Phylogenetic relationships of African sunbird-like warblers: Moho (Hypergerus atriceps), Green Hylia (Hylia prasina) and Tit-hylia (Pholidornis rushiae)

Abstract

Pholidornis, Hylia and Hypergerus are monotypic songbird genera that share insectivorous feeding habits and a common habitat in West African forests. Each of these genera has some sunbird-like characters as well as other characters that suggest affinities to sylvioid warblers. We briefly review previous phylogenetic hypotheses for these taxa and then present an analysis based on over 2 000 bases of mitochondrial sequence data for a broad range of Old World songbirds representing most families in Sibley and Ahlquist's (1990) superfamilies Passeroidea and Sylvioidea. Our analyses confirm the placement of Hypergerus and its sister taxon Eminia within a larger monophyletic family of African warblers Cisticolidae. We also find strong support for a sister relationship between Pholidornis and Hylia and evidence that this clade represents just one lineage in a diverse assemblage of Old World warblers that is probably paraphyletic or polyphyletic with respect to other sylvioid families. While a definitive placement of the Pholidornis/Hylia clade within Sylvioidea was not possible, a number of specific previous hypotheses can now be rejected: Pholidornis and Hylia are not closely related to sunbirds Nectariniidae, estrildid finches Estrildidae, or honey-eaters Meliphagidae. Our study underscores the problems that may be encountered in avian systematics: on the one hand, repeated evolution of sunbird-like morphological features (slender bill, brush-tipped tongues and long hyoid bones) potentially misleads traditional classification, while on the other hand, the rapid diversification of lineages at different points in avian evolution reduces the phylogenetic signal in molecular sequence data, making difficult the reconstruction of relationships among taxa resulting from an adaptive radiation.