Continent-wide genomics of hybridisation and speciation
Variation among populations evolves over time and can affect the ability and likelihood of diverging populations from interbreeding. At lower levels along the continuum of variation, diverging populations may hybridise, exchanging genes with each other, while at higher levels speciation occurs i.e. populations have diverged sufficiently that they do not interbreed. Of profound interest to evolutionary biologists is what mediates interbreeding between diverging populations. Is it divergence in visual and acoustic traits rendering opposite sex individuals across populations unattractive to one another? Or have physical or genetic traits diverged to the extent that any cross-population interbreeding results in a failure to produce viable or fertile offspring? Our study on tinkerbirds allows us to compare the extent of hybridisation across seven hybrid zones over much of the African continent (Fig. 1). Different subspecies meet at each contact zone and the outcome of their interactions varies among them, ranging from little evidence of interbreeding to rampant hybridisation. In this study we aim to quantify the extent to which song and feather colour divergence and the demographic history of populations mediate hybridisation and speciation across the continent. Having already worked extensively at the contact zone in Southern Africa, our focus on this project is several contact zones in East Africa, and specifically in Uganda, Tanzania, and Ethiopia. We are collaborating with Bridgett vonHoldt from Princeton University on genomics and bioinformatics, Andrea Fulgione from Max Planck Institute of Plant Breeding Research on demographic inference, Sophia Hayes from the Chemistry Department at UCY on Raman spectroscopy of forecrown feathers, and Florencia Noriega from CODE University Berlin on bioacoustics.
Figure 1. Distributions across sub-Saharan Africa of yellow-fronted (in yellow) and red-fronted tinkerbirds (in red). Different subspecies of the two species meet in several independent contact zones.