Data from: Flower resource and land management drives hoverfly communities and bee abundance in semi-natural and agricultural grasslands

1. Pollination is a key ecosystem service, and appropriate management,
particularly in agricultural systems, is essential to maintain a diversity
of pollinator guilds. However, management recommendations frequently focus
on maintaining plant communities, with the assumption that associated
invertebrate populations will be sustained. 2. We tested whether plant
community, flower resources and soil moisture would influence hoverfly
(Syrphidae) abundance and species richness in floristically-rich
semi-natural and floristically-impoverished agricultural grassland
communities in Wales (U.K.), and compared these to two Hymenoptera genera,
Bombus and Lasioglossum. Interactions between environmental variables were
tested using generalised linear modelling, and hoverfly community
composition examined using canonical correspondence analysis. 3. There was
no difference in hoverfly abundance, species richness, or bee abundance,
between grassland types. There was a positive association between hoverfly
abundance, species richness and flower abundance in unimproved grasslands.
However, this was not evident in agriculturally improved grassland,
possibly reflecting intrinsically low flower resource in these habitats,
or the presence of plant species with low or relatively inaccessible
nectar resources. There was no association between soil moisture content
and hoverfly abundance or species richness. 4. Hoverfly community
composition was influenced by agricultural improvement and the amount of
flower resource. Hoverfly species with semi-aquatic larvae were associated
with both semi-natural and agricultural wet grasslands, possibly because
of localised larval habitat. Despite the absence of differences in
hoverfly abundance and species-richness, distinct hoverfly communities are
associated with marshy grasslands, agriculturally improved marshy
grasslands and unimproved dry grasslands, but not with improved dry
grasslands. 5. Grassland plant community cannot be used as a proxy for
pollinator community. Management of grasslands should aim to maximise the
pollinator feeding resource, as well as maintain plant communities.
Retaining waterlogged ground may enhance the number of hoverflies with
semi-aquatic larvae.