Botanists have long identified bilaterally symmetrical (zygomorphic) flowers with more specialized pollination interactions than radially symmetrical (actinomorphic) flowers. Zygomorphic flowers facilitate more precise contact with pollinators, guide pollinator behaviour and exclude less effective pollinators. However, whether zygomorphic flowers are actually visited by a smaller subset of available pollinator species has not been broadly evaluated. We compiled 53 609 floral visitation records in 159 communities and classified the plants' floral symmetry. Globally and within individual communities, plants with zygomorphic flowers are indeed visited by fewer species. At the same time, zygomorphic flowers share a somewhat larger proportion of their visitor species with other co-occurring plants and have particularly high sharing with co-occurring plants that also have zygomorphic flowers. Visitation sub-networks for zygomorphic species also show differences that may arise from reduced visitor diversity, including greater connectance, greater web asymmetry and lower coextinction robustness of both plants and visitor species—but these changes do not necessarily translate to whole plant-visitor communities. These results provide context for widely documented associations between zygomorphy and diversification and imply that species with zygomorphic flowers may face a greater risk of extinction due to pollinator loss.

植物学家早就发现双侧对称（左右对称）花比径向对称（辐射对称）花具有更专业的授粉相互作用。对称花有利于与传粉者更精确的接触，指导传粉者的行为并排除效率较低的传粉者。然而，还没有广泛评估左右花是否真的被一小部分可用的授粉物种访问。我们编制了 159 个社区的 53 609 条花卉访问记录，并对植物的花卉对称性进行了分类。在全球和个别社区内，具有左右对称花的植物确实被较少的物种访问。同时，左右花与其他共生植物共享其访问物种的比例稍大一些，并且与也具有左右花的共生植物的共享率特别高。左右对称物种的访问子网络也显示出可能因访问者多样性减少而引起的差异，包括植物和访问者物种的更大联系、更大的网络不对称性和更低的共灭绝鲁棒性——但这些变化并不一定会转化为整个植物-访问者群落。这些结果为广泛记录的对称性和多样化之间的关联提供了背景，并暗示具有对称性花的物种可能因传粉媒介的丧失而面临更大的灭绝风险。左右对称物种的访问子网络也显示出可能因访问者多样性减少而产生的差异，包括植物和访问者物种的更大的联系、更大的网络不对称性和更低的共灭绝鲁棒性——但这些变化并不一定会转化为整个植物-访问者群落。这些结果为广泛记录的对称性和多样化之间的关联提供了背景，并暗示具有对称性花的物种可能因传粉媒介的丧失而面临更大的灭绝风险。左右对称物种的访问子网络也显示出可能因访问者多样性减少而引起的差异，包括植物和访问者物种的更大联系、更大的网络不对称性和更低的共灭绝鲁棒性——但这些变化并不一定会转化为整个植物-访问者群落。这些结果为广泛记录的对称性和多样化之间的关联提供了背景，并暗示具有对称性花的物种可能因传粉媒介的丧失而面临更大的灭绝风险。