Genetic study of the American horseshoe crab throughout its Mexican distribution. Conservation and management implications

The American Horseshoe crab, Limulus polyphemus , a species considered a phylogenetic relict, has been widely studied in its distribution in the United States due to its relevance in the fishing and biomedical industry. However, there is little information on the genetic status of the Mexican population which is relevant for the conservation of this endangered species. Here, using nuclear microsatellites markers, we evaluate the genetic diversity and structure of L. polyphemus in different localities of its Mexican distribution in the Yucatán Peninsula. A total of 103 individuals from four Mexican localities from the Gulf of Mexico (Champotón and Ría Celestún), northern coast of Yucatán (Yum Balam), to Caribbean coast (Sian Ka’an), were analyzed. Our results show low to moderately low values of different genetic diversity parameters and possible inbreeding processes for the two localities situated at the disttibution extremities (Champotón and Sian Ka’an). Also, we detected a strong genetic structure with two clusters, one pooling the Ría Celestún, Yum Balam and Sian Ka’an samples, and the other corresponding to Champotón, the most isolated population in the southern Gulf of Mexico. These patterns of genetic diversity could be related to anthropogenic activities (contamination, illegal fishing) that have impacted these populations for decades, resulting in a decrease in their populations.The observed genetic structure seems to be related to the dispersal behavior of the species and the circulation pattern on the Yucatán Shelf and the Campeche Bank. Our results highlighted the existence of two management units that should be considered in proposing management and conservation strategies for this species, especially focused on localities at critical risk.