The Ecological and Evolutionary Consequences of Clonality for Plant Mating

Many flowering plants exhibit dual reproductive modes, producing both sexual and asexual offspring. The commonest form of asexual reproduction is clonal growth, in which vegetative modules (ramets) are produced by the parental genotype (genet). In plants, sexual and asexual reproduction usually occur simultaneously, and this can lead to allocation trade-offs and antagonism between reproductive modes. Our review considers the ecological and evolutionary consequences of functional interactions between clonal reproduction and pollination and mating. Clonal reproduction is commonly associated with mass flowering, restricted pollen dispersal, and geitonogamous self-pollination, processes that can result in inbreeding depression and pollen discounting. We review evidence for the correlated evolution of clonality and sexual systems, particularly self-incompatibility, and identify several floral mechanisms that function to reduce mating costs by limiting selfing and pollen discounting. We conclude by discussing the loss of sexuality in clonal plants and consider the genetic and environmental basis of sexual dysfunction.