Global meta-analysis shows that threatened flowering plants have higher pollination deficits

Most flowering plant species rely on animal pollinators to reproduce, but insufficient pollen receipt, or pollen limitation, commonly occurs and is mediated by plant traits. Pollen limitation could either exacerbate extinction threat or arise as a consequence of population and range declines in threatened plants, leading to the expectation that pollen limitation should be higher in threatened compared to non-threatened plants. To test this, we perform a meta-analysis on a global dataset of pollen limitation from 2633 pollen supplementation experiments, integrating plant threat status and thirteen reproduction and life history traits. Threatened plant species have 26% higher levels of pollen limitation than non-threatened species. This pattern is moderated by plant traits and geographic location: we find higher levels of pollen limitation for threatened compared to non-threatened species for pollinator-dependent plants and for plants found in Asia and temperate zones. Using path analysis, we find that plant traits, study region, and threat status are causally linked to pollen limitation. We suggest that plant traits such as autofertility, which strongly predict pollen limitation, should be considered in global databases on plant threat. Further, preventing pollen limitation through habitat and pollinator management is a promising path to preventing plant extinction.