Rapid Life History Evolution in Feral Chickens (Gallus gallus) Involves both Ancestral and Artificially-Selected Traits

Animals that escape captivity experience powerful changes in selection regimes, but their evolutionary responses have not been well studied. We used genome scans and phenotypic data to assess how ancestral and/or artificially-selected traits have contributed to the success of Kauai Island’s feral, hybrid Gallus gallus (Red Junglefowl x domestic chickens). We found: 1) evidence of recent input to the gene pool from diverse domestic lineages, including “layer” breeds developed for enhanced, year-round egg production, 2) an accompanying shift from seasonal to year-round breeding, which likely abetted recent, exponential population growth, and 3) a selective sweep that favored the ancestral (Red Junglefowl) variant at a locus controlling broodiness, a maternal care behavior that was attenuated by domestication. Together, these results suggest that both ancestral and artificially-selected gene variants controlling reproductive traits (e.g. fecundity and maternal care) can be advantageous during feralization.