Institute of Biology/Geobotany and Botanical Garden, Martin Luther University Halle-Wittenberg, Germany.
German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Germany.
Ann Bot. 2021 Mar 24;127(4):565-576. doi: 10.1093/aob/mcaa067.
Non-native plant species are not restricted to lowlands, but increasingly are invading high elevations. While for both native and non-native species we expected variability of plant functional traits due to the changing environmental conditions along elevational gradients, we additionally assumed that non-native species are characterized by a more acquisitive growth strategy, as traits reflecting such a strategy have been found to correlate with invasion success. Furthermore, the typical lowland introduction of non-native species coming from multiple origins should lead to higher trait variability within populations of non-native species specifically at low elevations, and they might therefore occupy a larger total trait space.
Along an elevational gradient ranging from 55 to 1925 m a.s.l. on Tenerife, we collected leaves from eight replicate individuals in eight evenly distributed populations of five native and six non-native forb species. In each population, we measured ten eco-morphological and leaf biochemical traits and calculated trait variability within each population and the total trait space occupied by native and non-native species.
We found both positive (e.g. leaf dry matter content) and negative (e.g. leaf N) correlations with elevation for native species, but only few responses for non-native species. For non-native species, within-population variability of leaf dry matter content and specific leaf area decreased with elevation, but increased for native species. The total trait space occupied by all non-native species was smaller than and a subset of that of native species.
We found little evidence that intraspecific trait variability is associated with the success of non-native species to spread towards higher elevations. Instead, for non-native species, our results indicate that intermediate trait values that meet the requirements of various conditions are favourable across the changing environmental conditions along elevational gradients. As a consequence, this might prevent non-native species from overcoming abruptly changing environmental conditions, such as when crossing the treeline.
非本地植物物种不仅局限于低地，而且越来越多地入侵高海拔地区。虽然我们预计由于海拔梯度上环境条件的变化，本地和非本地物种的植物功能特性会有所不同，但我们还假设非本地物种具有更具掠夺性的生长策略，因为反映这种策略的特征已被发现与入侵成功相关。此外，非本地物种通常来自多个起源的低地引入，这应该会导致非本地物种在特定低海拔地区的种群内具有更高的特性变异性，因此它们可能占据更大的总特性空间。
在特内里费岛海拔 55 至 1925 米的海拔梯度上，我们从五个本地和六个非本地草本物种的八个均匀分布的种群中收集了八个重复个体的叶片。在每个种群中，我们测量了十个生态形态和叶片生化特性，并计算了每个种群内的特性变异性和本地和非本地物种所占据的总特性空间。
我们发现本地物种与海拔呈正相关（例如叶片干物质含量）和负相关（例如叶片氮含量），但非本地物种的响应很少。对于非本地物种，叶片干物质含量和比叶面积的种群内变异性随海拔升高而降低，但对于本地物种则增加。所有非本地物种所占据的总特性空间小于本地物种的特性空间。
我们几乎没有证据表明种内特性变异性与非本地物种向高海拔地区扩散的成功相关。相反，对于非本地物种，我们的结果表明，在海拔梯度上变化的环境条件下，满足各种条件要求的中间特性值是有利的。因此，这可能会阻止非本地物种克服突然变化的环境条件，例如当跨越林线时。
