Meeting Abstract
Uca pugnax is the most abundant fiddler crab species along the east coast of North America. Because it has such a broad range, it experiences large differences in climate and community composition between populations. Thus the species has the potential to show clinal variation. Fiddler crabs are sexually dimorphic with the males having one enlarged claw used both as an ornament to attract females and a weapon in combat with other males. We sampled five populations periodically for a full year from Massachusetts to Georgia and took measurements of the body and claw, and dissected out the hepatopancreas, a fat storage organ. We also measured population density, operational sex ratio (OSR), food availability, and large claw morphology for the final set of collections. There were significant differences in both average body and claw size among the sites. Northern males were smaller than southern males but showed larger claws for their body size. Analysis of claw weight versus claw length revealed that southern populations had lighter claws for their length than northern populations. This indicates that there is a higher incidence of cheating with claws that are impressive ornaments but not effective weapons, in the south. Clinal variation in sexually selected characters has been sparsely explored and has not previously been documented in a character that is both an ornament and a weapon.
