title: Museum specimens reveal loss of pollen host plants as key factor driving wild bee decline in The Netherlands.
abstract: Evidence for declining populations of both wild and managed bees has raised concern about a potential global pollination crisis. Strategies to mitigate bee loss generally aim to enhance floral resources. However, we do not really know whether loss of preferred floral resources is the key driver of bee decline because accurate assessment of host plant preferences is difficult, particularly for species that have become rare. Here we examine whether population trends of wild bees in The Netherlands can be explained by trends in host plants, and how this relates to other factors such as climate change. We determined host plant preference of bee species using pollen loads on specimens in entomological collections that were collected before the onset of their decline, and used atlas data to quantify population trends of bee species and their host plants. We show that decline of preferred host plant species was one of two main factors associated with bee decline. Bee body size, the other main factor, was negatively related to population trend, which, because larger bee species have larger pollen requirements than smaller species, may also point toward food limitation as a key factor driving wild bee loss. Diet breadth and other potential factors such as length of flight period or climate change sensitivity were not important in explaining twentieth century bee population trends. These results highlight the species-specific nature of wild bee decline and indicate that mitigation strategies will only be effective if they target the specific host plants of declining species.
authors.affiliation: Animal Ecology Team, Alterra, Wageningen University & Research Centre, 6700 AA Wageningen, The Netherlands; jeroen.scheper@wur.nl.
authors.forename: Jeroen
authors.initials: J
authors.lastname: Scheper
authors.affiliation: European Invertebrate Survey - The Netherlands, Naturalis Biodiversity Center, 2300 RA Leiden, The Netherlands;
authors.forename: Menno
authors.initials: M
authors.lastname: Reemer
authors.affiliation: Animal Ecology Team, Alterra, Wageningen University & Research Centre, 6700 AA Wageningen, The Netherlands;
authors.forename: Ruud
authors.initials: R
authors.lastname: van Kats
authors.affiliation: Experimental Plant Ecology, Institute for Water and Wetland Research, Radboud University Nijmegen, 6500 GL Nijmegen, The Netherlands; Team Vegetation, Forest and Landscape Ecology, Alterra, Wageningen University & Research Centre, 6700 AA Wageningen, The Netherlands;
authors.forename: Wim A
authors.initials: WA
authors.lastname: Ozinga
authors.affiliation: Resource Ecology Group, Wageningen University, 6700 AA Wageningen, The Netherlands;
authors.forename: Giel T J
authors.initials: GT
authors.lastname: van der Linden
authors.affiliation: Experimental Plant Ecology, Institute for Water and Wetland Research, Radboud University Nijmegen, 6500 GL Nijmegen, The Netherlands; Team Vegetation, Forest and Landscape Ecology, Alterra, Wageningen University & Research Centre, 6700 AA Wageningen, The Netherlands;
authors.forename: Joop H J
authors.initials: JH
authors.lastname: Schaminée
authors.affiliation: Nature Conservation and Plant Ecology Group, Wageningen University, 6700 AA Wageningen, The Netherlands; and Animal Ecology & Ecophysiology, Institute for Water and Wetland Research, Radboud University Nijmegen, 6500 GL Nijmegen, The Netherlands.
authors.forename: Henk
authors.initials: H
authors.lastname: Siepel
authors.affiliation: Animal Ecology Team, Alterra, Wageningen University & Research Centre, 6700 AA Wageningen, The Netherlands; Resource Ecology Group, Wageningen University, 6700 AA Wageningen, The Netherlands;
authors.forename: David
authors.initials: D
authors.lastname: Kleijn
mesh_terms: D000383:Agriculture; D000818:Animals; D001516:Bees / Q000502:physiology*; D049628:Body Size; D057231:Climate Change; D004463:Ecology; D053476:Extinction, Biological; D005260:Female; D035264:Flowers; D009144:Museums; D009426:Netherlands; D010944:Plants; D011058:Pollen; D054817:Pollination; D011157:Population Dynamics; D012621:Seasons
keywords: bee decline; crop pollination; floral resources; land use change; pollen preference