Sex-biased herbivory: a meta-analysis of the effects of gender on plant-herbivore interactions

We used sets of meta-analyses to review the evidence of sex-biased herbivory in dioecious plants as well as intersexual differences in plant characteristics that might affect herbivores. Thirtythree studies were reviewed to assess the effects of plant sex on herbivore abundance, survivorship and damage imposed to host plants, whereas 54 studies were reviewed for the effects of plant sex on plant morphological, physiological, and nutritional characteristics. The standardized mean difference between males and females was chosen as the measure to calculate effect sizes. Male plants exhibited significantly higher numbers of herbivores (d + + =1.074) and significantly higher herbivory measured in terms of plant damage (d + + =0.577) compared to female plants. Effects of plant sex on herbivore abundance were stronger for folivores and gallformers compared to the other guilds, whereas effects of plant sex on herbivore damage were stronger for flower predators compared to browsers and folivores. No difference in herbivore survivorship was observed between sexes. Male plants exhibited significantly more leaves (d + + =0.202), larger leaves (d + + =0.91), fewer flowers (d + + =-0.89) and longer stems (d + + =0.614) than female plants. Although male plants exhibited significantly lower concentrations of secondary compounds (d + + =-0.209) and other defenses (d + + =-0.53) than female plants, no difference in nutrient concentration, such as foliar nitrogen, was observed between sexes.