FAUCCI, A.*; HADFIELD, M.G.; Univ. of Hawaii, Honolulu; Univ. of Hawaii, Honolulu: Influence of larval mode on dispersal and genetic population structure of Hawaiian vermetids (Vermetidae:Gastropoda)

Although, high dispersal is a common feature of marine organisms, it has been difficult to document the movement of most marine species throughout the world’s oceans. It is possible, though, to use population genetic data as an indirect measure of dispersal in marine systems, as the degree of larval transport and gene flow result in characteristic genetic patterns. Vermetids are sessile, suspension-feeding gastropods found in shallow marine waters. They show a wide range of developmental patterns from obligate pelagic planktotrophic larvae, which reside in the plankton for several weeks, to direct developing benthic juveniles, which lack a planktonic phase. The vermetids in Hawaii comprise nine species in the four major vermetid genera. Most species are locally abundant and distributed throughout the coastal waters of the Hawaiian Islands. A 580-base pair region of the mitochondrial cytochrome oxidase I gene was sequenced for nine species of vermetids from among 16 Hawaiian Islands. Neighbor-joining, maximum-likelihood, and maximum-parsimony trees were produced. Preliminary data suggest some disparity between the morphological and genetic designations on the species and genus level. The genetic population structure of four species with different larval modes has been compared. Embryos of Dendropoma platypus and the gregarious species D. gregaria develop directly into crawling benthic juveniles; Vermetus alii produces short-term planktonic lecithotrophic larvae; and Serpulorbis variabilis produces obligate long-term planktotrophic larvae. The genetic data indicate that restricted larval dispersal has a strong effect and leads to highly structured populations. Phylogeographic questions concerning colonization patterns among the Hawaiian Islands have been addressed.