Phylogeny of Opsanus spp. (Batrachoididae) inferred from multiple mitochondrial-DNA sequences

Species of the toadfish genus Opsanus are increasingly used as experimental organisms in biomedicine and evolutionary/ecological physiology. Despite t heir importance, little is known of the phylogenetic relationships among Op sanus species. DNA sequence data for portions of the mitochondrial 12S rRNA , cytochrome oxidase I and cytochrome b genes were generated and analyzed f rom the four recognized Opsanus species and three outgroup taxa. Results of these analyses indicate an evolutionarily rapid divergence of three lineag es within the genus. O. beta and O. pardus were resolved within the same li neage, and could not be distinguished with these mitochondrial sequence dat a. These data and paleoclimatic theory support a hypothesis of speciation b ased on the formation of allopatric populations during periods of elevated water temperature in the northern Caribbean.