Microsatellite genotypes for Gambusia marshi

<p>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.</p> <p>2. Microsatellite loci were surveyed to infer genetic diversity and population structure of <i>Gambusia marshi</i>, a poeciliid fish endemic to the desert springs of the Cuatro Ciénegas basin and its outflow the Río Salado de Nadadores in Mexico.</p> <p>3. The Sierra de San Marcos and long-term isolation have played a vital role in shaping the current pattern of phylogeographic structure in<i> G. marshi</i>, and Bayesian clustering analysis revealed four genetic populations within <i>G. marshi</i> as well as a major east-west division of the of the species corresponding to the Sierra de San Marcos.</p> <p>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 <i>G. marshi</i> in Poza Anteojo is extremely divergent and should be considered as an independent management unit.</p>