The effect of size and autotomy on sexual competition of the mud crab Cyrtograpsus angulatus Dana.

DALEO PEDRO; LUPPI TOMAS; MENDEZ CASARIEGO AGUSTINA; ESCAPA MAURICIO; RIBEIRO PABLO; SILVA PAOLA; IRIBARNE OSCAR

MARINE BIOLOGY

SPRINGER

Año: 2009 vol. 156 p. 269 - 275

0025-3162

Size advantage in male–male competition overmates, combined with male preference over large females,is a common feature that can drive to size assortative matingand, eventually, sexual selection. In crabs, appendageautotomy can aVect assortative mating and opportunity forsexual selection by aVecting size advantage in matingcontests. In this work, we evaluate the eVect of size andappendage autotomy in generating assortative mating in themud crab Cyrtograpsus angulatus. Field observations ofguarding pairs in two diVerent populations show a positivecorrelation between carapace width of males and females inboth the populations. In one of the populations, incidenceof appendage autotomy was low and the variability in thesize of reproductive males was lower than the variability inthe size of randomly collected males (i.e. only larger maleswere successful in getting a female), whereas there was nodiVerences in the other population (i.e. most male sizeswere successful) where the incidence of appendage autotomywas very high, indicating that the importance of size ishigher when the incidence of autotomy is low. In this context,experiments (in both populations) show that, in contestsfor a female, larger males outcompete smaller onesonly when they had intact appendages. When males hadmissing chelipeds, winning or loosing against smallermales was random. This may lead to a decrease in theimportance of male size in populations with high incidenceof cheliped autotomy, aVecting assortative mating andopportunity for selection and, thus, aVecting selectivepressures