ON THE CONCEPT AND IMPLICATIONS OF GENETIC PURGING IN SMALL POPULATIONS

AURORA GARCIA-DORADO 

Genetic purging is increasingly considered a relevant factor in conservation genetics, as well as in evolutionary genetics. However, for a long time, it was de facto ignored when computing the expected evolution of population fitness under inbreeding (the inbreeding depression). More than a decade ago, I proposed a simple genetic analytical approximation to account for the consequences of genetic purging, the Inbreeding-Purging (IP) model. This note is intended to improve the insight on the meaning and consequences of purging using the frame of the IP model and its extension including continuous mutation and non-purging selection (the Full Model). I propose a more precise and conceptual definition of the inbreeding purged coefficient, which is a central parameter of the IP model. Then, using this definition, I provide a more straightforward deduction for the equation that predicts its evolution. I use the model to provide a unified discussion that clarifies the consequences of purging, including the pace and the efficiency of the process and the implications for the evolution of the deleterious burden, the inbreeding depression and the inbreeding load, which are relevant to evolutionary and conservation genetics and genomics.