ON THE REPRODUCTIVE BEHAVIOR OF THE FIDDLER CRAB UCA THAYERI, WITH COMPARISONS TO U. PUGILATOR AND U. VOCANS: EVIDENCE FOR BEHAVIORAL CONVERGENCE

Abstract

The fiddler crabs have been separated into two major species groups: the "broad fronts" (with wide spaces between their eyestalks) of the New World, which may show resourcebased mating systems, and the "narrow fronts" of the Indo-Pacific, which may show resource-free mating systems. A few species, however, are known to deviate both structurally and behaviorally from these patterns. One (Uca thayeri) was studied to determine why. My data show that U. thayeri has a resource-free mating system, behaves much like a narrow front, but possesses the reproductive physiology of a broad front. Studies by others indicate it is closely related to the broad fronts, yet shows many ecological similarities to the narrow fronts. The evidence suggests, then, that the reproductive behavior of U. thayeri is best explained by evolutionary convergence. This result constitutes further evidence that differences between the two groups are best viewed as alternative adaptations.