导读：进化理论认为，寄生虫和病原体要比它们的宿主进化的速度快，因为它们的代长短，且要经历严酷的筛选。但这就形成了一个悖论：宿主，或者说“寄生牺牲者”是如何不顾进化更快的寄生敌人的持续攻击而生存，甚至还发展繁荣呢……
结网虫侵袭欧洲防风草（图：Christine Hanrahan）
在自然界中，宿主是如何在寄生虫的攻击中生存下来？这个问题一直到目前都没有得到很好的解答。一个新的数目模型显示，当宿主和其寄生虫各自都有许多管理彼此间相互作用的特质时，宿主独特的进化优势可帮助它生存下来。
这个重要的研究成果也许解释人类以及动植物是如何进化以抵抗寄生虫的强攻的。
进化理论认为，寄生虫和病原体要比它们的宿主进化的速度快，因为它们的代长短，且要经历严酷的筛选。但这就形成了一个悖论：宿主，或者说“寄生牺牲者”是如何不顾进化更快的寄生敌人的持续攻击而生存，甚至还发展繁荣呢？
“为了研究这些特质的数量对共进化的影响，我们使用定量遗传学及基于个体的模拟来分析牺牲者-掠夺者系统的模型，”研究论文的作者Gilman说。“我们可以发现，当多个特质（而非单一某个特质）管理宿主与寄生虫之间的反应时，牺牲者在进化的军备竞赛中占得上风。”
在自然界，物种之间的相互作用通常受到多个特质的影响。例如，欧洲防风草对结网虫的抵抗取决于其开花的时期以及所有含有的具有杀虫特性的特定化学成分的浓度。相似地，硬骨鱼，例如金枪鱼和大比目鱼拥有多个防御性特质，比如粘膜屏障、杀灭性分泌物等，寄生虫必须克服这些防御才能成功寄生到宿主上。
研究表明，具有多个攻击与防御机制也许可以帮助被寄生一方进化并维持与寄生者之间的低互作率。此外，该研究认为，多特质的共进化也许可帮助植物限制食草动物所造成的损伤，这也许还可以解释为什么世界是绿色的。
Coevolution in multidimensional trait space favours escape from parasites and pathogens
R. Tucker Gilman, Scott L. Nuismer & Dwueng-Chwuan Jhwueng
Almost all species are subject to continuous attack by parasites and pathogens. Because parasites and pathogens tend to have shorter generation times and often experience stronger selection due to interaction than their victims do, it is frequently argued that they should evolve more rapidly and thus maintain an advantage in the evolutionary race between defence and counter-defence. This prediction generates an apparent paradox: how do victim species survive and even thrive in the face of a continuous onslaught of more rapidly evolving enemies5? One potential explanation is that defence is physiologically, mechanically or behaviourally easier than attack, so that evolution is less constrained for victims than for parasites or pathogens. Another possible explanation is that parasites and pathogens have enemies themselves and that victim species persist because parasites and pathogens are regulated from the top down and thus generally have only modest demographic impacts on victim populations. Here we explore a third possibility: that victim species are not as evolutionarily impotent as conventional wisdom holds, but instead have unique evolutionary advantages that help to level the playing field. We use quantitative genetic analysis and individual-based simulations to show that victims can achieve such an advantage when coevolution involves multiple traits in both the host and the parasite.
文献链接：https://www.nature.com/nature/journal/vaop/ncurrent/full/nature10853.html
