In a recent study, published in Ecology and evolution, researchers from SciLifeLab investigated the effect of linked selection on genetic diversity in two plant species, Arabidopsis lyrata and Capsella grandiflora. The results could help scientists understand the forces that shape genetic variation in natural populations.

Mutations, genetic drift – random loss of alleles in small populations – gene flow – transfer of genetic variation between populations – and natural selection are all part of shaping genetic diversity in natural populations. In addition, natural selection on genes can have a major impact on genetic diversity at genomic regions nearby, that are not themselves under selection. This process is called linked selection, and it is thought to have a major impact on genetic diversity in many species, including humans.

In the study (Mattila et al. 2019), led by SciLifeLab Fellow Tanja Slotte, researchers studied the effect of linked selection on genetic diversity in outcrossing populations of two plant species: Arabidopsis lyrata and Capsella grandiflora. In both populations, the researchers found evidence for a genome-wide effect of linked selection on genetic variation, but the effect was weaker in A. lyrata. The difference in the impact of linked selection is likely due to the different demographic histories of these populations. Indeed, the researchers showed that the A. lyrata population has undergone a recent dramatic population size reduction, which is expected to reduce the signature of linked selection.

This study thus empirically shows how differences in demographic history can affect the genome-wide impact of selection at linked sites. This is important for a more complete understanding of the forces that shape genetic variation in natural populations.

Photo: Tanja Slotte