The effects of selfing on lineage diversification across multiple genera

Summary The transition from outcrossing to self-fertilization is a major evolutionary trend in plants, with selfing long hypothesized an evolutionary dead end. Recent theories suggest that elevated extinction rates may be restricted to highly selfing rather than mixed-mating populations. Previous analyses of the effects of mating systems on diversification found mixed results, varying by focal clades and potentially suffering from several limitations. We collected data on three mating-system-related characters. We also collected life form data to indirectly distinguish between mixed mating and highly selfing. We estimated speciation and extinction rates for character states, and state transition rates in 27 genera. We find that outcrossing lineages diversify at higher rates than selfing lineages, while the impact of mating systems on speciation is not consistent across genera. Among self-compatible lineages, annuals/short-lived exhibit significantly lower diversification rates than perennials. Models incorporating hidden states often provide a better fit than those without. The results suggest that selfing lineages overall have lower diversification rates. This may be primarily contributed by elevated extinction rates in highly selfing lineages, which may also explain the prevalence of mixed-mating systems. However, the influences of mating systems on diversification may be often driven by other factors correlated with mating system transitions.