Data and code from: Interspecific allometry of sexual shape dimorphism in small-bodied and large-bodied geckos

At macroevolutionary scales and across species, levels of sexual
dimorphism often covary with body size, generating allometric trends.
While such patterns are most evident for sexual size dimorphism,
interspecific trends in sexual shape dimorphism (SShD) remain
underexamined. Furthermore, how such patterns are affected by the
evolution of small body size (miniaturization) is largely unknown. In this
study, we evaluated trends in SShD across 99 gecko species from two
families to determine whether small body sizes were associated with
increased shape dimorphism in the group. Head shape was characterized
using geometric morphometrics from surface scans of nearly 600
individuals, and levels of SShD were quantified for each species.
Phylogenetic comparative analyses were then used to evaluate evolutionary
patterns of shape dimorphism relative to body size across species. We
found considerable variation in the magnitude of SShD across taxa, with
some species displaying little dimorphism and others exhibiting large
sexual shape differences. Interspecific allometry of SShD differed between
the two families, with strong negative allometry observed in
Sphaeorodactylidae (a family with many small-bodied species), while in
Phyllodactylidae (a family containing few small-bodied species) patterns
were more isometric with no discernable trend. Notably, the greater SShD
displayed by small-bodied species corresponded with females exhibiting
more robust heads, which was consistent with sex-specific foraging
strategies and dietary differences observed in this group. Our study
reveals that interspecific allometry in traits other than body size can
have a pervasive influence on patterns of phenotypic diversity across the
tree of life.