Data from: Feeding specialisation and longer generation time are associated with relatively larger brains in bees

Despite their miniature brains, insects exhibit substantial variation in
brain size. Although the functional significance of this variation is
increasingly recognized, research on whether differences in insect brain
sizes are mainly the result of constraints or selective pressures has
hardly been performed. Here, we address this gap by combining prospective
and retrospective phylogenetic-based analyses of brain size for a major
insect group, bees (superfamily Apoidea). Using a brain dataset of 93
species from North America and Europe, we found that body size was the
single best predictor of brain size in bees. However, the analyses also
revealed that substantial variation in brain size remained even when
adjusting for body size. We consequently asked whether such variation in
relative brain size might be explained by adaptive hypotheses. We found
that ecologically specialized species with single generations have larger
brains —relative to their body size— than generalist or multi-generation
species, but we did not find an effect of sociality on relative brain
size. Phylogenetic reconstruction further supported the existence of
different adaptive optima for relative brain size in lineages differing in
feeding specialisation and reproductive strategy. Our findings shed new
light on the evolution of the insect brain, highlighting the importance of
ecological pressures over social factors and suggesting that these
pressures are different from those previously found to influence brain
evolution in other taxa.