Tropical forests shelter the highest species diversity worldwide, although genus diversity is lower than expected. In the species‐rich genera, species complexes are composed of closely‐related species that share large amounts of genetic variation. Despite the key role of species complexes in diversification, evolution and functioning of ecological communities, little is known on why species complexes arise and how they are maintained in Neotropical forests. Examining how individual phenotypes vary along environmental gradients, within and among closely‐related species within species complexes, can reveal processes allowing species coexistence within species complexes. We examined leaf functional trait variation with topography in a hyperdiverse tropical forest of the Guiana Shield. We collected leaf functional traits from 766 trees belonging to five species in two species complexes in permanent plots encompassing a diversity of topographic positions. We tested the role of topography on leaf functional trait variation with a hierarchical Bayesian model, controlling for individual tree diameter effect. We show that, mirroring what has been previously observed among species and communities, individual leaf traits covary from acquisitive to conservative strategy within species. Moreover, decreasing wetness from bottomlands to plateaus was associated with a shift of leaf traits from an acquisitive to a conservative strategy both across and within closely‐related species. Our results suggest that intraspecific trait variability widens species’ niches and converges at species’ margins where niches overlap, potentially implying local neutral processes. Intraspecific trait variability favors local adaptation and divergence of closely‐related species within species complexes. It is potentially maintained through interspecific sharing of genetic variation through hybridization.

中文翻译：

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地形持续驱动新热带森林树木物种复合体内的种内和种间叶性状变化

尽管属的多样性低于预期，但热带森林掩盖了全球最高的物种多样性。在物种丰富的属中，物种复合体由共享大量遗传变异的密切相关的物种组成。尽管物种复合体在生态社区的多样化，进化和功能中发挥着关键作用，但对于为什么物种复合体出现以及如何在新热带森林中维持物种知之甚少。研究个体表型在物种复合体中密切相关的物种之内和之间如何随环境梯度变化，可以揭示出允许物种复合体内部物种共存的过程。我们在圭亚那盾的一个高分异热带森林中检查了地形的叶片功能性状变异。我们从永久地块的两个物种复合体的766种树木（属于5种物种）中收集了叶片功能性状，涵盖了多种地形位置。我们使用分层贝叶斯模型测试了地形对叶片功能性状变异的作用，控制了单个树的直径效应。我们表明，反映以前在物种和群落中观察到的情况，个体叶片性状在物种内部从获取策略向保守策略转变。此外，从低地到高原的湿润程度降低与密切性状之间和内部的叶片性状从获取策略向保守策略的转变有关。我们的结果表明，种内性状变异性扩大了物种的生态位，并在生态位重叠的物种边缘收敛，潜在地暗示了本地中立过程。种内性状变异有利于物种复合体中近缘物种的局部适应和发散。它可能通过杂交通过遗传变异的种间共享而得以维持。