BACKGROUND Genetic parasites are ubiquitous satellites of cellular life forms most of which host a variety of mobile genetic elements including transposons, plasmids and viruses. Theoretical considerations and computer simulations suggest that emergence of genetic parasites is intrinsic to evolving replicator systems. RESULTS Using methods of bifurcation analysis, we investigated the stability of simple models of replicator-parasite coevolution in a well-mixed environment. We first analyze what appears to be the simplest imaginable system of this type, one in which the parasite evolves during the replication of the host genome through a minimal mutation that renders the genome of the emerging parasite incapable of producing the replicase but able to recognize and recruit it for its own replication. This model has only trivial or "semi-trivial", parasite-free equilibria: an inefficient parasite is outcompeted by the host and dies off, whereas an efficient one pushes the host out of existence, leading to the collapse of the entire system. We show that stable host-parasite coevolution (a non-trivial equilibrium) is possible in a modified model where the parasite is qualitatively distinct from the host replicator in that the replication of the parasite depends solely on the availability of the host but not on the carrying capacity of the environment. CONCLUSIONS We analytically determine the conditions for stable coevolution of genetic parasites and their hosts coevolution in simple mathematical models. It is shown that the evolutionary dynamics of a parasite that initially evolves from the host through the loss of the ability to replicate autonomously must substantially differ from that of the host, for a stable host-parasite coevolution regime to be established.

中文翻译：

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遗传寄生虫及其寄主的稳定共同进化机制：必须共同进化。

背景技术遗传寄生虫是细胞生命形式的普遍存在的卫星，其大多数具有多种移动遗传元件，包括转座子，质粒和病毒。理论上的考虑和计算机模拟表明遗传寄生虫的出现是不断发展的复制系统的内在因素。结果使用分叉分析方法，我们研究了在充分混合的环境中简单的复制子-寄生虫共进化模型的稳定性。我们首先分析看似最简单的这种类型的系统，该系统中的寄生虫通过最小突变使宿主基因组复制过程中发生进化，该突变使新兴寄生虫的基因组无法产生复制酶，但能够识别和识别招募它自己复制。此模型只有琐碎的或“