Divergencia genética como resultado de adaptación a alturas diferentes en Rana neotropicales del grupo Rana pipiens

Abstract

Frogs classified as Rana pipiens represent a group of closely related species. In this study, four populations belonging to this group, but inhabiting different environments at different altitudes in Costa Rica were compared in respect to (1) norphological variation and (2) reproductive compatibility. No cline was evident in the shape of the snout, but a significant decrease in size of both sexes was found to occur in a clinal manner with increase in altitude. Artificial crosses indicate a significant decrease in reproductive compatibility between the high-altitude population and those inhabiting lower altitudinal zones. It is proposed that the clinal change in size and the reduced viability of ''hybrids" between parents from high and low altitude populations may indicate a genetic divergence and formation of a new species in process by the frogs inhabiting the summit of Volcán Turrialba. Speciation by this mechanism may be occurring throughout the isthmus of Central America on numerous semi-isolated mountains and volcanoes.