检验谱系距离对种间生态差异和群落结构动态的预测

Species with larger phylogenetic distance usually have more ecological difference. This is a key assumption guiding the predictions of community structure and dynamic in the field of phylogenetic community ecology. However, several recent experimental studies found no significant or very weak linear relationship between the phylogenetic distance and ecological difference. This conflict triggered an ongoing debate about the scale and the strength of the link between phylogenetic distance and ecological difference, and exposed three major gaps in conventional studies. This proposal will reexamine the assumption in the light of three possible solutions to the above gaps using common tree species in the subtropical forests in Tiantong, Zhejiang province. Specifically, numerical simulations based on the best nonrandom evolution models of many key functional traits will be performed first to build a solid theoretical understanding of the link between phylogenetic distance and ecological difference. Second, a multispecies seedling experiment will be carried out under several key environmental gradients to improve the estimation of ecological difference in species interaction and habitat preference. Thus the expectations from above simulations can be tested against the experiment results. Finally, a 15-year spatiotemporal dynamic of 20ha Tiantong forest plot will be utilized to examine the power of phylogenetic distance in the prediction of ecological difference, forest community structure and dynamic. Results from the above simulations, experimental and observational studies in this proposal can provide valuable insights and data support for our solid understanding and accurate prediction of forest community structure and dynamic under ongoing climate change.

具有较大谱系距离的物种间常存在更多的生态差异。这是系统发育群落生态学预测群落结构和动态的核心假设之一。但近期多个实验发现种间谱系距离与生态差异间不存在显著或仅有极弱的线性关系。这一矛盾激发了生态学家对于谱系距离与生态差异在何种尺度和程度上存在联系的激烈争论，并暴露了以往相关研究的三点缺陷。围绕这一争论及对以往缺陷的改进，本项目拟以浙江天童亚热带常绿阔叶林常见乔木树种为研究对象，通过分析这些物种多个关键功能特征的进化规律，结合多性状非随机变异进化模型模拟研究谱系距离与生态差异间可能的联系尺度与程度；同时采用关键环境梯度下多物种幼苗种间互作和生境偏好实验更为精确地估计种间生态差异，检验上述模拟研究结果；最后，基于天童20ha样地15年的自然森林群落结构变化，检验谱系距离对种间生态差异和群落结构动态的预测能力，以期为进一步理解和运用谱系距离预测气候变化下群落结构和动态提供可靠理论依据和数据支撑。

具有较大谱系距离的物种间常存在更多的生态差异。这是系统发育群落生态学预测群落结构和动态的核心假设之一。但该假设是否成立仍存在激烈争论。本项目围绕这一争论，以浙江天童亚热带常绿阔叶林9个常见乔木树种的9801株幼苗为研究对象，通过理论模拟和为期3年的竞争实验发现：1）谱系距离与涉及13个功能性状的种间生态差间异并非是简单的线性关系；平方根或立方根转换虽然是当前最简洁且表现较好的转换方法，但这些转换严重依赖有关性状选择压力是否随机的假设；2）不同个体密度两物种配对竞争实验都一致表明，谱系距离与种间竞争强度无显著关系（低密度组P值：0.18；高密度组P值：0.55）；多物种混合竞争实验结果类似，谱系距离为0的种内个体间的竞争强度也没有显著大于种间竞争强度（P值：0.7）；3）涉及9类不同非生物环境的幼苗生长状况展示，谱系距离与种间生境偏好差异不存在显著相关性（P值：0.4）；4）进一步研究显示，来自种间互作或/和非生物环境对性状的反馈可能是导致上述谱系距离与种间生态差异关系不显著的原因之一。因为在本项目所有幼苗实验中，均可观测到种间性状差异会因种间互作或/和非生物环境而发生较大的改变。这些理论和实验研究都不支持系统发育群落生态学的核心假设，具有较大谱系距离的物种间不一定存在更多的生态差异。我们还提出并初步验证了一个新的原因：种间生态差异会随竞争环境和非生物环境而发生较大变化，因此固定不变的谱系距离可能无法预测随环境变化的种间生态差异。这些研究成果有助于重新审视谱系距离的生态含义，并为系统发育群落生态学的进一步发展提供可靠的理论依据和数据支撑。