Data from: Beyond neutral and forbidden links: morphological matches and the assembly of mutualistic hawkmoth-plant networks

A major challenge in evolutionary ecology is to understand how co-evolutionary processes shape patterns of interactions between species at community level. Pollination of flowers with long corolla tubes by long-tongued hawkmoths has been invoked as a showcase model of co-evolution. Recently, optimal foraging models have predicted that there might be a close association between mouthparts' length and the corolla depth of the visited flowers, thus favouring trait convergence and specialization at community level.
Here, we assessed whether hawkmoths more frequently pollinate plants with floral tube lengths similar to their proboscis lengths (morphological match hypothesis) against abundance-based processes (neutral hypothesis) and ecological trait mismatches constraints (forbidden links hypothesis), and how these processes structure hawkmoth–plant mutualistic networks from five communities in four biogeographical regions of South America.
We found convergence in morphological traits across the five communities and that the distribution of morphological differences between hawkmoths and plants is consistent with expectations under the morphological match hypothesis in three of the five communities. In the two remaining communities, which are ecotones between two distinct biogeographical areas, interactions are better predicted by the neutral hypothesis.
Our findings are consistent with the idea that diffuse co-evolution drives the evolution of extremely long proboscises and flower tubes, and highlight the importance of morphological traits, beyond the forbidden links hypothesis, in structuring interactions between mutualistic partners, revealing that the role of niche-based processes can be much more complex than previously known.

进化生态学领域的核心挑战之一，在于解析协同进化过程如何在群落尺度塑造物种种间互作模式。长舌天蛾为长花冠筒花传粉的互作体系，已被用作协同进化研究的标志性模型。近期，最优觅食模型预测，天蛾口器长度与所访花的花冠深度之间应存在紧密关联，由此推动群落水平的性状趋同与物种特化。
本研究中，我们针对三种假说检验天蛾是否更倾向于为喙长与花筒长度相近的植物传粉：即形态匹配假说（morphological match hypothesis）、基于物种多度的中性过程假说（neutral hypothesis），以及生态性状错配约束的禁联假说（forbidden links hypothesis）；同时解析这些过程如何塑造南美四个生物地理区域内五个群落的天蛾-植物互利共生网络结构。
我们在五个群落中均观测到性状趋同现象；且在其中三个群落中，天蛾与植物间的形态差异分布符合形态匹配假说的预期。剩余两个群落为两个不同生物地理区域的生态交错带，其互作模式更符合中性假说的预测。
本研究结果支持弥散协同进化推动极长喙与花筒演化的观点；同时强调，除禁联假说外，形态性状在构建互利共生伙伴间互作关系中的重要性，揭示出基于生态位的过程其作用远比此前认知更为复杂。