Microsatellite genotypes for Gambusia marshi

1. The valley of Cuatro Ciénegas in Coahuila, Mexico has the highest
degree of local endemism of any habitat in North America. Despite the arid
desert climate, the Cuatro Ciénegas basin harbors an extensive system of
permanent streams, wetlands, and spring fed pools. 2. Microsatellite loci
were surveyed to infer genetic diversity and population structure of
Gambusia marshi, a poeciliid fish endemic to the desert springs of the
Cuatro Ciénegas basin and its outflow the Río Salado de Nadadores in
Mexico. 3. The Sierra de San Marcos and long-term isolation have played a
vital role in shaping the current pattern of phylogeographic structure in
G. marshi, and Bayesian clustering analysis revealed four genetic
populations within G. marshi as well as a major east-west division of the
of the species corresponding to the Sierra de San Marcos. 4. Most sample
sites exhibited high levels of genetic differentiation, although there is
evidence for recent gene flow between some of these locations, presumably
facilitated by irrigation canals. Although all populations exhibit genetic
differentiation, the population of G. marshi in Poza Anteojo is extremely
divergent and should be considered as an independent management unit.