The Ecological and Evolutionary Consequences of Cleistogamy in Triodanis perfoliata

The evolution of mixed mating, which combines self- and cross-fertilization, has sparked vigorous debate. In this dissertation, I examined the reproductive ecology of clasping Venus’ looking glass (Triodanis perfoliata, (L.) Nieuwl), an annual species with a dimorphic, cleistogamous mixed mating system. Dimorphic cleistogamous plants produce both open, hermaphroditic, chasmogamous (CH) flowers and closed, obligate selfing, cleistogamous (CL) flowers, on the same individual plant. Cleistogamy is thought to be an adaptive strategy allowing for plastic reproductive allocation responses to pollinator and resource environment. In theory, the relatively cheap, closed flowers are favored when pollen and resources are scarce but open, potentially outcrossing flowers may have an adaptive advantage when selfed progeny suffer high inbreeding depression, decreased fitness following breeding between closely related relatives. My work revealed a breeding system that was responsive to pollination. Supplemental pollination increased the proportional production of closed flowers, likely due to plants conserving resources after pollination has occurred. I also showed that climate and soil variables predicted breeding system variation across a broad geographic range. Additionally, I documented low inbreeding depression in T. perfoliata; a typical result in historically selfing lineages due to purging of deleterious recessive alleles following exposure to selection in homozygous genotypes. A lack of inbreeding depression associated to selfing in T. perfoliata, together with evidence for the influence of pollination on reproductive allocation to flower types, and associations between resource availability and breeding system variation, implicate ecological rather than genetic factors to explain the maintenance of potentially outcrossing CH flowers in this species