Data from:Intraspecific variability improves environmental matching, but does not increase ecological breadth along a wet-to-dry ecotone

It is widely assumed that higher levels of intraspecific variability in one or more traits should allow species to persist under a wider range of environmental conditions. However, few studies have examined whether species that exhibit high variability are found in a wider range of environmental conditions, and whether variability increases the ability of a species to adapt to prevailing ecological gradients. We used four plant functional traits, specific leaf area (SLA), leaf dry matter content (LDMC), leaf carbon to nitrogen ratio (C:N) and maximum plant height in 49 species across a strong environmental gradient to answer three questions: 1) is there evidence for ‘high-variability’ species (that is, species which show high variability in multiple traits, simultaneously)? 2) are species with more variable traits present across a wider range of environmental conditions than less variable species? And 3) whether more variable species show better trait-environment matching to the prevailing abiotic (soil moisture) gradient at the site? We found little evidence for a ‘high-variability’ species. Variability was correlated for two leaf traits, SLA and LDMC, while variability in leaf traits and plant height were not correlated. We found little evidence that more variable species were present in more diverse conditions: only variation in SLA was correlated with a wider ecological niche breadth. For plant traits along the soil-moisture gradient, higher variability led to better trait-environment matching in half of measured traits. Overall, we found little support for the existence of ‘high-variability’ species, but that variability in SLA is correlated with a wider ecological breadth. We also found evidence that variation in traits can improve trait-environment matching, a relationship which may facilitate our understanding ecological breadth along prevailing gradients, and community assembly on the basis of traits.

学界普遍认为，某一或多个性状的种内变异（intraspecific variability）水平越高，物种便能在更广泛的环境条件下存续。然而，鲜有研究探讨性状变异水平较高的物种是否确实分布于更广的环境范围，以及性状变异是否能提升物种适应现有生态梯度的能力。我们选取沿一条显著环境梯度分布的49个物种的4种植物功能性状——比叶面积（specific leaf area, SLA）、叶片干物质含量（leaf dry matter content, LDMC）、叶碳氮比（leaf carbon to nitrogen ratio, C:N）以及最大株高，来解答三个核心问题：1）是否存在“高变异物种”，即同时在多种性状上表现出高变异水平的物种？2）性状变异程度更高的物种，是否比变异程度较低的物种分布于更广的环境范围？3）变异程度更高的物种，是否能更好地匹配该研究样地内主导的非生物（土壤湿度）梯度的性状-环境关系？研究结果显示，几乎没有证据支持“高变异物种”的存在。两种叶性状（比叶面积SLA与叶片干物质含量LDMC）的变异水平呈显著相关，而叶性状与株高的变异则无显著相关性。我们同样未发现足够证据表明，变异程度更高的物种分布于更多样的环境条件中：仅比叶面积SLA的变异与更广的生态位宽度呈显著相关。针对沿土壤湿度梯度分布的植物性状而言，半数被测性状的更高变异水平可带来更优的性状-环境匹配度。综合来看，我们几乎未找到支持“高变异物种”存在的证据，但比叶面积SLA的变异确实与更广的生态位宽度相关。我们还发现，性状变异能够提升性状-环境匹配度，这一关系或有助于我们理解沿现有环境梯度的生态位广度，以及基于性状的群落组装机制。