Peromyscus is a diverse North American genus of mouse, with habitats ranging from arid deserts to mountainous cloud forests. Along with these tremendously disparate habitats come comparably variable behaviors. For example, sharing of parental care and social monogamy are rare traits in mammals, but they have evolved at least twice in Peromyscus. Oldfield mice (Peromyscus polionotus), for example, live in sandy habitats at low population densities, and seem to have adapted to their sparse environments by forming pair bonds, with both sexes providing ample parental care. In contrast, the deer mouse (Peromyscus maniculatus) is tremendously widespread and has a promiscuous mating system similar to that found in many other rodents. Deer mice provide less parental care than do oldfield mice, with this difference being particularly pronounced in fathers.
Here, then, is an interesting opportunity for behavioral psychology studies. Despite their differences, these closely related species can be crossed to produce fertile offspring –– making them excellent subjects for exploring the genetic basis of behavioral variation. Authors [attached article] crossed the two species for two generations, producing hundreds of grandchildren (F2 generation) that of course varied, with regard to the genomic segments they inherited from each species.
Using quantitative genetics, authors proceeded to identify 12 genomic regions that affect parental care –– eight of which have sex-specific effects, suggesting that parental care can evolve independently in males and females. Furthermore, some DNA regions affect parental care broadly, whereas others affect specific behaviours, such as nest building. Of the genes linked to differences in nest-building behavior, vasopressin is differentially expressed in hypothalamus of the two species, with increased levels associated with less nest building. Using pharmacology in Peromyscus and chemogenetics in the Mus genus of mouse, authors cleverly demonstrated that vasopressin inhibits nest building but not other parental behaviours. These data indicate that variation in an ancient neuropeptide contributes to interspecific differences in parental care.
This work represents an exciting breakthrough in behavioral psychology: these experiments prove that species differences in a complex behavior can be traced back to differences in specific genes and circuits. This work therefore serves as a harbinger of exciting science to come. As non-model organisms become increasingly amenable to genetic and neuronal analysis –– researchers can begin to explore how brain and behavioural variation emerge from the complex interaction of an individual’s genomic architecture and the environment.
Nature 27 Apr 2o17; 544: 434–439 and News’N’Views ed, pp 418–419