Bartkowska Magdalena P, Johnston Mark O
Department of Biology, Life Sciences Centre, Dalhousie University, Halifax, Nova Scotia B3H 4J1, Canada.
Evolution. 2009 May;63(5):1103-17. doi: 10.1111/j.1558-5646.2008.00607.x. Epub 2009 Jan 6.
Self-fertilization is expected to reduce genetic diversity within populations and consequently to limit adaptability to changing environments. Little is known, however, about the way the evolution of self-fertilization changes the amount or pattern of the components of genetic variation in natural populations. In this study, a reciprocal North Carolina II design and maximum-likelihood methods were implemented to investigate the genetic basis of variation for 15 floral and vegetative traits in four populations of the annual plant Amsinckia spectabilis (Boraginaceae) differing in mating system. Six variance components were estimated according to Cockerham and Weir's "bio" model c. Compared to the three partially selfing populations, we found significantly lower levels of nuclear variance for several traits in the nearly completely self-fertilizing population. Furthermore, for 11 of 15 traits we did not detect nuclear variation to be significantly greater than zero. We also found high maternal variance in one of the partially selfing populations for several traits, and little dominance variance in any population. These results are in agreement with the evolutionary dead-end hypothesis for highly self-fertilizing taxa.
自花受精预计会降低种群内的遗传多样性，从而限制对不断变化环境的适应性。然而，对于自花受精的进化如何改变自然种群中遗传变异成分的数量或模式，人们了解甚少。在本研究中，采用了互交北卡罗来纳II设计和最大似然法，来研究一年生植物壮丽勿忘草（紫草科）四个交配系统不同的种群中15个花部和营养性状变异的遗传基础。根据科克伦和韦尔的“生物”模型c估计了六个方差成分。与三个部分自交的种群相比，我们发现近完全自花受精种群中几个性状的核方差水平显著更低。此外，对于15个性状中的11个，我们未检测到核变异显著大于零。我们还发现，在一个部分自交的种群中，几个性状存在较高的母本方差，而在任何种群中显性方差都很小。这些结果与高度自花受精类群的进化死胡同假说一致。
