The functional consequences of diversity in plant-pollinator interactions

The role of biological diversity in maintaining ecosystem functioning is a central issue in ecology. Most studies on diversity-functioning relationships have focused on ecosystem and community levels, leaving the extension of those relationships to other organization levels, such as populations, as a challenging and unsolved issue. Empirical studies have shown links between pollinator diversity and plant fecundity, suggesting that a diversity-functioning relationship at the population level may occur in pollination systems. We theoretically explored the effect of pollinator diversity on plant reproduction. We found that low pollinator diversity is beneficial when the most abundant pollinators are the most effective. In contrast, when the most effective pollinators are not the most abundant, we found an optimal value of pollinator diversity at which plant fecundity is maximized. When we parametrized our model with real data, we obtained that an increase in pollinator diversity was beneficial for the reproduction of some plants whereas it was harmful for other plants, the outcome depending exclusively on the differences in effectiveness among pollinators. Consequently, our theoretical approach suggests that in pollination systems the diversity-function relationship may be explained as the consequence of the interaction between among-pollinator differences in effectiveness and frequency of interaction, without the need to invoke additional ecological mechanisms.