Abstract
A phylogeny of the six North American species in the genus
Alosa, with representatives of three Eurasian species, was generated using mtDNA sequences. This was accomplished by obtaining sequences for three North American species and additional geographical sampling of the other three species. The subgenus
Alosa, including the formerly recognized subgenus
Caspialosa, formed a strongly supported monophyletic group.
Alosa alabamae was part of a polytomy with
Alosa sapidissima, which was interpreted to support the recognition of
A. alabamae as an incipient, yet distinct, species. The subgenus
Pomolobus was not recovered as a monophyletic group.
Alosa chrysochloris was basal to all other
Alosa, although this position was only weakly supported. Previous work had indicated that
Alosa pseudoharengus and
Alosa aestivalis are not reciprocally monophyletic, but additional sampling in this study did not detect any further cases of shared haplotypes between the two species. The phylogeny supports previous hypotheses that the evolution of North American
Alosa species in the Gulf of Mexico (
A. chrysochloris and
A. alabamae) was the result of two independent events. First, the ancestor of A. chrysochloris was isolated in the Gulf of Mexico, likely by the close of the Suwannee Straits, and this was followed later by dispersal of the ancestor of
A. alabamae around the Florida peninsula into the Gulf of Mexico sometime during or after the Pleistocene.
Keywords
Alosa,
mtDNA,
phylogeny,
shad.
Citation
Bowen, B.R.; Kreiser, B.R.; Mickel, P.F.; Schaefer, J.F.; Adams, S.B. 2008. Phylogenetic relationships among North American
Alosa species (Clupeidae). Journal of Fish Biology 72, 1188-1201