The Evolution of Ethological and Post-Mating Isolation

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Focusing on Appalachian salamanders (Desmognathus ochrophaeus and related species) whose biology is well characterized, the PI's: (1) developed and applied new experimental procedures for measuring sexual incompatibility, (2) established that geographically isolated populations of ochrophaeus have evolved substantial incompatibility, (3) found that the magnitude of incompatibility is related to the geographic separation of populations but only weakly related to genetic differentiation, (4) identified the critical courtship stages which underlie incompatibility, and (5) found some evidence for stronger incompatibility in areas where related species occur together. These results lay the groundwork for the detailed studies of sexual and developmental incompatibility that the PI's plan to pursue in this proposal. First, the PI's plan to identify the behavioral mechanisms responsible for the sexual incompatibility observed between geographically isolated populations of ochrophaeus. Because there are very few observational studies of sexual incompatibility in vertebrates and other animals, the proposed behavioral studies will greatly increase understanding how such incompatibility evolves. Second, the PI's plan to survey developmental incompatibility among ochrophaeus populations. This survey will enable the investigations to determine whether sexual and developmental incompatibility evolve in parallel, an issue that has never been resolved in vertebrates. Third, the PI's plan to take a statistical approach to the question of whether sexual incompatibility is enhanced in areas where related species occur together. Such enhancement has been the centerpiece in textbook discussions of the evolution of reproductive incompatibility, yet empirical support for the process is mixed. The PI's plan to test for enhanced sexual incompatibility in several transects through areas of co- existence, and to identify the behavioral basis of enhanced sexual incompatibility.