Genetic structure and historical and contemporary gene flow of Astyanaxmexicanus in the Gulf of Mexico slope: a microsatellite-based analysis.

BACKGROUND: Astyanax mexicanus from the river basins of the Gulf of Mexico slope are small freshwater fish that usually live in large groups in different freshwater environments. The group is considered successful due to its high capacity for dispersal and adaptation to different habitats, and the species present high morphological variability throughout their distribution in Mexico. This has produced the most extreme morphotype of the group; the hypogeous or troglobite, which has no eyes or coloration, and is probably the cause of taxonomic uncertainty in the recognition of species across the entire range. Most studies of A. mexicanus have mainly focused on cave individuals, as well as their adjacent surface locations, providing an incomplete evolutionary history, particularly in terms of factors related to dispersal and the potential corridors used, barriers to gene flow, and distribution of genetic variability. The aim of the present study is to determine the population structure and the degree and direction of genetic flow in this complex taxonomic group, incorporating geographic locations not previously included in analyses using microsatellite loci. Our aim is to contribute to the knowledge of the intricate evolutionary history of A. mexicanus throughout most of its range. METHODS: The present study included a set of several cave and surface locations of A. mexicanus, which have been widely sampled along the Gulf of Mexico slope, in a genetic population analysis using 10 microsatellite loci. RESULTS: Ten genetic populations or lineages were identified. In these populations, gene flow was recorded at two time periods. Historical gene flow, both inter and intra-basin, was observed among surface populations, from surface to cave populations, and among cave populations, whereas recording of contemporary gene flow was limited to intra-basin exchanges and observed among surface populations, surface to cave populations, and cave populations.

Microsatellite loci obtained by next generation sequencing on the sablefish (Anoplopoma fimbria).

Eleven microsatellite loci were developed and characterized for the sablefish, Anoplopoma fimbria. The markers were identified from sequences obtained by next generation sequencing. Thirty samples from Aleutians Islands were genotyped. The amplifications were performed with three different annealing temperature and amplification products were visualized in ABI 3500 Genetic Analyzer. No evidence for scoring errors was detected by stuttering or due large allele dropout and neither of the loci presented a high null allele frequency (> 0.2). The number means of alleles per locus was of 12.21 and mean of observed and expected heterozygosity were of 0.60 and 0.75 respectively. The sablefish represents a resource of high commercial value on the coasts of Japan, Russia, Canada and west coast of the United States and these new primers could be useful to future diversity and structure population studies.