Meeting Abstract

P2.3  Tuesday, Jan. 5  Competition drives the reliability of signalling in the two-toned fiddler crab (Uca vomeris). BYWATER, C.L.*; WILSON, R.S.; The University of Queensland; The University of Queensland c.bywater@uq.edu.au

Males of many species possess specialised weapons that are often displayed to resolve territorial disputes without direct physical contact. It is predicted that the evolution of increased weapon size should be associated with increased competition for resources and weapon strength should increase simultaneously with size (a reliable signal). In this study we tested this association by examining inter-population variation in the size and maximum strength of the enlarged claw of the two-toned fiddler crab (Uca vomeris). We also compared claw size and strength with population biomass and levels of competition. Fiddler crabs represent an ideal group for studying the evolution of weapon strength as males possess one enlarged and brightly coloured claw that is used both as a weapon during disputes with other males and to attract females during courtship. We examined 10 populations of U. vomeris in the creeks along the south-east coast of Queensland. We predicted that the increased competition that results from high population biomass would be associated with larger relative claw sizes and greater weapon performance. We estimated biomass and collected a sample of males from each population. We measured body size, claw size and maximum claw closing strength for each individual. We will discuss the variation observed in relative and absolute size of male weaponry among populations and the association with maximum strength and population biomass and level of competition.