Geographic variation in the mitochondrial DNA of the red shiner (Cyprinella lutrensis): the influence of Pleistocene glaciation on population dispersal and divergence

Abstract

Mitochondrial (mt)DNA restriction site variation was utilized to determine if significant phylogeographic structure occurs in the North American cyprinid fish Cyprinella lutrensis. Digestion patterns from 16 restriction endonucleases identified fifty mtDNA haplotypes among 127 individuals of Cyprinella lutrensis assayed from localities in the Gulf Coastal Plain, the Great Plains, and the Central Lowlands. Nucleotide sequence divergence among haplotypes was highly variable (mean + SE: 2.87% + 0.08; range: 0.14-9.24%). Maximumparsimony analysis and the neighbor joining method of tree construction revealed three major groupings (clades) of haplotypes that differed in geographic distribution. Divergence estimates between the basal clade, comprised of haplotypes primarily from the Brazos River in east Texas, and the remaining two clades, place C. lutrensis in the western Gulf Coastal Plain possibly during the mid-Pliocene. Nucleotide sequence divergence between the second clade, comprised of haplotypes from the Trinity and Calcasieu rivers in east Texas and southwestern Louisiana, respectively, and the third clade (comprised primarily of haplotypes from localities north of Texas and affected directly by Pleistocene glaciation), suggest that C. lutrensis colonized glaciated regions to the north during the mid-to late-Pleistocene. This hypothesis is supported by levels of intrapopulational nucleotide diversity in geographic localities outside of Texas and by geologic evidence. Despite marked geographic variation in morphometrics, meristics, and nuptial coloration, mtDNA variation in glaciated regions was not geographically structured, and subspecies of C. lutrensis were not identifiable by phylogenetic analysis of mtDNA.