Comparison of Phenotypic and Genetic Differentiation in South American Antwrens (Formicariidae)

We examined patterns and levels of genetic, morphometric, and plumage variation in Myrmotherula antwrens and related antbirds (Formicariidae). We derived matrices of distances independently for proteins, qualitative plumage traits, and measurements of study skins. Our goals were to assess concordance between the morphological (morphometric and plumage) and genetic patterns, to estimate phylogenetic relationships, and to test monophyly of Myrmotherula. Myrmotherula is not monophyletic. Analysis of allozymes shows that although the "gray" and "streaked" plumage types are closely related, the "checker-throated" Myrmotherula species are not closely related to the gray/streaked clade. Plumage divergence exceeds divergence in protein genes, whereas change in external morphology has been relatively conservative. Antwren speciation has been accompanied by differentiation of plumage types rather than by entry of species into new regions of morphometric space. Relatively large genetic distances among and within Myrmotherula species imply that these tropical taxa are older and more geographically subdivided than are most North American species. Neither plumage nor morphometrics alone correctly predicted the genetic relatedness among the taxa. We urge that taxonomic revisions be accompanied by molecular data, especially in species-rich tropical families.