Václavík Tomáš, Beckmann Michael, Cord Anna F, Bindewald Anja M
UFZ-Helmholtz Centre for Environmental Research, Department of Computational Landscape Ecology, Leipzig, Germany.
Palacký University Olomouc, Department of Ecology and Environmental Sciences, Faculty of Science, Olomouc, Czech Republic.
PLoS One. 2017 Apr 17;12(4):e0175671. doi: 10.1371/journal.pone.0175671. eCollection 2017.
Ultraviolet-B (UV-B) radiation is a key but under-researched environmental factor that initiates diverse responses in plants, potentially affecting their distribution. To date, only a few macroecological studies have examined adaptations of plant species to different levels of UV-B. Here, we combined herbarium specimens of Hieracium pilosella L. and Echium vulgare L. with a novel UV-B dataset to examine differences in leaf hair traits between the plants' native and alien ranges. We analysed scans of 336 herbarium specimens using standardized measurements of leaf area, hair density (both species) and hair length (H. pilosella only). While accounting for other bioclimatic variables (i.e. temperature, precipitation) and effects of herbivory, we examined whether UV-B exposure explains the variability and geographical distribution of these traits in the native (Northern Hemisphere) vs. the alien (Southern Hemisphere) range. UV-B explained the largest proportion of the variability and geographical distribution of hair length in H. pilosella (relative influence 67.1%), and hair density in E. vulgare (66.2%). Corresponding with higher UV-B, foliar hairs were 25% longer for H. pilosella and 25% denser for E. vulgare in records from the Southern as compared to those from the Northern Hemisphere. However, focusing on each hemisphere separately or controlling for its effect in a regression analysis, we found no apparent influence of UV-B radiation on hair traits. Thus, our findings did not confirm previous experimental studies which suggested that foliar hairs may respond to higher UV-B intensities, presumably offering protection against detrimental levels of radiation. We cannot rule out UV-B radiation as a possible driver because UV-B radiation was the only considered variable that differed substantially between the hemispheres, while bioclimatic conditions (e.g. temperature, precipitation) and other considered variables (herbivory damage, collection date) were at similar levels. However, given that either non-significant or inconclusive relationships were detected within hemispheres, alternative explanations of the differences in foliar hairs are more likely, including the effects of environment, genotypes or herbivory.
紫外线B（UV-B）辐射是一个关键但研究不足的环境因素，它能引发植物的多种反应，可能影响其分布。迄今为止，只有少数宏观生态研究考察了植物物种对不同水平UV-B的适应性。在此，我们将毛连菜（Hieracium pilosella L.）和蓝蓟（Echium vulgare L.）的标本与一个新的UV-B数据集相结合，以研究这些植物在原生范围和外来范围内叶毛性状的差异。我们使用叶面积、毛密度（两种植物）和毛长度（仅毛连菜）的标准化测量方法，对336份标本的扫描图像进行了分析。在考虑其他生物气候变量（即温度、降水）和食草作用的影响后，我们研究了UV-B暴露是否能解释这些性状在原生范围（北半球）和外来范围（南半球）的变异性和地理分布。UV-B解释了毛连菜毛长度变异性和地理分布的最大比例（相对影响为67.1%），以及蓝蓟毛密度变异性和地理分布的最大比例（66.2%）。与北半球记录相比，南半球记录中，毛连菜的叶毛长25%，蓝蓟的叶毛密度高25%，这与更高的UV-B相对应。然而，分别关注每个半球或在回归分析中控制其影响时，我们发现UV-B辐射对毛性状没有明显影响。因此，我们的研究结果并未证实先前的实验研究，即叶毛可能对更高强度的UV-B做出反应，推测是为了抵御有害水平的辐射。我们不能排除UV-B辐射作为一个可能的驱动因素，因为UV-B辐射是唯一在半球之间有显著差异的考虑变量，而生物气候条件（如温度、降水）和其他考虑变量（食草损害、采集日期）处于相似水平。然而，鉴于在半球内检测到的关系要么不显著，要么不确定，叶毛差异的其他解释更有可能，包括环境、基因型或食草作用的影响。
