A crop–pollinator inter-play approach to assessing seed production patterns in faba bean under two pollination environments

Abstract

Understanding the inter-play plant–pollinator is essential to develop ecosystem services of faba bean and improved populations for low-input systems. We analyzed the phenotypic selection exerted by pollinators on floral traits involved in the plant pollinator inter-play. We test whether variation in pollinator-related floral traits is associated with differences among plants in seed production patterns. We used open pollination and pollinator-exclusion environments to examine pollinator mediated selection and selection for autonomous selfing in six gene-pools of Vicia faba over three consecutive years. We recorded, by using Digital Image Analysis, functional floral traits related to attraction, sexual dimension, and vector matching/pollen transfer efficiency. Nine production components were measured to categorize seed production patterns. Our approach used a series of Multivariate Regression Analyses (MRA) to explore which floral traits provided the best models to explain seed production patterns in each gene-pool and pollination environment. MRA showed that variation in the incidence of pollinator-mediated selection on floral traits or in the selection for autonomous selfing can substantially contribute to differences in seed patterns. The underlying floral mechanisms are specific to the gene-pool and largely unrelated among gene-pools. Consistent results among gene-pools involved no evidence of pollinator-mediated selection as result of the floral traits under study on the main predictors of crop yield, pods and seeds per plant. However, relevant predictors of crop yield such as pod length and seed dimensions and weight were pollinator-dependent because of pollinator-mediated selection on sexual dimension, floral display and vector matching traits. We caution against dismissing pollinator-mediated selection as driver of seed production patterns variation which may be influenced by the gene-pool and by the gene-pool × pollination environment interaction.