باکتری Wolbachia نرخ نسبت جنسی را در جمعیت های درون زاد و برون زاد زنبور پارازیتویید Habrobracon hebetor افزایش می دهد

The adult sex ratio is a fundamental concept in population biology, sexual selection and evolution, being essential for the survival and dynamics of species populations. Adaptation of the sex ratio to the environment is accomplished by various mechanisms such as inbreeding, mating behavior, resource constraints, and the presence of endosymbionts such as Wolbachia. Wolbachia are obligatory endosymbionts which are mainly observed in the reproductive system of arthropods. The transmission of this bacterium is vertically by egg cytoplasm, hence to increase its distribution, it changes the host sex ratio in different ways. We previously showed that Wolbachia induce cytoplasmic incompatibility and affect reproductive behavior in the parasitoid wasp, Habrobracon hebetor. In this study, we questioned whether the presence of Wolbachia affect sex ratio of the H.hebetor inbreed lines. Four isolines of the parasitoid wasp including two Wolbachia infected (W+) and two Wolbachia cured (W–) lines were generated using tetracycline treatment and maintained for 10 generations in the laboratory condition at 25 ± 5 ºC, 60 ± 5% RH and a photoperiod of 16:8 h to promote inbreeding in the lines. The individuals used in the crosses (i.e. W+♀× W+♂, W–♀× W–♂) were derived from a propagation line and thus all individuals are expected to be closely related. We used ten pairs for each crosses and the sex ratio of these inbred lines (IW–and IW+) were then recorded for 10 generations (G11 to G20). Two outbred line (i.e. OW– and OW+) of this parasitoid wasp were used as the control. The sex ratio rate of IW–, IW+, OW– and OW+ were respectively as follow: 9.05±3.31, 27.80±6.90, 52.67±4.16 and 63.96±2.16. These results showed that sex ratio rate of the outbred lines were significantly higher than those of the inbred lines throughout the generations. Moreover, Wolbachia enhanced sex ratio in the both inbred and outbred lines compared to their respective lines without Wolbachia. Therefore, it seems that Wolbachia enhance sex ration rate of this parasitoid wasp in both inbred and outbred conditions. Males are dead end for Wolbachia while females are able to transfer this bacterium to the next generation. Considering females as a result of sexual reproduction in this insect, these results revealed that Wolbachia infection might have promoted sexual reproduction to generate more female offspring and propagate in the population.