UCE data for Tlaloc hildebrandi (Cyprinodontiformes:Profundulidae)
A variety of hierarchical gene flow models have been proposed to explain the distribuion of genetic variation in aquatic environments. These models, including the Stream Hierarchy (SH), Death Valley (DV), Headwater (HW), and Widespread Gene flow (WG) models, provide testable hypotheses that focus on the degree of within basin or within stream network connectivity and an organism's dispersal abilities. We tested these gene flow models using Tlaloc hildebrandi (Profundulidae, Cyprinodontiformes), a freshwater fish endemic to the highlands of the Grijalva-Usumacinta River basin in southern Mexico. Samples were collected from all four sub-basins occupied including the Amarillo (endorheic), Chenalho (Lower Rio Grijalva) and the Jatate and Tzaconeja (Upper Rio Usumacinta) to test four hierarchical gene flow models. Ultraconserved Element data (UCEs) were gathered from 44 individuals and submitted to phylogenetic analyses. Tlaloc hildebrandi was recovered as monophyletic, but the sub-basins were not recovered as monophyletic. In addition, we generated SNPs from the UCEs to analyze the data in a population genetic framework. These results were slightly different, depending on analysis, such that two (STRUCTURE analysis) or three (DAPC analysis) genetic groupings were recovered. Overall, the results of this study provide support for the SH model which predicts high gene flow within basins, but some partitioning basins. Some individuals from the Jatate sub-basin conformed to the HW model, due to historic connections among headwater streams and rivers of the Jatate and Amarillo-Chenalho clades/clusters, with the greatest degree of gene flow occurring from the Grijalva to the Usumacinta basins, two geographically proximate basins that have been hypothesized to have previous connections.