Abstract：
Some parasitic fungi can increase fitness by modifying the behavior of their hosts. These behaviors are known as extended phenotypes because they favor parasitic gene propagation. Here, we studied three lineages of Ophiocordyceps, a fungus that infects ants, altering their conduct before death. According to fungal strategy, ants may die in leaf litter, with entwined legs in branches, under the moss mat, or biting plant tissue. It is critical for parasites that the corpses stay at these places because Ophiocordyceps exhibit iteroparity, possibly releasing spores in multiple life cycles. Thus, we assumed substrate cadaver permanence as a fungi reproductive proxy and corpse height as a proxy of cadaver removal. We hypothesize that biting vegetation and dying in higher places may increase the permanence of ant corpses while avoiding possible corpse predation on the forest floor. We monitored over a year more than 4000 zombie ants in approximately 15 km2 of undisturbed tropical forest in central Amazonia. Our results show a longer permanence of corpses with increasing ground height, suggesting that the parasites may have better chances of releasing spores and infecting new hosts at these places. We found that the zombie ants that last longer on the substrate die under the moss mat in tree trunks, not necessarily biting vegetation. The biting behavior appears to be the most derived and complex mechanism among Ophiocordyceps syndromes. Our results put these findings under a new perspective, proposing that seemingly less complex behavioral changes are ecologically equivalent and adaptative for other parasite lineages.
摘要：
一些寄生真菌可以通过改变其宿主的行为来增加适应性。这些行为被称为扩展表型，因为它们有利于寄生基因的传播。这里,我们研究了冬虫夏草的三个谱系，一种感染蚂蚁的真菌，在死前改变他们的行为。根据真菌策略，蚂蚁可能会死在落叶中,树枝上缠绕的腿，在苔藓垫下，或者咬植物组织.对于寄生虫来说，尸体留在这些地方是至关重要的，因为冬虫夏草表现出迭代性，可能在多个生命周期中释放孢子。因此，我们假设基质尸体的持久性作为真菌生殖代理，尸体高度作为尸体去除的代理。我们假设咬植被和在较高地方死亡可能会增加蚂蚁尸体的持久性，同时避免在森林地面上可能的尸体捕食。我们在亚马逊中部约15平方公里的未受干扰的热带森林中监测了超过4000只僵尸蚂蚁。我们的结果表明，随着地面高度的增加，尸体的持久性更长，这表明寄生虫在这些地方可能有更好的机会释放孢子并感染新宿主。我们发现在基质上持续更长时间的僵尸蚂蚁在树干的苔藓垫下死亡，不一定咬人的植被。咬人行为似乎是冬虫夏草综合征中最复杂和最复杂的机制。我们的结果将这些发现置于一个新的视角下，提出看似不太复杂的行为变化在生态上是等同的，并且适应其他寄生虫谱系。
