Disentangling historical biogeography and anthropogenic introductions: a case study of Red Shiner, Cyprinella lutrensis.

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

Year: 2013 (xlv)

Abstract

Cyprinella lutrensis, Red Shiner, is a widespread complex of morphologically variable forms. Early studies of mtDNA variation showed significant phylogeographic structuring of the species across its range. We studied mitochondrial ND4 sequences of individuals collected from the Pecos, Canadian, Delaware, and Rio Grande in New Mexico, and found 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 and meristic and geomorphometric data 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. Recent introduction of a divergent form does not appear to explain the observed pattern because haplotypes are not shared between rivers and appear to have evolved in situ. However, 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 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 C. lutrensis, with the first event occurring approximately 4-5 million years ago (mya) during the Pliocene. Subsequently, the Rio Grande and Pecos Rivers were isolated more recently (roughly 1 - 2 mya).