Pollinator community and generalisation of pollinator spectra changes with plant niche width and local dominance

Floral traits are assumed to be the main determinants of plant's pollinator spectrum, yet a majority of temperate plant species possess traits allowing to a certain degree of generalisation of their pollinator spectrum. The actual level of pollinator spectrum generalisation is likely to be the result of both plant floral traits and the diversity and abundance of plant species a plant co-occurs with. We expect that plant species co-occurring in highly diverse plant communities should host more generalised pollinator spectra.In the present study, we explore the degree to which the composition and generalisation of plant-pollinator spectra depend on the plant's niche width (measured as co-occurrence with other plant species) and its local dominance (as measured by mean cover in the community). For this purpose, we compiled a database of >250 plant species pollinator spectra from the literature and coupled it with data on plant niche width and local dominance based on the Czech National Phytosociological Database.Species with wider niches had on average more generalised pollinator spectra, ranging from bumblebee-dominated spectra to diptera- and/or nitidulid beetle-dominated spectra, which was strongly related to plant phylogeny. Plants with bumblebee-dominated spectra had neither wide niches nor niche specialists.The majority of plants had either muscid-, hoverfly- or nitidulid-dominated or completely generalised pollinator spectra. Among such plants, higher local dominance increased the proportion of opportune muscids in pollinator spectrum, while hoverflies showed the opposite pattern. Honeybees although rather infrequent in pollinator spectra also showed a strong preference for locally dominant plant species.Synthesis: The composition of a plant's pollinator spectrum is not independent of other aspects of the plant's life history, namely niche width and the ability to dominate the community. Wider plant species niches result in more generalised pollinator spectra, supporting our hypothesis that habitat generalists are less prone to specialisation on particular pollinator groups. Conversely, the ability to dominate local plant communities influenced pollinator spectra mainly through specific responses of individual pollinator groups.