Islands provide ideal model systems to examine the factors influencing biodiversity, yet knowledge of microbial biodiversity on islands remains scarce. We collected a dataset from 101 rock pools along a freshwater to brackish water transition on islands of the Baltic Sea and investigated the patterns and drivers of community composition and species richness of diatoms, cyanobacteria and non-cyanobacteria bacteria among islands. We also examined whether environmental heterogeneity increased beta diversity and species richness within islands. Among islands, the patterns in community composition were concordant among the microbial groups, with distinct changes along the freshwater–brackish gradient. The patterns in species richness were context-dependent for each microbial group. In general, richness patterns were most strongly associated with nutrient concentrations or the distances to potential sources of immigrants, whereas no positive relationships between ecosystem size and richness were found. Within islands, environmental heterogeneity was positively correlated with the beta diversity of each microbial group, but not species richness. Our findings provide novel insights into the factors influencing microbial biodiversity. The results suggest that island microbial biodiversity patterns are influenced by species sorting and dispersal-related mechanisms and highlight the importance of environmental heterogeneity for beta diversity.

中文翻译：

---

影响波罗的海岛屿内部和岛屿之间三个微生物群落生物多样性的因素

岛屿提供了理想的模型系统来检查影响生物多样性的因素，但关于岛屿微生物多样性的知识仍然很少。我们收集了波罗的海岛屿上沿淡水向咸水过渡的 101 个岩池的数据集，并研究了岛屿间硅藻、蓝藻和非蓝藻细菌群落组成和物种丰富度的模式和驱动因素。我们还检查了环境异质性是否增加了岛屿内的β多样性和物种丰富度。在岛屿中，微生物群落的群落组成模式是一致的，沿淡水-微咸水梯度有明显的变化。物种丰富度的模式取决于每个微生物群的背景。一般来说，丰富度模式与养分浓度或与潜在移民来源的距离最密切相关，而生态系统大小与丰富度之间没有发现正相关关系。在岛屿内，环境异质性与每个微生物群的β多样性呈正相关，但与物种丰富度无关。我们的研究结果为影响微生物多样性的因素提供了新的见解。结果表明，岛屿微生物多样性模式受物种分类和扩散相关机制的影响，并突出了环境异质性对β多样性的重要性。环境异质性与每个微生物群的β多样性呈正相关，但与物种丰富度无关。我们的研究结果为影响微生物多样性的因素提供了新的见解。结果表明，岛屿微生物多样性模式受物种分类和扩散相关机制的影响，并突出了环境异质性对β多样性的重要性。环境异质性与每个微生物群的β多样性呈正相关，但与物种丰富度无关。我们的研究结果为影响微生物多样性的因素提供了新的见解。结果表明，岛屿微生物多样性模式受物种分类和扩散相关机制的影响，并突出了环境异质性对β多样性的重要性。