Data from: Brain size evolution in pipefishes and seahorses: the role of feeding ecology, life history and sexual selection

Brain size varies greatly at all taxonomic levels. Feeding ecology, life
history and sexual selection have been proposed as key components in
generating contemporary diversity in brain size across vertebrates.
Analyses of brain size evolution have, however, been limited to lineages
where males predominantly compete for mating and females choose mates.
Here, we present the first original data set of brain sizes in pipefishes
and seahorses (Syngnathidae) a group in which intense female mating
competition occurs in many species. After controlling for the effect of
shared ancestry and overall body size, brain size was positively
correlated with relative snout length. Moreover, we found that females, on
average, had 4.3% heavier brains than males and that polyandrous species
demonstrated more pronounced (11.7%) female-biased brain size dimorphism.
Our results suggest that adaptations for feeding on mobile prey items and
sexual selection in females are important factors in brain size evolution
of pipefishes and seahorses. Most importantly, our study supports the idea
that sexual selection plays a major role in brain size evolution,
regardless of on which sex sexual selection acts stronger.