Evolutionary and biogeographic patterns of the Badidae (Teleostei: Perciformes) inferred from mitochondrial and nuclear DNA sequence data

We reconstructed phylogenetic relationships of the family Badidae using both mitochondrial and nuclear nucleotide sequence data to address badid systematics and to evaluate the role of vicariant speciation on their evolution and current distribution. Phy-logenetic hypotheses were derived from complete cytochrome b (1,140 base pairs) sequences of 33 individuals representing 13 badid species, and using three species of Nandidae as outgroups. Additionally, we sequenced the nuclear RAG1 (1,473 base pairs) and Tmo-4C4 (511 base pairs) genes from each of the badid species and one representative of the outgroup. Our molecular data provide the first phylogenetic hypothesis of badid intrarelationships. Analysis of the mitochondrial and nuclear nucleotide sequence data sets resulted in well-supported trees, indicating a basal split between the genera Dario and Badis, and further supporting the division of the genus Badis into five species groups as suggested by a previous taxonomic revision of the Badidae. Within the genus Badis, mitochondrial and nuclear phylogenies differed in the relative position of B. kyar. We also used our molecular phylogeny to test a vicariant speciation hypothesis derived from geological evidence of large-scale changes in drainage patterns in the Miocene affecting the Irrawaddy- and Tsangpo-Brahmaputra drainages, in the southeastern Himalaya. Within both genera, Badis and Dario, we observed a divergence into Irrawaddy- and Tsangpo-Brahmaputra clades. Using a cytb substitution rate of 8.2 x 10(-9) (substitutions x base pair(-1) x year(-1), we tentatively date this vicariant event at the Oligocene-Miocene boundary (19-24Myr). It is concordant with a hypothesized paleo connection of the Tsangpo river with the Irrawaddy drainage that was most likely interrupted during Miocene orogenic events through tectonic uplifts in eastern Tibet. Our data, therefore, indicate a substantial role of vicariant-based speciation shaping the current distribution patterns of badids.