EvoLunch Seminar: Alexander Mackintosh (Uppsala University)

Hybridisation is a common phenomenon in nature, yet reconstructing the history of gene flow between species in any real detail remains challenging. In this talk I will present an emerging approach for inferring population history that uses reconstructed genealogical trees rather than genome sequence data directly. In the first part of the talk I will focus on genealogies of modern humans. I will introduce a new way of summarising genealogies which shows that genetic variation in humans is incompatible with a history of panmixia in deep time. By considering alternative models of population history I find that the data can instead be explained by the ancestors of modern humans descending from two populations that diverged more than 1 MYA. I will conclude by demonstrating how an analysis of genealogical trees can resolve a complex history of speciation: on the island of Tenerife, Argyranthemum sundingii and A. lemsii (Asteraceae) are hypothesised to have arisen by independent hybridisation events between A. broussonetii and A. frutescens. My analysis of genealogical trees from these species challenges this idea and favours a simpler history. Together these examples show the power of using reconstructed genealogical trees to infer the evolutionary history of subdivided populations and hybridising species.