BILEWITCH, J.P.; University of Toronto: Gorgonian Systematics and Phylogeography in Bermuda: Implications for Gene Flow Across the Gulf Stream

The morphological and genetic differences within populations of five common species of gorgonian soft corals were compared to current taxonomic descriptions and estimates of gene flow between Bermuda and The Bahamas. Measurements of skeletal elements (sclerites) included classification of shapes, their sizes, colours, and abundance within the coenenchyme and were recorded as captured digital images from light microscopy and from scanning electron microscope (SEM) images. Sclerite data was then examined for morphological differences among Bermudian individuals and between Bermudian and Bahamian populations. Since the composition of the colony’s proteinaceous core is also taxonomically informative, SEM images of fractures through the central axes were used for information on the specific organization of mineral and organic components. Genetic divergence among species and higher taxa was estimated from mtDNA sequences of the gene encoding for a mismatch repair gene homologue (MSH). Population-level variability was examined using the rDNA sequence of the ITS1-5.8S-ITS2 region. Each locus was amplified with gorgonian-specific primers and cloned products were sequenced with an automated DNA analyzer. DNA sequences and coded morphological data were combined and compared in maximum parsimony analyses in order to infer taxonomic and biogeographical relationships. Maximum likelihood-produced phylogenies of molecular data were also used to test the relationships of the five study species, which are currently listed in three families within two suborders. Preliminary results indicate inconsistencies between current taxonomy and that suggested by an integrated molecular and morphological phylogeny.