Assessing behavioral associations in a hybrid zone through social network analysis: complex assortative behaviors structure associations in a hybrid quail population

Behavior can strongly influence rates and patterns of hybridization between animal populations and species. Yet, few studies have examined reproductive behaviors in natural hybrid zones within the fine-scale social structure in which they take place. We use radio-frequency identification (RFID) tags with social network analyses to test whether phenotypic similarity in plumage and mass correlate with social behavior throughout a breeding season in a California and Gambel’s quail hybrid zone. We use a novel approach to partition phenotypic variation in a way that does not confound differences between sexes and species, and illustrate the complex ways that phenotype and behavior structure the social environment, mating opportunities, and male-male associations. Associations within the admixed population were random with respect to species-specific plumage, but showed strong patterns of assortment based upon sexually dimorphic plumage, monomorphic plumage, and mass. Weak
behavioral reproductive isolation in this admixed population may be the result of complex patterns of phenotypic assortment based upon multiple traits, rather than a lack of phenotypic discrimination. More generally, our results inform the utility of social network analyses for analyzing behavioral factors affecting genetic exchange between populations and species.