Urbanization poses a major threat to biodiversity and food security, as expanding cities, especially in the Global South, increasingly compete with natural and agricultural lands. However, the impact of urban expansion on agricultural biodiversity in tropical regions is overlooked. Here we assess how urbanization affects the functional response of farmland bees, the most important pollinators for crop production. We sampled bees across three seasons in 36 conventional vegetable-producing farms spread along an urbanization gradient in Bengaluru, an Indian megacity. We investigated how landscape and local environmental drivers affected different functional traits (sociality, nesting behavior, body size, and specialization) and functional diversity (functional dispersion) of bee communities. We found that the functional responses to urbanization were trait specific with more positive than negative effects of gray area (sealed surfaces and buildings) on species richness, functional diversity, and abundance of most functional groups. As expected, larger, solitary, cavity-nesting, and, surprisingly, specialist bees benefited from urbanization. In contrast to temperate cities, the abundance of ground nesters increased in urban areas, presumably because larger patches of bare soil were still available beside roads and buildings. However, overall bee abundance and the abundance of social bees (85% of all bees) decreased with urbanization, threatening crop pollination. Crop diversity promotes taxonomic and functional diversity of bee communities. Locally, flower resources promote the abundance of all functional groups, and natural vegetation can maintain diverse pollinator communities throughout the year, especially during the noncropping season. However, exotic plants decrease functional diversity and bee specialization. To safeguard bees and their pollination services in urban farms, we recommend (1) preserving seminatural vegetation (hedges) around cropping fields to provide nesting opportunities for aboveground nesters, (2) promoting farm-level crop diversification of beneficial crops (e.g., pulses, vegetables, and spices), (3) maintaining native natural vegetation along field margins, and (4) controlling and removing invasive exotic plants that disrupt native plant–pollinator interactions. Overall, our results suggest that urban agriculture can maintain functionally diverse bee communities and, if managed in a sustainable manner, be used to develop win–win solutions for biodiversity conservation of pollinators and food security in and around cities.

中文翻译：

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热带大城市城乡景观中农田蜜蜂的功能多样性

城市化对生物多样性和粮食安全构成了重大威胁，因为不断扩大的城市，尤其是在全球南方，越来越多地与自然和农业用地竞争。然而，城市扩张对热带地区农业生物多样性的影响却被忽视了。在这里，我们评估城市化如何影响农田蜜蜂的功能反应，农田蜜蜂是作物生产最重要的传粉者。我们在印度大城市班加罗尔沿城市化梯度分布的 36 个传统蔬菜生产农场的三个季节对蜜蜂进行了采样。我们调查了景观和当地环境驱动因素如何影响蜜蜂群落的不同功能特征（社会性、筑巢行为、体型和专业化）和功能多样性（功能分散）。我们发现对城市化的功能反应是特定于特征的，灰色区域（密封表面和建筑物）对物种丰富度、功能多样性和大多数功能组的丰度的积极影响大于消极影响。正如预期的那样，更大、更孤独、洞穴筑巢的蜜蜂，以及令人惊讶的专业蜜蜂，都从城市化中受益。与温带城市相比，城市地区地面筑巢鸟的数量有所增加，这可能是因为道路和建筑物旁边仍有大片裸露的土壤。然而，总体蜜蜂丰度和社会蜜蜂（占所有蜜蜂的 85%）的丰度随着城市化而下降，威胁到作物授粉。作物多样性促进了蜜蜂群落的分类学和功能多样性。在当地，花卉资源促进了所有功能组的丰富，自然植被可以全年保持多样化的传粉者群落，尤其是在非作物季节。然而，外来植物会降低功能多样性和蜜蜂的专业化。为了保护城市农场中的蜜蜂及其授粉服务，我们建议 (1) 保护农田周围的半天然植被（树篱），为地上筑巢者提供筑巢机会，(2) 促进有益作物（例如豆类、蔬菜和香料），(3) 维持田地边缘的本地天然植被，以及 (4) 控制和移除破坏本地植物与传粉者相互作用的外来入侵植物。总体而言，我们的研究结果表明，都市农业可以维持功能多样的蜜蜂群落，如果以可持续的方式进行管理，