Effect of gut bacteria on fitness of the Chinese citrus fly, Bactrocera minax (Diptera: Tephritidae)

Abstract

A likely symbiotic association between tephritid fruit flies and gut bacteria has been recognized since the beginning of the last century. However, direct evidence for a link between gut bacteria and fruit fly fitness is still limited or absent for many species. Similar to other tephritids, the gut of Bactrocera minax (Enderlein) (Diptera: Tephritidae) is known to contain bacteria throughout the life stage, but what, if any, impact these bacteria have on B. minax fitness is entirely unknown. In order to elucidate the effects of bacteria on the fitness of B. minax, resident bacteria were isolated from the adult gut using culture-dependent techniques. Adult fly diets were subsequently supplemented with three bacterial isolates (Klebsiella pneumonia, Citrobacter braakii and Pantoea dispersa), or bacteria were removed from flies by antibiotics treatment: untreated adults provided a control. Adult fitness parameters (male and female longevity, female fecundity, male copulation number) were measured for the two treatments and one control group. Results were complex depending on the fitness parameter measured and the bacterial species. Compared to the controls, antibiotic treated B. minax had significantly decreased fecundity, but male and female longevity was increased. When flies were fed diets supplemented with any of the three bacterial isolates, female fecundity was significantly enhanced. However, only Citrobacter braakii significantly increased male mating frequency than control males. The results show that gut bacteria directly influence fitness of B. minax, but impacts are dependent on the bacterial species and the fitness parameters measured.