Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA, 95060, USA.
Department of Biology, California Polytechnic State University, San Luis Obispo, CA, 93401, USA.
New Phytol. 2022 Nov;236(4):1572-1583. doi: 10.1111/nph.18464. Epub 2022 Sep 24.
The evolution of hummingbird pollination is common across angiosperms throughout the Americas, presenting an opportunity to examine convergence in both traits and environments to better understand how complex phenotypes arise. Here we examine independent shifts from bee to hummingbird pollination in the Neotropical spiral gingers (Costus) and address common explanations for the prevalence of transitions from bee to hummingbird pollination. We use floral traits of species with observed pollinators to predict pollinators of unobserved species and reconstruct ancestral pollination states on a well-resolved phylogeny. We examine whether independent transitions evolve towards the same phenotypic optimum and whether shifts to hummingbird pollination correlate with elevation or climate. Traits predicting hummingbird pollination include small flower size, brightly colored floral bracts and the absence of nectar guides. We find many shifts to hummingbird pollination and no reversals, a single shared phenotypic optimum across hummingbird flowers, and no association between pollination and elevation or climate. Evolutionary shifts to hummingbird pollination in Costus are highly convergent and directional, involve a surprising set of traits when compared with other plants with analogous transitions and refute the generality of several common explanations for the prevalence of transitions from bee to hummingbird pollination.
蜂鸟传粉在整个美洲的被子植物中是普遍存在的，这为研究特征和环境的趋同进化提供了机会，从而更好地理解复杂表型是如何产生的。在这里，我们研究了来自新世界螺旋姜属（Costus）中独立的从蜜蜂传粉向蜂鸟传粉的转变，并探讨了导致从蜜蜂传粉向蜂鸟传粉转变普遍存在的常见解释。我们利用已知传粉者的物种的花部特征来预测未观察到的物种的传粉者，并在一个分辨率较高的系统发育树上重建祖先的传粉状态。我们检验了独立的转变是否朝着相同的表型最优方向进化，以及向蜂鸟传粉的转变是否与海拔或气候有关。预测蜂鸟传粉的特征包括小花大小、颜色鲜艳的花被和缺乏蜜导。我们发现许多物种向蜂鸟传粉转变，没有逆转，蜂鸟花具有单一的共享表型最优，而且传粉与海拔或气候之间没有关联。Costus 中向蜂鸟传粉的进化转变是高度趋同和定向的，与具有类似转变的其他植物相比，涉及到一组令人惊讶的特征，并反驳了几种常见的关于从蜜蜂传粉向蜂鸟传粉转变普遍存在的解释的普遍性。
