Rapid loss of self-incompatibility in experimental populations of the perennial outcrossing plant Linaria cavanillesii

Transitions from self-incompatibility (SI) to self-compatibility (SC) in angiosperms may be frequently driven by selection for reproductive assurance when mates or pollinators are rare, and are often succeeded by loss of inbreeding depression by purging. Here we use experimental evolution to investigate the spread of SC from one such population of the perennial plant Linaria cavanillesii into SI populations that still have high inbreeding depression. We introduced SC individuals at different frequencies into replicate experimental populations of L. cavanillesii that varied in access to pollinators. Our experiment revealed a rapid shift to SC in all replicates, driven by both greater seed set and greater outcross siring success of SC individuals. We discuss our results in the light of computer simulations that confirm the tendency of SC to spread into SI populations under the observed conditions. Our study illustrates the ease with which SC can spread among populations, a requisite for species-wide transitions from SI to SC.