Conservation genetics of the tropical gar (Atractosteus tropicus, Lepisosteidae)

摘要

The tropical gar (Atractosteus tropicus) is the smallest member of the family Lepisosteidae; yet this species has a large socioeconomic impact in Mexico and Central America where it is traditionally harvested commercially and for subsistence. While natural populations of tropical gar have been dwindling throughout its natural range, it is also an emergent aquaculture species that is produced in local hatcheries and grown out in privately owned ponds. The increased pressure on natural populations of A. tropicus and its increasing use in aquaculture production poses potential conflicts for the management and conservation of natural populations. Here, we investigated the population genetic structure of tropical gar populations, including over 200 individuals sampled in Mexico, El Salvador, and Costa Rica. Using 11 microsatellite loci, we identified three genetic clusters with distinct geographic distributions, including a cluster in drainages along the Pacific versant of Central America, a cluster in the Grijalva and Usumacinta River basins that drain into the Gulf of Mexico, and a cluster in the Rio San Juan that drains into the Caribbean Sea. Given the degree of divergence observed, these results indicate the potential presence of evolutionary significant units within tropical gar that warrant separate fisheries and conservation management. We also found that tropical gar from an aquaculture facility along the Pacific versant of Mexico were derived from Atlantic versant populations, indicating that individuals have already been translocated across biogeographic boundaries. We discuss how such translocations can negatively impact the natural population structure of tropical gar and provide recommendations for future research and aquaculture practices.