Data to accompany 'New evidence suggests no sex bias in herbivory or plant defence'

Dioecious plants can exhibit sexual dimorphism across a
suite of plant traits, including susceptibility to herbivory and secondary
chemistry. One hypothesis is that, due to greater costs of
reproduction in females, males should grow faster and invest less in
defense, resulting in male-biased herbivory. Indeed, a series of papers
and a prominent meta-analysis have established male-biased herbivory as a
robust result. However, more recent reviews have raised questions about
how general the pattern is, citing the low breadth of taxon
sampling. The literature on this topic has not been formally quantified by
meta-analysis in over 15 years. Here we report the results of a
meta-analysis of studies that measured sex bias in either herbivory and/or
secondary defense in 71 dioecious plant species. We
added 58 observations of herbivory and 41 of secondary
chemistry to the original. We control for non-independence of effects from
the same study and taxonomic group to address critiques of earlier
studies. For secondary chemistry, we found no support for any consistent
difference between male and female plants. For herbivory, results
are directionally similar to earlier reports, although not statistically
significant once we accounted for taxonomic group and study. We also
found that the magnitude and direction of the effect of plant
sex on herbivory declines, with earlier studies reporting a
stronger male-bias. We discuss our results in light of the ‘decline
effect’ and consider whether the datasets exhibit signs of evidence of the
type(s) of biases that can result in declining effect sizes over time.