Autopolyploid establishment under gametophytic self-incompatibility: the impact of self-fertilization and pollen limitation

Abstract

Polyploidy is widespread in plants, yet the establishment of neo-polyploids is limited by minority cytotype exclusion (MCE). As polyploidy has been associated with higher selfing rates in empirical studies, a shift from self-incompatibility (SI) to self-compatibility (SC) may help overcome MCE, particularly under ga-metophytic SI (GSI) with non-self-recognition where an automatic shift to SC is associated with polyploidy. We investigated theoretically the joint evolution of polyploidy and self-compatibility and its impact on tetraploid establishment in initially diploid populations with GSI under different pollen limitation scenar-ios, and with fixed or variable selfing rates for polyploids. It is shown that, for high pollen limitation scenarios, autotetraploids can invade an initially diploid population only when the selfing rates are high. Under low pollen limitation, the conditions for tetraploid invasion are less restrictive (selfing rates above 0.3). These results apply to scenarios with either fixed or variable selfing rates in polyploids, but in the latter, high mutation rates of the selfing rate are needed for polyploidy to invade. These results suggest that tetraploid establishment is possible through the evolution of selfing, without introducing a non-functional S-allele. However, the conditions strongly depend on the degree of pollen limitation.