On Genetic and Phenotypic Distances

The notion of ‘genetic distance’ between individuals and between populations plays a central role in population genetic analysis of diversity and differentiation. It has also been a focal point of some recent interest as empirical and theoretical studies have often made somewhat contradictory claims. I will trace the source of some of the confusion and suggest new perspectives for capturing the relevance of genetic distances to work on ‘ancestry inference’ and to models of phenotypic distance, and present a model that allows assessing the veracity of conclusions stemming from empirical analysis. In particular, I will show how the inferential leaps from genetic to phenotypic distance in the study of ‘population structure’ is hardly straightforward, and is highly contingent on simplifying assumptions with regard to the quantitative trait model and the putative selection pressure on the target trait.