Long‐term surveys support declines in early‐season forest plants used by bumble bees

Journal of Applied Ecology
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Abstract

  1. Populations of bumble bees and other pollinators have declined over the past several decades due to numerous threats, including habitat loss and degradation. However, we can rarely investigate the role of resource loss due to a lack of detailed long‐term records of forage plants and habitats.
  2. We use 22‐year repeated surveys of more than 262 sites located in grassland, forest, and wetland habitats across Illinois, USA to explore how the abundance and richness of bumble bee food plants have changed over the period of decline of the endangered rusty patched bumble bee (Bombus affinis).
  3. We document a decline in abundance of bumble bee forage plants in forest understories, which our phenology analysis suggests provide the primary nectar and pollen sources for foundress queens in spring, a critical life stage in bumble bee demography. By contrast, the per‐unit area abundance of food plants in primarily midsummer‐flowering grassland and wetland habitats has not declined. However, the total area of grasslands has declined across the region resulting in a net loss of grassland resources.
  4. Synthesis and applications. Our results suggest a decline in spring‐flowering forest understory plants is a previously unappreciated bumble bee stressor, compounding factors like agricultural intensification, novel pathogen exposure, and grassland habitat loss. These findings emphasize the need for greater consideration of habitat complementarity in bumble bee conservation. We conclude that continued loss of early‐season floral resources may add additional stress to critical life stages of bumble bees and limit restoration efforts if not explicitly considered in pollinator conservation.
Publication type Article
Publication Subtype Journal Article
Title Long‐term surveys support declines in early‐season forest plants used by bumble bees
Series title Journal of Applied Ecology
DOI 10.1111/1365-2664.13886
Edition Online First
Year Published 2021
Language English
Contributing office(s) Fort Collins Science Center
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