Evolutionary Relationships of Minnows in the Genus Luxilus (Teleostei: Cyprinidae) as Determined from Cytochrome b Sequences

Despite use of several character sets, phylogenetic relationships among species groups of the cyprinid genus Luxilus remain unresolved. To address this problem, cytochrome b was sequenced from representatives of each taxonomic unit within the genus and from several outgroups. When all outgroups were included, distance and parsimony analyses identified a single topology: (((L. cerasinus, L. zonatus group) L. cornutus group) L. coccogenis group). However, this topology was not appreciably better than alternative hypotheses from different character sets, and monophyly of the genus was not well supported. Saturation effects associated with contrasts involving the outgroup Cyprinella may have impacted resolution. When only Lythrurus was used as the outgroup, the same topology was recovered, and, except for the placement of L. cerasinus, relationships were well supported. General concordance of these results with those based on morphological characters provides support for a close relationship of the cornutus and zonatus groups and for basal position of the coccogenis group.