Ivermectin Resistance in Dung Beetles Exposed for Multiple Generations

Core Concepts

Dung beetles do not develop resistance to ivermectin after 18 generations of exposure, indicating low potential for adaptation. The study reveals that genetic variation does not explain the observed responses to ivermectin.

Abstract

The study focused on investigating the resistance of dung beetles, specifically Euoniticellus intermedius, to ivermectin after multiple generations of exposure. Results showed that despite continuous exposure, the beetles did not develop resistance or improve performance in contaminated dung. Toxicity experiments revealed no significant improvement in performance across generations or when compared to control lines at different concentrations of ivermectin. Genetic analyses indicated low heritability and genetic variation for ivermectin response, suggesting limited evolutionary potential. Overall, the findings suggest a pessimistic scenario for dung beetles facing ivermectin contamination in pastures.

Stats

Ivermectin excreted intact in cattle dung remains active for several months.
Ivermectin-treated insects produce less offspring with reproductive disadvantages.
Insects like horn flies have shown resistance to ivermectin after multiple generations.
Resistance ratios were calculated based on LC50 values between control and exposed lines.
Genetic variation does not explain phenotypic variance for measured traits.

Quotes

"Toxicity experiments confirmed that dung beetles did not improve performance in contaminated dung across generations."
"Genetic analyses showed low heritability and genetic variation for ivermectin response."
"The study highlights a pessimistic scenario for dung beetles facing ivermectin contamination."

Key Insights Distilled From

Ivermectin resistance in dung beetles exposed for multiple generations

by Tokman,D. G.... at www.biorxiv.org 05-10-2023

https://www.biorxiv.org/content/10.1101/2023.05.08.539900v4

Deeper Inquiries

How might the lack of resistance development impact ecosystem services provided by dung beetles?

The lack of resistance development in dung beetles exposed to ivermectin can have significant implications for the ecosystem services they provide. Dung beetles play a crucial role in nutrient recycling, soil health, and pest control through their activities of burying and consuming dung. If populations of dung beetles are unable to develop resistance to contaminants like ivermectin, it could lead to declines in their numbers or even local extinctions. This would disrupt the natural processes of decomposition and nutrient cycling, affecting soil fertility and overall ecosystem health. As a result, other organisms dependent on these ecosystem services may also be negatively impacted.

Could intermittent exposure to contaminants like ivermectin lead to different evolutionary outcomes compared to constant exposure?

Intermittent exposure to contaminants like ivermectin could indeed lead to different evolutionary outcomes compared to constant exposure. In this study with dung beetles exposed across multiple generations, the intermittent nature of the exposure did not result in the development of resistance. Constant exposure is often associated with stronger selection pressures that can drive rapid evolution towards resistance in target species. However, intermittent exposure may allow for periods where selection pressure is reduced or absent, potentially slowing down or preventing the evolution of resistance. Additionally, intermittent exposure may not provide consistent conditions for adaptive responses or genetic changes necessary for developing resistance over time.

What implications could these findings have for broader conservation efforts beyond just dung beetle populations?

The findings from this study on ivermectin resistance in dung beetles have broader implications for conservation efforts beyond just this specific population:

Impact on Biodiversity: The inability of non-target species like dung beetles to develop resistance highlights the vulnerability of various organisms to anthropogenic contaminants used in agriculture.
Ecosystem Resilience: The decline or loss of important ecological players like dung beetles can disrupt ecosystems and reduce their resilience against environmental stressors.
Conservation Strategies: Conservationists need to consider not only direct threats but also indirect impacts such as contaminant effects on non-target species when designing conservation strategies.
Policy Decisions: These findings emphasize the importance of sustainable agricultural practices and responsible use of chemicals that can harm non-target organisms.
Research Priorities: Further research into understanding how different species respond (or fail) under selective pressures from contaminants will be essential for informing conservation actions aimed at protecting biodiversity and ecosystem functioning amidst human-induced environmental changes.

These implications underscore the interconnectedness between human activities, wildlife populations, and overall ecosystem health – highlighting the need for holistic approaches in conservation planning and management strategies moving forward