Department of Invasion Ecology, Institute of Botany, The Czech Academy of Sciences, Průhonice CZ-252 43, Czech Republic Department of Ecology, Faculty of Science, Charles University in Prague, Viničná 7, Prague CZ-128 44, Czech Republic
Department of Invasion Ecology, Institute of Botany, The Czech Academy of Sciences, Průhonice CZ-252 43, Czech Republic.
AoB Plants. 2015 Apr 1;7:plv033. doi: 10.1093/aobpla/plv033.
Many invasive species are considered competitively superior to native species, with the strongest competition expected in species with similar niches and/or in closely related species. However, competition outcome is strongly context-dependent as competitive strength varies along environmental gradients, and life stages, and also depends on abundances. To explore the importance of these factors, we examined competition effects in an experiment with three Impatiens species (Balsaminaceae) widespread in central Europe and sharing similar life-history characteristics and habitats: the native I. noli-tangere, and two invasive species, I. parviflora and I. glandulifera. We compared their competitive strength and reciprocal impacts under two levels of water and light availability, two overall planting densities and three competitor densities. We assessed species performance (ability to complete the life-cycle, biomass and fecundity) and temporal competition dynamics in a garden pot experiment. Environmental variables had lower explanatory power than overall planting and competitor density, which indicates the importance of competitive interactions when evaluating plant performance and potential invasion success. Despite poor and delayed germination, the invasive I. glandulifera attained dominance even at a high competitor density and was competitively superior across all treatments, exceeding the height of both congeners. Impatiens parviflora was competitively weakest, having a negligible impact on both native I. noli-tangere and invasive I. glandulifera. The intermediate competitive strength of the native I. noli-tangere probably results from its intermediate height, and good germination rate and timing. The difference in height among species increased during the experiment when I. glandulifera was involved; this species continues growing until autumn, enhancing its competitive superiority. The results provide a mechanistic understanding for the competitive exclusion of native I. noli-tangere that occurs in stands with I. glandulifera, but the limited impact of I. parviflora on I. noli-tangere in their mixed stands.
许多入侵物种被认为在竞争中具有优势，与本地物种相比，具有相似生态位和/或密切相关的物种之间的竞争最为激烈。然而，竞争结果强烈依赖于环境梯度，竞争强度随环境梯度而变化，而且还取决于生物量。为了探索这些因素的重要性，我们在一个实验中研究了三种在中欧广泛分布的凤仙花属物种（凤仙花科）的竞争效应，它们具有相似的生活史特征和栖息地：本地的 Impatiens noli-tangere，以及两种入侵物种，I. parviflora 和 I. glandulifera。我们比较了它们在两种水分和光照水平、两种总种植密度和三种竞争密度下的竞争强度和相互影响。我们在花园盆栽实验中评估了物种的表现（完成生命周期的能力、生物量和繁殖力）和时间竞争动态。环境变量的解释能力低于总种植密度和竞争密度，这表明在评估植物表现和潜在入侵成功时，竞争相互作用很重要。尽管发芽不良且延迟，入侵的 I. glandulifera 即使在高竞争密度下也能占据优势地位，并且在所有处理中都具有竞争优势，超过了两个同属种的高度。I. parviflora 的竞争能力最弱，对本地的 I. noli-tangere 和入侵的 I. glandulifera 的影响可以忽略不计。本地的 I. noli-tangere 的中等竞争能力可能是由于其中等高度、良好的发芽率和时机。当涉及到 I. glandulifera 时，物种之间的高度差异在实验过程中增加；该物种会持续生长到秋季，增强其竞争优势。研究结果为解释在与 I. glandulifera 混合的林分中本地的 I. noli-tangere 被竞争排斥的机制提供了依据，但 I. parviflora 对 I. noli-tangere 的影响有限。
