Phylogeography, morphology and ecological niche modelling to explore the evolutionary history of Azure-crowned Hummingbird (Amazilia cyanocephala, Trochilidae) in Mesoamerica

Abstract

The Pleistocene climate cycles and mountain uplift both affected the diversification of taxa in Mesoamerica. Yet, phylogeographic breaks and demographic responses of co-distributed taxa are not congruent. Investigation of more species with widespread distributions across Mexico and Central America will help shed light on how Earth historical events shaped biodiversity in this region. The Azure-crowned Hummingbird (Amazilia cyanocephala) is widely distributed from eastern Mexico into Central America and has been divided into three subspecies by morphology and geographic isolation. To investigate the evolutionary history of the species, we sequenced a non-coding mtDNA fragment along with a nuclear marker across its distribution, and analysed morphological and ecological variation and distributional projections derived from ecological niche modelling. Overall, mtDNA supported genetic differentiation among A. cyanocephala populations, which generally supports the existence of four lineages: two A. c. cyanocephala lineages separated by the Isthmus of Tehuantepec (east and west), A. c. guatemalensis populations separated by the Motagua-Polochic-Jocotan fault system, and the isolated A. c. chlorostephana in Honduras and Nicaragua. However, morphological data were not consistent with this phylogeographic result. The potential distribution of suitable habitat for A. cyanocephala was expanded during the Last Glacial Maximum and more contracted and fragmented during the Last Inter-Glacial and the Present. These models are consistent with a preglacial demographic expansion in A. c. cyanocephala. Mitochondrial genetic diversity and current precipitation seasonality were negatively correlated when analysing all populations. We suggest that isolation and habitat differences have both played a role in the recent diversification of A. cyanocephala. Inferences about the demographic consequences of isolation and subspecies recognition await further study.