Genetic and genomic evidence suggest incipient speciation with phenotypic divergence across an environmental barrier in a forest passerine (Pipraeidea melanonota)

CAMPAGNA, LEONARDO; BARREIRA, ANA S.; LIJTMAER, DARÍO A.; LAVINIA, PABLO D.; TUBARO, PABLO L.

Portland, Orengon

Congreso; Evolution 2017; 2017

American Society of Naturalists, Society for the Study of Evolution

The Neotropics possess the highest avian diversity of the world. Most of this richness is found in rainforests, like theAmazonia, the Atlantic Forest and the Yungas (Fig. 1A). There have been plenty of evolutionary studies in the Amazonbasin, but little is known about the diversification history of the Yungas avifauna, and only recently there has been anincrease in the number of evolutionary studies in the the Atlantic Forest. The latter, however, have focused mainly onendemic bird species. Even though the Atlantic Forest and the Yungas are currently isolated by the open vegetationcorridor (OVC) conformed by the Caatinga, the Cerrado and Chaco (Fig.1), these forests have experienced cycles ofconnection and disconnection associated with Neogene and Quaternary climatic fluctuations and geotectonic events. The Fawn-breasted Tanager (Pipraeidea melanonota) is a South American forest bird with a distribution fragmented intwo main regions east and west of the OVC. These allopatric populations match its two subspecies (Fig. 1A,B):venezuelensis (P. m. v.) to the west from Venezuela to north-western Argentina, and melanonota (P. m. m.) to the eastin Brazil, Paraguay, Uruguay and north-eastern Argentina. We explored the phylogeographic patterns of P. melanonotain order to assess the impact of the OVC on its evolutionary history. We employed an integrative approach combininggenetic, phenotypic (plumage coloration) and behavioral (vocalizations) evidence. DISCUSSION & MAIN CONCLUSIONS1- Our results suggest a recent (< 0.2 Myr) separation betweenP. m. m. and P. m. v., but the subspecies appear to have experiencedprevious series of contact and isolation promoted by the cyclicconnections and disconnections between the Atlantic Forest and theYungas (Batalha-Filho et al. 2013, Trujillo-Arias et al. 2017).2- Signs of previous historical connections could have been erasedby positive selection at the mtDNA and/or demographic events, twofactors for which we found evidence (not shown; Lavinia 2016).3- This shallow genetic divergence contrasts with the significantplumage coloration differentiation found between P. m. m. andP. m. v., which could have evolved through natural (i.e. habitat) and/orsexual selection.4- The OVC might represent an environmental barrier for thesubspecies at present day. However, the historical connectionsexperienced by P. melanonota differentiates this species from otherswith populations that have not been in contact after their splitbetwen the rainforests (Lavinia et al. 2015, Lavinia 2016).5- The latter reinforces the idea that diversification histories areidiosincratic as distinct taxa can respond differently to the sameevolutionary driver.6- Future analyses should focus on assessing the genetic bases ofthe plumage color differentiation reported here, and on exploring thecurrent gene flow between these allopatric populations