Selfing rates vary with floral display, pollinator visitation and plant density in natural populations of Mimulusringens

Abstract

Variation in selfing rates within and among populations of hermaphroditic flowering plants can strongly influence the evolution of reproductive strategies and the genetic structure of populations. This intraspecific variation in mating patterns may reflect both genetic and ecological factors, but the relative importance of these factors remains poorly understood. Here, we explore how selfing in 13 natural populations of the perennial wildflower Mimulus ringens is influenced by (a) pollinator visitation, an ecological factor, and (b) floral display, a trait with a genetic component that also responds to environmental variation. We also explore whether genetically based floral traits, including herkogamy, affect selfing. We found substantial variation among populations in selfing rate (0.13–0.55). Selfing increased strongly and significantly with floral display, among as well as within populations. Selfing also increased at sites with lower pollinator visitation and low plant density. However, selfing was not correlated with floral morphology. Overall, these results suggest that pollinator visitation and floral display, two factors that interact to affect geitonogamous pollinator movements, can influence the selfing rate. This study identifies mechanisms that may play a role in maintaining selfing rate variation among populations.

Habitat effects on reproductive phenotype, pollinator behavior, fecundity, and mating outcomes of a bumble bee–pollinated herb

“…Population differences in fecundity, facilitated selfing, and outcrossing could arise from contrasts in the local pollination environments and plant phenotypes, and their interacting effects on pollinator behavior. Relevant features of the pollination environment include the availability and density of potential mates (Delmas et al, 2015(Delmas et al, , 2016Christopher et al, 2021), the abundance and diversity of pollen vectors (Brunet and Sweet, 2006;Delmas et al, 2015Delmas et al, , 2016Yin et al, 2016;Leibman et al, 2018), and the presence of other plant species that facilitate or compete for vector service (Caruso, 2000;Bell et al, 2005). In general, fecundity and cross-mating benefit from more mates and more pollinators (Herlihy and Eckert, 2004;Christopher et al, 2021;Richardson et al, 2021), but they suffer from competition for pollinators and interspecific pollination (Caruso, 2000;Bell et al, 2005).…”

“…In animal‐pollinated species, interpopulation variation in the fraction of outcrossed seeds is often attributed to interacting effects of the local frequency of pollinator visitation on the incidence of cross‐pollination and floral traits that enable autonomous self‐pollination when cross‐pollination is limited (Barrett et al, 1989; Kalisz et al, 2004; Moeller and Geber, 2005; Eckert et al, 2009; Leibman et al, 2018). However, differences in mating among populations may also be attributable to less‐studied causes related to pollinators' effectiveness and the quality of their visits (Hargreaves et al, 2010; Christopher et al, 2021). Most obviously, pollinators often facilitate self‐pollination within (facilitated autogamy) or among (geitonogamy) a plant's flowers (Harder and Barrett, 1995; Eckert, 2000; Owen et al, 2007), the incidence of which can vary among populations (Christopher et al, 2021).…”

Selfing-outcrossing as a gradient, not a dichotomy: propensity for selfing varies within a population of hermaphroditic animals

“…Individual-level variation in selfing propensity has not been fully acknowledged in the matingsystem literature, which has traditionally been focused on the species (5)(6)(7)(8) or population level (10,11). The variation discovered here was cryptic in two ways.…”

Outcrossing rates in an experimentally admixed population of self-compatible and self-incompatible Arabidopsis lyrata

“…That patterns of selfing appear to have been driven by extrinsic features of SC A. lyrata populations, including plant densities and patterns of pollinator behavior coincides with the results of a recent study of Mimulus ringens . In that study, extrinsic features of populations, including plant densities, the size of floral displays, and patterns of within- versus between-plant foraging by pollinators, not intrinsic features of flowers (e.g., degree of herkogamy), appear to be the main processes driving variation in selfing rates among populations (Christopher et al 2021 ). In our experimental garden, the high density of plants together with the occurrence of synchronous flowering (Gorman et al 2020a ) likely contributed to patterns of intra-plant foraging by pollinators, resulting in opportunities for geitonogamy and lower outcrossing rates for plants from SC populations.…”