Niches and radiations: a case study on the Andean sapphire‐vented puffleg Eriocnemis luciani and coppery‐naped puffleg E. sapphiropygia (Aves, Trochilidae)

Abstract

The interaction between ecology and evolution, particularly with regard to speciation processes, remains a main topic of scientific research. Andean hummingbirds have undergone a remarkable radiation, with many species exhibiting patchy distributions and, in some cases, taxonomic controversy. An example is the sapphire‐vented puffleg Eriocnemis luciani; ssp. baptistae, luciani and meridae, which some authors merge with the coppery‐naped puffleg E. sapphiropygia; ssp. catharina and sapphiropygia. Each group is distributed either north or south from the Huancabamba Depression, the major biogeographical barrier within the tropical Andes. We investigated whether these subspecies share some niche characteristics despite their geographical separation and determined their meaning in the context of the speciation process of trochilids in the tropical Andes. For each subspecies, we performed geographical predictions and paired tests of niche conservatism in environmental space. Geographical predictions included separate regions for subspecies catharina and sapphiropygia, while the predicted regions for subspecies luciani and baptistae greatly overlapped. The E. l. luciani model predicted a single pixel near to the potential area of E. l. meridae, known only from a unique, old record. Subspecies luciani and baptistae exhibited the greatest niche overlap among the pairs of taxa for most variables. However, our results clearly indicated niche divergence for the four members of the E. luciani–sapphiropygia complex, independent of the similarities or slight dissimilarities in their respective backgrounds, indicating that other forces in addition to variation in environmental parameters, such as natural selection or genetic drift, are driving the radiation of these hummingbirds. This finding coincides with the unusually high speciation rates reported for Andean hummingbirds. Thus, the currently accepted taxonomy within the E. luciani–sapphiropygia complex may be even more convoluted than indicated by previous studies. Hence, the results of our study are a wakeup call to include the exploration of lineage diversification in biodiversity‐related efforts.