Population genomics of transitions to selfing in Brassicaceae model systems

TL;DR

This paper reviews how transitions from outcrossing to selfing in Brassicaceae affect genetic diversity, adaptation, and genome evolution, highlighting recent genomic studies and future research directions.

Contribution

It synthesizes current knowledge on the population genomics of selfing transitions in Brassicaceae and discusses future research avenues using genomic and theoretical approaches.

Findings

Selfing transitions impact genetic variation and adaptive potential.

Genomic data reveal when and where selfing occurred in Brassicaceae.

Future studies will explore positive selection and demography effects.

Abstract

Many plants harbor complex mechanisms that promote outcrossing and efficient pollen transfer. These include floral adaptations as well as genetic mechanisms, such as molecular self-incompatibility (SI) systems. The maintenance of such systems over long evolutionary timescales suggests that outcrossing is favorable over a broad range of conditions. Conversely, SI has repeatedly been lost, often in association with transitions to self-fertilization (selfing). This transition is favored when the short-term advantages of selfing outweigh the costs, primarily inbreeding depression. The transition to selfing is expected to have major effects on population genetic variation and adaptive potential, as well as on genome evolution. In the Brassicaceae, many studies on the population genetic, gene regulatory and genomic effects of selfing have centered on the model plant Arabidopsis thaliana and the crucifer genus Capsella. The accumulation of population genomics datasets have allowed detailed investigation of where, when and how the transition to selfing occurred. Future studies will take advantage of the development of population genetics theory on the impact of selfing, especially regarding positive selection. Furthermore, investigation of systems including recent transitions to selfing, mixed mating populations and/or multiple independent replicates of the same transition will facilitate dissecting the effects of mating system variation from processes driven by demography.