Phylogeography of Marine Meiofaunal Nemerteans of the Ototyphlonemertes Fila Species Complex

Abstract

PHYLOGEOGRAPHY OF MARINE MEIOFAUNAL NEMERTEANS OF THE OTOTYPHLONEMERTES FILA SPECIES COMPLEX By Alexander Tulchinsky A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science at Virginia Commonwealth University. Virginia Commonwealth University, 2006 Major Director: J.M. Turbeville Department of Biology Morphological conservatism combined with intraspecific variability has obstructed studies of speciation and species boundaries among marine meiofauna. Ototyphlonemertes is a genus of meiofaunal nemerteans inhabiting the interstitial spaces of marine sediments. Its members lack pelagic larvae and dispersal potential is believed to be poor. A phylogeographic study of OtotyphlonemertesJila is presented using mitochondrial (cox3) and nuclear (ISSR) molecular markers. Deep genetic divergence (approximately 18% in cox3) was observed between sympatric mitochondrial lineages in Florida. This divergence ... Vll l was reflected in the nuclear marker as well, suggesting the presence of two cryptic species. The first contains Florida and New England populations separated by 3% cox3 sequence divergence and showing no evidence of ongoing gene flow. The second contains two codistributed mitochondria1 clades in Florida separated by 3% cox3 sequence divergence and showing exchange of nuclear alleles. Surprisingly, relatively little fine-scale structuring was found, suggesting that passive dispersal is significant over moderate geographical distances.