Document Type

Article

Publication Title

Molecular Ecology

Publication Date

2025

Keywords

bombus, gene expression, pathogens, pesticides, RNA-seq, species decline

Abstract

Bumble bee (Bombus Latreille) populations of certain species have declined precipitously in North America over several decades. Hypotheses for declines include exposure to the pathogen Nosema bombi and neonicotinoid pesticides. Importantly, populations of some bumble bee species remain stable despite their presumed exposure to these same stressors. We hypothesise that declining and stable species exhibit distinct responses to N. bombi and neonicotinoids, detectable as differential gene expression profiles. To test this, we exposed larvae of Bombus occidentalis (declining) and B. impatiens (stable) to N. bombi and to the neonicotinoid imidacloprid, plus a combination of both. RNA-seq analysis revealed almost no overlap between these species in gene expression responses to the individual stressors. There was more overlap of differentially expressed genes for the combined-stressor condition, but hundreds of genes still showed species-specific expression differences. To test whether the differential molecular responses could be associated with declining and stable species, we performed quantitative PCR on 20 selected genes, adding two additional species B. terricola (declining) and B. griseocollis (stable). These responses did not separate out by species decline status; each of the four species exhibit species-specific responses. Overall, these results highlight that generalising mechanisms and causes of decline across different species may be misleading, as diverse species respond molecularly in a species-specific manner to particular environmental stressors.

Funding Source

This work was supported by a US Department of Agriculture NIFA Grant (2017-67013-26536) to S.A.C. and B.M.S. Through the writing of the paper, B.M.S. was further supported by a Great Lakes Restoration Initiative award from the US Fish and Wildlife Service's Threatened and Endangered Species Template (F22AP02271-00). This article was published Open Access thanks to a transformative agreement between Milner Library and Wiley.

Comments

First published in Molecular Ecology (2025): https://doi.org/10.1111/mec.70042

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

DOI

10.1111/mec.70042

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