Molecular phytogeny of eastern Pacific porcelain crabs, genera Petrolisthes and Pachycheles, based on the mtDNA 16S rDNA sequence: Phylogeographic and systematic implications

Porcelain crabs, genera Petrolisthes and Pachycheles, are diverse and abund ant members of the eastern Pacific near-shore decapod crustacean community. Morphology-based taxonomic analyses of these crabs have determined groupin gs of affiliated species, but phylogenetic relationships remain unknown. We used sequence data from the mitochondrial 16S rRNA gene of 46 species of e astern Pacific porcelain crabs to perform phylogenetic analyses by distance and parsimony methods. Our results are used to compare the taxonomic signi ficance of morphological and molecular characters, to examine sequence dive rgence rates of crab 16S rRNA genes, and to analyze the phylogeographic his tory of these crabs. Our phylogenetic trees indicate that the genus Petroli sthes is divided into two main clades, reflecting morphological features. O ne clade contains primarily tropical species, and the other contains specie s from throughout the eastern Pacific, as well as species in the genera All opetrolisthes and Liopetrolisthes. Phylogenetic trees of Pachycheles sugges t an antitropical distribution; north and south temperate species form one clade and tropical species form a second clade. Sequence divergence rates o f the 16S rRNA gene from three pairs of geminate species can be used to dat e divergence times, and we discuss porcelain crab phylogeographic patterns in relation to paleogeographic events. (C) 2001 Academic Press.