Lewarch, C. L. | bioRxiv Science

bioRxiv2023

Evolution of gene expression across brain regions in behaviorally divergent deer mice

The evolution of innate behaviors is ultimately due to genetic variation likely acting in the nervous system. Gene regulation may be particularly important because it can evolve in a modular brain-region specific fashion through the concerted action of cis- and trans-regulatory changes. Here, to investigate transcriptional variation and its regulatory basis across the brain, we perform RNA sequencing (RNA-Seq) on ten brain subregions in two sister species of deer mice (Peromyscus maniculatus and P. polionotus) - which differ in a range of innate behaviors, including their social system - and their F1 hybrids. We find that most of the variation in gene expression distinguishes subregions, followed by species. Interspecific differential expression (DE) is pervasive (52-59% of expressed genes), whereas the number of DE genes between sexes is modest overall ([~]3%). Interestingly, the identity of DE genes varies considerably across brain regions. Much of this modularity is due to cis-regulatory divergence, and while 43% of genes were consistently assigned to the same gene regulatory class across subregions (e.g., conserved, cis-, or trans-regulatory divergence), a similar number were assigned to two or more different gene regulatory classes. Together, these results highlight the modularity of gene expression differences and divergence in the brain, which may be key to explain how the evolution of brain gene expression can contribute to the astonishing diversity of animal behaviors.

evolutionary biology↗

bioRxiv2017

The evolution of thermoregulatory nesting behaviour in Peromyscus mice

Structures built by animals, such as nests, often can be considered extended phenotypes that facilitate the study of animal behaviour. For rodents, nest building is both an important form of behavioural thermoregulation and a critical component of parental care. Changes in nest structure or the prioritization of nesting behaviour are therefore likely to have consequences for survival and reproduction, and both biotic and abiotic environmental factors are likely to influence the adaptive value of such differences. Here we first develop a novel assay to investigate interspecific variation in the nesting behaviour of deer mice (genus Peromyscus). Using this assay, we find that, while there is some variation in the complexity of the nests built by Peromyscus mice, differences in the latency to begin nest construction are more striking. Four of the seven taxa examined here build nests within an hour of being given nesting material, but this latency to nest is not related to ultimate differences in nest structure, suggesting that the ability to nest is relatively conserved within the genus, but species differ in their prioritization of nesting behaviour. We also find that latency to nest is not correlated with body size, climate, or the construction of burrows that create microclimates. However, the four taxa with short nesting latencies all have monogamous mating systems, suggesting that differences in nesting latency may be related to social environment. This detailed characterization of nesting behaviour within the genus provides an important foundation for future studies of the genetic and neurobiological mechanisms that contribute to the evolution of behaviour.

animal behavior and cognition↗