Abstract:
Many traits in diverse organisms – related to morphology, size, or the risk of common diseases – are highly polygenic, i.e., influenced by a large number of genetic variants across the genome. However, the consequences of natural selection acting on polygenic traits remain poorly understood. A major complication is that polygenic selection causes different genetic variants to evolve in a correlated manner, with the scale of correlation depending on myriad factors – whether variants are tightly linked,
how stochastic evolution is (due to finite population sizes), and how structured populations are (e.g., due to subdivision into smaller groups that rarely mix). In this talk, I will explore some of these complexities – focusing in particular on how linkage between selected variants and population structure shape polygenic adaptation and its signatures in genomic data. I will illustrate the utility of coarse-grained descriptions
of polygenic evolution – in terms of continuous blocks of genome (as opposed to discrete variants) and effective parameters (that average over ‘fast’ evolutionary processes). These descriptions provide a principled way of understanding which genetic details matter for the distribution of genetic variation across different spatial, temporal and genomic scales and to what extent we can hope to make inferences about the individual genes involved in adaptation or speciation from genomic data.