Genetic Status of San Felipe Gambusia
Authors: Anthony A. Echelle, Sherri McClure-Baker, María de Lourdes Lozano-Vilano, Gary P. Garrett, Robert J. Edwards
Year: 2010 (xlii)
Abstract
The San Felipe Gambusia Gambusia clarkhubbsi was described in 2003 from San Felipe Creek, a tributary of the Rio Grande in south Texas. The species differs from its closest relative, Spotfin Gambusia G. krumholzi in various features of pigmentation. Gambusia clarkhubbsi was unknown until 1997, when it first appeared in collections from San Felipe Creek. We used variation in mtDNA (cytb; 400 bp) and six microsatellite loci to assess the distinctiveness of the two species. For mtDNA, G. clarkhubbsi had a single haplotype that was present in 95% of 100 G. krumholzi from seven populations. Microsatellite diversity was slightly lower in 2 samples of G. clarkhubbsi (N = 37 and 38; He = 0.28) than in the 7 collections of G. krumholzi (N = 12-14; He = 0.28 vs 0.33-0.39). No loci was diagnostic of the two species, but, in a PCA plot based on microsatellites, the scatter of G. clarkhubbsi individuals showed no overlap with a tight cluster of individuals from the 7 population samples of G. krumholzi. Correspondingly, AMOVAs based on FST and RST attributed, respectively, 26% and 77% of total diversity to differences between the two species. Based strictly on molecular genetics, the San Felipe Gambusia qualifies as a distinct management unit within the G. krumholzi complex.