Evolution of cytochrome b and the molecular systematics of Ammocrypta (Percidae : Etheostomatinae)

Investigations of phylogenetic relationships using comparative morphologica l characters have led to the hypothesis that Ammocrypta is the sister taxon of the Etheostoma subgenus Ioa. Subsequent molecular analyses have not rec overed this proposed relationship. In this investigation, variation in comp lete cytochrome b sequences sampled from 27 percid species, representing al l darter genera and all species of Ammocrypta,, is examined in a phylogenet ic context. Third codon purine transitions are saturated when all darter sp ecies examined are compared; however, saturation is not detected in any cha racter class among species of Ammocrypta. Maximum-parsimony analysis, which excludes potentially homoplasious character classes, and maximum-likelihoo d analysis of cytochrome b sequences statistically reject the hypothesis th at Ammocrypta is the sister taxon of the Etheostoma subgenus loa. Etheostom a is not recovered as monophyletic; however, the hypothesis of monophyly ca nnot be rejected using maximum-parsimony and maximum-likelihood methods. Mo rphological characters are combined with cytochrome b sequences in a total evidence analysis of relationships within Ammocrypta. A novel hypothesis of relationships is proposed, which includes a sister-taxon relationship betw een A. clara and A. pellucida. With regard to relationships among species o f Ammocrypta, the morphological data do not significantly conflict with the cytochrome b data. Morphological characters provide additional synapomorph ies supporting the hypothesis that A. beani and A. bifascia are sister taxa . The biogeographic implications of the total evidence analysis are discuss ed, and the continued taxonomic placement of Ammocrypta in Etheostoma is di scouraged.