Characterization of novel microsatellite markers from the worldwide invasive ascidian Styela plicata

Ten polymorphic microsatellites loci were isolated and characterized from the invasive ascidian Styela plicata by 454 pyrosequencing. From over a hundred potential microsatellite regions, 18 were selected for screening and 10 were retained based on amplification success and marker polymorphism in a sample of 39 individuals from Spain and the United States of America. The number of alleles per locus ranged from 3 to 10, with an average of 6.4 (+/- 2.5 SD). None of the loci showed significant linkage disequilibrium or evidence of large allele drop out or scoring errors. Departure from Hardy-Weinberg equilibrium was observed for two loci in the Spanish population and five loci in the American population, where drastic annual shifts in population genetic structure have been observed. These markers will facilitate further studies on the genetic structure of this species at small spatial and temporal scales.