Equal reproductive success of phenotypes in the Larus glaucescens–occidentalis complex

摘要: Glaucous-winged gulls Larus glaucescens and western L. occidentalis hybridize extensively where their ranges overlap along the coasts of Washington Oregon, producing a continuum phenotypic intergrades between two parental species. Th is zone often considered an example geographically bounded hybrid superiority, but studies relative success among types hybrids have not provided consistent support for this model. We tested predictions dynamic-equilibrium superiority hypotheses by studying mate choice reproductive on Protection Island, Washington, largest breeding colony glaucous-winged/western within zone. e hypothesis posits that hybridization due to dispersal balances selection against less fi t assortative mating adaptive. Geographically are better than ecotone environments which species adapted, preference mates Additionally, we investigated whether hatching nest site correlated Island gulls. assigned index each sample bird examining plumage melanism bare part coloration in eld. Sheltered nests contained larger clutches exhibited increased success, habitat was associated with index. Western gull-like pairs produced smaller third eggs; however, clutch size or success. did exhibit mating. In short, nd strong either hypothesis. – Pacifi c Northwest has been subject several since were rst noted early twentieth century (Dawson