近日，国际杂志Oikos刊登了中国科学院西双版纳热带植物园胡跃华博士等的最新研究成果“Dominant species and dispersal limitation regulate tree species distributions in a 20-ha plot in Xishuangbanna, southwest China。”，研究人员在物种共存机制上的研究获新进展。
热带森林高多样性的物种如何共存？群落生态学当中主流的生态位分化理论和中性理论都分别试图解释物种共存的机制，尽管在世界多个大型固定样地得到不同程度的验证，却难以完全解释这一核心问题。目前，大部分生态学家倾向于将此二者相结合，但是生态位主导、作用相当还是中性主导？基于此，西双版纳20公顷大样地乔木树种分布的最新研究结果给出一些新的解读。
中国科学院西双版纳热带植物园胡跃华博士等对西双版纳20公顷大样地乔木树种分布研究发现：生态位和中性过程对于物种共存的贡献并不是一个简单的孰大孰小问题。对于具有较长生活史的乔木树种而言，在其各个生活史阶段生态位和中性过程的相对重要性是不断变化的——中性过程在小径级的幼树阶段占优；随着径级增大，生态位过程在成年大树阶段起主导作用。这是因为幼树的分布与种子的散布过程紧密相关，而种子的散布过程具有极强的随机性，因此中性散布过程主导了幼树的空间分布；由于空间的异质性分化，从幼树到大树的过程中，环境的过滤作用逐渐成为物种分布的决定因素，大树的分布与环境异质性相关性增强，所以生态位过程决定了大树的分布。（生物谷Bioon.com）
doi:10.1111/j.1600-0706.2011.19831.x
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Dominant species and dispersal limitation regulate tree species distributions in a 20-ha plot in Xishuangbanna, southwest China
Yue-Hua Hu, Li-Qing Sha, F. Guillaume Blanchet, Jiao-Lin Zhang, Yong Tang, Guo-Yu Lan and Min Cao
Habitat heterogeneity and dispersal limitation are widely considered to be the two major mechanisms in determining tree species distributions. However, few studies have quantified the relative importance of these two mechanisms at different life stages of trees. Moreover, rigorous quantification of the effects of dominant tree species in determining species distributions has seldom been explored. In the present study, we tested the hypothesis that the distribution of tree species is regulated by different mechanisms at different life history stages. In particular, we hypothesised that dispersal limitation regulates the distribution of trees at early life stages and that environmental factors control the distribution of trees as they grow, because of niche differentiation resulting from environmental filtering. To test this, trees in 400-m2 quadrats in a 20-ha plot in Xishuangbanna, southwest China were grouped into four classes on the basis of the diameter at breast height (DBH) that roughly represent different stages in the life history of trees. A neighbourhood index was computed to represent a neutral spatial autocorrelation effect. We used both biotic (dominant species) and abiotic (topography and soil) predictor variables to model the distribution of each target species while controlling for spatial autocorrelation within each of the DBH classes. To determine which factors played the largest role in regulating target species distribution, the simulated annealing method was used in model selection based on Akaike information criterion (AIC) values. The results showed that the relative importance of neutral and niche processes in regulating species distribution varied across life stages. The neutral neighbourhood index played the most important role in determining the distributions of small trees (1 cm ≤ DBH ≤ 10 cm), and dominant species, as biotic environmental predictor variables, were the next most important regulators for trees of this size. Environmental predictor variables played the most important role in determining the distributions of large trees (10 cm ≤ DBH). This finding builds on previous research into the relative importance of neutral and niche processes in determining species distributions regardless of life stages or DBH classes.
