Deterministic tropical tree community turnover: evidence from patterns of functional beta diversity along an elevational gradient

Explaining the mechanisms that produce the enormous diversity within and between tropical tree communities is a pressing challenge for plant community ecologists. Mechanistic hypotheses range from niche-based deterministic to dispersal-based stochastic models. Strong tests of these hypotheses require detailed information regarding the functional strategies of species. A few tropical studies to date have examined trait dispersion within individual forest plots using species trait means in order to ask whether coexisting species tend to be more or less functionally similar than expected given a null model. The present work takes an alternative approach by: (i) explicitly incorporating population-level trait variability; and (ii) quantifying the functional beta diversity in a series of 15 tropical forest plots arrayed along an elevational gradient. The results show a strong pattern of decay in community functional similarity with elevation. These observed patterns of functional beta divers...阐释驱动热带树木群落内部与群落间极高多样性的形成机制，是植物群落生态学家亟待解决的紧迫挑战。相关机制假说涵盖基于生态位（niche）的确定性模型与基于扩散的随机模型两大类。对这些假说开展严谨检验，需要获取物种功能策略的详尽数据。迄今为止，仅有少量热带森林研究借助物种性状均值，对单块森林样地内的性状分布（trait dispersion）展开分析，以此探究共存物种的功能相似性是否偏离零模型（null model）的预期结果。本研究采用了差异化的研究路径：其一，明确纳入种群水平的性状变异；其二，对沿海拔梯度布设的15块热带森林样地序列的功能β多样性（functional beta diversity）进行量化分析。研究结果显示，群落功能相似性随海拔升高呈现显著衰减的规律。本次观测到的功能β多样性模式……