Sexual differences in the pattern of spatial variation in the brachypterous grasshopper Podisma sapporensis (Orthoptera: Podisminae)

Abstract

We examined sexual dimorphism and its geographical pattern in 10 morphological characters, including the genitalia, in the brachypterous grasshopper Podisma sapporensis. Conspicuous sexual dimorphism was observed in all characters. In nine characters, variance in females was significantly greater than in males. Sexual differences among populations varied more in the genitalia than in other characters. Spatial autocorrelation analysis demonstrated that there was no geographical trend in the female genitalia, whereas significant autocorrelation existed in the male genitalia. These results suggest that cryptic female choice is responsible for the autocorrelation pattern of the male genitalia, while random genetic drift or a larger effect of environment has created the geographical pattern of the female genitalia.