Genetic and morphological basis of variation in pup vocalization behavior in deer mice
Authors: Maya Woolfolk; Nicholas Jourjine; Sade McFadden; John Emory Sabatini; Hopi Hoekstra
Affiliation: Department of Molecular & Cellular Biology, Department of Organismic & Evolutionary Biology, Museum of Comparative Zoology, Howard Hughes Medical Institute, Harvard University, Cambridge, MA
Keywords: Complex traits
Infant vocalization is a behavior critical for eliciting care from parents across vertebrates; in many mammals, vocalizations also serve to establish social bonds between parents and offspring. Deer mice (genus Peromyscus) are a group of closely related but behaviorally diverse rodents that offer an opportunity to study natural variation in pup vocal behavior. We first designed and optimized a protocol to record pup vocalizations following isolation from their parents and analyzed these recordings using recently developed machine-learning tools for computational bioacoustics. We identified significant interspecific differences in temporal and acoustic features of pup cries, several of which evolved repeatedly between species. Next, by cross-fostering pups between species with different vocal behaviors, we found that these vocal differences are not significantly influenced by the postnatal environment, suggesting instead they likely have a strong genetic component. By measuring pup vocalizations in F1 hybrids, we found that some spectral and temporal features of vocalizations exhibit different patterns of dominance. To further investigate the genetic basis of this behavioral variation, we performed quantitative trait locus (QTL) mapping with 576 F2 individuals generated by intercrossing two sister species: P. maniculatus and P. polionotus. We first found that some acoustic features (e.g., pitch) and vocalization rate are uncoupled, suggesting that they are under separate genetic control. Indeed, we identified several loci significantly associated with species-specific differences in pup vocal behavior. In conjunction with this genetic approach, we also targeted the mechanistic basis of vocal variation by performing histological and morphometric analyses of the primary vocal organ, the larynx, which suggests there are potential contributions of laryngeal morphology to variation in acoustic features such as pitch. In this system, we are uncovering mechanisms underlying natural variation in pup vocal behavior to identify genetic and morphological bases of behavioral evolution.