ABSTRACT
Porcelain crabs, genera Petrolisthes and Pachycheles, are diverse and abundant members of the eastern Pacific near-shore decapod crustacean community. Morphology-based taxonomic analyses of these crabs have determined groupings of affiliated species, but phylogenetic relationships remain unknown. We used sequence data from the mitochondrial 16S rRNA gene of 46 species of eastern Pacific porcelain crabs to perform phylogenetic analyses by distance and parsimony methods. Our results are used to compare the taxonomic significance of morphological and molecular characters, to examine sequence divergence rates of crab 16S rRNA genes, and to analyze the phylogeographic history of these crabs. Our phylogenetic trees indicate that the genus Petrolisthes is divided into two main clades, reflecting morphological features. One clade contains primarily tropical species, and the other contains species from throughout the eastern Pacific, as well as species in the genera Allopetrolisthes and Liopetrolisthes. Phylogenetic trees of Pachycheles suggest an antitropical distribution; north and south temperate species form one clade and tropical species form a second clade. Sequence divergence rates of the 16S rRNA gene from three pairs of geminate species can be used to date divergence times, and we discuss porcelain crab phylogeographic patterns in relation to paleogeographic events.
Subject(s)
Brachyura/genetics , DNA, Mitochondrial/genetics , Phylogeny , RNA, Ribosomal, 16S/genetics , Animals , Brachyura/classification , DNA, Mitochondrial/chemistry , Evolution, Molecular , Geography , Molecular Sequence Data , Sequence Analysis, DNASubject(s)
Molecular Biology/methods , Specimen Handling/methods , Vertebrates , Animals , Biological Evolution , DNA/analysis , DNA, Mitochondrial/genetics , DNA, Mitochondrial/isolation & purification , Documentation , Gene Amplification , Indicators and Reagents , Laboratories/organization & administration , Museums , Polymerase Chain Reaction/methods , Proteins/analysis , RNA/analysis , Solutions , Tissue PreservationABSTRACT
Restriction site variation in mitochondrial DNA (mtDNA) of the American oyster (Crassostrea virginica) was surveyed in continuously distributed populations sampled from the Gulf of St. Lawrence, Canada, to Brownsville, Texas. mtDNA clonal diversity was high, with 82 different haplotypes revealed among 212 oysters with 13 endonucleases. The mtDNA clones grouped into two distinct genetic arrays (estimated to differ by about 2.6% in nucleotide sequence) that characterized oysters collected north vs. south of a region on the Atlantic mid-coast of Florida. The population genetic "break" in mtDNA contrasts with previous reports of near uniformity of nuclear (allozyme) allele frequencies throughout the range of the species, but agrees closely with the magnitude and pattern of mtDNA differentiation reported in other estuarine species in the southeastern United States. This concordance of mtDNA phylogenetic pattern across independently evolving species provides strong evidence for vicariant biogeographic processes in initiating intraspecific population structure. The post-Miocene ecological history of the region suggests that reduced precipitation levels in an enlarged Floridian peninsula may have created discontinuities in suitable estuarine habitat for oysters during glacial periods, and that today such population separations are maintained by the combined influence of ecological gradients and oceanic currents on larval dispersal. The results are consistent with the hypothesis that historical vicariant events, in conjunction with contemporary environmental influences on gene flow, can result in genetic discontinuities in continuously distributed species with high dispersal capability.
