Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06511, USA.
Oecologia. 2012 Apr;168(4):1091-102. doi: 10.1007/s00442-011-2157-z. Epub 2011 Oct 21.
To improve the understanding of how native plant diversity influences invasion, we examined how population and community diversity may directly and indirectly be related to invasion in a natural field setting. Due to the large impact of the dominant C(4) grass species (Andropogon gerardii) on invasion resistance of tallgrass prairie, we hypothesized that genetic diversity and associated traits within a population of this species would be more strongly related to invasion than diversity or traits of the rest of the community. We added seeds of the exotic invasive C(4) grass, A. bladhii, to 1-m(2) plots in intact tallgrass prairie that varied in genetic diversity of A. gerardii and plant community diversity, but not species richness. We assessed relationships among genetic diversity and traits of A. gerardii, community diversity, community aggregated traits, resource availability, and early season establishment and late-season persistence of the invader using structural equation modeling (SEM). SEM models suggested that community diversity likely enhanced invasion indirectly through increasing community aggregated specific leaf area as a consequence of more favorable microclimatic conditions for seedling establishment. In contrast, neither population nor community diversity was directly or indirectly related to late season survival of invasive seedlings. Our research suggests that while much of diversity-invasion research has separately focused on the direct effects of genetic and species diversity, when taken together, we find that the role of both levels of diversity on invasion resistance may be more complex, whereby effects of diversity may be primarily indirect via traits and vary depending on the stage of invasion.
为了更好地理解乡土植物多样性如何影响入侵，我们在自然田间环境中检验了种群和群落多样性如何直接和间接与入侵相关。由于优势 C4 草种（Andropogon gerardii）对高草草原的入侵抗性有很大影响，我们假设该物种种群内的遗传多样性及其相关特征与入侵的关系比群落内其他物种的多样性或特征更为密切。我们在遗传多样性和 A. gerardii 植物群落多样性不同、但物种丰富度相同的完整高草草原 1 平方米样方中添加了外来入侵 C4 草种 A. bladhii 的种子。我们采用结构方程模型（SEM）来评估 A. gerardii 的遗传多样性和特征、群落多样性、群落聚集特征、资源可利用性以及入侵种在早期建立和后期存活之间的关系。SEM 模型表明，群落多样性可能通过增加社区聚集的比叶面积来间接促进入侵，因为幼苗建立的微气候条件更为有利。相比之下，种群或群落多样性都没有直接或间接与入侵幼苗后期存活相关。我们的研究表明，尽管许多多样性-入侵研究分别侧重于遗传和物种多样性的直接影响，但综合来看，我们发现这两个层次的多样性对入侵抗性的作用可能更为复杂，多样性的影响主要是间接的，通过特征表现出来，而且还取决于入侵的阶段。
