Variação geográfica e genética de Hemitriccus minor (Aves: Tyrannidae) na bacia do rio Madeira

Abstract

Studies of the biogeography of Amazonian birds have revealed geographic distributions delimited by large rivers. However, to what extent has this geographic variation been well described? In this study, I analyzed molecular genetic geographic variation in Hemitriccus minor in the Rio Madeira basin. Based on maximum parsimony, maximum-likelihood, AMOVA, and nested clade analyses of a 642 bp-section of the mitochondrial cytochrome b gene, I confirmed a new distributional pattern in this species complex. Results indicated that H. minor is not a monophyletic species; it is paraphyletic, the complete clade also including H. spodiops. In contrast to the current classification, H. minor contains two distinct populations west of the Rio Madeira; one, H. m. pallens, is sister to H. spodiops and occurs only in flooded forests, mostly west of the Purus and Negro rivers; the other, as yet unnamed, occurs in the interior of upland and flooded forests in part of the Madeira-Purus interfluve and is most closely related to the populations of H. minor found east of the Madeira. The situation for the populations east of the Madeira is not as clear; however, results indicate the presence of two small sister clades differentiated from the remaining populations. These two appear to be delimited geographically by small rivers, showing a geographic pattern previously described only in Amazonian primates. Based on nested clade analysis, a vicariant event is probably responsible for the genetic divergence encountered between these populations. Molecular data, then, detected a new pattern of geographic variation in H. minor and reinforce the importance of modern methods in the study of Amazonian biogeography.