of S. balanoides were sampled along an 800 kilometer North American Atlantic transect to assess population genetic structure in this ecologically critical species. The haplotype network to the right shows the signature of a deep evolutionary split, suggesting extended periods of evolution in isolated subpopulations for this species.
Ecological genetics of the Mpi polymorphism in barnacles
The mannose-6-phosphate enzyme is polymorphic in Semibalanus, and balancing selection has been hypothesized as the mechanism for the maintenance of diversity. Until recently investigations of this protein have relied on the old, but extremely useful, technique of allozyme electrophoresis. I have taken the next step in this system by cloning and sequencing this gene to find patterns of indicative of selection at the DNA level. I am also incorporating Illumina data to frame the question of how evolution has proceeded at this locus in the context of whole genome evolution in Semibalanus.
Gene Expression and Hypoxic Stress In Fundulus heteroclitus
I do work on F. heteroclitus in collaboration with the U.S. Environmental Protection Agency offices in Narragansett, RI and the Whitehead Lab at Louisiana State University. We have used microarrays to examine how hypoxic stress influences gene expressionin hybrid population.
Phylogenetic comparative methods strengthen the evidence for reduced genetic diversity among endangered tetrapods
This has been a side project for me that stems out of a general interest in what dictates effective population sizes in species. Barnacle work has convinced me that the Hedgecock effect (Hedgecock, 1994) is very real and the variance in reproductive success is tightly linked with maximum fecundity. As a result, Ne, and by extension genetic diversity, should vary non-randomly with phylogeny. The tree on the right is a hand built tetrapod tree with 894 tips. I have arrayed diversity data on the tree and am using it find the correlation between genetic diversity and extinction risk. I hope this project will help demonstrate the importance of using the comparative method in conservation.