Small-scale genetic connectivity of bicolor damselfish ( Stegastes partitus) recruits in Mexican Caribbean reefs

The analysis of genetic similarities among marine populations is a key method for use in connectivity studies intended to provide information for management strategies. The present study aimed at assessing the connectivity levels of subpopulations of bicolor damselfish ( Stegastes partitus) recruits at a small scale (~200 km) among four reefs in the Mexican Caribbean. Samples were collected from 13 sites nested in two Marine Parks (Cozumel and Xcalak), one Biosphere Reserve (Chinchorro Bank) and one unprotected area (Mahahual). A total of 713 samples were genetically characterized by means of seven microsatellite DNA markers and were analyzed on a hierarchical basis. A strong genetic structure was detected among sites with a weak but significant genetic structure among reefs, the combination of which has not been reported in previous studies. These results appear to be related to a “sweepstake-chance effect” combined with oceanographic factors. An isolation by distance test, in addition to a hierarchical Bayesian method, revealed that neither distance among sites and reefs nor any of 10 environmental factors tested could be used to explain the genetic differences observed. The results suggest that conservation strategies for S. partitus based on local scales are likely to be effective.