The effect of experimental pollinator decline on pollinator-mediated selection on floral traits.

Human-mediated environmental change, by reducing mean fitness, is hypothesized to strengthen selection on traits that mediate interactions among species. For example, human-mediated declines in pollinator populations are hypothesized to reduce mean seed production by increasing the magnitude of pollen limitation and thus strengthen pollinator-mediated selection on floral traits that increase pollinator attraction or pollen transfer efficiency. To test this hypothesis, we measured two female fitness components and six floral traits of plants exposed to supplemental hand-pollination, ambient open-pollination, or reduced open-pollination treatments.