Abstract

Climate changes during the late Pleistocene influenced the demography and distribution of species in Patagonia. During the last glacial maximum (LGM), ice sheets covered a great extent of the temperate rainforest in the western Patagonian Andes. The persistence of forest species in refugia during the LGM has been debated for many vertebrates, but rarely for birds. The Green-backed Firecrown (Sephanoides sephaniodes) is an important avian pollinator distributed from the south of the Atacama Desert (28 degrees S) to Tierra del Fuego (54 degrees S) in South America. We evaluated the species' evolutionary history, combining molecular data and models for past and current species distribution. Our results show two distinct haplogroups: the genetically diverse North-South clade (NS) restricted to the Mediterranean and coastal temperate regions that exhibits a signature of population expansion after LGM, and the Austral-East clade (AE) confined to the temperate intermountain range, eastern temperate, and sub-Antarctic regions, with lower genetic diversity and evidence of a more recent population expansion. This AE clade and the past distribution models support the species survival in valleys and lowlands south of the ice sheets limit during LGM until the present. A secondary contact zone was observed with haplotypes from the AE clade distributed in low frequency along with the northern areas. Our results support the paleorefugia hypothesis during the LGM with postglacial secondary contact.