Coevolution drives the emergence of complex traits and promotes evolvability.
Coevolution drives the emergence of complex traits and promotes evolvability.
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DOI：
10.1371/journal.pbio.1002023
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发表时间：
2014-12
期刊：
影响因子：
9.8
通讯作者：
Ofria C
中科院分区：
文献类型：
--
作者：
Zaman L;Meyer JR;Devangam S;Bryson DM;Lenski RE;Ofria C
使用数字宿主-寄生虫模型系统的实验表明，共同进化可以驱动复杂性状和更多可进化基因组的出现。作为一个历史事实，复杂生物特征的进化是显而易见的，但其潜在原因——包括自然选择的作用——却备受争议。古尔德认为，从必然简单的开始随机游走，随着时间的推移，会产生越来越复杂的现象。另一些人则认为，包括共同进化军备竞赛在内的选择，可以系统地将生物体推向更复杂的特征。方法上的挑战在很大程度上阻碍了对这些假设的实验检验。使用Avida数字进化平台，我们表明宿主和寄生虫的共同进化相对于其他方式大大增加了生物体的复杂性。随着寄生虫进化以对抗抗性宿主的增加，寄生虫种群保留了过去共同进化状态的遗传记录。因此，宿主通过执行越来越复杂的函数来差别化地逃避。我们表明，共同进化在宿主和寄生虫频率之间的独特反馈是复杂性进化的关键过程。引人注目的是，宿主进化出的基因组在表型上也更容易进化，类似于在细菌病原体中观察到的偶然性位点现象。由于共同进化在自然界中无处不在，我们的研究结果支持一个普遍的模型，即拮抗相互作用和自然选择共同有利于增加复杂性和进化性。在数十亿年的时间里，生命已经进化成今天遍布地球的极其多样化和复杂的有机体。虽然进化往往趋向于增加复杂性，但更复杂的特征并不一定使生物体更适合。那么，什么时候以及为什么更复杂更受青睐呢？一种假设是，宿主和寄生虫之间的对抗性共同进化可以通过促进防御和反防御的军备竞赛来驱动更复杂特征的进化。在这里，通过使用大量自我复制的主机程序和寄生程序（它们从宿主那里窃取处理能力），我们证明了共同进化促进了复杂性，并剖析了它是如何做到的。我们发现，为了共同进化驱动复杂的性状，必须出现共同进化谱系的多样性，而不是简单的升级。令人惊讶的是，共同进化还有第二个效应；它促进了更多可进化宿主的进化。因此，在进化的宿主基因组中，赋予寄生虫抗性的突变发生的频率很高，这有助于共同进化的宿主逃离它们的寄生虫。我们对人工系统的实验表明，自然普遍存在的共同进化过程如何促进复杂性和有利于可进化性。
Experiments using a digital host-parasite model system show that coevolution can drive the emergence of complex traits and more evolvable genomes. Homepage Title: Parasitism Drives the Evolution of Complexity The evolution of complex organismal traits is obvious as a historical fact, but the underlying causes—including the role of natural selection—are contested. Gould argued that a random walk from a necessarily simple beginning would produce the appearance of increasing complexity over time. Others contend that selection, including coevolutionary arms races, can systematically push organisms toward more complex traits. Methodological challenges have largely precluded experimental tests of these hypotheses. Using the Avida platform for digital evolution, we show that coevolution of hosts and parasites greatly increases organismal complexity relative to that otherwise achieved. As parasites evolve to counter the rise of resistant hosts, parasite populations retain a genetic record of past coevolutionary states. As a consequence, hosts differentially escape by performing progressively more complex functions. We show that coevolution's unique feedback between host and parasite frequencies is a key process in the evolution of complexity. Strikingly, the hosts evolve genomes that are also more phenotypically evolvable, similar to the phenomenon of contingency loci observed in bacterial pathogens. Because coevolution is ubiquitous in nature, our results support a general model whereby antagonistic interactions and natural selection together favor both increased complexity and evolvability. Over billions of years, life has evolved into the extraordinarily diverse and complex organisms that populate the Earth today. Although evolution often proceeds toward increasing complexity, more complex traits do not necessarily make organisms more fit. So when and why is greater complexity favored? One hypothesis is that antagonistic coevolution between hosts and parasites can drive the evolution of more complex traits by promoting arms races with increased defenses and counter-defenses. Here, by using populations of self-replicating host computer programs and parasitic programs, which steal processing power from their hosts, we demonstrated that coevolution promotes complexity and dissected how it does so. Instead of simple escalation, we found that a diversity of coevolving lineages must arise for coevolution to drive complex traits. Surprisingly, coevolution had a second effect; it promoted the evolution of more evolvable hosts. As a consequence, mutations in the evolved host genomes that confer resistance to parasites occur at high rates, which help the coevolved hosts outrun their parasites. Our experiments with an artificial system demonstrate how the naturally ubiquitous process of coevolution can promote complexity and favor evolvability.