DOI: 10.5061/dryad.kwh70rz47
title: Database of plant-flower visitor interactions from Ireland

description: Beneficial insects provide valuable services upon which we rely, including
 pollination. Pollinator conservation is a global priority, and a
 significant concern in Ireland, where over half of extant bee species have
 declined significantly in recent decades. As flower-visiting insects rely
 on flowering plants, one way to conserve and promote pollinator
 populations is to protect high-quality habitat. We analysed the structure
 of insect-flower interactions from multiple habitat categories in a large
 database of interactions from Ireland. Our primary goals were to compare
 spatial and temporal variation in Irish network structures, compare Irish
 networks to published networks from other countries, and provide
 evidence-based recommendations for pollinator conservation in Ireland by
 identifying well-visited plant species that may promote high pollinator
 diversity, abundance, and functional complementarity. Habitat types within
 Ireland differed substantially: semi-natural grasslands had the highest
 pollinator species richness and largest number of unique pollinator
 species, while intensively-managed habitats exhibited negative asymmetry
 (more plant than pollinator species). This negative asymmetry is notable
 because most plant-pollinator networks exhibit a positive asymmetry.
 Within intensively-managed habitats, agricultural and urban habitats
 differed. Urban habitats had the highest number of non-native plant
 species while agricultural habitats had the lowest pollinator species
 richness. We also found Irish networks varied across the growing season,
 where July had the highest plant and insect species richness. When
 comparing Irish networks to published networks from other countries, we
 found Irish networks had a higher ratio of plant species to pollinator
 species, and that this difference was most evident in agricultural
 habitats. This ratio means the typical network asymmetry (more pollinator
 than plant species) was flipped (more plant than pollinator species) in
 the Irish network. We conclude that conserving semi-natural grasslands in
 Ireland will be an essential component of pollinator conservation and
 identify thirty-five plant species important for restoring semi-natural
 habitats.
description: The data used for these analyses were collated from six different
 studies in Ireland where obligately flower-visiting insects (specifically
 Lepidoptera, bees, and hoverflies) were observed/collected while foraging
 on flowers. The surveyor recorded both insect and plant identification to
 the highest resolution possible and took samples where field
 identification was not possible. These interactions were recorded from May
 through August in 2009-2011 and 2017 and April through October in 2018.
 The surveyor assigned the habitat type for each sampling event according
 to the Fossitt guide to habitat types of Ireland. In most cases, the
 surveyor also quantified the floral abundance of the different plant
 species visited during a transect. Altogether, these constituted 800
 surveys and ~ 940 hours of sampling time over more than 709,721
 m<sup>2</sup> of transect area. We observed/collected 4,538
 specimens representing 148 insect visitor species on 239 plant species. Of
 the plant species identified in this study, 74 were not native to
 Ireland.
description: From these datasets, we automatically excluded any data where the
 host plant or insect visitor was not resolved to at least genus. We
 included some specimens identified to genus only, as some plant and insect
 taxa were difficult/impossible to resolve to species, often listed as
 “aggregates” (e.g. <em>Taraxacum agg.</em> and
 <em>Bombus lucorum</em> <em>agg</em>.). Only one
 study reported plant species present that did not receive visits (“true
 zeroes”), so we excluded these records. For the phenological comparisons,
 we included all remaining data, but when comparing habitat types, we
 excluded records where the surveyor included more than one habitat type in
 a single survey. When ranking species importance, we only included data
 where the surveyor counted the number of floral units (e.g.
 inflorescences, racemes, umbels) to quantify visitation rate (number of
 flower visitors per unit floral area).