Sex differences in the genetic architecture of aggressiveness in a sexually dimorphic spider

Sex differences in the genetic architecture of behavioral traits can offer critical insight into the processes of sex‐specific selection and sexual conflict dynamics. Here, we assess genetic variances and cross‐sex genetic correlations of two personality traits, aggression and activity, in a sexually size‐dimorphic spider, Nuctenea umbratica. Using a quantitative genetic approach, we show that both traits are heritable. Males have higher heritability estimates for aggressiveness compared to females, whereas the coefficient of additive genetic variation and evolvability did not differ between the sexes. Furthermore, we found sex differences in the coefficient of residual variance in aggressiveness with females exhibiting higher estimates. In contrast, the quantitative genetic estimates for activity suggest no significant differentiation between males and females. We interpret these results with caution as the estimates of additive genetic variances may be inflated by nonadditive genetic effects. The mean cross‐sex genetic correlations for aggression and activity were 0.5 and 0.6, respectively. Nonetheless, credible intervals of both estimates were broad, implying high uncertainty for these estimates. Future work using larger sample sizes would be needed to draw firmer conclusions on how sexual selection shapes sex differences in the genetic architecture of behavioral traits. We test for differences between the sexes in genetic variances and examine the cross‐sex genetic correlations, of two important personality traits, aggression and activity in novel environments, in a sexually size dimorphic spider with distinct variation between male and female life history strategies. The present study contributes to expanding our knowledge on the genetic bases of behavioural traits by providing quantitative genetic estimates in aggressiveness and activity in the orb‐weaving spider N. umbratica. Our findings further suggest sex differences in the heritability and coefficient of residual variance in aggressiveness, but future work to test cross‐sex genetic correlations in behavioural traits using a larger sample size would be needed to draw firmer conclusions regarding these correlations.