ROMANO, S.L.; University of the Virgin Islands, St. Thomas: Utility of multilocus phylogenetic analysis for assessing species differences in scleractinian corals of Caribbean Porites

Resolution of species boundaries in scleractinian corals is problematic: relationships among closely related species are difficult to resolve even with a combination of morphological, behavioral, reproductive, allozyme and molecular data. Despite unusual characteristics of scleractinian molecular evolution, multilocus DNA analyses have proven insightful for understanding relationships among closely related species. The genus Porites is one of only eight cosmopolitan scleractinian genera and is an important component of coral reefs worldwide, including the Caribbean. The taxonomic history of the genus is long and confused due to overlapping intraspecific and interspecific morphological variability. Studies based on skeletal morphology, characters of the living animal, proteins, and limited numbers of DNA sequences have not clearly resolved relationships within the genus although some concordance between morphology and genetics is observed. Here the potential for a multilocus phylogenetic analysis to resolve relationships within Caribbean Porites is evaluated. Ten samples of each of five different morphotypes were collected from St. Thomas, USVI and analyzed morphometrically. Three mitochondrial gene regions (the putative control region and two mitochondrial introns) and two nuclear gene regions (the ribosomal internal transcribed spacers and a calmodulin intron) were PCR amplified from genomic DNA extractions. The combined DNA sequences from these gene regions are approximately 2300 bp in length. Phylogenetic analysis of the aligned sequences allows testing of two hypotheses: 1) color morphs of Porites astreoides are genetically indistinguishable; and 2) the branching forms P. porites, P. furcata, and P. divaricata are genetically distinct from each other.