A RECONSIDERATION OF SONGBIRD PHYLOGENY, WITH EMPHASIS ON THE EVOLUTION OF TITMICE AND THEIR SYLVIOID RELATIVES

The phylogeny of oscine passerines was estimated by comparing 27 speci es using DNA-DNA hybridization. In the process, the finer structure of the ''sylvioids'' was examined (1) to assess the phylogenetic proposa ls of Sibley and Ahlquist (1990, Phylogeny and classification of birds , Yale Univ. Press, New Haven, Connecticut) and (2) to develop a frame work for studies of sylvioid historical ecology. Many of Sibley and Ah lquist's phylogenetic proposals were supported, including their divisi on of the oscines into two clades: corvids and passerids. However, the ir division of the passerids into three clades, Muscicapoidea, Sylvioi dea, and Passeroidea, was not supported; neither their Sylvioidea nor their Passeroidea is monophyletic. The improved picture of oscine phyl ogeny presented here permits a more rigorous historical analysis of co nvergence, adaptation, phylogenetic constraint, and other evolutionary phenomena. For example, the sister group of the seed-caching Paridae is the Remizidae (including the verdin, Auriparus), not the nuthatches (Sittidae), which also cache seeds. Thus, seed caching arose separate ly in the Paridae and Sittidae and is likely to be a key innovation fo r these groups, i.e., an adaptation responsible for their diversificat ion. Similar cases of convergence and thus potential opportunities for eco-phylogenetic study are common throughout the passerines. Unfortun ately, such study is hampered by the difficulty of resolving passerine phylogeny, which is characterized by many short internodes.