The different sources of variation in inbreeding depression, heterosis and outbreeding depression in a metapopulation of Physa acuta.

Understanding how parental distance affects offspring fitness, i.e., the effects of inbreeding and outbreeding in natural populations, is a major goal in evolutionary biology.

No correlation between inbreeding depression and delayed selfing in the freshwater snail Physa acuta.

Inbreeding depression, one of the main factors driving mating system evolution, can itself evolve as a function of the mating system (the genetic purging hypothesis). Classical models of coevolution between mating system and inbreeding depression predict negative associations between inbreeding depression and selfing rate, but more recent approaches suggest that negative correlations should usually be too weak or transient to be detected within populations. Empirical results remain unclear and restricted to plants.