Mealor Brian A, Hild Ann L
Department of Renewable Resources, University of Wyoming, Box 3354, Laramie, Wyoming 82071, USA.
Mol Ecol. 2006 Jul;15(8):2291-300. doi: 10.1111/j.1365-294X.2006.02931.x.
Ecological impacts of invasive plant species are well documented, but the genetic response of native species to invasive dominance has been often overlooked. Invasive plants can drastically alter site conditions where they reach dominance, potentially exerting novel selective pressures on persistent native plant populations. Do native plant populations in old exotic invasions show evidence of selection when compared to conspecific populations in adjacent, noninvaded areas? We employ amplified fragment length polymorphism (AFLP) analysis to screen a large number of loci from two native grass species (Hesperostipa comata (Trin. & Rupr.) Barkworth and Sporobolus airoides Torr.) that occur in old infestations of the invasive forb Acroptilon repens. We then compare observed locus by locus F(ST) values with distributions of F(ST) estimated from simulation models under expectation of neutrality. We also compare the proportion of loci possibly linked to selection and those not linked to selection which exhibit parallel trends in divergence between two community types (invaded, noninvaded). Few loci (H. comata, 2.6%; S. airoides, 8.7%) in the two native grasses may be linked to genes under the influence of selection. Also, loci linked to selection showed a greater portion of parallel trends in divergence than neutral loci. Genetic similarities between community types were less than genetic similarity within community types suggesting differentiation in response to community alteration. These results indicate that a small portion of scored AFLP loci may be linked to genes undergoing selection tied to community dominance by an invasive species. We propose that native plants in communities dominated by exotic invasives may be undergoing natural selection.
入侵植物物种的生态影响已有充分记载，但本地物种对入侵优势的遗传反应却常常被忽视。入侵植物能极大地改变它们达到优势地位的场地条件，可能对留存的本地植物种群施加新的选择压力。与相邻未受入侵地区的同种植物种群相比，长期受外来入侵影响地区的本地植物种群是否显示出选择的迹象呢？我们采用扩增片段长度多态性（AFLP）分析，从两种本地禾本科植物（针茅（Hesperostipa comata (Trin. & Rupr.) Barkworth）和碱茅（Sporobolus airoides Torr.））中筛选大量基因座，这些植物生长在入侵性杂草顶羽菊（Acroptilon repens）的长期侵扰区域。然后，我们将逐个基因座观察到的F(ST)值与在中性预期下通过模拟模型估计的F(ST)分布进行比较。我们还比较了可能与选择相关的基因座比例和与选择无关的基因座比例，这两类基因座在两种群落类型（受入侵、未受入侵）之间的分化中呈现出平行趋势。两种本地禾本科植物中很少有基因座（针茅为2.6%；碱茅为8.7%）可能与受选择影响的基因相关。此外，与选择相关的基因座在分化中呈现平行趋势的比例高于中性基因座。群落类型之间的遗传相似性低于群落类型内部的遗传相似性，这表明对群落改变存在响应差异。这些结果表明，一小部分已评分的AFLP基因座可能与受选择影响的基因相关，这些选择与入侵物种的群落优势有关。我们认为，在外来入侵物种主导的群落中，本地植物可能正在经历自然选择。
