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/ abstract摘要：穆勒棘轮和红皇后在淡水蜗牛性别维持中的作用研究尽管无性生殖比有性生殖具有两倍的生殖优势，但大多数真核生物分类群都是有性生殖。虽然有几种机制在理论上可以维持性，但都需要假设限制其适用性。最近的理论表明，突变积累和寄生虫压力之间的相互作用比单独作用的任何一种机制都能在较少的限制条件下维持性。更具体地说，毒力寄生导致的无性谱系瓶颈会增加遗传漂变的强度，从而增加有害突变积累和谱系灭绝的速度，而寄生严重的谱系相对于寄生较少的谱系。拟议的研究将通过使用线粒体DNA序列信息来估计受去势吸虫感染不同频率影响的淡水蜗牛混合有性/无性种群的无性谱系的年龄和突变分布来检验这些预测。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自然界中的性，将对围绕维持性的机制的争论做出有价值的贡献。这些结果将引起进化和自然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.