Data from: Are weapon allometries steeper in major or minor males? A meta-analysis

Competition for mates can drive the evolution of exaggerated weaponry and
male dimorphism associated with alternative reproductive tactics. In
terrestrial arthropods, male dimorphism is often detected as non-linear
allometries, where the scaling relationship between weapon size and body
size differs in intercept and/or slope between morphs. Understanding the
patterns of non-linear allometries is important as it can provide insights
into threshold evolution and the strength of selection experienced by each
morph. Numerous studies in male-dimorphic arthropods have reported that
allometric slopes of weapons are shallower in large “major” males compared
to small “minor” males. Because this pattern is common among beetles that
undergo complete metamorphosis (holometabolous), researchers have
hypothesized that the slope change reflects resource depletion during
pupal development. However, no comprehensive survey has examined the
generality of this trend. We systematically searched the literature for
reports of weapon allometries in male dimorphic species and conducted a
phylogenetically controlled meta-analysis to explore the factors
influencing the difference in slopes between morphs. Our search identified
59 effect sizes from 19 studies, 50 species, and 5 orders of terrestrial
arthropods. We found strong evidence that metamorphosis type influences
the patterns of weapon allometries. Slopes were significantly steeper in
minor males compared to major males in holometabolous species, but there
was no difference in slopes between morphs in hemimetabolous species
(i.e., those that undergo incomplete or no metamorphosis). These results
support the hypothesis that holometabolous species face a resource ceiling
during pupal development that limits the exaggeration of weapon size.