Bruy David, Hattermann Tom, Barrabé Laure, Mouly Arnaud, Barthélémy Daniel, Isnard Sandrine
AMAP, IRD, CIRAD, CNRS, INRA, Université de Montpellier, Montpellier, France.
AMAP, IRD, Herbier de Nouméa, Nouméa, New Caledonia.
Front Plant Sci. 2018 Dec 4;9:1775. doi: 10.3389/fpls.2018.01775. eCollection 2018.
The diversification of ecological roles and related adaptations in closely related species within a lineage is one of the most important processes linking plant evolution and ecology. Plant architecture offers a robust framework to study these processes as it can highlight how plant structure influences plant diversification and ecological strategies. We investigated a case of gradual evolution of branching architecture in spp. (Rubiaceae), forming a monophyletic group in New Caledonia that has diversified rapidly, predominantly in rainforest understory habitats. We used a transdisciplinary approach to depict architectural variations and revealed multiple evolutionary transitions from a branched (Stone's architectural model) to a monocaulous habit (Corner's architectural model), which involved the functional reduction of branches into inflorescences. We propose an integrative functional index that assesses branching incidence on functional traits influencing both assimilation and exploration functions. We showed that architectural transitions correlate with ecologically important functional traits. Variation in ecologically important traits among closely relatives, as supported by the architectural analysis, is suggestive of intense competition that favored divergence among locally coexisting species. We propose that Pleistocene climatic fluctuations causing expansion and contraction of rainforest could also have offered ecological opportunities for colonizers in addition to the process of divergent evolution.
一个谱系中密切相关物种的生态角色多样化及相关适应是连接植物进化与生态的最重要过程之一。植物结构提供了一个强大的框架来研究这些过程，因为它能突出植物结构如何影响植物多样化和生态策略。我们研究了茜草科植物分支结构逐渐进化的一个案例，该科植物在新喀里多尼亚形成一个单系类群，且迅速多样化，主要分布在雨林林下栖息地。我们采用跨学科方法来描绘结构变化，并揭示了从分支状（斯通结构模型）到单茎习性（科纳结构模型）的多次进化转变，这涉及到将分支功能简化为花序。我们提出了一个综合功能指数，该指数评估影响同化和探索功能的功能性状上的分支发生率。我们表明结构转变与具有重要生态意义的功能性状相关。结构分析支持的近缘种间具有重要生态意义的性状变异表明，激烈的竞争有利于当地共存物种间的分化。我们提出，更新世气候波动导致雨林的扩张和收缩，除了趋异进化过程外，也可能为殖民者提供了生态机会。
