Density affects mating mode and large male mating advantage in a fiddler crab

PABLO D. RIBEIRO; PEDRO DALEO; OSCAR O. IRIBARNE

OECOLOGIA

SPRINGER

Lugar: Berlin; Año: 2010 vol. 164 p. 931 - 941

0029-8549

Fiddler crabs show two different mating modes: either females search and crabs mate underground in males’ burrows, or males search and crabs mate on the surface near females’ burrows. We explored the relationship between crab density, body size, and the searching behavior of both sexes and the occurrence of both mating modes in the fiddler crab Uca uruguayensis. We found that crabs change their mating mode depending on their size and crab density. Crabs mated mostly on the surface at low densities, and underground at high densities. The proportion of wandering receptive females but not courting males accounted for the variation in mating modes. This suggests that whether crabs mate underground (or on the surface) is determined by the presence (or absence) of searching females. We found that the change in the mating mode affected the level of assortative mating; males mating underground were bigger than those mating on the surface, suggesting active female choice. Given that fiddler crabs experience multiple reproductive cycles they are prone to show behavioral plasticity in their mating strategy, whenever payoffs by using different mating modes differ between reproductive events. Our results suggest that the incorporation of different levels of environmental variability may be important in theoretical models for the understanding of the evolution of alternative mating tactics and strategies.