PETTENGILL, J.B.; HADFIELD, M.G.; SCHUG, M.D.; WENDT, D.E.; University of North Carolina at Greensboro; Kewalo Marine Laboratory; University of North Carolina at Greensboro; Cal Poly, San Luis Obispo: Assessment of Genetic Biogeography of the Polychaete Tubeworm Hydroides elegans using microsatellites

For sessile marine invertebrate animals with free-swimming larvae, the longevity of the larval stage would seem to be particularly important in maintaining genetic continuity among adult populations. To examine this general notion, we isolated and characterized six highly polymorphic microsatellite loci for the polychaete tubeworm Hydroides elegans. Using four of those loci, we genotyped between 9 and 47 individuals from 7 sub-populations located in the Atlantic, Pacific, and Indian Oceans and in the Mediterranean Sea. Allele frequencies indicated that the degree of difference between observed and expected heterozygosity placed 10 (out of 28) population-by-locus couplets out of Hardy-Weinberg Equilibrium, warranting caution when interpreting Wright�s F-statistics. The results of the genetic analyses showed a significant degree of overall population sub-structure (Fst=0.1; P<0.05). However, estimates of the migration rate and pairwise Fst suggest that there is little genetic differentiation between populations. For example, the number of migrants per generation (Nm) between populations from Australia and Singapore was estimated to be 23.79. Furthermore, the pattern of genetic variation does not support isolation by distance and the degree of relatedness between pairs of populations was not uniform, which suggests that other factors affect the movement of individuals between distant populations. It is likely that anthropogenic dispersal of H. elegans on ship hulls (and not larval dispersal) is responsible for movement of individuals across such vast distances.