Data from: Sexual size dimorphism as a determinant of fighting performance dimorphism in Anolis lizards

Rensch’s Rule describes a pattern of interspecific allometry in which
sexual size dimorphism (SSD) increases with size among closely related
species (i.e., among a group of related species, the largest ones tend to
show more male-biased SSD). Sexual selection is often invoked to explain
Rensch’s Rule, as larger male sizes are assumed to be favoured by sexual
selection due to increased competitive ability they confer. Often the
correlation between size and the trait under sexual selection is not well
described. For example, a link between size and male fighting performance
is often assumed, but rarely measured in studies of Rensch’s Rule. We
studied a sexually selected performance trait, bite force in Anolis
lizards, to determine whether patterns of SSD are linked to the allometry
of performance dimorphism at the macroevolutionary level. Additionally, we
tested whether allometric patterns of performance dimorphism differ
between mainland and island species, as the latter have likely evolved
under a stronger sexual selection regime. We found that SSD overwhelmingly
explains the relationship between performance dimorphism and size in
anoles, as expected under a sexual selection model for Rensch's Rule.
However, the average value of performance dimorphism was higher in island
than in mainland species, suggesting that these groups differ in
performance dimorphism for reasons unrelated to size. Head size dimorphism
was associated with residual performance dimorphism across all anoles, but
did not fully explain the difference in performance dimorphism between
island and mainland species. Together, these findings highlight the need
to interpret Rensch’s Rule patterns of body size evolution cautiously, as
allometric patterns of performance dimorphism and size dimorphism might
not be equivalent.