A Reconsideration of Songbird Phylogeny, with Emphasis on the Evolution of Titmice and their Sylvioid Relatives

Abstract

The phylogeny of oscine passerines was estimated by comparing 27 species using DNA-DNA hybridization. In the process, the finer structure of the “sylvioids” was examined (1) to assess the phylogenetic proposals of Sibley and Ahlquist (1990, Phylpgeny and classification of birds, Yale Univ. Press, New Haven, Connecticut) and (2) to develop a framework for studies of sylvioid historical ecology. Many of Sibley and Ahlquist's phylogenetic proposals were supported, including their division of the oscines into two clades: corvids and passerids. However, their division of the passerids into three clades, Muscicapoidea, Sylvioidea, and Passeroidea, was not supported; neither their Sylvioidea nor their Passeroidea is monophyletic. The improved picture of oscine phylogeny presented here permits a more rigorous historical analysis of convergence, 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 separately in the Paridae and Sittidae and is likely to be a key innovation for these groups, i.e., an adaptation responsible for their diversification. Similar cases of convergence and thus potential opportunities for ecophylogenetic study are common throughout the passerines. Unfortunately, such study is hampered by the difficulty of resolving passerine phylogeny, which is characterized by many short internodes.