A phylogenetic analysis of the Accipitridae (class Aves).
The avian family Accipitridae is a large, diverse family composed of approximately 230 species divided into 56 genera. The evolutionary relationships among Acciptrid taxa have been examined previously using phenetic and parsimony approaches and a variety of data sets. These studies have resulted in conflicting phylogenies, presumably due to the high level of homoplasy, perhaps, the result of convergence on diet. To develop a firm understanding of the relationships among the major species groups (i.e., morphological types) an analysis of DNA sequence data from the mitochondrial encoded cytochrome-b gene was undertaken. Parsimony, distance and maximum likelihood methods were used to explore the phylogenetic relationships among the Accipitridae. Major findings of the molecular study includes support for the polyphyly of the Kite genera and the sister group relationship of the Osprey (Pandion) with Acciptrid taxa. Evidence based on branch length analysis suggest one or two of periods of rapid morphological diversification. Osteological characters from 44 genera were analyzed alone, and in concert with molecular data. These data yielded phylogenetic trees that were very similar to those trees produced solely by the molecular data. Statistical support for the osteological tree, as demonstrated by bootstrap values, was very weak; supporting, only partially, the clade of old world vultures (Aegypiinae). The phylogenetic signal contained in the osteological data set was estimated using the g1 statistic determined from random tree length distributions. G1 values were found to be dependent on the frequency distribution of character states. Analysis of the g1 statistic from native and shuffled data sets was found to be a less biased method of examining a data set for phylogenetic signal. Divergence times estimated from branch lengths suggest that the Accipitridae diverged from other diurnal raptors approximately 75 million years ago. Clades representing the major morphological diversity among the Accipitridae diverged about 40 million years ago over a period of approximately 7 million years.
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