The decline of bees compromises pollination services and connectivity of plant populations, both wild and domesticated. The aim of this study was to evaluate bee diversity in natural wetland island-like habitats — called kettle holes — embedded in an agricultural landscape and its relationship with spatial parameters (kettle-hole area, isolation, neighboring land-use diversity), as well as further bee relevant and local factors (flower, vegetation, and tree cover). We sampled 36 kettle holes in an agricultural landscape north of Berlin, Germany, using color traps and identified 77 bee species, representing ca. 20% of the total diversity of the region. Our results showed that neither kettle-hole area nor density of neighboring kettle holes (isolation) alone affected bee diversity; however, the combination of both did: larger and less isolated kettle holes enhanced bee diversity. In addition, habitat quality (i.e. higher flower availability) within the kettle holes positively influenced bee diversity. These results suggested that flowering plants occurring in the kettle holes are an important foraging resource for bee species. Bee communities respond differently to the environment depending on their functional traits related to sociality. In particular eusocial bee abundance was negatively affected by land-use types at 100 and 500 m distance, as well as vegetation cover, area and isolation, suggesting that eusocial bees might depend more on the quality of the habitat within and surrounding the kettle holes than solitary bees. Surprisingly, bee body size was not associated with any environmental factor tested. Our study identified that a combination of large, high-quality kettle holes providing a high cover of insect pollinated flowers within a high density network of kettle holes, enhances bee diversity in intensively managed agricultural landscapes.

蜜蜂的减少损害了野生和驯化植物种群的授粉服务和连通性。本研究的目的是评估嵌入农业景观中的天然湿地岛状栖息地（称为壶穴）中的蜜蜂多样性及其与空间参数（壶穴面积、隔离、邻近土地利用多样性）的关系，以及作为进一步的蜜蜂相关和本地因素（花卉、植被和树木覆盖）。我们使用颜色陷阱在德国柏林以北的农业景观中对 36 个水壶洞进行了采样，并确定了 77 种蜜蜂物种，大约代表了 77 种蜜蜂。占该地区总多样性的 20%。我们的结果表明，单独的壶穴面积和相邻壶穴的密度（隔离）都不会影响蜜蜂的多样性；然而，两者的结合确实：更大和更少孤立的水壶孔增强了蜜蜂的多样性。此外，壶穴内的栖息地质量（即较高的花卉可用性）对蜜蜂的多样性有积极影响。这些结果表明，壶穴中的开花植物是蜜蜂物种的重要觅食资源。蜜蜂群落对环境的反应不同，这取决于它们与社会性相关的功能特征。特别是，真社会性蜜蜂的丰度受到 100 和 500 m 距离的土地利用类型以及植被覆盖、面积和隔离的负面影响，这表明真社会性蜜蜂可能更多地依赖于壶洞内和周围的栖息地质量，而不是孤独的蜜蜂。令人惊讶的是，蜜蜂的体型与任何测试的环境因素无关。我们的研究发现，大量、