Rice Kevin J, Mack Richard N
Department of Agronomy and Range Science, University of California, 95616, Davis, CA, USA.
Department of Botany, Washington State University, 99164, Pullman, WA, USA.
Oecologia. 1991 Sep;88(1):91-101. doi: 10.1007/BF00328408.
By incorporating demographic analyses of fitness components (e.g., survival and reproduction) within a reciprocal sowing design, we tested for 3 consecutive years whether local adaptation has occurred in the alien grass Bromus tectorum (cheatgrass) within 7 habitats along an environmental gradient from arid steppe to subalpine forest in the Intermontain Region of western North America. Patterns of emergence and survival were strongly influenced by the local environment. In terms of survival, expression of significant local adaptation in Tsuga heterophylla habitat varied among years. In contrast, relative differences in flowering time among seed sources were stable across sites and years. Populations from the arid steppe were the earliest to flower; flowering was latest in populations from the mesic Tsuga heterophylla habitat. In terms of net reproductive rate, evidence for local adaptation in B. tectorum was obtained in populations from habitats representing environmental extremes: an arid, saline site dominated by the shrub Sarcobatus vermiculatus and clearings within the cool, mesic Tsuga heterophylla forest habitat. Unlike the plants introduced from other sites, members of the resident population at the Sarcobatus site flowered and produced seeds before soil water became limiting. In contrast, net reproductive rates in other habitats were sometimes the lowest for populations in their home site. This lack of an advantage for local populations within more environmentally moderate sites suggests that limited dispersal may restrict the rate at which superior genotypes are introduced into a particular site.
通过在相互播种设计中纳入对适合度组成部分（如存活和繁殖）的种群统计学分析，我们连续三年在北美西部山间地区从干旱草原到亚高山森林的环境梯度上的7个栖息地，测试外来禾本科植物小花碱茅（cheatgrass）是否发生了本地适应性。出苗和存活模式受当地环境的强烈影响。就存活而言，异叶铁杉栖息地显著本地适应性的表现随年份而变化。相比之下，不同种子源之间开花时间的相对差异在不同地点和年份是稳定的。来自干旱草原的种群最早开花；在中生的异叶铁杉栖息地的种群中开花最晚。就净繁殖率而言，在代表极端环境的栖息地的小花碱茅种群中获得了本地适应性的证据：一个以灌木蛭石肉叶刺茎藜为主的干旱、盐碱地，以及凉爽、中生的异叶铁杉森林栖息地中的林中空地。与从其他地点引入的植物不同，肉叶刺茎藜地点的本地种群成员在土壤水分成为限制因素之前就开花并结籽。相比之下，其他栖息地的净繁殖率有时在其原生地的种群中是最低的。在环境较为温和的地点，本地种群缺乏这种优势，这表明有限的扩散可能会限制优良基因型引入特定地点的速度。
