Molecular systematics of Characodon: Phylogeny based on a nuclear locus

Abstract

Characodon is a genus of livebearing fishes whose two extant species (C. lateralis and C. audax) inhabit localities along the Río Mezquital of Durango, Mexico. This lineage of Goodeidae (Cyprinodontiformes) is critical to study because of its biogeographic and phylogenetic positions within the group, and both species are of conservation concern. A recent mitochondrial DNA analysis contradicts the published taxonomy, and suggests that Characodon has diverged into northern and southern populations. This, coupled with the observation that the morphological characteristics used in the original species descriptions might be flawed, has led me to study the phylogenetic relationships among populations using a third kind of evidence, nuclear DNA. The flanking regions of a microsatellite locus, amplified and sequenced using standard protocols, were compared for 20 specimens representing one population of C. audax and six populations of C. lateralis. Four non-Characodon outgroups were used to root the phylogeny. The DNA sequences of C. audax were found to be identical to those of the northern C. lateralis, and the southern C. lateralis were recovered as a clade that excluded the northern populations, consistent with the mitochondrial analysis. A relative dearth of sequence variation means this finding should be evaluated cautiously, but it appears that morphological, mitochondrial, and nuclear evidence are in agreement that Characodon diversity needs to be redescribed. This project was supported by the Biology Department and Honors Program of the University of North Georgia.