The evolution and maintenance of deeply divergent lineages of red shiner, Cyprinella lutrensis, in the Rio Grande watershed

Authors: Tracy A. Diver, Thomas F. Turner, Megan J. Osborne

Year: 2012 (xliv)

Abstract

Cyprinella lutrensis, Red Shiner, is widely distributed throughout North America. The species is a widespread complex of variable forms in the United States and Mexico. Early studies of mitochondrial DNA variation showed significant phylogeographic structuring of the species across its range. We studied mitochondrial ND4 sequences of individuals collected from the Pecos River and Rio Grande in New Mexico revealing two deeply divergent lineages (consistent with genus-level differences) that co-occurred in both rivers. To evaluate the origin and maintenance of this variation we 1) compared mtDNA with nuclear markers to evaluate whether mtDNA lineages were reproductively isolated and 2) quantified levels of genetic diversity within each lineage to understand the probable colonization history of the basin. Haplotypes between the two rivers are not shared, suggesting complete isolation, and levels of genetic diversity are surprisingly low within each lineage, with measures of mtDNA diversity comparable to endangered species. Low levels of genetic diversity suggest the Red Shiner has historically experienced population bottlenecks. Morphological analysis and DNA sequences from the nuclear RAG-1 gene are not correlated to mtDNA haplotypes, suggesting no reproductive isolation between lineages. We conclude that the Upper Rio Grande Basin was colonized twice by divergent lineages of Red Shiner, with the first event much older than the second. Subsequently, the Rio Grande and Pecos Rivers were isolated more recently, leading to divergence of each lineage across the basin.