Abstract
We studied the distribution of two wild species of cichlid fishes, Amatitlania myrnae and A. septemfasciatus, analyzing if hybridization between species is occurring or not in the coastal freshwater watersheds of Costa Rica. Flooding in these regions, coupled with Costa Rica’s unique topography, often result in the formation of contact points between distinct rivers that are otherwise geographically separated, thus leading to temporary opportunities for hybridization to occur. The goal of this study is to investigate how riverine fish species are maintained in the wild through identifying the mechanisms in which genes are spatially distributed and mixed (or not mixed) between adjacent populations of two sister cichlid species. This research consisted of capturing underwater photos and videos of the fish at each location in order to determine the presence of horizontal stripes along the lateral sides of the body – a phenotype that is distinct and specific to the breeding behaviors of the species involved in this study. With IACUC approval, photos were taken at multiple sites, far and near the contact point, to compare the control groups to the individuals found within the contact zone. Ultimately, results showed that there were no horizontal stripes on A.myranae in the contact zone, suggesting that there is no visual evidence of hybridization occurring between the two sister species. These findings aim to supplement future genetic research on these species and improve our understanding of gene flow in wild freshwater fish populations, as well as the forces that give structure to these communities.