Population genetics, phylogeography, and systematics of the thornyhead rockfishes (Sebastolobus) along the deep continental slopes of the North Pacific Ocean

Population genetic, phylogeographic, and systematic relationships are eluci dated among the three species comprising the thornyhead rockfish genus Seba stolobus (Teleostei: Scorpaenidae). Genetic variation among sampling sites representing their extensive ranges along the deep continental slopes of th e northern Pacific Ocean is compared using sequence data from the left doma in of the mtDNA control region. Comparisons are made among the shortspine t hornyhead (S. alascanus) (from seven locations), the longspine thornyhead ( S. altivelis) (from five sites), which are sympatric in the northeast, and the broadbanded thornyhead (S. macrochir) (a single site) from the northwes t. Phylogenetic trees rooted to Sebastes show that S. macrochir is the sist er taxon of S. alascanus and S. altivelis. Intraspecific genetic variabilit y is appreciable, with most individuals having unique haplotypes. Gene flow is substantial among some locations and others diverged significantly. Gen etic divergences among sampling sites for S. alascanus indicate an isolatio n by geographic distance pattern. Genetic divergences for S. altivelis are unrelated to the hypothesis of isolation by geographic distance and appear to be more consistent with the hypothesis of larval retention in currents a nd gyres. Differences in geographic genetic patterns between the species ar e attributed to life history differences in their relative mobilities as ju veniles and adults.