Global declines in biodiversity have raised the question about its functional significance. The importance of biodiversity for ecosystem functioning has been studied for several systems. However, studies about diversity effects in pollination - as an important ecosystem process - are extremely scarce. We set up a mesocosm experiment with 14 different flowering plant species in 59 flight cages of eight square meters inhabited by different combinations of one to five wild bee species (and controls). Thereby, we are able to test the biodiversity-functioning relationship for pollinator diversity for the first time in a realistic scenario, controlling for abundance and environmental effects, analyzing underlying mechanisms and differentiating between complementarity and identity effects.
Results/Conclusions
All plant species, representing a diverse array of plant families and flower types, expressed some degree of pollinator dependence, although this strongly varied between species. Despite strong species identity effects of plants as well as bees, a general trend for a positive effect of pollinator diversity on pollination success has been found. Results on analyses on the underlying mechanisms of complementarity and identity effects, the significance of functional traits and changing interaction networks with bee diversity will be presented.
We conclude that biodiversity-ecosystem functioning relationships in pollination systems are strongly dependent on the pollination system of the plants in question. General effects on plant communities are difficult to predict, because the community composition of plants as well as of bee pollinators plays a major role.