Data from: No gains for bigger brains: functional and neuroanatomical consequences of relative brain size in a parasitic wasp

Heritable genetic variation in relative brain size can underlie the
relationship between brain performance and the relative size of the brain.
We used bidirectional artificial selection to study the consequences of
genetic variation in relative brain size on brain morphology, cognition
and longevity in Nasonia vitripennis parasitoid wasps. Our results show a
robust change in relative brain size after 26 generations of selection and
6 generations of relaxation. Total average neuropil volume of the brain
was 16% larger in wasps selected for relatively large brains than in wasps
selected for relatively small brains, whereas the body length of the
large-brained wasps was smaller. Furthermore, the relative volume of the
antennal lobes was larger in wasps with relatively large brains. Relative
brain size did not influence olfactory memory retention, whereas wasps
that were selected for larger relative brain size had a shorter longevity,
which was even further reduced after a learning experience. These effects
of genetic variation on neuropil composition and memory retention are
different from previously described effects of phenotypic plasticity in
absolute brain size. In conclusion, having relatively large brains may be
costly for N. vitripennis, whereas no cognitive benefits were recorded.