Exploring the contact zones between Ecuadorian Hillstar (Oreotrochilus chimborazo) subspecies

We investigated the contact zones between subspecies of the Ecuadorian Hillstar (Oreotrochilus chimborazo). This species occupies both Andean cordilleras, from the southern tip of Colombia to the paramos of south Ecuador. The subspecies O. c. jamesonii inhabits all the paramos in this range, except for those of the Chimborazo volcano, where it is replaced by O. c. chimborazo. Genetic analyses suggest that these subspecies may be in contact north and south of the Chimborazo volcano. Since contact north of the Chimborazo volcano has been documented, our main goal was to verify the presence of a contact zone south of the Chimborazo volcano. Between July 2021 and July 2022, we visited 29 localities within the range of this species north and south of the Chimborazo volcano, in the central-east Andes of Ecuador, and explored previous data to revise the geographic distribution of the species. We found that subspecies O. c. chimborazo and O. c. jamesonii are syntopic at a site located 65 km south of Chimborazo volcano. Along the central-eastern Andes, we only found O. c. jamesonii. We also recorded O. c. chimborazo between the Chimborazo and Quilotoa volcanoes and found no evidence of males with intermediate plumages. The available data suggest that the contact zone between these subspecies spans a north-to-south band of approximately 130 km of the western Andes of Ecuador. However, at the center of that stretch at the Chimborazo plateau, only O. c. chimborazo has been found. We confirmed the coexistence of Ecuadorian Hillstar subspecies in at least 1 locality south of the Chimborazo volcano. Whether this coexistence implies contemporary gene flow between both subspecies should be addressed in future studies.