一项研究说，果蝇携带的共生细菌可以影响果蝇的交配偏好。进化论认为，进化的引擎――自然选择不仅对生物的基因起作用，也对生物携带的任何共生微生物的基因起作用。为了确定共生细菌是否影响果蝇的交配偏好并驱动着进化，Eugene Rosenberg及其同事用果蝇进行了交配偏好的测试，这些果蝇是在含有糖浆或淀粉的食物源中喂养的。这组作者报告说，在经过一代的生长后，喂养糖浆的果蝇更喜欢与同类果蝇交配，而不是与淀粉喂养的果蝇交配。
这组作者发现，这种偏好至少持续了37代，但是让果蝇服用抗生素从而杀死它们的共生细菌的时候，这种偏好终止了，这提示这种细菌而非食物源驱动着这种偏好。通过解读这种细菌的遗传蓝图，这组作者确定了植物乳杆菌（Lactobacillus plantarum）是这种交配偏好的部分触发原因。此外，这种细菌很可能通过改变果蝇角质层的性激素浓度从而影响了交配偏好。这组作者说，这些发现提示共生细菌可能影响交配选择和物种形成。
推荐英文摘要：
PNAS doi: 10.1073/pnas.1009906107
Commensal bacteria play a role in mating preference of Drosophila melanogaster
Gil Sharona, Daniel Segala, John M. Ringob, Abraham Hefetzc, Ilana Zilber-Rosenbergd, and Eugene Rosenberga,1
aDepartment of Molecular Microbiology and Biotechnology, Tel Aviv University, Tel Aviv 69978, Israel;
bSchool of Biology and Ecology, University of Maine, Orono, ME 04469;
cDepartment of Zoology, Tel Aviv University, Tel Aviv 69978, Israel; and
d18 Rachavat Ilan St., Givat Shmuel 51905, Israel
Development of mating preference is considered to be an early event in speciation. In this study, mating preference was achieved by dividing a population of Drosophila melanogaster and rearing one part on a molasses medium and the other on a starch medium. When the isolated populations were mixed, “molasses flies” preferred to mate with other molasses flies and “starch flies” preferred to mate with other starch flies. The mating preference appeared after only one generation and was maintained for at least 37 generations. Antibiotic treatment abolished mating preference, suggesting that the fly microbiota was responsible for the phenomenon. This was confirmed by infection experiments with microbiota obtained from the fly media (before antibiotic treatment) as well as with a mixed culture of Lactobacillus species and a pure culture of Lactobacillus plantarum isolated from starch flies. Analytical data suggest that symbiotic bacteria can influence mating preference by changing the levels of cuticular hydrocarbon sex pheromones. The results are discussed within the framework of the hologenome theory of evolution.
