Molecular evolution, systematics, and zoogeography of the rockfish subgenus Sebastomus (Sebastes, Scorpaenidae) based on mitochondrial cytochrome b and control region sequences

Sebastomus is one of the most species-rich subgenera of Sebastes, whose mon ophyly is well supported by morphological and molecular data. We present th e first description of the complete nucleotide sequence of the mitochondria l cytochrome b gene and the partial sequence of the control region of the 1 4 species of Sebastomus. We used these data in phylogenetic analyses to inv estigate their evolutionary relationships. Extremely low levels of sequence divergence indicated a recent ancestry of these species, suggesting a very rapid radiation within the last million years. The molecular data revealed two main clades within Sebastomus, each with species of different affiniti es that invaded new habitats from the subgeneric center of distribution. Th e rapid speciation in this lineage was manifested in the poor resolution of some nodes in the phylogeny. Internal fertilization and viviparity in Seba stes may have played an important role in the sudden acquisition of reprodu ctive barriers during its radiation. The mitochondrial DNA data suggest tha t prolific speciation in Sebastomus may have been associated with rapid lin eage sorting punctuated by allopatric reproductive isolation subsequent to dispersal events and, perhaps, by sympatric reproductive isolation associat ed with internal fertilization. (C) 1999 Academic Press.