INVESTIGATING RELATEDNESS WITHIN BREEDING UNITS OF THE HIGHLY SOCIAL BUSHTIT (PSALTRIPARUS MINIMUS)

Cooperative breeding systems represent an array of varied reproductive strategies and remain a topic of interest in behavioral ecology (i.e., Riehl 2013, Cornwallis et al. 2017). Different manifestations of cooperative breeding, such as cooperative polyandry, no doubt have unique evolutionary pressures tied to local ecologies which have led to their proliferation. Of particular interest are species that show flexibility in their use of reproductive strategies, wherein individuals may choose one strategy over another given a specific circumstance. Here, I used double-digest restriction site-associated DNA sequencing (i.e., ddRAD-seq) to investigate bushtit (Psaltriparus minimus) reproductive strategies and the relatedness between interacting adults. Specifically, I investigated two questions: i) do bushtit females engage in extra-pair copulations? (EPCs), and ii) are additional conspecifics at a nest (i.e., supernumeraries) relatives or parents? Using six years of behavioral data in conjunction with five years of genetic data, I found that while bushtits are primarily monogamous, they also engage in EPCs, cooperative polyandry, and kin-directed helping. Comparisons are made to other species, but ultimately further research and understanding of species that showcase a flexible array of reproductive strategies is needed and could elucidate the evolutionary pathways leading to and from cooperation.