Evolution Of Selfing Syndrome Research Articles

Evolution of selfing syndrome and its influence on genetic diversity and inbreeding: A range-wide study in Oenothera primiveris.

PremiseTo avoid inbreeding depression, plants have evolved diverse breeding systems to favor outcrossing, such as self‐incompatibility. However, changes in biotic and abiotic conditions can result in selective pressures that lead to a breakdown in self‐incompatibility. The shift to increased selfing is commonly associated with reduced floral features, lower attractiveness to pollinators, and increased inbreeding. We tested the hypothesis that the loss of self‐incompatibility, a shift to self‐fertilization (autogamy), and concomitant evolution of the selfing syndrome (reduction in floral traits associated with cross‐fertilization) will lead to increased inbreeding and population differentiation in Oenothera primiveris. Across its range, this species exhibits a shift in its breeding system and floral traits from a self‐incompatible population with large flowers to self‐compatible populations with smaller flowers.MethodsWe conducted a breeding system assessment, evaluated floral traits in the field and under controlled conditions, and measured population genetic parameters using RADseq data.ResultsOur results reveal a bimodal transition to the selfing syndrome from the west to the east of the range of O. primiveris. This shift includes variation in the breeding system and the mating system, a reduction in floral traits (flower diameter, herkogamy, and scent production), a shift to greater autogamy, reduced genetic diversity, and increased inbreeding.ConclusionsThe observed variation highlights the importance of range‐wide studies to understand breeding system variation and the evolution of the selfing syndrome within populations and species.

Balancing selection in self‐fertilizing populations

Self-fertilization commonly occurs in hermaphroditic species, either occasionally or as the main reproductive mode. It strongly affects the genetic functioning of a population by increasing homozygozity and genetic drift and reducing the effectiveness of recombination. Balancing selection is a form of selection that maintains polymorphism, which has been extensively studied in outcrossing species. Yet, despite recent developments, the analysis of balancing selection in partially selfing species is limited to specific cases and a general treatment is still lacking. In particular, it is unclear whether selfing globally reduced the efficacy of balancing selection as in the well-known case of overdominance. I provide a unifying framework, quantify how selfing affects the maintenance of polymorphism and the efficacy of the different form of balancing selection, and show that they can be classified into two main categories: overdominance-like selection (including true overdominance, selection variable in space and time, and antagonistic selection), which is strongly affected by selfing, and negative frequency-dependent selection, which is barely affected by selfing, even at multiple loci. I also provide simple analytical results for all cases under the assumption of weak selection. This framework provides theoretical background to analyze the genomic signature of balancing selection in partially selfing species. It also sheds new light on the evolution of selfing species, including the evolution of selfing syndrome, the interaction with pathogens, and the evolutionary fate of selfinglineages.

Evolution of reproductive traits and selfing syndrome in the sub-endemic Mediterranean genus Centaurium Hill (Gentianaceae)

Abstract In flowering plants, the shift from outcrossing to selfing is associated with a set of correlated changes in morphological and reproductive features known as the ‘selfing syndrome’. Species of the sub-endemic Mediterranean genus Centaurium Hill (Gentianaceae) exhibit a wide array of flower traits related to pollination biology and different ploidy levels. We explored if the evolutionary transitions of seven flower traits and life cycle, typically associated with the selfing syndrome, are related to polyploidy, diversification patterns, divergence times and the geological and climatic history of the Mediterranean Basin. Using 26 species of Centaurium we reconstructed a phylogenetic tree, inferred the ancestral states of the selected traits, estimated their phylogenetic signal and tested the correlative evolution among them. We found a significant increase in diversification rates during the Quaternary. Anther length, flower size, herkogamy and polyploidy undergo rapid state transitions without phylogenetic signal that could be the result of adaptation for selfing. Changes in character states do not show evidence of correlative evolution among them, as would be predicted during the evolution of selfing syndrome. The evolution of reproductive traits in Centaurium has probably relied on a more diverse array of drivers than just reproductive assurance or polyploidy events.