Quantifying the effects of population bottlenecks and inbreeding on genetic variation underlying fitness in natural populations is central to understanding the potential limits to natural selection. One approach is to estimate heterosis in crosses between populations, thus revealing deleterious mutations that have become fixed within populations by random genetic drift. In a recent study published in AoB PLANTS, Oakley et al. estimated heterosis in selfing and outcrossing populations of the perennial herb Arabidopsis lyrata. They found massive heterosis in selfing populations, but strong heterosis even in outcrossing populations. Combined with other sources of information, their results suggest a common history of population bottlenecks, with possibly severe bottlenecks associated with the transition to selfing.
