LTREB: A long-term Study of Host-parasite Interactions

解释遗传重组的广泛分布和维持被广泛认为是进化生物学家面临的最有趣的挑战之一，人们提出了大量的生态学和遗传学假说来解释为什么克隆繁殖不能普遍取代种群中的遗传重组个体。事实证明，对比这些替代方案很困难，但对克隆和重组个体共存的种群的研究极大地帮助了这一努力。这种混合种群在新西兰淡水蜗牛中很常见，它被用作评估不同假说的模型系统。在过去的研究中，没有发现对彩票假说、生殖保证假说或纠缠银行假说的支持。相比之下，过去的工作表明，重组个体的频率与幼虫吸虫感染的流行在空间上是相关联的。这一结果与寄生虫的时间滞后、频率相关的选择阻止克隆宿主消除重组宿主的想法是一致的--红皇后假说。但是，仍然需要对这一假设进行直接检验。这项LTREB研究将允许在混合种群中测量随着时间的推移重组和克隆个体的频率。长期的数据将对这样一种假设进行检验，即寄生虫的滞后选择阻止了自然种群中的克隆个体取代重组个体。

Lively0128510Explaining the widespread distribution and maintenance of genetic recombination is widely regarded as one of the most interesting challenges facing evolutionary biologists, and a large number of ecological and genetical hypotheses have been suggested to explain why clonal reproduction has not generally replaced genetically recombining individuals in populations. Contrasting these alternatives has proven difficult, but the effort is greatly aided by studies of populations in which clonal and recombinant individuals coexist. Such mixed populations are common in the freshwater New Zealand snail, Potamopyrgus antipodarum, which has been used as a model system for evaluating different hypotheses. In past studies, no support for the lottery hypothesis, the reproductive assurance hypothesis, or the tangled bank hypothesis has been found. In contrast, past work has shown that the frequency of recombinant individuals is spatially coupled with the prevalence of infection by larval trematodes. This result is consistent with the idea that time-lagged, frequency-dependent selection by parasites prevents the elimination of recombinant hosts by clonal hosts - the Red Queen hypothesis. But, direct tests of this hypothesis are still needed. This LTREB research will allow measurement in mixed populations of the frequency of recombinant and clonal individuals over time. Long-term data will provide a test of the hypothesis that time-lagged selection by parasites prevents the replacement of recombinant individuals by clonal individuals in natural populations.