Rice Kevin J, Mack Richard N
Department of Agronomy and Range Science, University of California-Davis, 95616, Davis, CA, USA.
Department of Botany, Washington State University, 99164, Pullman, WA, USA.
Oecologia. 1991 Sep;88(1):77-83. doi: 10.1007/BF00328406.
An understanding of how genetic differentiation and phenotypic plasticity may interact to promote the spread of an introduced species requires information on the hierarchical distribution of genetic variation within the species in its new range. For example, a lack of genetic variation within marginal populations of an introduced species may slow its rate of spread into new habitats. In a glasshouse study, we examined the phenotypic variation among populations, among families, within families, and the homogeneity of variances within families for morphological and life history characters of an alien, self-pollinating annual grass, Bromus tectorum. The populations of B. tectorum studied were collected from both large, central populations in steppe habitats and small, peripheral populations in forest sites along a broad temperature-moisture gradient in western North America. Most variation in average flowering time was due to differences among seed source populations; among family variation contributed less than 20% to the total variance for flowering time. Populations from arid steppe habitats were the earliest flowering while the population from the most mesic forest habitat was last to flower. In contrast, the within-family variance was a major contributor to the total variance for plant dry weight, seed number per plant, total seed weight, and individual seed weight. The amount of total variation explained by among-family differences ranged between 18% for average seed weight to 30% for total plant dry weight. There was no consistent difference in within-population genetic variability between large, central populations in steppe habitats and smaller, potentially more isolated populations in forest habitats. Significant heterogeneity in within-family variance in some of the source populations suggest that families differ in the capacity for phenotypic response to environmental variation. Considered independently from source population, there was no consistent trend linking a particular trait to increased heterogeneity of within-family variances.
要理解遗传分化和表型可塑性如何相互作用以促进外来物种的扩散，需要了解该物种在新分布范围内遗传变异的层次分布信息。例如，外来物种边缘种群缺乏遗传变异可能会减缓其向新栖息地扩散的速度。在一项温室研究中，我们研究了外来自花授粉一年生草本植物——雀麦的种群间、家系间、家系内的表型变异，以及家系内形态和生活史特征方差的同质性。所研究的雀麦种群采集于北美西部沿广泛温度 - 湿度梯度的草原栖息地的大型中心种群和森林地带的小型边缘种群。平均开花时间的大部分变异是由于种子源种群之间的差异；家系间变异对开花时间总方差的贡献不到20%。来自干旱草原栖息地的种群最早开花，而来自最湿润森林栖息地的种群最后开花。相比之下，家系内方差是植物干重、单株种子数、种子总重和单粒种子重总方差的主要贡献因素。家系间差异解释的总变异量范围从平均种子重的18%到植物总干重的30%。草原栖息地的大型中心种群和森林栖息地较小且可能更孤立的种群在种群内遗传变异性方面没有一致的差异。一些种子源种群家系内方差存在显著的异质性，这表明家系在对环境变异的表型响应能力上存在差异。独立于种子源种群考虑时，没有一致的趋势将特定性状与家系内方差的异质性增加联系起来。
