Meeting Abstract

112.4  Monday, Jan. 7  Sexual dimorphism of Hemidactylus frenatus along a latitudinal cline: testing Rench’s rule in an ectotherm with intense male-male competition in lower latitudes CAMERON, S.F.*; WILSON, R.S.; Uni of QLD, Australia; Uni of QLD, Australia s.cameron3@uq.edu.au

Rench’s rule predicts that animal populations with greater average body sizes should exhibit higher magnitudes of sexual dimorphism. As higher latitudes are commonly associated with greater average body sizes, a latitudinal cline in sexual dimorphism is also expected to follow suit. However, given sexual dimorphism is driven by gender differences in reproductive fitness, any increases in male-male competition in lower latitude populations could counteract Rench’s rule. To investigate this idea it is necessary to examine a species with intense male-male competition and quantify inter-sexual differences in both morphological and whole-animal performance traits. We used Hemidactylus frenatus as they are found along a large latitudinal range across Australia and are likely to experience intense male-male competition in lower latitudes due to a warmer climate and higher densities. We predicted the magnitude of sexual dimorphism would be stabilized along their latitudinal range due to the interacting effects of Rench’s rule at higher latitudes and increasing male-male competition in lower latitudes. We found greater average body sizes for populations from higher latitudes, however no evidence for Rench’s rule as there was no associated increase in sexual dimorphism with latitude. In contrast, whole-animal performance exhibited a negative correlation with latitude, where individuals from populations from lower latitudes had greater relative biting performances than those from higher latitudes, although no latitudinal variation in inter-sexual differences in performance was found.