SPECIATION-WITH-[LOTS-OF]-GENE FLOW IN TWO INTRIGUING ARCHIPELAGO BIRD RADIATIONS

Darwin considered that new species arise when populations competing for resources diverge in order to occupy distinct niches. The subsequent understanding of the genetic mechanisms underlying heredity brought a major hurdle to this model: recombination. Gene flow between competing populations easily destroys the combination of traits that make each distinct. For most of the 20th Century it was deemed that only geographic isolation could overcome this problem. It is now widely accepted that evolutionary divergence can occur in the presence of gene flow if selection is strong enough to counteract it. However, unambiguous examples of speciation-with-gene-flow remain rare, but whether that is because it rarely happens or because it is very difficult to prove remains debated. Closely related species on small, isolated, islands offer unique opportunities to gain insights into the interplay between selection and gene flow during speciation. In this talk I will present the latest findings on two oceanic island finches radiations: the only two cases in birds where speciation seems to have occurred fully in sympatry – and following very much the path first hypothesized by Darwin.

Martim Melo is in CIBIO since 2009, where he joined the POPGEN and TROPBIO groups. He is a research associate at the Percy FitzPatrick Institute of African Ornithology at the University of Cape Town and the coordinator of the ornithological research program of the twin-lab CIBIO-ISCED based in Lubango, Angola. He is broadly interested in the processes generating diversity – from identifying the factors that drive population divergence to the evolution of reproductive isolation (speciation). His research has focused on the diversification of the bird fauna of Africa, and in particular in its oceanic and ecological islands – natural speciation centers that are amenable for the study of this complex process.

Image credits: Peter Ryan