DISSERTATION RESEARCH "Clinal variation for life history in a freshwater snail"

在新西兰淡水蜗牛Potamopyrgus antipodarum的两个湖泊种群中观察到了生殖模式的逐渐变化。克隆女性占主导地位的深栖息地，而交叉的男性和女性占主导地位的浅水区。两个湖中的蜗牛都被一种吸虫寄生虫感染，它使所有个体绝育，并且在浅水区更为普遍。在蜗牛的生活史（LH）性状的渐变也被发现，浅水蜗牛成熟时比深水蜗牛小。该项目将确定寄生虫频率的差异是否与异花受精的频率呈正相关，并与新西兰南岛20个湖泊中蜗牛种群LH性状的差异呈正相关。PI将确定生殖模式，寄生虫的流行，以及是否可以通过实验室实验在交叉感染的个体中进化出对感染的抗性。 P. antipodarum研究系统非常适合使用野外数据来测试重要的进化理论，提供关于寄生作用在多大程度上塑造宿主种群的信息。此外，蠕虫是人类和家养动物的重要病原体。根据世界卫生组织的数据，有2亿人感染了引起血吸虫病的吸虫，血吸虫病对公共卫生的影响仅次于疟疾。尽管如此，人们对蜗牛种群在传播这些蠕虫方面的影响知之甚少，这些蠕虫与本研究中研究的蠕虫具有相似的生命周期。因此，这项国际性的多实验室研究应该会引起旨在控制这些疾病的组织的兴趣。

A gradual change in the reproductive mode has been observed in two lake populations of the freshwater New Zealand snail, Potamopyrgus antipodarum. Clonal females dominate deep habitats, while cross-fertilizing males and females dominate the shallow regions. Snails in both lakes are infected by a trematode parasite, Microphallus sp., which sterilizes all individuals, and is more prevalent in shallow regions. A cline in the snail's life history (LH) traits has also been found where shallow-water snails mature at a smaller size than deep-water snails. This project will determine whether the difference in parasite frequency is positively correlated with the frequency of cross-fertilization and with differences in LH traits for snail populations in 20 lakes on the South Island of New Zealand. The PIs will determine reproductive mode, parasite prevalence, and whether resistance to infection can evolve in cross-fertilizing individuals using laboratory experiments. The P. antipodarum study system is well suited to test important evolutionary theories using field data, providing information on the extent to which parasitism shapes a host population. Moreover, trematode worms are important disease agents in both humans and domesticated animals. According to the World Health Organization, 200 million people are infected by the trematodes that cause Schistosomiasis, which is second to malaria in its public health impact. Nonetheless, little is known about the effects of the snail populations in spreading these worms, which have similar life cycles to the worms studied in this research. Thus, this international, multi-lab investigation should interest organizations that aim to control these diseases.