Dna-dna Hybridization Evidence for Subfamily Structure among Hummingbirds

--We used DNA-DNA hybridization to determine large-scale phylogenetic structure among hummingbirds (Trochilidae). Analyses of complete matrices of ATto and ATmoa, statistics among eight hummingbird genera and a swift generated the same fully resolved topology, which bootstrapping and jackknifing analyses supported at the 100% level. The data are consistent with monophyly for the traditional hermit (Phaethornithinae) and nonhermit (Trochilinae) subfamilies, and with placement of the hermitlike Tooth-billed Hummingbird (Androdon aequatorialis) and Green-fronted Lancebill (Doryfera ludoviciae) among trochilines. Among the trochilines examined, D. ludoviciae is more closely related to the Sparkling Violet-ear (Colibri coruscans) than to A. aequatorialis, and the Collared Inca (Coeligena torquata) is the sister group to these three. Among the hermits examined, the White-tipped Sicklebill (Eutoxeres aquila) represents the first branch, followed by the White-whiskered Hermit (Phaethornis yaruqui), and the closely related Bronzy Hermit (Glaucis aenea) and Bandtailed Barbthroat (Threnetes ruckeri). Evolutionary rate estimates from AT• trees corrected for nonadditivity indicate significant rate variation among lineages. Calibration of divergence times with the earliest-known fossil swift suggests that the diverse Andean radiation of trochilines is comprised of at least two lineages (C. torquata, D. ludoviciae/C. coruscans) whose origins date to a period of uplift during the mid-Miocene. Received 10 September 1992, accepted 17 December 1993. FAMOUS FOR THEIR characteristic adaptations to feeding at flowers, the more than 330 hummingbird species comprise one of the principal evolutionary radiations among birds. Current efforts to understand the diversification of hummingbirds are limited by lack of the historical framework necessary for the study of evolutionary pattern and process. There is little doubt that hummingbirds constitute a monophyletic group. However, current hummingbird classifications are still based largely on 19thcentury studies that relied on bill and plumage characters (Elliot 1879, Boucard 1895, Hartert 1900, Ridgway 1911, Simon 1921), which are now known to be influenced greatly by feeding and social behaviors (Feinsinger and Colwell 1978). Construction of a hummingbird phylogeny is handicapped by the paucity of fossils, and by the extensive and varied modifications to trochilid locomotor and feeding systems that obscure morphological homologies (Cohn 1968). For these reasons, biochemical methods for 3 Current address: Corporaci6n Ornito16gica del Ecuador (CECIA), P.O. Box 17-17-906 Quito, Ecuador. phylogeny construction should provide essential clues to hummingbird evolution. These techniques allow comparison across a wide taxonomic range in measures that are independent of anatomy. In this paper, we examine the largescale structure of the hummingbird radiation with DNA-DNA hybridization, a technique that provides an objective measure of overall genomic similarity. The long-standing distinction between the hermit (Phaethornithinae) and nonhermit (Trochilinae) subfamilies (Reichenbach 1854, Cabanis and Heine 1860, Gould 1861, Ridgway 1911) provides the starting point for insights into hummingbird phylogeny. As currently recognized, the approximately 30 hermit hummingbirds typically are forest dwellers with decurved bills and dull monomorphic plumage, whereas most of the about 300 nonhermits have broader ecological ranges, straight bills, and often iridescent, sexually dichromatic plumages (Stiles 1981, Collins and Paton 1989, Paton and Collins 1989, Bleiweiss 1990). Our primary objective was to test monophyly for the subfamilies. In addition, we sought to determine the subfamilial placement of the problematic genJanuary 1994] Hummingbird Phylogeny 9 TABLE 1. Summary of species and specimens used, with each individual identified by its DNA extraction number. Voucher specimens deposited as study skins or skeletons in collections of University of Wisconsin Zoological Museum or Museo Ecuatoriano de Ciencias Naturales. Glaucis aenea. Encampamento de CODESA, 21.6 road km from Pedro Vicente Maldonado, Provincia Pichincha, Ecuador (1135, 1136, 1137, 1138). Threnetes ruckeri. Centro Cientifico Rio Palenque, 56 km SW Santo Domingo de los Colorados, on Rio Babo, Provincia de Los Rios (1277, 1278); Encampamento de CODESA, 21.6 road km from Pedro Vicente Maldonado, Provincia de Pichincha (1355, 1356), Ecuador. Phaethornis yaruqui. Hacienda Santa Isabel, 2.6 km above Toache along Rio Pilat6n (1158, 1159); Encampamento de CODESA, 21.6 road km from Pedro Vicente Maldonado, Provincia de Pichincha (1351, 1352), Ecuador. Eutoxeres aquila. Encampamento de CODESA, 21.6 road km from Pedro Vicente Maldonado, Provincia de Pichincha, Ecuador (1162, 1163, 1401, 1402). Androdon aequatorialis. Encampamento de CODESA, 21.6 road km from Pedro Vicente Maldonado, Provincia de Pichincha, Ecuador (1397, 1398, 1435, 1436). Doryfera ludoviciae. Below Hacienda Santa Rosa on Rio Cinto, Provincia de Pichincha, Ecuador (1353, 1354, 1437, 1438). Colibri coruscans. Tumbaco, Provincia de Pichincha, Ecuador (1357, 1358, 1403, 1404). Coeligena torquata. Below Hacienda Santa Rosa on Rio Cinto, Provincia de Pichincha, Ecuador (1279, 1280, 1399, 1400). Chaetura pelaœica. Town of McFarland, Dane County, Wisconsin (1049, 1050, 1148, 1441). era Androdon and Doryfera; their superficial resemblance to hermits has led some to place them within that assemblage (Peters 1945, Meyer de Schauensee 1966), whereas others have placed one or both of these genera among nonhermits (Ridgway 1911, Wetmore 1968, Zusi and Bentz 1982, Stiles and Skutch 1989).