We studied microsatellites to quantify levels of genetic variation in the eastern oyster (Crassostrea virginica) within and among Texas bays. By determining the level of diversity, we will provide information that may be used to improve restoration. Although oysters have pelagic larvae that can travel long distances, due to low water exchange rates in Texas, we expected to find a relatively high amount of variation distributed among bays. We began by extracting DNA using a Qiagen DNeasy kit from 25 oysters from six Texas bays, and then amplified five known microsatellite loci using PCR. We scored microsatellites on a CEQ 8800 and used Arlequin 3.11 to calculate levels of heterozygosity and to estimate the amounts of variation along the coast. We also used Analysis of Molecular Variance (AMOVA) on the scored microsatellite data to estimate the distribution of variation among bays.
The mean observed heterozygosity was 0.416 with a standard deviation of 0.010. The results of the AMOVA showed that most of the variation was within individuals at 60%. The variation within bays was 34%, and among bays was 6%. The FST results were similar to the variation among bays at 0.0604 (P = 0.0207). These data indicate low but significant genetic differentiation among bays, which is actually high for a marine species with pelagic larvae. With higher variation among Texas bays there is potential for using genetic markers for tracking larval settlement thus improving prospects for oyster reef restoration.