When male bees don't get lucky

Date:
April 25, 2022
Source:
University of Wu"rzburg
Summary:
Do pesticides have anything to do with the decline in bee
populations? A research team has now found a connection between
fenbuconazole and the insects' mating behavior.



FULL STORY ==========================================================================
Bees are among the most important pollinators on earth. They pollinate
not only plants with beautiful flowers, but also many crops. But despite
the insects' great importance for humans and nature, their population
is declining.

Researchers cite various possible causes for this, including
pesticides. This factor has now been investigated in a study
by an international research team with the participation of the Julius-Maximilians-University (JMU) Wu"rzburg.

They found that pesticides are probably a major factor in the reproduction
of bees.


==========================================================================
In bees, males are produced from unfertilized eggs. Female bees, on
the other hand, are created produced through the mating of males and
females. The research team wanted to find out what factors might be contributing to the decline in the bee population. It focused on early
stages of the insects' reproduction. Horned mason bees (Osmia cornuta)
were exposed to a low-toxicity, non-lethal dose of the fungicide
fenbuconazole. Fungicides are used to fight fungi and spores as crop
protection agents.

Female mason bees evaluate male quality signals when choosing a mating
partner -- most importantly their odor and thoracic vibrations. "If
the fungicide has an effect on male quality signals, this should
increase the likelihood that pesticide-exposed males will be rejected
by females," explains entomologist and lead author of the study, Samuel
Boff. Boff conducted his research at JMU and University of Milan and is
now a research associate at the Institute of Evolutionary Ecology and Conservation Genomics at Ulm University.

A clear result As a result, male bees exposed to the fungicide
were more likely to be rejected by females. "We also found that the pesticide-exposed males vibrate their thoracic muscle less and also had
a different odor composition than the un- exposed males," Boff said. He concludes: "The decline in bee populations in agricultural landscapes
could therefore be explained by the effect of pesticides on insect mating behavior." This paper is the first study to show that a fungicide with
low toxicity has an impact on the reproduction of bees in the mating
phase. "Our study shows that the early stages of bee reproduction must be included in the risk assessment of pesticides," says also Professor Thomas Schmitt, Chair of Animal Ecology and Tropical Biologist at JMU. He was
also involved in the study. Boff hopes for broader testing of different
classes of pesticides on bee behavior and their chemical signals: "So that
more effective bee protection can really take place." Further steps The
next steps include conducting further experiments on mating behavior, as
the researchers want to find out whether different classes of pesticides
also affect the mating decisions of other wild bee species. They also
recommend bee monitoring programs to compare reproductive outcomes of
wild bees in areas with pesticide exposure and in ecological areas.

The research team has published their results in the Journal of Applied Ecology. In addition to Boff (JMU/Ulm) and Schmitt (JMU), Professor
Daniela Lupi (University of Milan, Italy) and several scientists from
Germany and Brazil were also involved in the study. It was funded by
the Italian foundation "Fondazione Cariplo."

========================================================================== Story Source: Materials provided by University_of_Wu"rzburg. Original
written by Kristian Lozina. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Samuel Boff, Taina Conrad, Josue' Raizer, Marten Wehrhahn,
Melis Bayer,
Anna Friedel, Panagiotis Theodorou, Thomas Schmitt, Daniela
Lupi. Low toxicity crop fungicide (fenbuconazole) impacts
reproductive male quality signals leading to a reduction of mating
success in a wild solitary bee.

Journal of Applied Ecology, 2022; DOI: 10.1111/1365-2664.14169 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/04/220425104913.htm

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