Invasion status and phylogenetic relatedness predict cost of heterospecific pollen receipt: implications for native biodiversity decline

Understanding the mechanisms by which invasive species affect native plants is a central challenge. Invasive plants have been shown to reduce pollinator visitation to natives and increase pollen quantity limitation. However, visitation and conspecific pollen delivery are only two components of the pollination process; post-pollination interactions on the stigma (heterospecific pollen [HP] receipt) could intensify pre-pollination responses to invasion. Here we used meta-analysis to test the hypotheses that invasive plants are more detrimental as HP donors than natives ones, and that HP donors that are closely related to the recipients have stronger effects on fruit and seed production compared to distantly related ones. Invasive HP donors reduced fruit and seed production of recipients to a greater degree than native ones, and this was more intense for HP donors closely related to natives. Related donors were more detrimental overall. Synthesis: These results suggest that the total effec...