Marine Science

Marine Science

Senior Theses 2009

Caroline Storer

Molecular population structure and biogeography of the Gulf pipefish, Syngnathus scovelli, in Florida waters

Thesis Committee: Bill Szelistowski (chair), Steve Denison, Peter Meylan

The population genetics of the Gulf pipefish, Syngnathus scovelli, is interesting because although this species does not have good dispersal ability, water temperature and salinity do not restrict its distribution in Florida like they do for many other marine fish and invertebrates. In this study, fish were collected during 2007, 2008, and 2009 from St. Johns River, Merritt Island, and Fort Pierce on the Atlantic coast, from Pensacola, Apalachicola/St. Josephs Bays, Tampa Bay, and Charlotte Harbor on the Gulf coast, and from the Upper Florida Keys. Using a 487 bp portion of the mtDNA control region 29 polymorphic loci and 42 haplotypes were identified. There was regional population structuring within both the Gulf and Atlantic and fish from the Florida Keys grouped with Gulf fish. No haplotypes were shared between Gulf and Atlantic locations, and all locations in the Atlantic were significantly differentiated from all Gulf locations in pairwise AMOVA. This appears to be a result of a historic separation of Gulf and Atlantic S. scovelli populations, and a current barrier to gene flow in SE Florida. Maximum parsimony and neighbor-joining haplotype phylogenies indicated that Atlantic fish consist of a single lineage nested within Gulf haplotypes, and molecular clock estimates suggest that the Gulf-Atlantic divergence occurred during the mid to late Pleistocene. It is proposed that Gulf and Atlantic fish remained isolated during decreases in sea surface temperature coinciding with glacial advances as their ranges were compressed into southern Florida, and that subsequent range expansion in conjunction with differential lineage sorting gave rise to S. scovelli’s present distribution and evolutionary relationships.

Student Research