Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, Hubei, China.
Oecologia. 2012 Oct;170(2):373-82. doi: 10.1007/s00442-012-2328-6. Epub 2012 Apr 11.
Herbivory can reduce plant fitness, and its effects can be increased by competition. Though numerous studies have examined the joint effects of herbivores and competitors on plant performance, these interactive effects are seldom considered in the context of plant invasions. Here, we examined variation in plant performance within a competitive environment in response to both specialist and generalist herbivores using Chinese tallow as a model species. We combined tallow plants from native and invasive populations to form all possible pairwise combinations, and designated invasive populations as stronger neighbours and native populations as weaker neighbours. We found that when no herbivory was imposed, invasive populations always had higher total biomass than natives, regardless of their neighbours, which is consistent with our assumption of increased competitive ability. Defoliation by either generalist or specialist herbivores suppressed plant growth but the effects of specialists were generally stronger for invasive populations. Invasive populations had their lowest biomass when fed upon by specialists while simultaneously competing with stronger neighbours. The root/shoot ratios of invasive populations were lower than those of native populations under almost all conditions, and invasive plants were taller than native plants overall, especially when herbivores were present, suggesting that invasive populations may adopt an "aboveground first" strategy to cope with herbivory and competition. These results suggest that release from herbivores, especially specialists, improves an invader's performance and helps to increase its competitive ability. Therefore, increasing interspecific competition intensity by planting a stronger neighbour while simultaneously releasing a specialist herbivore may be an especially effective method of managing invasive plants.
食草作用会降低植物的适应性，而竞争会增加这种影响。尽管有许多研究考察了食草动物和竞争者对植物性能的联合影响，但这些相互作用在植物入侵的背景下很少被考虑。在这里，我们使用中国乌桕作为模型物种，在竞争环境中检查了植物性能的变化，以应对专门和一般的食草动物。我们将来自本地和入侵种群的乌桕植物组合成所有可能的成对组合，并将入侵种群指定为更强的邻居，而将本地种群指定为较弱的邻居。我们发现，在没有食草作用的情况下，入侵种群的总生物量总是高于本地种群，无论它们的邻居是谁，这与我们假设的竞争力增强是一致的。无论是一般还是专门的食草动物都会抑制植物生长，但对于入侵种群，专家的影响通常更强。当专门的食草动物同时与更强的邻居竞争时，入侵种群的生物量最低。在几乎所有条件下，入侵种群的根/茎比都低于本地种群，而入侵植物的总体高度高于本地植物，尤其是在有食草动物存在的情况下，这表明入侵种群可能采用“先地上部分”的策略来应对食草作用和竞争。这些结果表明，食草动物的释放，特别是专门的食草动物，会提高入侵种的性能，并有助于提高其竞争力。因此，通过种植更强的邻居同时释放专门的食草动物来增加种间竞争强度，可能是管理入侵植物的一种特别有效的方法。
