SIGDP in Ecology and Department of Crop and Soil Sciences, 116 ASI Building, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Ecol Appl. 2012 Jul;22(5):1413-20. doi: 10.1890/11-2107.1.
As the number of biological invasions increases, the potential for invader-invader interactions also rises. The effect of multiple invaders can be superadditive (invasional meltdown), additive, or subadditive (invasional interference); which of these situations occurs has critical implications for prioritization of management efforts. Carduus nutans and C. acanthoides, two congeneric invasive weeds, have a striking, segregated distribution in central Pennsylvania, U.S.A. Possible hypotheses for this pattern include invasion history and chance, direct competition, or negative interactions mediated by other species, such as shared pollinators. To explore the role of resource competition in generating this pattern, we conducted three related experiments using a response-surface design throughout the life cycles of two cohorts. Although these species have similar niche requirements, we found no differential response to competition between conspecifics vs. congeners. The response to combined density was relatively weak for both species. While direct competitive interactions do not explain the segregated distributional patterns of these two species, we predict that invasions of either species singly, or both species together, would have similar impacts. When prioritizing which areas to target to prevent the spread of one of the species, it is better to focus on areas as yet unaffected by its congener; where the congener is already present, invasional interference makes it unlikely that the net effect will change.
随着生物入侵数量的增加，入侵物种之间相互作用的可能性也在增加。多个入侵物种的影响可能是超加性的（入侵崩溃）、加性的或亚加性的（入侵干扰）；这些情况中的哪一种发生对管理工作的优先排序具有关键意义。两种同源入侵杂草 Carduus nutans 和 C. acanthoides 在宾夕法尼亚州中部有一个显著的、分离的分布。这种模式的可能假说包括入侵历史和机会、直接竞争或由其他物种介导的负相互作用，如共享传粉者。为了探索资源竞争在产生这种模式中的作用，我们使用响应面设计在两个队列的整个生命周期中进行了三项相关实验。尽管这些物种具有相似的生态位需求，但我们发现同种与同属种之间的竞争没有差异反应。两种物种对组合密度的反应都相对较弱。虽然直接竞争相互作用并不能解释这两个物种分离的分布模式，但我们预测，这两个物种中的任何一个单独入侵，或两个物种一起入侵，都会产生类似的影响。在确定优先考虑哪些区域来防止一个物种的传播时，最好关注那些尚未受到其同属种影响的区域；在同属种已经存在的地方，入侵干扰使得净效应不太可能改变。
