Parasitism and the Maintenance of Genetic Variation in a Partial Parthenogen

进化生物学中最有趣的问题之一 问题是：为什么这么多自然种群 男性和女性？ 换句话说：为什么女性 无性繁殖，从而只产生克隆的女儿？ 假设没有伴随的生殖力下降，一种罕见的无性生殖 女性会产生两倍的女儿（四倍于 许多孙女）作为平均的性女性;和未经检查， 最终克隆体会呈指数级增长 取代了种群中的有性生殖的女性和男性。的 有性生殖在面对优势的时候仍然存在， 克隆表明，生产变量 后代 然而，目前还不清楚这是什么。 优势是。 为了解决这个问题，重要的是研究物种 同时具有两种繁殖模式， 以供比较。 在其中一个物种中，新西兰的淡水 蜗牛的有性繁殖与发病率相关， 寄生虫感染，这与 变异后代的产生是有利的 有高寄生风险的人群。 的目标 本研究的目的是：（1）确定是否有遗传 宿主-寄生虫相互作用的基础，（2）确定是否 寄生虫可以通过以下方式阻止性个体的消除： 一个或多个克隆，和（3）评估寄生虫对 蜗牛种群内遗传多样性的维持。 除了解决有关性的重要问题外， 与克隆繁殖相比，这些研究的结果 对研究疾病的重要意义 通过蜗牛媒介（如人）循环的类似蠕虫 血吸虫病），以及生物敌人在 保护自然种群的遗传多样性。

One of the most intriguing questions in evolutionary biology at the present time is: why do so many natural populations have males and females? Stated in another way: why don't females reproduce asexually and thereby produce only clonal daughters? Assuming no concomitant reduction in fecundity, a rare asexual female would produce twice as many daughters (and four times as many granddaughters) as the average sexual female; and unchecked, the resulting clone would grow exponentially, eventually replacing the sexual females and males in the population. That sexual reproduction persists in the face of the advantage of clones suggests that there is an advantage to producing variable offspring. It is currently unknown, however, what this advantage is. To address the question, it is important to study species that have both reproduction modes, so that there is a firm basis for comparison. In one such species, a freshwater New Zealand snail, sexual reproduction is correlated with the incidence of infection by parasitic worms, which is consistent with the idea that the production of variable progeny is favored in populations where there is a high risk of parasitism. The goals present study are to: (1) determine whether there is a genetic basis to the host-parasite interaction, (2) establish whether parasites can prevent the elimination of sexual individuals by one or more clones, and (3) to assess the effect of parasites on the maintenance of genetic diversity within snail populations. In addition to addressing important questions regarding sexual versus clonal reproduction, the results of these studies have important implications for the study of diseases caused by similar worms that cycle through snail vectors (e.g. human schistosomiasis), and the role that biological enemies play in preserving genetic diversity of natural populations.