Evidence of philopatry in white mullet Mugil curema (Pisces: Mugilidae)

Mugil curema is a common species in America and some African coastal areas. It is thought to perform reproductive migrations to the open sea and possibly spawn in estuarine waters. Previous studies described it as a species complex composed of cryptic species, which could be explained by reproductive isolation and/or philopatric behavior. In order to assess genetic diversity, genetic structure and philopatry in M. curema, we sequenced and analyzed two mitochondrial genes (control region and Cytochrome Oxidase Subunit I [COI]) and 10 microsatellite loci from adult individuals from 10 locations in the Gulf of Mexico, one in the Atlantic Ocean, and three in the Mexican Pacific. The mitochondrial results showed two genetic groups: Gulf of Mexico (GOM) and Mexican Pacific (MP). There was relatively high genetic distance between the groups (4.5 % for COI and 11.7 % for the control region), but they did share haplotypes. In addition, two genetic groups were found within the MP group, which could constitute cryptic lineages. The microsatellite results showed genetic connection between GOM and MP, probably as a consequence of recent contact. The results also showed genetic structure within GOM and MP; genetic subgroups differed between the sexes in the GOM (F_ST=0.348 ♂ and 0.275 ♀), but not the MP (F_ST=0.233 ♂ and 0.166 ♀). The results of genetic structure and gene flow support the hypothesis of regional philopatry in males in the GOM and both sexes in the MP. The difference between regions could be explained by the fact that these are located geographically on different oceanic slopes. We recommend that areas where there is strong mixing of males and females and high genetic diversity be considered conservation priorities.