Taxonomy, Phylogeny, and Biogeography of the Hummingbird Genus <i>Thalurania</i> GOULD, 1848 (Aves: Trochilidae)

Abstract

A taxonomic revision of the genus Thalurania was carried out based on plumage coloration and morphometric data. Variance in these data was assessed across the whole range of each species. A new methodology of plumage coloration coding for analysis was presented. This methodology enabled statistical treatment of plumage coloration as a set of parameters. Furthermore, it enabled statistical comparison between groups of localities and between subsets of taxa. Diagnosability of taxonomic entities at the level of the subspecies within each taxon was analysed. The presence of discrete groups of neighbouring localities, distinguishable through the analyses of these data, was also sought. Where subspecies appeared not to be diagnosable, or where subsets of the taxon analysed were clearly distinguishable from other such subsets, relevant taxonomic changes were proposed. The taxonomic changes amounted to: <br /> - Corroboration of a zone of intergradation between T. colombica townsendi and T. c. venusta. <br /> - Correct identification of the specimens along the Sierra de Perijá and the western shores of Lake Maracaibo as T. c. rostrifera with a consequent extension of its range <br /> - Reconsideration of the ranges of T. fannyi hypochlora and T. f. verticeps, with the discussion of the possibility of the latter being an intergradation between the former and the nominate taxon T. f. fannyi. <br /> - Classification of T. furcata jelskii, T. f. orenocensis, T. f. baeri, and T. f. simoni as invalid taxa. These were all identified as specimens pertaining to zones of intergradation between the other subspecies of T. furcata. <br /> - Invalidation of T. furcata furcatoides as a subspecies, although it is stressed that further analyses and collecting effort would be necessary to completely verify these results. <br /> - Designation and description of a new species T. sp. nov., from the Western Cordillera in Colombia (Valdés-Velásquez, submitted). <br /> Based on these new taxonomic changes, a phylogenetic analysis with plumage coloration and plumage pattern characters of male and female specimens was carried out. This analysis resulted in a perfectly resolved cladogram depicting T. glaucopis as most basal, with a sequence of differentiation from T. watertonii, T. furcata, T. fannyi, and T. colombica. It was not thought prudent to include T. ridgwayi and the new taxon T. sp. nov. in the phylogenetic analysis, due to the fact that no female data were available for them. <br /> This resulting phylogeny was used as the basis for a biogeographic and speciation-history analysis of the group. The geographical distribution was treated analogously to the phylogenetic analysis, with the areas as taxa, and the taxa within each area as characters (presence and absence as character states). Rather than shedding light on the biogeography of the areas included in the analysis (since only one clade was available), this section did result in a probable speciation scenario for the Thalurania group. <br /> This study postulates that this clade is older than assumed until now. The origins of the lineage must lie in the mid-Miocene, and the main vicariant events that promoted the speciation of the group can be found in the marine incursions of the late-Miocene throughout South America, the uplift of the Andes in the north-west, and the accretion of the Choco area and final rise of the Panama land bridge, with the subsequent attachment of Central America to the southern continent after the mid-Miocene. At the subspecies level the distribution of the different entities can best be explained through the Quaternary climatic fluctuations and the ‘refuge theory’ or through marine incursions and the ‘island theory’.