Genetic and morphometric divergence in the Garnet-Throated Hummingbird (Aves: Trochilidae).

Cloud forests are one of the most endangered ecosystems in the Americas, as well as one of the richest in biological diversity in the world. The species inhabiting these forests are susceptible to environmental changes and characterized by high levels of geographic structure. The Garnet-Throated Hummingbird, mainly inhabits cloud forests, but can also be found in other habitats. This species has a highly restricted distribution in Mesoamerica, and five disjunct regions have been delimited within the current geographic distribution of the species from Mexico to Honduras. According to variation in size and color, three subspecies have been described: restricted to the Mexican highlands and Guatemala, distributed in Guerrero (Mexico), and , distributed in the highlands from Honduras and El Salvador. We analyzed the levels of geographic structure in and its taxonomic implications. We used mitochondrial and nuclear DNA to analyze genetic variation, demographic history, divergence times, reconstructed a multilocus phylogeny, and performed a species delimitation analyses. We also evaluated morphological variation in 208 specimens. We found high levels of genetic differentiation in three groups, and significant variation in morphological traits corresponding with the disjunct geographic populations. presents population stability with the highest genetic variation explained by differences between populations. Divergence time estimates suggest that split from its sister group around 10.55 million years ago, and the diversification of the complex was dated ca. 0.207 Mya. The hypotheses tested in the species delimitation analyses validated three independent lineages corresponding to three disjunct populations. This study provides evidence of genetic and/or morphometric differentiation between populations in the complex where four separate evolutionary lineages are supported: (1) populations from the Sierra Madre Oriental and the highlands of Oaxaca (), (2) populations from the highlands of Guerrero (), (3) populations from the highlands of Chiapas and Guatemala (this is a non-previously proposed potential taxon: ), and (4) populations from the highlands of Honduras and El Salvador (). The main promoters of the geographic structure found in the complex are likely the Isthmus of Tehuantepec as a geographic barrier, isolation by distance resulting from habitat fragmentation, and climatic conditions during the Pleistocene.