In a small Mediterranean island (South Sardinia), we compared two non-native plant communities (respectively dominated by Malephora crocea and Mesembrianthemum cristallinum), located on an insular rocky cliff syntopic with a nesting gull’s colony, with a native one (with Limonium sardoum dominant) used as a “control” (without nesting colony). Uni-variate metrics of diversity, Whittaker plot and non-metric multi-dimensional scaling (NMMS) with Morisita distance, evidenced a clear pattern with non-native communities less rich, less even and less diverse, when compared to native assemblage. Limonium native community is probably competitive toward the Malephora community in the absence of gulls but tends to be outcompeted by Malephora in the presence of these seabirds. In this regard, our data suggest a hypothesis that should be tested in future: i.e. those non-native Malephora- and Mesembrynathemum-dominated plant assemblages are favored in those sites where the dropping of gulls creates a nitrophytic environment. Differences in exposition could appear also important to explain the occurrence of the two non-native communities (with Mesembryanthemum crystallinum located along the sea-exposed cliff and Malephora in the internal side, toward the inland).

在一个小地中海岛国（南撒丁岛），我们比较两个非原生植物群落（分别由主导Malephora大黄鱼和Mesembrianthemum cristallinum），位于同一个嵌套海鸥的殖民地一个孤立岩石峭壁同室，与原生一个（有补血sardoum显性）用作“控制”（没有嵌套殖民地）。与本地组合相比，单变量多样性度量、惠特克图和具有 Morisita 距离的非度量多维标度 (NMMS) 证明了非本地社区不那么丰富、不那么均匀和不那么多样化的清晰模式。Limonium本地社区可能对Malophora具有竞争力没有海鸥的社区，但在有这些海鸟的情况下，往往会被Malophora 击败。在这方面，我们的数据提出了一个应该在未来进行检验的假设：即那些非本地的海鸥和Mesembrynathemum占主导地位的植物组合在海鸥坠落创造了一个含氮环境的那些地点受到青睐。暴露的差异对于解释两个非本地群落的出现也很重要（Mesembryanthemum crystallinum位于暴露于海的悬崖上，而Malephora位于内侧，朝向内陆）。