Data from: A trade-off between reproductive investment and maternal cerebellum size in a precocial bird

Natural selection favours increased investment in reproduction, yet
considerable variation in parental investment is observed in natural
populations. Life-history theory predicts that this variation is
maintained by a trade-off between the benefits of increased reproductive
investment and its associated costs for the parents. The nature of these
costs of reproduction, however, remains poorly understood. The brain is an
energetically highly expensive organ and increased reproductive investment
may, therefore, negatively affect brain maintenance. Using artificial
selection lines for high and low prenatal maternal investment in a
precocial bird, the Japanese quail (Coturnix japonica), we provide
experimental evidence for this hypothesis by showing that increased
prenatal provisioning negatively affects the size of a particular brain
region of the mother, the cerebellum. Our finding suggests that cognitive
demands may constrain the evolution of parental investment, and vice
versa, contributing to the maintenance of variation in reproductive
behaviour in animal populations.