DOI: 10.5061/dryad.gqnk98snn
title: Effects of different types of low-intensity management on plant-pollinator interactions in Estonian grasslands

description: In the face of global pollinator decline, extensively-managed grasslands
 play an important role in supporting stable pollinator communities.
 However, different types of extensive management may promote particular
 plant species and thus particular functional traits. As the functional
 traits of flowering plant species (e.g. flower size and shape) in a
 habitat determine the identity and frequency of pollinator visitors, they
 can also influence the structures of plant-pollinator interaction
 networks. The aim of this study was to examine how the type of
 low-intensity traditional management influences plant and pollinator
 composition, the structure of plant-pollinator interactions, and their
 mediation by floral and insect functional traits. Specifically, we
 compared mown wooded meadows to grazed alvar pastures in western Estonia.
 We found that both management types fostered equal diversity of plants and
 pollinators, and overlapping, though still distinct, plant and pollinator
 compositions. Wooded meadows had significantly higher connectance and
 specialisation, while alvar pastures achieved higher Shannon diversity at
 a standardised sampling of interactions. Pollinators with small body sizes
 and short proboscis lengths were more specialised in their preference for
 particular plant species and the specialisation of individual pollinators
 was higher in alvar pastures than in wooded meadows. All in all, the two
 management types promoted diverse plant and pollinator communities, which
 enabled the development of equally even and nested pollination networks.
 The same generalist plants and pollinators were important for the
 pollination networks of both wooded meadows and alvar pastures; however,
 they were complemented by management-specific species, which accounted for
 differences in network structure. Therefore, the implementation of both
 management types in the same landscape helps to maintain high species and
 interaction diversity.
description: We sampled plants,
 pollinators, and plant-pollinator interactions on three wooded meadows and
 three alvar pastures in early July 2018. Ten 30 x 2 m transects with a
 minimum distance of 20 m from each other were representatively positioned
 at each site. At each transect, a botanist identified all flowering plants
 to species and estimated the cover of flowering individuals over the total
 transect area. Each of the ten transects per site were subsequently
 surveyed for flower-visiting insects for 15 minutes, not including
 processing time for caught insects, for a total of 150 minutes of
 observation per site and 450 minutes of observation per management type.
 During this period, two surveyors slowly walked back and forth along each
 transect searching for insects (Lepidoptera, Hymenoptera, or Diptera) that
 were interacting with the reproductive parts of flowers and noted down the
 interaction. Most Lepidoptera and bumblebees were visually identified in
 the field, while all other insects were collected and pinned. Among
 insects, 87.6% of individuals were identified to species level and 88.9%
 were identified to genus level by an entomological specialist. The
 remainder, mainly non-syrphid Diptera, were identified to family and
 morphospecies level. We selected a suite of insect
 functional traits known to influence plant-pollinator interactions from
 the relevant taxonomic literature.  The two insect traits selected, body
 length and proboscis length, were related to foraging range, flower
 choice, and efficiency in acquiring floral resources. Insect traits were
 grouped into qualitative classes (Proboscis: Short: 0-3.99 mm, Medium:
 4-7.99 mm, Long &gt;8 mm; Body length: Small: 0-4.99mm, Medium:
 5-9.99mm, Large &gt;10mm). To test for significance
 differences between the roles of plant and pollinator species in the
 plant-pollinator network, we used the Kruskal-Wallis test with the sampled
 species-level network index (species strength, partner diversity, and
 specialisation d') as the response variable by species as the
 explanatory variable. Further, we used pairwise Wilcoxon rank sum tests
 with the Benjamini-Hochberg correction for multiple testing for pair-wise
 p-values of differences between species. In this case, the null hypothesis
 states that there are no significant differences between species indices
 within a network, or that any observed difference is due to chance alone.
 We assumed a significance threshold of 5%.
description: Plant_pollinator_interactions_Estonia2018: The results of the
 plant-pollinator interaction survey at each transect and site.
 Plant_survey_Estonia2018: The results of the plant survey at each
 transect and site (flowering plants only). Appendix B2:
 Functional traits of all insect species, including species name, family
 name, proboscis length (mm), proboscis size class (short, medium, long),
 proboscis literature reference, body length (mm), body length size class
 (small, medium, large), and body length literature reference.
 Appendix F1: (A) Results of Kruskal-Wallis tests testing for
 significant differences between species indices (species strength, partner
 diversity, specialisation d’) of the species within the management type
 and (B) results of Wilcoxon rank sum tests with the Benjamini-Hochberg
 correction for multiple testing for pair-wise p-values of differences
 between species.