Schachner Lauren J, Mack Richard N, Novak Stephen J
School of Biological Sciences, Washington State University, Pullman, Washington 99164 USA.
Am J Bot. 2008 Dec;95(12):1584-95. doi: 10.3732/ajb.0800225. Epub 2008 Oct 31.
Biological invasions can be substantially influenced by the genetic sampling associated with a species' introduction. As a result, we assessed the genetic and evolutionary consequences of the entry and spread of the invasive grass Bromus tectorum (cheatgrass) across the United States midcontinent through an analysis of 54 populations, using enzyme electrophoresis. On average, these populations display 1.04 alleles per locus (A), 4.1% percent polymorphic loci per population (%P) and an expected mean heterozygosity (H(exp)) value of 0.009. Heterozygotes, which have been rarely reported for B. tectorum in North America, occur in three populations in the midcontinent and are likely novel multilocus genotypes that arose postimmigration. The midcontinent distribution of multilocus genotypes suggests that plant immigrants came directly from either the native range or the eastern United States, or both. Continued dispersal of preadapted genotypes and the assembly of populations that are genetic admixtures may enhance this invasion by increasing both the genetic diversity within populations and the selection of novel genotypes arising from occasional outcrossing. The potential for postimmigration evolution in most species points to the largely unrecognized need to block the introduction of new, potentially aggressive genotypes of an alien species already in the United States.
生物入侵会受到与物种引入相关的遗传采样的显著影响。因此，我们通过酶电泳分析了54个种群，评估了入侵性禾本科植物雀麦（cheatgrass）在美国中西部大陆的传入和扩散所带来的遗传和进化后果。这些种群平均每个位点显示1.04个等位基因（A），每个种群有4.1%的多态性位点（%P），预期平均杂合度（H(exp)）值为0.009。杂合子在北美雀麦中很少被报道，出现在中西部大陆的三个种群中，很可能是移民后出现的新的多位点基因型。多位点基因型在中西部大陆的分布表明，植物移民直接来自原生范围或美国东部，或两者皆有。预先适应的基因型的持续扩散以及作为遗传混合体的种群的聚集，可能会通过增加种群内的遗传多样性以及偶尔异交产生的新基因型的选择来增强这种入侵。大多数物种移民后进化的可能性表明，在美国已经存在的外来物种中，很大程度上需要阻止引入新的、可能具有侵略性的基因型，但这一点尚未得到充分认识。
