Polyploidy and self-compatibility: is there an association?

•  Researchers have hypothesized that self-compatibility (SC) should be more common in polyploid taxa than their diploid counterparts because of selection for reproductive assurance and/or the expected decline in inbreeding depression associated with having 'extra' gene copies. Support for this view has come from an observed breakdown of self-incompatibility (SI) in some species with a gametophytic system (GSI). The purpose of this research was to assess the strength of this relationship across a wider array of SI systems. •  A large database, of diploid chromosome numbers, ploidy levels, and types of SI system, was assembled for angiosperm species and used to test for an association between ploidy and SC. •  No strong association was found between SC and polyploidy at the level of species or families, and there was no evidence that those having a functional SI system also had fewer polyploid taxa or that most polyploids experience a breakdown in SI. •  These results challenge the assumption that self-fertilization is strongly associated with polyploidy and suggest directions for further research on the evolution of polyploidy in relation to SI.