The Relationships of the Wrentit as Indicated by DNA-DNA Hybridization

-The relationships of the Wrentit (Chamaea fasciata) have been debated since its discovery in 1845. The titmice (Parus), babblers (Timaliini), Old World warblers (Sylviini), bushtits (Psaltriparus), wrens (Troglodytidae), and mockingbirds (Mimini) have been suggested as its closest relatives. Many authors have placed the Wrentit in a monotypic family, Chamaeidae. DNA-DNA hybridization comparisons between the homologous nucleotide sequences of the single-copy DNAs of the Wrentit and other passerines indicate that Chamaea is most closely related to the babblers and the Old World warblers, and that the latter two groups are ecotypes of a single, varied, monophyletic assemblage. The Wrentit is annroximatelv eauidistant from the sylviines and the timaliines, but ecologically it is a babbler. _ The Wrentit (Chamaea fasciata) occurs in chaparral and other dense, brushy, plant formations in western Oregon, California, and northwestern Baja California. The question of its affinities to other passerines has been debated since the 1850’s. Sibley (1970:57-60) reviewed the taxonomic history of the Wrentit and presented electrophoretic comparisons between its egg white proteins and those of many other oscine taxa. He concluded that the total evidence did not offer a clear choice between the sylviine warblers and the timaliine babblers as the closest relatives of Chamaea and that the question of the “relationships of the wren-tit remains open and further evidence should be presented before the affinities of the wren-tit are considered to have been proved beyond doubt” (p. 60). More recently, Sibley and Ahlquist (1980) concluded that Chamaea is a babbler. In the present paper we offer additional data showing that the sylviine warblers and timaliine babblers are actually ecotypes of a single varied assemblage and that the Wrentit probably was derived from an