Department of Entomology, The Pennsylvania State University, 501 ASI Building, University Park, PA 16802, USA; Huck Institutes of the Life Sciences, Millennium Sciences Complex, 101 Huck Life Sciences Building, The Pennsylvania State University, University Park, PA 16802, USA.
Department of Entomology, The Pennsylvania State University, 501 ASI Building, University Park, PA 16802, USA; Department of Biology, The Pennsylvania State University, Muller Lab, 208 Curtin Road, State College, PA 16801, USA; Huck Institutes of the Life Sciences, Millennium Sciences Complex, 101 Huck Life Sciences Building, The Pennsylvania State University, University Park, PA 16802, USA.
Curr Biol. 2019 Nov 4;29(21):3735-3738.e2. doi: 10.1016/j.cub.2019.09.004. Epub 2019 Oct 24.
The manipulation of animal behavior by parasitic organisms is one of the most complex adaptations to have arisen via natural selection. Among the most impressive examples of behavioral manipulation are the zombie-ant fungi [1]. In this association, ants are controlled to leave the colony and perform a stereotyped death grip behavior, where they bite onto vegetation over foraging trails, before being killed for the post mortem fungal growth. Manipulation functions to provide a platform outside the nest, from which fungal parasites actively shoot out spores, targeting foraging ants because within colony transmission is prevented by strong social immunity exhibited by social insect societies [2, 3]. It is not clear how such complex examples of host manipulation arose. To address this, we performed a broad-scale phylogenetic reconstruction of the order Hypocreales, to which the zombie-ant fungi, Ophiocordyceps, belong. In order to understand the patterns of host association and host switching along the evolution of Ophiocordyceps, we performed ancestral character state reconstruction analysis. We found that zombie-ant fungi likely arose from an ancestor that infected beetle larvae residing in soil or decaying wood, similar to extant beetle-infecting Ophiocordyceps species. Surprisingly, the jump led to an extensive species radiation observed after the development of behavioral manipulation. We suggest that the jump from solitary beetle larva to ants within a colony exposed the fungus to the robust social immunity of ant societies.
寄生虫操纵动物行为是通过自然选择产生的最复杂的适应之一。在行为操纵的最令人印象深刻的例子中，有僵尸蚂蚁真菌[1]。在这种共生关系中，蚂蚁被控制离开蚁群并执行一种刻板的死亡抓握行为，在那里它们咬住觅食路径上的植被，然后被杀死以进行死后真菌生长。这种操纵功能为巢外提供了一个平台，真菌寄生虫从那里积极地射出孢子，以觅食蚂蚁为目标，因为在蚁群中，由社会昆虫社会表现出的强烈社会免疫会阻止传播[2,3]。目前尚不清楚这种复杂的宿主操纵是如何产生的。为了解决这个问题，我们对僵尸蚂蚁真菌所属的子囊菌目进行了广泛的系统发育重建。为了了解在僵尸真菌进化过程中宿主关联和宿主转换的模式，我们进行了祖先特征状态重建分析。我们发现，僵尸蚂蚁真菌可能起源于感染生活在土壤或腐烂木材中的甲虫幼虫的祖先，类似于现存的感染甲虫的 Ophiocordyceps 物种。令人惊讶的是，这种跳跃导致了行为操纵发展后观察到的广泛物种辐射。我们认为，从单独的甲虫幼虫跳跃到蚁群中的蚂蚁，使真菌暴露在蚂蚁社会强大的社会免疫之下。
