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Utility of fluctuating asymmetry as an indicator of pesticide stress in honeybees

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posted on 2022-08-26, 00:29 authored by Casey ForsterCasey Forster

Honeybee colonies are failing at record levels which threatens the ecological and economic services they provide. Pesticides are likely involved, but detecting their sublethal effects is difficult. Fluctuating asymmetry (FA) is considered an indicator of developmental stress, so here we tested whether FA is an indicator of sublethal pesticide exposure. Imidacloprid (a widely used insecticide) seriously damages honeybee foraging performance at sublethal concentrations. We assessed whether exposure to sublethal concentrations of imidacloprid changed honeybee FA. Additionally, we explored how the method of sampling honeybees influenced FA estimates. We sampled foragers, newly emerged, and within-hive bees treated with 0, 5, or 100 ppb imidacloprid. Landmark-based geometric morphometrics assessed forewing asymmetry. We found imidacloprid did not increase honeybee FA and FA was lower in foragers than other samples. Additionally, directional asymmetry (DA; which does not infer developmental stress) was higher in within-hive than newly emerged honeybees. Overall, FA is an unsuitable indicator of sublethal imidacloprid exposure in honeybees. However, to improve other future FA assessments, investigators should consider what sampling strategies are appropriate as sampling can impact the degree of FA detected. DA must also be adequately accounted for in FA estimates as it appears more prevalent and varying than previously thought.


Table of Contents

Chapter 1: Fluctuating asymmetry: a potential biomarker for pesticide stress -- Chapter 2: Project investigation: effect of imidacloprid on honeybee fluctuating asymmetry and the effect of sampling on fluctuating asymmetry estimates -- References -- Supplementary material


Date of submission: 11th November 2020 Submitted as part of requirements for completion of the degree of Master of Research

Awarding Institution

Macquarie University

Degree Type

Thesis MRes


Thesis (MRes), Macquarie University, Faculty of Science and Engineering, 2021

Department, Centre or School

Department of Biological Sciences

Year of Award


Principal Supervisor

Andrew Barron

Additional Supervisor 1

Lizzy Lowe


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