Department of Biological Sciences, Plant Biology, Aarhus University, DK-8000 Århus C, Denmark.
Ann Bot. 2010 Nov;106(5):813-22. doi: 10.1093/aob/mcq176. Epub 2010 Sep 7.
The successful spread of invasive plants in new environments is often linked to multiple introductions and a diverse gene pool that facilitates local adaptation to variable environmental conditions. For clonal plants, however, phenotypic plasticity may be equally important. Here the primary adaptive strategy in three non-native, clonally reproducing macrophytes (Egeria densa, Elodea canadensis and Lagarosiphon major) in New Zealand freshwaters were examined and an attempt was made to link observed differences in plant morphology to local variation in habitat conditions.
Field populations with a large phenotypic variety were sampled in a range of lakes and streams with different chemical and physical properties. The phenotypic plasticity of the species before and after cultivation was studied in a common garden growth experiment, and the genetic diversity of these same populations was also quantified.
For all three species, greater variation in plant characteristics was found before they were grown in standardized conditions. Moreover, field populations displayed remarkably little genetic variation and there was little interaction between habitat conditions and plant morphological characteristics.
The results indicate that at the current stage of spread into New Zealand, the primary adaptive strategy of these three invasive macrophytes is phenotypic plasticity. However, while limited, the possibility that genetic diversity between populations may facilitate ecotypic differentiation in the future cannot be excluded. These results thus indicate that invasive clonal aquatic plants adapt to new introduced areas by phenotypic plasticity. Inorganic carbon, nitrogen and phosphorous were important in controlling plant size of E. canadensis and L. major, but no other relationships between plant characteristics and habitat conditions were apparent. This implies that within-species differences in plant size can be explained by local nutrient conditions. All together this strongly suggests that invasive clonal aquatic plants adapt to a wide range of habitats in introduced areas by phenotypic plasticity rather than local adaptation.
入侵植物在新环境中的成功传播通常与多次引入和多样化的基因库有关，这有助于其对多变的环境条件进行局部适应。然而，对于克隆植物而言，表型可塑性可能同样重要。本研究检测了新西兰淡水三种非本地克隆繁殖的大型植物（水蕴草、加拿大水马齿和大茨藻）的主要适应策略，并试图将观察到的植物形态差异与栖息地条件的局部变化联系起来。
在具有不同化学和物理性质的一系列湖泊和溪流中，采集了具有大量表型多样性的野外种群。在一个共同的花园生长实验中，研究了这些物种在培养前后的表型可塑性，并量化了这些相同种群的遗传多样性。
对于所有三种物种，在标准化条件下生长之前，植物特征的变化更大。此外，野外种群的遗传多样性非常低，栖息地条件和植物形态特征之间几乎没有相互作用。
研究结果表明，在这些入侵大型植物向新西兰扩散的当前阶段，其主要的适应策略是表型可塑性。然而，尽管遗传多样性有限，但不能排除种群之间的遗传多样性可能在未来促进生态型分化的可能性。因此，这些结果表明，入侵的克隆水生植物通过表型可塑性适应新引入的地区。无机碳、氮和磷对控制加拿大水马齿和大茨藻的植物大小很重要，但植物特征与栖息地条件之间没有明显的其他关系。这意味着植物大小的种内差异可以用当地的营养条件来解释。综上所述，这强烈表明，入侵的克隆水生植物通过表型可塑性而不是局部适应来适应引入地区的广泛栖息地。
