Differences in the geographic patterns of genitalic and nongenitalic morphological characters in Podisma sapporensis (Podisminae) were examined using the hierarchical testing procedure in common principal component analysis. This analysis was used to evaluate the extent to which the covariance structure among characters varies geographically in both sexes. Males exhibited consistency in the covariance structure among populations both in genitalic and nongenitalic characters, whereas the covariance structures of female genitalic and nongenitalic characters were not stable geographically. We suggest that the conspicuous sexual difference in covariance structure results from different selective pressures acting on genitalia: stabilizing selection is responsible for the stability of male genitalia, whereas variability in female is the result of directional sexual selection varying among populations.
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Vol. 93 • No. 1