Molecular phylogeny and biogeography of the marine shrimp Penaeus

The evolutionary relationships among 13 species representing all six subgen era of the shrimp genus Penaeus were examined using 558 bp of mitochondrial (mt) DNA from the cytochrome oxidase subunit I gene. Analyses of this sequ ence revealed high genetic divergence between species (d = 8-24%), a findin g which contrasts with previous work, which indicated that genetic diversit y, based on electrophoretic analysis of allozymes, was extremely low in Pen aeus. Three tree-building methods (maximum parsimony, neighbor joining, and maximum likelihood) were concordant in indicating that current subgenera a ssignments do not reflect evolutionary partitions within the genus Penaeus. While the molecular phylogenies cast doubt on the validity of subgenera, t he observed relationships are concordant with biogeographic boundaries acro ss the tropical range of Penaeus. Both the western Atlantic and eastern Pac ific contain monophyletic species pairs which cluster together in all analy ses. The Indo-Pacific contains a putative basal taxa (P. indicus), the deep est mtDNA lineages, and the highest diversity, including representatives of all three primary lineages observed in Penaeus. These data are consistent with the suggestion by Ball ct al. (1990) that Penaeus arose in the Indo-Pa cific and radiated eastward and westward to account for the current circumt ropical distribution of the genus. This phylogenetic framework for Penaeus will enhance the scientific foundations for wildlife resource management an d breeding experiments (hybridization and related manipulations) designed t o improve the commercial value of captive strains. (C) 1998 Academic Press.