DISSERTATION RESEARCH: An Investigation of the Role of Interaction between Muller's Ratchet and the Red Queen in the Maintenance of Sex in a Freshwater Snail

摘要论文研究：Muller棘齿与红皇后相互作用在淡水蜗牛性别维持中的作用的研究尽管无性生殖比有性生殖有两倍的生殖优势，但大多数真核生物都是有性生殖的。 虽然理论上有几种机制可以维持性别，但所有这些机制都需要限制其适用性的假设。 最近的理论表明，突变积累和寄生虫压力之间的相互作用可以在限制较少的条件下维持性比单独作用的机制。 更具体地说，由有毒寄生引起的无性谱系的重复检查将增加遗传漂变的强度，从而增加相对于较少寄生的谱系，在严重寄生的谱系中有害突变积累和谱系灭绝的速率。 拟议的研究将通过使用线粒体DNA序列信息来评估这些预测，以估计来自混合性/无性种群的淡水蜗牛的无性系内的年龄和突变分布，这些淡水蜗牛受到去势吸虫感染频率的影响。这个项目的结果，第一个已知的解决机制之间的相互作用是否可以维持性的性质，将是一个宝贵的贡献，围绕维持性的机制的辩论。 这些结果将引起进化和保护生物学家的广泛兴趣。

AbstractDISSERTATION RESEARCH: An Investigation of the Role of Interaction between Muller's Ratchet and the Red Queen in the Maintenance of Sex in a Freshwater SnailLivelyDEB-0308382Despite the two-fold reproductive advantage of asexual over sexual reproduction, most eukaryotic taxa are sexual. Although there are several mechanisms that can theoretically maintain sex, all require assumptions that limit their applicability. Recent theory has shown that interaction between mutation accumulation and parasite pressure can maintain sex under less restrictive conditions than under either mechanism acting alone. More specifically, the bottlenecking of asexual lineages caused by virulent parasitism will increase the strength of genetic drift and thus the rates of deleterious mutation accumulation and lineage extinction in heavily parasitized lineages relative to less parasitized lineages. The proposed study will examine these predictions by using mitochondrial DNA sequence information to estimate the age of and mutational distribution within asexual lineages from mixed sexual/asexual populations of a freshwater snail that are afflicted by varying frequencies of infection by a castrating trematode. The results of this project, the first known to address whether interaction between mechanisms can maintain sex in nature, will be a valuable contribution to the debate surrounding the mechanisms underlying the maintenance of sex. The results would be of wide interest to evolutionary and conservation biologists.