题目：Trade-offs between physical and chemical carbon-based leaf defence: of intraspecific variation and trait evolution 物理与化学防御之前的权衡：种内差异及形状进化视角
Summary
1.Despite recent advances in studies on trade-offs between plant defence traits, little is known about whether trade-offs reflect (i) evolutionary constraints at the species level or (ii) allocation constraints at the individual level. Here, we asked to which degree physical and chemical carbon-based leaf defence traits covary within and across species. 虽然最近有一些植物在不同防御性状之间存在权衡的研究，但是我们还是不明白这种权衡究竟是反映了（i）受进化限制的物种间的差异，还是（2）受资源限制的个体间的差异。
2.We assessed leaf toughness, leaf total phenolic and tannin concentrations for 51 subtropical tree spe-cies. Species trait means, sample-specific values and phylogenetically independent contrasts were used in regression analyses. Phylogenetic signals and trait evolution were assessed along the phylogeny. 我们选取了51种亚热带树种，分别测量了他们的叶片韧性（物理防御），叶片总酚和单宁含量（化学防御）。这些性状呢，我们有按物种进行平均，也有直接用个体水平值进行回归分析。（phylogenetically independent contrasts是什么鬼？不过既然我们的研究主要是(ii) allocation constraints at the individual level，不涉及phylogeny,我暂时偷个懒。）我们还检测了这三种性状的系统发育信号及其在系统发育树上的进化。
3.Analyses of species-level trait means revealed significant negative trait covariations between physical and chemical defence traits in analyses over all species. 在物种水平，物理防御跟化学防御的物种性状平均值呈负相关。 These covariations were inconsistent at the within-species level. 但是这些负相关性，在种内并不总是存在。
All three defence aspects showed strong phylogenetic signals, but differed in the degree of conservatism along the phylogeny. 三种性状都有显著的系统发育信号，但是信号强弱有差别。
Inclusion of intraspecific trait variability significantly decreased the strength of these covariations. 如果使用个体水平数据（猜测使用了混合模型，用物种作为随机效应）则降低了性状之间的相关性。 Strong negative covariations were detected between physical and chemical defence traits when phylogenetic non-independence was accounted for. 加入系统发育关系之后物理防御与化学防御性状之间的相关性有所增强。
4.Synthesis. We addressed two sources of variation (allocation and evolution) independently from each other in the context of trait interrelationships. 总结起来： 我们在性状相关性的这个框架下分析了两种不同的形状变异来源（种内和种间）。 The observed negative covariations hint at the existence of a trade-off between physical and chemical defence traits. 性状之间的负相关暗示了物理防御跟化学防御之间的折中。
The finding that intraspecific trait variation contributed less to this relationship suggests that the trade-off is dominated by evolutionary constraints rather than by carbon allocation constraints. 种内性状差异的这个折中不明显，表明这个折中主要是受进化影响，而不是受C资源分配影响。
末了，我只能说，这个作者也太能写了！我瞎猜他设计的时候并没有想用物种均值（有个体数据，谁会愿意用均值呢），但个体水平数据显著性不好，于是又用了物种均值，发现信号很强！这下才想出了(i) evolutionary constraints at the species level or (ii) allocation constraints at the individual level这么高大上的解释。系统发育分析当然是常规操作了。
其实在这类研究中加入进化的解释角度是很有意义的，但生态学家不一定能想到，想到也不一定能写好。Respect!