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Insecticide-resistant fruit flies show reproductive difficulties

Staff Writer |
Fruit flies that developed a genetic resistance to the insecticide DDT have lower success at mating than those without similar changes, according to a study published last month in the journal Behavior Genetics.

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The results were surprising to researchers, given that the resistance developed through changes to a single allele (a variation of a single gene).

“It is amazing that even if all the genes are exactly the same, having this one gene expressed at a higher level has all these effects,” said Professor Nina Wedell, PhD, of the Centre for Ecology and Conservation on Exeter’s Penryn Campus in Cornwall, UK to

The study raises possible concerns about the effect of pesticide exposure to non-target (not the focus of pesticide use) insects that are integral to a healthy ecology and food web.

In conducting their investigation, researchers studied the biological fitness costs associated with the development of an insecticide resistance gene.

After scientists bred resistant flies in the lab, they set up a series of “competitive mating trials,” comparing both courtship behavior and the impact of size on male fruit flies’ mating success.

In general, resistant males were found to be smaller than flies that did not contain the genetic variation.

However, even when larger than non-resistant males, insecticide-resistant fruit flies were less likely to be successful in the study’s competitive mating trials.

While researchers indicate size played an important role in differences between mating success, they note a number of other factors were also at play.

In addition to being smaller, males carrying the resistance allele also chased females and performed courtship displays at a lower rate.

And after they performed a courtship display, they were less likely to make an attempt to mate.

In addition, these males waited more than two times as long as non-resistant males before mating, a term called “copulation latency,” indicating that resistant males were less attractive to females.

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