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Abstract:
Background: Symbiotic microbes represent a driving force of evolutionary innovation by conferring novel
ecological traits to their hosts. Many insects are associated with microbial symbionts that contribute to their host’s
nutrition, digestion, detoxification, reproduction, immune homeostasis, and defense. In addition, recent studies
suggest a microbial involvement in chemical communication and mating behavior, which can ultimately impact
reproductive isolation and, hence, speciation. Here we investigated whether a disruption of the microbiota through
antibiotic treatment or irradiation affects cuticular hydrocarbon profiles, and possibly mate choice behavior in the
tsetse fly, Glossina morsitans morsitans. Four independent experiments that differentially knock down the multiple
bacterial symbionts of tsetse flies were conducted by subjecting tsetse flies to ampicillin, tetracycline, or gammairradiation
and analyzing their cuticular hydrocarbon profiles in comparison to untreated controls by gas
chromatography – mass spectrometry. In two of the antibiotic experiments, flies were mass-reared, while individual
rearing was done for the third experiment to avoid possible chemical cross-contamination between individual flies.
Results: All three antibiotic experiments yielded significant effects of antibiotic treatment (particularly tetracycline)
on cuticular hydrocarbon profiles in both female and male G. m. morsitans, while irradiation itself had no effect on
the CHC profiles. Importantly, tetracycline treatment reduced relative amounts of 15,19,23-trimethylheptatriacontane,
a known compound of the female contact sex pheromone, in two of the three experiments,
suggesting a possible implication of microbiota disturbance on mate choice decisions. Concordantly, both female
and male flies preferred non-treated over tetracycline-treated flies in direct choice assays.
Conclusions: While we cannot exclude the possibility that antibiotic treatment had a directly detrimental effect on
fly vigor as we are unable to recolonize antibiotic treated flies with individual symbiont taxa, our results are
consistent with an effect of the microbiota, particularly the obligate nutritional endosymbiont Wigglesworthia, on
CHC profiles and mate choice behavior. These findings highlight the importance of considering host-microbiota
interactions when studying chemical communication and mate choice in insects.
