Explosive speciation in the New World Dendroica warblers

I. J. Lovette, E. Bermingham
1999 Proceedings of the Royal Society of London. Biological Sciences  
The 27 species of Dendroica wood-warblers represent North America's most spectacular avian adaptive radiation. Dendroica species exhibit high levels of local sympatry and di¡er in plumage and song, but the group contrasts with other well-known avian adaptive radiations such as the Hawaiian honeycreepers and Galapagos ¢nches in that Dendroica species have di¡erentiated modestly in morphometric traits related to foraging. Instead, sympatric Dendroica tend to partition resources behaviourally and
more » ... hey have become a widely cited example of competitive exclusion. We explored the temporal structure of Dendroica diversi¢cation via a phylogeny based on 3639 nucleotides of protein-coding mitochondrial DNA(mtDNA). The taxa sampled included 60 individuals representing 24 Dendroica species and a variety of other paruline warbler and outgroup species. Mitochondrial divergences among Dendroica species were generally large (mean pairwise interspeci¢c distances, 10.0%) and many species were rooted in a basal polytomy. The prevalence of long terminal branches indicates that these species have evolved e¤cient isolating mechanisms that have prevented mtDNA introgression despite the many opportunities for hybridization resulting from local sympatry. Comparisons with a null model of random bifurcation^extinction demonstrate that cladogenesis in Dendroica has been clustered non-randomly with respect to time, with a signi¢cant burst of speciation occurring early in the history of the genus, possibly as long ago as the Late Miocene or Early Pliocene periods. Although this non-random clustering of speciation is consistent with the pattern expected of an adaptive radiation, the age of the Dendroica radiation suggests it is an'ancient species £ock' in which most extant species represent lineages that have long been evolutionarily independent.
doi:10.1098/rspb.1999.0825 pmcid:PMC1690178 fatcat:cuaxboov45euxn2ysvolu2aeyi