A Two-Part Measure of Degree of Invasion for Cross-Community Comparisons

Abstract:  Invasibility is a critical feature of ecological communities, especially for management decisions. To date, invasibility has been measured in numerous ways. Although most researchers have used the richness (or number) of exotic species as a direct or indirect measure of community invasibility, others have used alternative measures such as the survival, density, or biomass of either a single or all exotic species. These different measures, even when obtained from the same communities, have produced inconsistent results and have made comparisons among communities difficult. Here, we propose a measure of the degree of invasion (DI) of a community as a surrogate for community invasibility. The measure is expressed as 2 independent components: exotic proportion of total species richness and exotic proportion of total species abundance (biomass or cover). By including richness and abundance, the measure reflects that the factors that control invasibility affect both of these components. Expressing exotic richness and abundance relative to the richness and abundance of all species in a community makes comparisons across communities of different sizes and resource availability possible and illustrates the importance of dominance of exotic species relative to natives, which is a primary management concern associated with exotic species.     

确定力量和随机性在生境可入侵性中的重要性

许多土著群落的物种组成可被外来植物改变,并因此失去原有的生态功能.随着全球化的提速,这样的改变已经是我国生态环境安全的重要风险源.揭示土著群落可入侵性的机制,阐明群落抵抗外来种的主控因素,可为入侵预警和生态系统保护提供理论基础.通过分析土著群落可入侵性主要理论的生态学原理发现,这些理论聚焦于天敌、资源、非资源因素及其相...