Combinando filogeografia e genética da paisagem para compreender a evolução de Xenopipo atronitens (Aves; Pipridae), uma espécie característica das campinas Amazônicas

Abstract

The family Pipridae (Aves: Passeriformes) is exclusively Neotropical and its species occur mainly in forested habitats. The Pipridae are phylogeneticaly related to the Tyrannoidea and the Cotingoidae superfamilies albeit some relationships among genera in this family are still unresolved. Particularly, the phylogenetic position of the genus Xenopipo remains undefined. Three species of the genus occur on the Andes: X. holochlora, X. flavicapilla, X. unicolor. Xenopipo uniformis occurs on the Tepuis (Brazil, Guiana and Venezuela) while X. atronitens occurs on the Amazonian lowlands, with a disjunct distribution associated with areas of white-sand stunted forest (campinas/campinaranas). The relationships between Xenopipo and other genera in this family as well as those among species within this genus were studied. In the phylogenetic analysis, X. atronitens and X. uniformis appear as a well supported clade, confirming their sister relationship. Xenopipo unicolor showed no defined relationship with any of the Pipridae taxa, even with the other Xenopipo species. Therefore, the monophily of the genus Xenopipo could not be confirmed and its relationship to the other Pipridae genera remains uncertain. The split between X. uniformis and X. atronitens ocurred at 8.85 My ago, approximately. The isolation between high elevation habitats in the Tepuis and the Amazonian lowlands during the Miocene could have triggered the separation between X. atronitens on the campinas and X. uniformis on the Tepuis highlands through allopatric speciation. The campinas are open vegetation habitats strictly associated to white-sand soils heterogeneously distributed throughout Amazonia. Xenopipo atronitens, a white-sand stunted forest specialist bird species, was studied as a model to infer the effects of climate changes in the recent past on birds restricted to white-sand vegetation areas. Furthermore, the relative importance of different landscape characteristics in explaining the genetic variability of X. atronitens was estimated. Thus, a phylogeographic analysis of X. atronitens was carried out and the relationship between landscape metrics and genetic diversity of the species was studied. Low genetic variability among populations was found, but some population structure was detected. The main phylogeographic breaks were across the Amazonas, Branco and Madeira Rivers. This result indicates the importance of várzea habitats as a barrier to gene flow between populations. Conversely, terra-firme and igapó areas appear to be more permeable barriers to X. atronitens. Geographic distance also influenced the genetic distance between populations. Xenopipo atronitens showed demographic growth in the recent past (25,000 years before present, aprox.) that may be related to a recent genesis of white-sand soil areas or to the climatic oscillations during the last glacial maximum. The landscape analysis showed the importance of historical and current aspects in generating genetic variability of the species. The genetic structure of Jaú populations were mostly influenced by historical factors, while genetic variability of populations in the Aracá and Uatumã landscapes are related to the availability and proximity of campina habitats.