University of Nantes, Angers, Le Mans (L'UNAM), Agrocampus West, Centre of Angers, Institute of Genetics, Environment and Plant Protection (UMR 1349 IGEPP), 2, rue André Le Nôtre, F-49045, France.
Am J Bot. 2013 Jun;100(6):1162-70. doi: 10.3732/ajb.1200500. Epub 2013 May 29.
Although there is much empirical evidence for local adaptation in plant populations, spatial scales and drivers are still poorly understood. We used the annual species Brassica nigra to (1) test scales of differentiation and adaptation among coastal wetland and inland river-valley populations and (2) analyze herbivory as a potential driver of local plant adaptation. •
In a common garden experiment, we compared seven populations collected at different geographic scales in both habitat types. To evaluate adaptation to herbivory, we removed the aphid Brevicoryne brassicae from half of the plants. In a reciprocal transplant experiment, we tested local adaptation in two coastal and two river-valley populations. Natural colonization by dominant herbivore species was recorded. •
In the common garden, the river-valley populations showed a higher performance than the coastal ones, whereas large-scale differentiation within habitats was small. Such a differentiation among plant populations was also found in spontaneous infestation by several herbivore groups but not in the plant response to aphid removal. In the reciprocal transplant experiment at natural sites, both plant populations performed better in their home habitat, indicating local adaptation to environmental differences between coastal and river-valley sites. A lower aphid infestation on local plants suggests a contribution of herbivores to local plant adaptation and illustrates the need for reciprocal transplant experiments to evaluate this contribution. •
Our study demonstrates that adaptive differentiation among habitats may be stronger at relatively small scales than large-scale adaptation within these habitats. It provides new insights into the role of herbivory in driving local plant adaptation.
尽管有大量证据表明植物种群存在局部适应，但空间尺度和驱动因素仍了解甚少。我们使用一年生物种黑芥（Brassica nigra）来：（1）检验沿海湿地和内陆河谷种群之间的分化和适应尺度；（2）分析食草作用作为局部植物适应的潜在驱动因素。
在一个共同花园实验中，我们比较了在两种生境类型中不同地理尺度收集的七个种群。为了评估对食草作用的适应，我们从一半的植物上移除了蚜虫（Brevicoryne brassicae）。在一个双向移植实验中，我们测试了两个沿海和两个河谷种群的局部适应。记录了优势食草物种的自然定殖情况。
在共同花园中，河谷种群的表现优于沿海种群，而在生境内的大规模分化则较小。在几个食草动物群体的自发侵袭中也发现了这种植物种群之间的分化，但在植物对蚜虫去除的反应中则没有。在自然地点的双向移植实验中，两个植物种群在其原生境中表现更好，表明它们对沿海和河谷地点之间环境差异的局部适应。本地植物上较低的蚜虫侵袭表明食草动物对本地植物适应的贡献，并说明了需要进行双向移植实验来评估这种贡献。
我们的研究表明，相对于这些生境内的大尺度适应，生境之间的适应性分化在相对较小的尺度上可能更强。它为食草作用在驱动局部植物适应中的作用提供了新的见解。
