Ludwig-Maximilians-Universität, Department Biologie II, Evolutionsökologie, Grosshaderner Str, 2, D-82152 Planegg-Martinsried, Germany.
BMC Evol Biol. 2012 Jan 27;12:12. doi: 10.1186/1471-2148-12-12.
Cyclical parthenogenetic water fleas of the genus Daphnia have become a prominent model organism in ecology and evolution. In the past, analyses of their population structure have been limited by the prevailing use of allozyme markers, which in general do not allow for the distinction of individual clones. In this study, we used 10 microsatellite markers to track changes in the taxonomic and clonal composition of Daphnia populations, and traced the abundance of the most common clones in two European reservoirs. One of the localities was inhabited by a single species of the Daphnia longispina complex (D. galeata), the other by two parental species (D. galeata and D. longispina) and their interspecific hybrids. The study took place during the transition from summer stratification to autumn mixing, representing a period of major environmental change within lake habitats.
In both reservoirs, we observed temporal (generation-to-generation) and spatial (along the heterogeneous reservoir environment) changes in Daphnia community structure. In the single-species reservoir, the clonal diversity of D. galeata increased with time, as a few dominant clones were replaced by a higher number of less common clones. A loss in selective advantage for the dominant clones may have been due to gradual changes in the environment, or due to selection acting in a negative frequency-dependent manner. In the multispecies reservoir, there were no apparent temporal trends in clonal diversity but we observed significantly lower clonal diversity in the interspecific hybrids than in the coexisting parental species, supporting the existence of reproductive barriers between the parental genomes.
Our study, tracing clonal lineages of Daphnia in time and space by the fine-resolution markers, contributes to the understanding of how clonal reproduction impacts community structure in cyclically parthenogenetic organisms.
周期性孤雌生殖水蚤属的水蚤已成为生态学和进化领域的重要模式生物。过去，对其种群结构的分析受到流行的同工酶标记物的限制，这些标记物通常无法区分个体克隆。在这项研究中，我们使用 10 个微卫星标记来跟踪 Daphnia 种群的分类和克隆组成的变化，并追踪了两个欧洲水库中最常见克隆的丰度。其中一个地点由长刺水蚤复合体（D. galeata）的单一物种组成，另一个由两个亲种（D. galeata 和 D. longispina）及其种间杂种组成。该研究发生在从夏季分层到秋季混合的过渡期间，这是湖泊栖息地内主要环境变化的时期。
在两个水库中，我们观察到 Daphnia 群落结构的时间（代际）和空间（沿不均匀的水库环境）变化。在单一物种水库中，D. galeata 的克隆多样性随时间增加，因为少数优势克隆被更多数量的不太常见的克隆所取代。优势克隆丧失选择优势可能是由于环境的逐渐变化，也可能是由于负频率依赖选择的作用。在多物种水库中，克隆多样性没有明显的时间趋势，但我们观察到种间杂种的克隆多样性明显低于共存的亲种，这支持了亲本基因组之间存在生殖障碍。
我们的研究通过精细分辨率的标记物追踪了 Daphnia 的克隆谱系，有助于理解克隆繁殖如何影响周期性孤雌生殖生物的群落结构。
