Institute for Ecosystem Research/Geobotany, Kiel University, Olshausenstrasse 75, Kiel, 24118, Germany.
Institute of Biology/Geobotany and Botanical Garden, Martin Luther University Halle-Wittenberg, Am Kirchtor 1, Halle, 06108, Germany.
Ecology. 2019 May;100(5):e02665. doi: 10.1002/ecy.2665. Epub 2019 Apr 8.
Ultraviolet (UV) radiation intensities differ among global regions, with significantly higher levels in the southern hemisphere. UV-B may act as an environmental filter during plant invasions, which might particularly apply to plant species from Europe introduced to New Zealand. Just like for any other abiotic or biotic filter, successful invaders can cope with novel environmental conditions via plastic responses and/or through rapid adaptation by natural selection in the exotic range. We conducted a multispecies experiment with herbaceous plants in two common gardens located in the species' native and exotic ranges, in Germany and New Zealand, respectively. We used plants of German and New Zealand origin of eight species to test for adaptation to higher UV-B radiation in their new range. In each common garden, all plants were exposed to three radiation treatments: (1) ambient sunlight, (2) exclusion of UV-B while transmitting ambient UV-A, and (3) combined exclusion of UV-B and UV-A. Linear mixed-effect models revealed significant effects of UV-B on growth and leaf traits and an indication for UV-B-induced biomass reduction in both common gardens pointing to an impact of natural, ambient UV radiation intensities experienced by plants in the northern and in the southern hemisphere. In both common gardens, the respective local plants (i.e., German origins in Germany, New Zealand origins in New Zealand) displayed enhanced productivity and aboveground biomass allocation, thus providing evidence for recent evolutionary processes in the exotic range. Genetic differentiation between different origins in consequence of divergent local selection pressures was found for specific leaf area. This differentiation particularly hints at different selective forces in both ranges while only little evidence was found for an immediate selective effect of high UV-B intensities in the exotic range. However, reaction norm slopes across ranges revealed higher plasticity of exotic individuals in functional leaf traits that might allow for a more sensitive regulation of photoprotection measures in response to UV-B. During the colonization, New Zealand populations might have been selected for the observed higher phenotypic plasticity and a consequently increased ability to successfully spread in the exotic range.
紫外线（UV）辐射强度在全球各地区有所不同，南半球的水平明显更高。在植物入侵过程中，UV-B 可能充当环境过滤器，这可能特别适用于从欧洲引入新西兰的植物物种。与任何其他非生物或生物过滤器一样，成功的入侵物种可以通过可塑性反应和/或通过在异国范围内的自然选择进行快速适应来应对新的环境条件。我们在德国和新西兰的两个普通花园中进行了一个多物种草本植物实验，这些花园分别位于物种的原生和外来范围。我们使用了来自德国和新西兰的 8 个物种的植物，以测试它们在新范围内对更高 UV-B 辐射的适应性。在每个普通花园中，所有植物都暴露在三种辐射处理下：（1）环境阳光，（2）排除 UV-B 同时传输环境 UV-A，（3）排除 UV-B 和 UV-A 的组合。线性混合效应模型显示，UV-B 对生长和叶片性状有显著影响，并且在两个普通花园中都有迹象表明 UV-B 诱导的生物量减少，这表明北半球和南半球植物经历的自然环境 UV 辐射强度有影响。在两个普通花园中，各自的本地植物（即在德国的德国起源，在新西兰的新西兰起源）显示出生产力和地上生物量分配的增强，从而为异国范围的最近进化过程提供了证据。由于不同的局部选择压力，不同起源之间的遗传分化在特定叶面积上发现。这种分化特别暗示了两个范围的不同选择力，而在异国范围内几乎没有发现高 UV-B 强度的直接选择效应的证据。然而，跨范围的反应规范斜率显示出异国个体在功能叶片性状上的更高可塑性，这可能允许对 UV-B 进行更敏感的光保护措施调节。在殖民化过程中，新西兰种群可能因观察到的更高表型可塑性而被选择，从而增加了在异国范围内成功传播的能力。
