Data from: The causal relationship between sexual selection and sexual size dimorphism in marine gastropods

Sexual size dimorphism is widespread among dioecious species but its
underlying driving forces are often complex. A review of sexual size
dimorphism in marine gastropods revealed two common patterns: firstly,
sexual size dimorphism, with females being larger than males, and secondly
females being larger than males in mating pairs; both of which suggest
sexual selection as being causally related with sexual size dimorphism. To
test this hypothesis, we initially investigated mechanisms driving sexual
selection on size in three congeneric marine gastropods with different
degrees of sexual size dimorphism, and, secondly, the correlation between
male/female sexual selection and sexual size dimorphism across several
marine gastropod species. Male mate choice via mucus trail following (as
evidence of sexual selection) was found during the mating process in all
three congeneric species, despite the fact that not all species showed
sexual size dimorphism. There was also a significant and strong negative
correlation between female sexual selection and sexual size dimorphism
across 16 cases from seven marine gastropod species. These results suggest
that sexual selection does not drive sexual size dimorphism. There was,
however, evidence of males utilizing a similar mechanism to choose mates
(i.e. selecting a female slightly larger than own size) which may be
widespread among gastropods, and in tandem with present variability in
sexual size dimorphism among species, provide a plausible explanation of
the observed mating patterns in marine gastropods.