The introduction of exotic species to new regions offers opportunities to test fundamental questions in ecology, such as the context-dependency of community structure and assembly. Annual grasslands provide a model system of a major unidirectional introduction of plant species from Europe to North America. We compared the community structure of grasslands in two Mediterranean regions by surveying plots in Spain and in California with similar environmental and management conditions. All species found in Spanish grasslands were native to Spain, and over half of them (74 of 139 species) are known to have colonized California. In contrast, in California, over half of the species (52 of 95 species) were exotic species, all of them native to Spain. Nineteen species were found in multiple plots in both regions (i.e., shared species). The abundance of shared species in California was either similar to (13 species) or greater than (6 species) in Spain. In California, plants considered pests were more likely than non-pest species to have higher abundance. Co-occurring shared species tended to maintain their relative abundance in native and introduced communities, which indicates that pools of exotic species might assemble similarly at home and away. These findings provide interesting insights into community assembly in novel ecosystems. They also highlight an example of startling global and local floristic homogenization.

中文翻译：

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入侵的收件人加利福尼亚草场和西班牙推定捐助草场的植物群落大会

将外来物种引入新地区提供了机会来检验生态学中的基本问题，例如社区结构和集会的背景依赖性。一年生的草原提供了从欧洲到北美的主要植物物种单向主要引进的模型系统。我们通过调查西班牙和加利福尼亚具有相似环境和管理条件的地块，比较了两个地中海地区的草地群落结构。在西班牙草原上发现的所有物种都起源于西班牙，其中一半以上（139种中的74种）已知已定居于加利福尼亚。相反，在加利福尼亚州，一半以上的物种（95种中的52种）是外来物种，所有这些物种都原产于西班牙。在两个地区的多个地块中发现了19种（即共有物种）。加利福尼亚共有物种的丰富度与西班牙类似（13种）或大于（6种）。在加利福尼亚州，被认为是害虫的植物比非害虫物种具有更高的丰度。共生共有物种往往在本地和引进社区中保持相对丰富，这表明外来物种池可能在国内和国外相似地聚集。这些发现为新型生态系统中的社区聚集提供了有趣的见解。他们还突出了一个令人震惊的全球和本地植物同质化的例子。共生共有物种往往在本地和引进社区中保持相对丰富，这表明外来物种池可能在国内和国外相似地聚集。这些发现为新型生态系统中的社区聚集提供了有趣的见解。他们还突出了一个令人震惊的全球和本地植物同质化的例子。共生共有物种往往在本地和引进社区中保持相对丰富，这表明外来物种池可能在国内和国外相似地聚集。这些发现为新型生态系统中的社区聚集提供了有趣的见解。他们还突出了一个令人震惊的全球和本地植物同质化的例子。