Muller M-H, Poncet C, Prosperi J M, Santoni S, Ronfort J
UMR Diversité et Génomes des Plantes Cultivées, INRA, Domaine de Melgueil, Mauguio, France.
Mol Ecol. 2006 May;15(6):1589-602. doi: 10.1111/j.1365-294X.2006.02851.x.
DNA sequence polymorphism carries genealogical information and allows for testing hypotheses on selection and population history, especially through coalescent-based analysis. Understanding the evolutionary forces at work in plant domestication and subsequent selection is of critical importance for the management of genetic resources. In this study, we surveyed DNA sequence diversity at two assumed neutral nuclear loci in the wild-domesticated species complex of alfalfa (Medicago sativa L.). A high level of polymorphism was detected. The domesticated pool contains on average 31% less diversity than the wild pool, but with a high heterogeneity among loci. Coalescent simulations of the domestication process showed that this result cannot be explained by assuming a constant population size but is rather consistent with a demographic bottleneck during domestication. A very low level of divergence was detected between the wild and the domesticated forms as well as between the related subspecies of the M. sativa species complex. However, the originality of the Spanish wild populations, already observed based on mitochondrial DNA polymorphism, was confirmed. These results, together with patterns of intrapopulation polymorphism, suggest that nuclear sequence polymorphism could be a promising tool, complementary to mitochondrial DNA and phenotypic evaluations, to investigate historical demographic and evolutionary processes.
DNA序列多态性携带系谱信息，并允许对选择和种群历史的假设进行检验，特别是通过基于溯祖理论的分析。了解植物驯化及后续选择过程中起作用的进化力量对于遗传资源的管理至关重要。在本研究中，我们调查了苜蓿（紫花苜蓿）野生-驯化物种复合体中两个假定的中性核基因座的DNA序列多样性。检测到高水平的多态性。驯化群体的多样性平均比野生群体少31%，但基因座间存在高度异质性。对驯化过程的溯祖模拟表明，这一结果不能通过假定种群大小恒定来解释，而是与驯化过程中的种群瓶颈相一致。在野生型和驯化型之间以及紫花苜蓿物种复合体的相关亚种之间检测到非常低水平的分化。然而，基于线粒体DNA多态性已经观察到的西班牙野生种群的独特性得到了证实。这些结果与种群内多态性模式一起表明，核序列多态性可能是一种有前途的工具，可作为线粒体DNA和表型评估的补充，用于研究历史种群动态和进化过程。
