Plant complementarity increases pollinator abundance

Background/Question/Methods

Much of the recent work examining ecosystem function has been spurred by the desire to understand the implications of biodiversity loss. The majority of the work in the past two decades has focused on community productivity, where it has been consistently shown that assemblages with high species richness are more productive and provide more ecosystem services than assemblages with less diversity. This difference in community productivity between these assemblages has been attributed to species complementarity, where more diverse assemblages have a greater probability of including species that exhibit niche partitioning. To examine this complementarity effect beyond community productivity we examined pollination in multispecies assemblages. The aim of the study was to determine if there is a positive complementarity effect on pollination. This study was done using a long-term experimental field study at the Koffler Scientific Reserve in Ontatio, Canada. Weekly plot observations were conducted in order to determine identity and abundance of visiting pollinators, along with determining the floral production of each plant species.

Results/Conclusions

The results show that there is temporal niche partitioning for flowering time between species from different plant families. This segregation in flowering time was measured by average flower abundance over the duration of the field season. Due to this segregation it was found that diverse assemblages remained in flower longer than less diverse assemblages (R² = 0.44, P<0.01). The increase in flowering time meant that there was an increased likelihood of pollinators being attracted to those assemblages, which underpins the richness effect for pollinators. Interestingly, there was no complementarity effect found for flower abundance, meaning that diverse assemblages did not produce more flowers than less diverse ones. However, there was a significant relationship between complementarity and pollinator abundance (P<0.01). As different plant species may represent different resources for pollinators, we can infer that diverse assemblages do better than less diverse ones because they have a continuous supply of resources available for pollinators. These findings suggest that biodiversity loss could severely impact pollination. The decrease in pollinator abundance could then lead to positive feedback on the community as plant reproductive success could decline, and therefore increasing the negative effect of biodiversity loss.