Restoring locally adapted eastern oysters, Crassostrea virginica, to New York Harbor Estuary; how ‘local’ must they be?
April 22, 2013
Academic Building A G008, 5:00 PM
In restoration biology it is crucial to know the spatial scale over which genotypes are exchangeable without incurring strong fitness costs so that genotypes are matched with appropriate habitats. Typically the degree of local adaption at a particular spatial scale depends on a balance between immigration from other habitats and the strength of selection. Species with high gene flow, as indicated by spatially homogeneous neutral allele frequencies, are therefore assumed to have few adaptive differences at small spatial scales. However, in species with high fecundity and early mortality, strong differential viability selection across habitats may recurrently produce extensive functional genetic differentiation among adult populations surviving in adjacent habitats. We are testing this hypothesis with the eastern oyster, Crassostrea virginica, because of widespread interest in restoration of oyster populations and important implications for the selection of wild broodstock to be used in hatchery-based restoration. We tested for local adaptation of oyster populations at two spatial scales. First, we used reciprocal transplants across a latitudinal ecotone (~300 km) and found significant genotype (population source) by environment interactions for two important fitness-related phenotypic traits. Second, within a single estuary we tested for functional genetic differentiation among adults at low and high salinity by experimentally testing their larvae for differential salinity tolerances. Larval survivorship across salinity treatments was best explained by interactions between broodstock acclimation, broodstock source population and treatment salinity, consistent with functional genetic differentiation in response to environmental selection gradients within a single estuary. To further test this hypothesis and measure the extent of functional genetic differentiation we are following up these phenotypic tests by making genomic comparisons across oyster populations within New York Harbor Estuary.
I live in Ithaca, NY, where I teach introductory and conservation genetics to Natural Resources majors at Cornell and hope for ski-able snow. I worked as afield biologist and studied cranial morphometrics before turning to genetics to address my most passionate questions involving evolutionary processes. My current research goals are to understand the ecological, demographic and historical processes that generate population substructure and species diversity, particularly in coastal marine ecosystems, and to make these findings relevant to conservation and management when possible. In marine environments there are few absolute barriers to dispersal, yet population genetic substructure and cryptic species are common in marine taxa with high dispersal potential. This implicates cryptic physical barriers to dispersal or strong diversifying selection generating population substructure. My work focuses on both these possibilities by using genetic markers to test for larval retention and nonrandom gene flow limiting population admixture,and by testing for the effects of natural selection at both genetic and phenotypic levels.
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