Dr. Hernán López-Fernández and co-authors recently published a paper titled "Dispersal Across Headwaters Determines Fish Population Structure Between Interdigitating River Systems in the Guiana Shield Highlands" in Ecology and Evolution.
ABSTRACT
Riverine aquatic species primarily occupy the dendritic networks that define river basins, and population-structure models for riverine taxa, including freshwater fishes, generally assume strictly longitudinal dispersal within these networks. River config-urations, however, are dynamic: hydrologic connections change seasonally and over geologic time, potentially enabling out-of-network dispersal, a process that remains poorly studied. Because such dispersal violates key assumptions of existing models,
its prevalence may require the development of new frameworks for understanding riverine population structure. To test for out-of-network connectivity between interdigitating river systems, we analyzed genetic population structure in Krobia potaroensis, a cichlid fish endemic to the rivers draining the Pakaraima Mountains in western Guyana, South America. We detected geneticassociations among populations that do not correspond to contemporary river configurations, indicating historical or ongoingdispersal between adjacent river systems. These results demonstrate that within-network longitudinal dispersal cannot alwaysbe assumed and that alternative dispersal routes can shape population structure, genetic diversity, and genetic differentiation inriverine taxa.
