Data from: Environmental gradients and the evolution of successional habitat specialization: a test case with 14 Neotropical forest sites

1. Successional gradients are ubiquitous in nature, yet few studies have systematically examined the evolutionary origins of taxa that specialize at different successional stages. Here we quantify successional habitat specialization in Neotropical forest trees and evaluate its evolutionary lability along a precipitation gradient. Theoretically, successional habitat specialization should be more evolutionarily conserved in wet forests than in dry forests due to more extreme microenvironmental differentiation between early and late successional stages in wet forest. 2. We applied a robust multinomial classification model to samples of primary and secondary forest trees from 14 Neotropical lowland forest sites spanning a precipitation gradient from 788 to 4000 mm annual rainfall, identifying species that are old growth specialists and secondary forest specialists in each site. We constructed phylogenies for the classified taxa at each site and for the entire set of classified taxa, and tested whether successional habitat specialization is phylogenetically conserved. We further investigated differences in the functional traits of species specializing in secondary vs. old-growth forest along the precipitation gradient, expecting different trait associations with secondary forest specialists in wet vs. dry forests since water availability is more limiting in dry forests and light availability more limiting in wet forests. 3. Successional habitat specialization is non-randomly distributed in the angiosperm phylogeny, with a tendency towards phylogenetic conservatism overall and a trend toward stronger conservatism in wet forests than in dry forests. However, the specialists come from all the major branches of the angiosperm phylogeny, and very few functional traits showed any consistent relationships with successional habitat specialization in either wet or dry forests. 4. Synthesis: The niche conservatism evident in the habitat specialization of Neotropical trees suggests a role for radiation into different successional habitats in the evolution of species-rich genera, though the diversity of functional traits that lead to success in different successional habitats complicates analyses at the community scale. Examining the distribution of particular lineages with respect to successional gradients may provide more insight into the role of successional habitat specialization in the evolution of species-rich taxa.1. 演替梯度在自然界中普遍存在，但鲜有研究系统探究在不同演替阶段特化的类群的进化起源。本研究对新热带林树木（Neotropical forest trees）的演替生境特化程度进行量化，并评估其沿降水梯度的进化可塑性（evolutionary lability）。理论上，由于湿林内早期与晚期演替阶段的微环境分化更为极端，演替生境特化在湿林中应比在旱林中具有更强的系统发育保守性。 2. 我们基于覆盖年降雨量788至4000 mm降水梯度的14个新热带低地林样地的原始林与次生林树木样本，构建了稳健的多项分类模型（multinomial classification model），以此识别每个样地内的老龄林专性物种与次生林专性物种。我们为每个样地的分类类群以及所有分类类群的集合构建了系统发育树（phylogenies），并检验演替生境特化是否具有系统发育保守性。此外，我们还探究了沿降水梯度下，次生林专性物种与老龄林专性物种的功能性状差异；鉴于旱林中水分可获得性更为受限，而湿林中光照可获得性更为受限，我们预期湿林与旱林中的次生林专性物种会呈现出不同的性状关联模式。 3. 演替生境特化在被子植物系统发育（angiosperm phylogeny）中呈非随机分布，整体上表现出系统发育保守性的趋势，且湿林内的保守性趋势较旱林更为显著。不过，所有专性物种均源自被子植物系统发育的各大主要分支，且在湿林或旱林中，仅有极少数功能性状与演替生境特化存在一致的关联。 4. 综合与结论：新热带林树木生境特化中所体现的生态位保守性（niche conservatism）表明，进入不同演替生境的适应辐射在物种丰富属的演化中发挥了一定作用；不过，在不同演替生境中促成物种成功的功能性状多样性，使得群落尺度的分析更为复杂。针对演替梯度探究特定演化支的分布情况，或可更深入地揭示演替生境特化在物种丰富类群演化中的作用。