MARTIN, RA*; PFENNIG, DW; University of North Carolina at Chapel Hill; University of North Carolina at Chapel Hill: Kin competition and the evolution of polyphenism

Because they share similar phenotypes and needs, competition for resources should be greatest among closely related individuals. One way to minimize such harmful competition is to disperse from the natal environment. However, geographic dispersal may be limited by environmental or evolutionary constraints. For example anuran tadpoles cannot disperse from their natal pond during development. An alternative to dispersal in geographical space is dispersal in developmental space. Kin competition in populations with limited dispersal could select for divergence of resource use among kin and thereby lead to the evolution of trophic polyphenism. Spadefoot toad tadpoles, Spea multiplicata, develop in ephemeral ponds, show kin recognition and display trophic polyphenism. I used these tadpoles to test the critical assumption that competition for resources is greatest among kin by comparing growth and survival of kin and nonkin pairs under food limitation. Kin and nonkin treatments did not differ significantly in mass, snout vent length or time to metamorphosis. Thus, the strength of competition between kin was not more intense than competition among unrelated individuals.