Data from: Greater pollination generalization is not associated with reduced constraints on corolla shape in Antillean plants

Flowers show important structural variation as reproductive organs but the evolutionary forces underlying this diversity are still poorly understood. In animal-pollinated species, flower shape is strongly fashioned by selection imposed by pollinators, which is expected to vary according to guilds of effective pollinators. Using the Antillean subtribe Gesneriinae (Gesneriaceae), we tested the hypothesis that pollination specialists pollinated by one functional type of pollinator have maintained more similar corolla shapes through time due to more constant and stronger selection constraints compared to species with more generalist pollination strategies. Using geometric morphometrics and evolutionary models, we showed that the corolla of hummingbird specialists, bat specialists, and species with a mixed-pollination strategy (pollinated by hummingbirds and bats; thus a more generalist strategy) have distinct shapes and that these shapes have evolved under evolutionary constraints. However, we did not find support for greater disparity in corolla shape of more generalist species. This could be because the corolla shape of more generalist species in subtribe Gesneriinae, which has evolved multiple times, is finely adapted to be effectively pollinated by both bats and hummingbirds. These results suggest that ecological generalization is not necessarily associated with relaxed selection constraints.

作为生殖器官，花卉展现出显著的结构多样性，但支撑这一多样性的演化驱动力迄今仍未得到充分阐释。在动物传粉物种中，花形主要由传粉者施加的选择压力塑造，而这类选择压力预计会随有效传粉者类群的差异而发生变化。本研究以安的列斯群岛苦苣苔亚族（Gesneriinae，苦苣苔科Gesneriaceae）为研究材料，验证了如下假说：相较于采用泛化传粉策略的物种，仅由单一功能型传粉者完成传粉的特化类群，因面临更恒定且更强的选择约束，其花冠形态在演化历程中会保持更高的相似性。本研究借助几何形态测量学（geometric morphometrics）与演化模型开展分析，结果显示：蜂鸟传粉特化类群、蝙蝠传粉特化类群，以及采用混合传粉策略（由蜂鸟与蝙蝠共同传粉，属于更泛化的传粉模式）的物种，其花冠形态各具独特特征，且上述形态均在演化约束下完成演化。然而，本研究并未发现泛化程度更高的物种其花冠形态差异更为显著的相关证据。这一现象或可得到如下解释：苦苣苔亚族中多次独立演化出的泛化传粉物种，其花冠形态已历经精细适配，能够同时高效实现蝙蝠与蜂鸟介导的传粉过程。本研究结果表明，生态泛化策略未必与选择约束的松弛存在关联。