Linkage between community assemblage of floral traits and pollinator fauna: a comparison among six geographical regions

The persistence of angiosperm communities largely depends on pollinator-mediated interactions. However, the importance of plant–pollinator interactions has often been overlooked in studies of plant community assembly. This study aims to assess the influence of plant–pollinator interactions on the assembly of plant communities. We compared the distribution of three floral traits (colour, symmetry, and tube length) across approximately 650 animal-pollinated plant species in six plant communities located in distinct geographical regions: Mongolian grassland, Japanese grassland, Japanese alpine zone, Swedish subalpine zone, Swedish alpine zone, and New Zealand alpine zone. Additionally, we examined the pollinator fauna in each community, focusing on the taxon-specific usage of floral traits by pollinators. The composition of all floral traits was predictably linked to taxonomic composition of the pollinator fauna and taxon-specific preferences of pollinators for certain floral traits. Furthermore, the dispersion of floral morphology depends on composition of pollinator fauna, rather than phylogenetic dispersion of plant communities. Interestingly, while composition of flower symmetry was largely linked to plant family composition, compositions of flower colour and tube length were almost independent of plant family composition. Our study suggests that pollinator fauna influences the assembly of floral traits. Analysis considering plant family composition suggests that the assembly process could be either ecological, where plant–pollinator interactions select for specific functional traits from a pre-existing pool, or evolutionary, where traits evolve in response to the pollinator environment within a community. This highlights the dual pathways through which pollinator fauna influences plant community assemblages.