Positive Correlation between Pesticide Consumption and Longevity in Solitary Bees: Are We Overlooking Fitness Trade-Offs?

Abstract

The ubiquitous use of pesticides is one major driver for the current loss of biodiversity, and the common practice of simultaneously applying multiple agrochemicals may further contribute. Insect toxicology currently has a strong focus on survival to determine the potential hazards of a chemical routinely used in risk evaluations. However, studies revealing no effect on survival or even indicating enhanced survival are likely to be misleading, if potential trade-offs between survival and other physiological factors are overlooked. Here, we used standard laboratory experiments to investigate the sublethal (i.e., food consumption) and lethal (i.e., survival) effects of two common agricultural pesticides (Roundup® and clothianidin) on adult female solitary bees, Osmia bicornis. The data showed no significant effect of the treatment on cumulative survival; however, a significant positive correlation between herbicide and insecticide exposure and age was revealed, i.e., bees exposed to higher dosages lived longer. As no significant differences in daily food consumption were observed across treatment groups, increased food intake can be excluded as a factor leading to the prolonged survival. While this study does not provide data on fitness effects, two previous studies using solitary bees observed significant negative effects of neonicotinoid insecticides on fitness, yet not on survival. Thus, we conjecture that the observed non-significant effects on longevity may result from a trade-off between survival and reproduction. The data suggest that a focus on survival can lead to false-negative results and it appears inevitable to include fitness or at least tokens of fitness at the earliest stage in future risk assessments.

The neonicotinoid thiamethoxam impairs male fertility in solitary bees, Osmia cornuta

“…Here, we used standard laboratory methods (Strobl et al, 2019;Strobl et al, 2020) to investigate infertility in male bees, Osmia cornuta, exposed to field-realistic concentrations of the neonicotinoid insecticide thiamethoxam. For that purpose, we measured the effects of thiamethoxam on survival, food consumption, and sperm traits.…”

A systematic scoping review of the methodological approaches and effects of pesticide exposure on solitary bees

“…Investigations focusing on aspects of nesting activity including the number of nesting bees [ 60 , 78 ], number of brood cells produced [ 51 , 52 , 57 , 60 , 62 , 69 , 74 , 78 – 80 ], number of nests/female [ 45 , 57 , 70 ], and the number of days spent nesting have been published. The effects of exposure to pesticide mixtures on foraging activity [ 55 , 68 – 70 , 81 ], flight [ 71 , 73 , 81 ], food consumption by adults [ 75 , 76 , 82 ] and nesting [ 55 , 68 – 71 , 73 , 81 , 83 , 84 ] have also been investigated. Generally, effects observed depend on the pesticide(s) studied, and, since there are limited investigations, clear trends are difficult to establish.…”

Stem-nesting Hymenoptera in Irish farmland: empirical evaluation of artificial trap nests as tools for fundamental research and pollinator conservation

“…For example, in our study, the first species to emerge was O. bicornis, and the last was M. versicolor, which began emerging 5 d after the last O. bicornis had emerged. However, Strobl et al (2020) found that median longevity of female O. bicornis maintained under laboratory conditions was 21 d, and that some individuals lived for 70 d, suggesting these species could easily overlap in terms of adult activity periods.…”