No sex in fungus-farming ants or their crops
No sex in fungus-farming ants or their crops
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DOI：
10.1098/rspb.2009.0313
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发表时间：
2009-07-22
影响因子：
4.7
通讯作者：
Mueller, Ulrich G.
中科院分区：
文献类型：
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作者：
Himler, Anna G.;Caldera, Eric J.;Mueller, Ulrich G.
无性繁殖给无性物种带来了进化障碍，使它们容易灭绝，因为无性繁殖产生新的基因型，清除有害突变的速度比有性繁殖要慢。在这里，我们报告了蚂蚁中第一个完全无性繁殖的案例，真菌生长的蚂蚁Mycocepurus smithii，蚁后无性繁殖，而工蚁是不育的，这是双重谜，因为m.s smithii的无性繁殖群体也依赖无性真菌作为食物。退化的雌性交配解剖，广泛的野外和实验室调查，以及DNA指纹表明，这种广泛分布的蚂蚁物种是完全无性的。母系遗传的细菌（如沃尔巴克氏菌，红柱头菌）和真菌品种可以被排除为诱导无性繁殖的媒介。密氏雌虫的无性繁殖群体提供了一种独特的系统来测试社会性昆虫的亲子冲突和生殖监管理论。蚁农和真菌作物的无性性挑战了传统观点，即有性农民蚂蚁超越了有性作物病原体的共同进化，从而弥补了其无性作物的脆弱性。要么是农民和作物的双重无性可能使寄主出于未知的原因充分利用无性的优势，要么是在作物之间的频繁切换（共生重新结合）产生了新的抗真菌组合，这可能弥补了斯密氏杆菌无性性的任何进化缺陷。
Asexual reproduction imposes evolutionary handicaps on asexual species, rendering them prone to extinction, because asexual reproduction generates novel genotypes and purges deleterious mutations at lower rates than sexual reproduction. Here, we report the first case of complete asexuality in ants, the fungus-growing ant Mycocepurus smithii, where queens reproduce asexually but workers are sterile, which is doubly enigmatic because the clonal colonies of M. smithii also depend on clonal fungi for food. Degenerate female mating anatomy, extensive field and laboratory surveys, and DNA fingerprinting implicate complete asexuality in this widespread ant species. Maternally inherited bacteria (e. g. Wolbachia, Cardinium) and the fungal cultivars can be ruled out as agents inducing asexuality. M. smithii societies of clonal females provide a unique system to test theories of parent-offspring conflict and reproductive policing in social insects. Asexuality of both ant farmer and fungal crop challenges traditional views proposing that sexual farmer ants outpace coevolving sexual crop pathogens, and thus compensate for vulnerabilities of their asexual crops. Either the double asexuality of both farmer and crop may permit the host to fully exploit advantages of asexuality for unknown reasons or frequent switching between crops (symbiont reassociation) generates novel ant-fungus combinations, which may compensate for any evolutionary handicaps of asexuality in M. smithii.