Lively C M
Department of Biology, Indiana University, Bloomington, IN 47405, USA.
J Evol Biol. 2009 Oct;22(10):2086-93. doi: 10.1111/j.1420-9101.2009.01824.x. Epub 2009 Sep 1.
Why don't asexual females replace sexual females in most natural populations of eukaryotes? One promising explanation is that parasites could counter the reproductive advantages of asexual reproduction by exerting frequency-dependent selection against common clones (the Red Queen hypothesis). One apparent limitation of the Red Queen theory, however, is that parasites would seem to be required by theory to be highly virulent. In the present study, I present a population-dynamic view of competition between sexual females and asexual females that interact with co-evolving parasites. The results show that asexual populations have higher carrying capacities, and more unstable population dynamics, than sexual populations. The results also suggest that the spread of a clone into a sexual population could increase the effective parasite virulence as population density increases. This combination of parasite-mediated frequency-dependent selection, and density-dependent virulence, could lead to the coexistence of sexual and asexual reproductive strategies and the long-term persistence of sex.
为什么在大多数真核生物的自然种群中，无性生殖的雌性没有取代有性生殖的雌性呢？一个有前景的解释是，寄生虫可以通过对常见克隆体施加频率依赖型选择（红皇后假说）来抵消无性生殖的繁殖优势。然而，红皇后理论的一个明显局限在于，从理论上讲，似乎要求寄生虫具有高毒性。在本研究中，我提出了一个关于有性生殖雌性和无性生殖雌性与共同进化的寄生虫相互作用的种群动态竞争观点。结果表明，无性生殖种群比有性生殖种群具有更高的承载能力和更不稳定的种群动态。结果还表明，随着种群密度增加，一个克隆体扩散到有性生殖种群中会增加寄生虫的有效毒性。这种寄生虫介导的频率依赖型选择和密度依赖型毒性的结合，可能导致有性和无性生殖策略的共存以及性别的长期存在。
