John Welch
About
Research Area
With the explosion of whole-genome sequencing, it became clear that species boundaries are more porous than many had imagined, with many “good” species undergoing extensive hybridisation and gene exchange. Between-species hybridisation is also of growing interest in conservation biology, with anthropogenic changes in species range bringing once-isolated groups into secondary contact, and deliberate translocations between isolated populations used as a conservation tool – albeit controversially. These developments are controversial because hybridisation, with its injection of novel genetic variation, can be a “double-edged sword”. If the variation is useful, this can facilitate adaptive evolutionary change, but if the variants prove incompatible, this can harm the admixed population, even leading to “extinction by hybridisation”.
I investigate these questions using the tools of mathematical quantitative- and population- genetics, and the comparative analysis of genome sequence data (the latter in collaboration with empiricists, working on a range of animal and plant systems). The broad goals are to infer the effects of past hybridisations, and predict the outcomes of future hybridisations, to make interventions more timely and effective.
Project Interests
What, exactly, should we measure to predict the outcome of a novel hybridisation? The answer will probably be some measure of genetic interaction, but many are available, and we don’t know which – in any – could give us the predictive power we need.
How might demographic context alter the outcomes of hybridisation? For example, how different is selection in a “hybrid swarm” (where hybrids mate with other hybrids), versus “introgressive hybridisation” (where most hybrids mate with a parental types)? This question can be addressed using both theory and data, e.g. by inferring natural selection from wild-sampled or lab-crossed hybrid genomes.