生物多样性, 2011, 19(3): 275-283 doi: 10.3724/SP.J.1003.2011.09275

综述

群落构建研究的新进展: 进化和生态 相结合的群落谱系结构研究

牛红玉1,2, 王峥峰1, 练琚愉1, 叶万辉,1,*, 沈浩1

1 (中国科学院华南植物园, 广州 510650)

2 (中国科学院研究生院, 北京 100049)

New progress in community assembly: community phylogenetic structure combining evolution and ecology

Hongyu Niu1,2, Zhengfeng Wang1, Juyu Lian1, Wanhui Ye,1,*, Hao Shen1

1 South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650

2 Graduate University of the Chinese Academy of Sciences, Beijing 100049

通讯作者: *E-mail:why@scib.ac.cn

编委: 葛学军

责任编辑: 时意专

收稿日期: 2011-01-13   接受日期: 2011-03-15   网络出版日期: 2011-05-20

基金资助: 国家自然科学基金委对外交流项目.  31061160188

Corresponding authors: *E-mail:why@scib.ac.cn

Received: 2011-01-13   Accepted: 2011-03-15   Online: 2011-05-20

摘要

群落如何构建是群落生态学中的重要问题。群落谱系结构研究将物种间的亲缘进化关系运用到群落生态学研究中, 利用物种的系统发育状况推测历史因素对现有群落的影响, 为推断影响群落组成的生态学机制提供了有效方法。群落谱系结构的研究方法是首先建立可代表群落物种库的超级系统进化树, 然后计算群落内物种间的谱系距离, 最后通过统计方法检测其与随机模型下的谱系距离是否有显著差异来获得谱系结构(如谱系聚集、谱系发散), 从而揭示群落构建中的关键生态过程(如生境过滤、竞争作用)。群落谱系结构与空间尺度、分类群尺度、时间尺度等不同研究尺度有关。在小的空间尺度下, 随着分类群尺度降低、树木年龄级增大, 群落谱系结构从聚集逐渐转为发散;而随群落空间尺度的增大, 谱系趋向于聚集。谱系结构受到环境因素影响, 因此分析集合群落下的谱系可以揭示区域生态过程的影响。另外, 群落谱系结构研究还有助于探讨中性理论、密度制约假说等生态学理论, 并预测干扰作用下的群落演化趋势。在利用谱系结构深入探讨群落构建成因时, 需要基于生态特征和环境变量共同分析, 同时考虑小尺度局域过程(群落的微环境或群落内种间相互作用等)和大尺度区域过程(地史过程和物种形成等), 并可结合生态控制实验, 以确认群落构建的关键因素。在研究方法和手段上, 今后需要注重通过选择合适的基因片段建立系统树, 然后通过生态特征来加以校正, 以更准确地反映物种间的亲缘距离。另外, 获得谱系树后还需要寻找更加合理的统计模型和指数, 增加统计分析和解决问题的能力。

关键词: 群落生态学 ; 系统进化树 ; 尺度 ; 功能性状

Abstract

Community assembly has long been an important issue in community ecology. The study of community phylogenetic structure, which applies phylogeny to community ecology studies, has provided an effective way to disentangle the most important ecological processes that drive community assembly. Studying the phylogenetic structure of a community involves firstly the construction of a supertree representing the species pool of the community, then a calculation of phylogenetic distances between all species within the community, and finally an inference of phylogenetic structure (e.g., clustering, overdispersion) obtained by statistically testing whether the obtained phylogenetic distances are different from those expected under random model, hence revealing key ecological processes involved in community assembly (e.g., habitat filtering, competition exclusion). Community phylogenetic structure is different when studied at different taxonomic, spatial or temporal scales. At small spatial scales, community phylogenetic pattern tends to change from clustering to overdispersion with decreasing taxonomical scale or increasing tree age class, while the pattern tends to be tighter clustering at larger spatial scales. Phylogenetic information also indicates the influence of environmental factors and studying community phylogeny at the metacommunity level helps to understand regional ecological processes. In addition, phylogenetic structure can help to explore neutral theory, density-dependent hypothesis and other theories in ecology, and even to predict community dynamics and evolution under disturbance. The future application of phylogenetic structure to disclosing underlying causes of community assembly demands the joint analysis of ecological traits and environment factors and, the consideration of both local processes (e.g., microenviroment, biological interactions) and regional processes (e.g., geological history, speciation). In terms of methodological aspects, to construct a phylogenetic tree, appropriate gene segments should be used and the tree needs to be corrected using ecological traits in order to reflect more exact phylogenetic distances among species. Furthermore, more effective statistical models and indices are needed to increase statistical power.

Keywords: community ecology ; phylogenetic tree ; scales ; functional traits

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本文引用格式

牛红玉, 王峥峰, 练琚愉, 叶万辉, 沈浩. 群落构建研究的新进展: 进化和生态 相结合的群落谱系结构研究. 生物多样性[J], 2011, 19(3): 275-283 doi:10.3724/SP.J.1003.2011.09275

Hongyu Niu, Zhengfeng Wang, Juyu Lian, Wanhui Ye, Hao Shen. New progress in community assembly: community phylogenetic structure combining evolution and ecology. Biodiversity Science[J], 2011, 19(3): 275-283 doi:10.3724/SP.J.1003.2011.09275

物种多样性的维持机制即群落构建(community assembly)的成因, 一直以来都是群落生态学家讨论的焦点。群落内现有物种组成是进化过程和生态过程共同作用的结果, 分析物种间亲缘关系可以反映现有群落形成的历史过程(黄建雄等, 2010)。但是, 过去生态学家常用物种多样性指标来表征群落内物种的丰富度, 不考虑物种间亲缘关系(Monk et al., 1969; Loya, 1972; Tunnicliffe, 1981; Goldberg & Miller, 1990)。尽管一些学者也使用种/属比来反映群落物种组成(Elton, 1946; Moreau, 1948; Simber- loff, 1970), 认为种/属比越大, 群落内共存的亲缘关系相近的物种越多, 反之则群落内物种的亲缘关系较远。然而, 同属内物种也是不等价的, 在种/属比相同的情况下, 其所反映的多样性也可能差异很大, 因为包含的物种可能是近期分化的, 亲缘关系较近;也有可能是早期分化的, 亲缘关系相对较远。所以, 仅以种/属比来反映群落内物种的亲缘关系, 并以此从进化方面揭示群落构建的成因仍然是不够准确的。

随着分子生物学技术在生态学中的逐渐渗透, 系统进化研究也被运用到群落生态学中。使用DNA序列的进化关系来代表物种间的亲缘关系, 不仅能更加有效地衡量群落物种组成, 还可以分析群落谱系结构(phylogenetic structure), 即利用物种的系统发育状况来推测历史因素对现有群落的影响, 通过分析群落内物种谱系亲缘关系是否有一定规律来探究群落构建的主要原因(Webb, 2000; Webb et al., 2002)。一般来说, 亲缘关系越近的物种, 生态特征可能越相似, 对类似环境的适应能力就越一致, 即生态位越相似(Darwin, 1859; Prinzing et al., 2001)。在一个群落中, 如果生境过滤作用占主导地位, 则相同生境将筛选出适应能力相似、亲缘关系偏近的物种; 相反, 竞争排斥作用会使生态位相似的物种无法共存于同一环境, 则群落内物种亲缘关系较远。因此, 进化和生态相结合的群落谱系结构研究, 可以从进化角度深入地分析群落物种组成现状和原因, 为有效推测影响群落物种组成的不同生态学机制提供了实验解决方法, 并有助于完善宏观生态学理论。

1 群落谱系结构的研究方法

Webb(2000)首次试验性地将谱系树(phylogen- etics tree)运用到群落生态学研究, 分析了热带雨林森林群落的构建机制, 为物种多样性的研究提供了新方向。随后, Webb等(2002)又进一步系统地阐述了群落谱系结构研究的具体操作方法, 主要步骤包括: 首先, 建立可代表群落物种库的超级系统进化树(supertrees)。然后, 通过分析群落内物种在系统进化树的位置, 计算物种间的谱系距离, 在随机模型下(假设物种分布随机)标准化谱系距离, 获得亲缘关系指数。例如, 净亲缘指数(net relatedness index, NRI)是标准化样方内所有物种对的平均谱系距离(mean phylogenetic distance, MPD); 最近亲缘指数(nearest taxon index, NTI)则是标准化样方内每个物种的最近谱系距离的平均值(mean nearest taxon index, MNTD)。最后通过检测谱系亲缘关系指数的大小, 即统计检测谱系距离观测值与零假设期望值的差异, 来检测群落是否存在谱系结构。如果亲缘关系指数与零假设没有显著差异, 说明无显著谱系结构(no phylogenetic structure)或者称谱系随机(后文均用“谱系随机”表示); 如果物种间亲缘关系指数显著大于随机零假设, 说明群落具有显著的谱系结构, 呈现出谱系聚集(phylogenetically clustered); 相反, 物种间亲缘关系指数显著小于随机零假设, 呈现出谱系发散(phylogenetically overdispersed)。

获得群落谱系结构后, 推测群落构建成因的前提假设是亲缘关系越近, 生态特征越相似, 因而使用谱系距离来代表生态特征距离。Darwin(1859)很早就提出, 亲缘关系近的物种间竞争大于关系较远的物种, 其内涵与谱系结构研究的假设一致。Prinzing等(2001)也发现不同物种对光、土壤湿度、pH等环境因子的耐受性与物种之间的谱系亲缘关系呈正相关: 关系越近, 对环境的耐受度越相似。但是, 该假设的合理性受到质疑。Webb等(2002)在阐述谱系结构研究方法时, 就指出生态性状的进化特征对群落构建的解释有着重要影响。他们提出功能性状按进化特征应该划分为保守性状(conserved traits)和趋同性状(convergence traits)。前者的相似性性状是由同一性状进化而来的, 这类性状与谱系亲缘关系正相关, 具有谱系特征(phylogenetic signal); 后者的相似性性状是由起源不同的性状独立进化而来, 是与谱系亲缘无关的性状, 即不具有谱系特征(no phylogenetic signal)。因此, 如果选用不同的功能性状进行群落构建研究, 其结果将大相径庭。如果选用的是保守性状, 生境过滤聚集了具有相似特征的近缘物种, 表现为谱系聚集, 竞争排斥作用导致具有相似特征的物种分散, 表现为谱系发散; 如果性状是趋同进化而来的, 生境过滤后虽聚集了性状相似的物种, 但它们之间的亲缘关系并不相近, 表现为谱系发散, 而因竞争排斥作用留下的具有不同性状的物种间亲缘关系可能会没有规律, 表现为谱系随机或者谱系聚集(表1)(Webb et al., 2002; Kraft et al., 2007)。

表1   不同生态性状进化特征和不同群落构建过程下的群落期望谱系结构(引自Webb et al., 2002; Kraft et al., 2007)

Table 1  Patterns of community phylogenetic dispersion predicted to be produced by various community assembly processes and different evolutionary characteristic of ecological traits (after Webb et al., 2002; Kraft et al., 2007)

群落构建过程
Community assembly processes
生态性状的进化特征 Evolutionary characteristic of ecological traits
生态性状保守 Traits conserved生态性状趋同 Traits convergent
中性构建 Neutral assembly谱系随机 Random dispersion谱系随机 Random dispersion
生境过滤作用 Habitat filtering谱系聚集 Cluster dispersion谱系发散 Overdispersion
竞争排斥作用 Competitive exclusion谱系发散 Overdispersion谱系随机或谱系聚集Random or cluster dispersion

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此后, 一些研究选取了物种的某些生态性状, 分析其进化特征是保守的还是易变的, 以验证这个假设的正确度。结果发现, 虽然大多数生态性状是谱系保守的(如Chazdon et al., 2003; Swenson et al., 2007), 但是仍有一些生态性状被发现是进化易变的(如Cavender-Bares et al., 2004; Fine et al., 2006)。由于一个物种所具有的众多生态特征的集合就构成了其特有的生态位, 一些研究针对生态位的进化特征展开分析, 希望从中找到一定的规律。Peterson等(1999)在墨西哥分别从鸟类、哺乳类和蝴蝶中选择多对近缘种进行研究, 发现经过几百万年的独立进化后, 姐妹物种之间的气候生态位仍相似, 说明了气候生态位的保守性。Wiens和Graham(2005)以及Wiens等(2010)则假定生态位保守(niche conservatism)是成立的, 通过分析该假说对异域物种形成(allopatric speciation)、物种多样性格局(patterns of species richness)、食物网(food web)等各种生态现象的解释效果, 反过来验证得出生态位保守假说具有较高实用性和正确性。他们将生态位保守定义为生态特征维持不变的趋势, 其中就包含了谱系生态位保守性(phylogenetic niche conservatism), 即近缘种具有维持相似生态特征的趋势。因此, 群落谱系研究的前提就是生态位保守假说中的谱系生态位保守假说。

但是关于生态位保守假说也有一些质疑。如Losos等(2003)认为生态位在进化上是易变的。这可能是因为生态位的范畴也是不同的。Silvertown等(2006a, b)将生态位分类, 提出决定生境内α物种多样性的“α生态位性状”在进化上易变, 与谱系亲缘关系不相关; 而决定物种在不同生境内生存的“β生态位性状”是谱系保守的, 与谱系亲缘关系正相关。他们认为不同进化方式的α和β生态位是生境过滤后的必然结果, 物种必须拥有保守的β生态位来适应相同生境, 同时又有易变的α生态位来适应同一生境内的竞争和共存。

因此, 直接用物种之间的亲缘关系距离分析群落多样性的维持机制, 一定要注意其前提假设。在具体研究中, 可以适当选择一系列与研究目的相关的生态性状, 分析其进化特征后, 结合谱系研究结果, 共同揭示群落构建成因。

2 群落谱系结构与研究尺度之间的关系

在已有的众多群落谱系结构研究中, 尽管出现各种结果(谱系随机、谱系聚集或者发散), 但是大多数群落内, 尤其是植物群落内, 物种亲缘关系往往呈现出非随机格局(Vamosi et al., 2009)。同时, 随着研究的深入, 人们发现不同的空间或者谱系尺度下群落谱系结构不同, 反映出群落构建成因会由于尺度的不同而存在差异(Cavender-Bares et al., 2006; Kembel & Hubbell, 2006; Swenson et al., 2006)。

许多研究发现谱系结构与空间尺度(spatial scale)具有一定的相关性, 即随着群落空间尺度的增大, 谱系结构从发散逐渐转为聚集(Swenson et al., 2007)。Slingsby和Verboom(2006)以及Silva和Batalha(2009)均发现小空间抑制了亲缘关系近的物种共存, 呈现出显著的谱系发散。Kembel和 Hubbell(2006)研究巴拿马热带雨林植物群落的谱系结构后, 发现随着空间尺度的增大(从100 m2到1 ha), 谱系结构有逐渐聚集的趋势。Swenson等(2007)进一步研究5个大样地的多个空间尺度下的谱系结构, 也得出了类似的规律: 小于100 m2的小空间尺度上, 谱系趋向于发散, 大于100 m2后谱系就开始趋向聚集。然而, 黄建雄等(2010)研究古田山常绿阔叶林群落不同尺度(取样半径为5 m、25 m、50 m、75 m、100 m)下的谱系结构时, 均发现显著的谱系聚集, 这很可能是因为这些尺度主要是属于大于75 m2的大尺度。但是他们同时还发现, 海拔、地形、土壤等环境因子对不同尺度群落的影响力不同: 对小尺度群落影响较小, 而对大尺度则影响显著, 这间接地证实了大尺度偏向于谱系聚集的结论。

谱系结构随着空间尺度变化的可能原因是: 小空间尺度下的生境较为均质, 资源相对有限, 导致群落构建中物种之间的竞争排斥作用占优势; 随着空间尺度增大, 环境变量逐渐增多, 生境过滤成为群落构建的主导因素(Willis et al., 2010)。

此外, Swenson等(2006)的研究还发现, 所选择的物种库的空间尺度也会影响谱系结构。物种库是指一个地区可进入某一特定群落的潜在物种数目(方精云等, 2009)。我们难以判断一个群落的物种库到底有多大, 但至少包含了该群落调查到的所有物种。因此, 研究一个群落的谱系结构时, 至少要选择该群落内所有物种作为小空间尺度物种库, 也可以扩大范围, 选择该群落所在区域的所有物种作为大空间尺度物种库来进行分析。Swenson等(2006)发现, 物种库的空间尺度越大, 越可能发生谱系聚集。这证实了群落生境过滤是物种定居于某个区域的首要限制因素, 从而导致大尺度物种库下, 群落呈现为谱系聚集; 而小尺度物种库代表了生境过滤后的物种库, 说明经过一定的筛选后, 竞争排斥作用成为主要构建因素, 小的物种库下群落呈现为谱系发散。可见, 谱系结构研究并不是要否定某一生态过程, 而是希望找到影响目标群落的关键生态 过程。

谱系结构与分类群尺度(taxonomic scale)相关, 随着分类群尺度的降低, 谱系结构会越来越发散(Vamosi et al., 2009)。Cavender-Bares等(2004)研究了美国佛罗里达州的一个小于100 m2的森林群落内17个栎属物种, 结果发现栎属群落谱系发散。后来Cavender-Bares等(2006)的研究进一步扩展到3个群落, 发现以所有植物、被子植物、乔木或者灌木分别分析时, 群落都主要表现为谱系聚集; 但是如果只分析群落内某一属植物(栎属、松属、冬青属)的谱系结构时, 群落谱系显著发散或者随机。Swenson等(2006)也发现分类群尺度对谱系结构影响的类似结果。

以上的研究都证实了分类群尺度越小, 物种间竞争越激烈, 谱系结构越可能发散, 此现象说明竞争排斥作用抑制了相近物种在同一群落内生存, 亲缘关系越近, 物种间的竞争越激烈。

谱系结构与时间尺度相关。一方面, 植物的径级大小体现了物种生长的时间尺度。随着径级增大, 群落谱系结构趋于发散(Swenson et al., 2007)。Swenson等(2007)为了评估时间对谱系的影响, 按径级大小划分为5个尺度来研究不同龄级的林冠层植物的谱系结构, 发现小径级的谱系聚集或者随机, 而大径级的谱系结构则趋向于发散格局。这可能是因为母树种子受到扩散限制, 小树聚集生长, 表现为谱系聚集; 随着树木个体的长大, 彼此之间的竞争加强, 存活的物种间地理距离变远, 整体表现为谱系发散。另一方面, 群落的成熟度也反映了群落发展的时间尺度。Letcher (2010)研究了不同演替阶段下的植物群落谱系结构, 发现随着演替的深入, 谱系结构也更加趋于发散, 并且谱系发散也更加趋向于大径级群落。

综上可知, 群落谱系结构研究需要考虑尺度的影响, 不同空间和时间尺度下的群落, 其构建成因不同。一般来说, 在小空间尺度下, 群落谱系结构会随着分类尺度的增大, 从发散趋向于聚集, 而随着树木年龄的增加, 群落谱系逐渐从聚集趋向发散; 但是, 当空间尺度足够大时, 谱系结构则呈现为聚集, 不再受到时间尺度或者分类群尺度的影响(Swenson et al., 2007)。Vamosi等(2009)试图找到群落谱系结构从发散转为聚集的空间尺度和分类群尺度的临界点, 认为至少面积小于5 ha, 分类群是科及科以下水平的群落会由于内部激烈的竞争作用呈现出谱系发散,并称这个范围为Darwin- Hutchinson zone; 超出这个范围后, 竞争作用可能就不再占优势, 谱系结构开始改变。但是他们也提到谱系结构受到多个生态过程的综合影响, 这个边界的准确性还需要以后进一步的检验。因此, 分析某一群落谱系结构时, 要明确指出研究群落的空间尺度、建立谱系树的物种库的空间尺度, 以及所研究物种的分类群尺度等, 才能准确揭示这些尺度下的群落维持机制。

3 环境因素对群落谱系结构的影响

生境过滤是群落内物种生存的首要决定因子, 环境因素对群落内物种组成有着非常重要的作用。例如, Barberan和Casamayor(2010)研究不同生境浮游生物的谱系结构后, 发现海洋浮游生物的群落谱系结构聚集程度大于内陆湖群落, 他们认为这是由海洋盐分组成和浓度产生显著过滤作用的结果。不同的地形结构也会影响谱系结构。Graham等(2009)发现海拔高度对蜂鸟群落的谱系结构有重要影响, 表现出高海拔群落谱系聚集, 低海拔群落谱系分散的现象。同样, Kembel和Hubbell(2006)也发现巴拿马大样地内高海拔生境下的植物群落表现为谱系聚集, 沼泽和斜坡生境的群落则为谱系发散。但是, 黄建雄等(2010)在分析古田山大样地的植物群落研究中发现, 高海拔区域谱系发散, 低海拔谱系聚集。

由上可见, 尽管不同的生境可能形成不同的谱系结构, 但是目前并没有统一的规律来说明一种生境一定会对应一种特定的谱系结构。这是因为一个群落的物种多样性不仅受环境条件、生物间相互作用等局域因素的影响, 还受到地史过程、物种形成等区域过程的影响(Ricklefs, 1987; Eriksson, 1993; Zobel, 2001; 方精云等, 2009)。由于在区域过程的影响下, 不同的群落的物种库是不同的, 我们不能简单地从不同历史背景和不同气候条件下的群落中获得环境对谱系影响的相同规律。例如, 过去的地质历史事件(如冰期)可能会导致研究群落所在区域内适应低温的物种为某单一类群的物种, 从而产生高海拔低温地区的群落谱系聚集, 但是没有受到冰期影响的群落很可能就不会出现这种情况。

集合群落(metacommunity)是指具有潜在相互作用的物种相关联的一系列小格局群落(Leibold et al., 2004)。这类群落往往种库资源一致, 却包含了不同环境变量下的群落。因此, 将群落谱系结构研究推广到集合群落水平, 在相同物种库构建谱系树下比较不同群落的结构, 排除了物种库的空间尺度对谱系结构的影响, 将可以更加准确地了解环境梯度对群落构建的影响(Pillar & Duarte, 2010)。另外, Graham和Fine(2008)还将传统的β多样性和群落谱系学整合, 提出了谱系β多样性(phylobetadiversity), 通过测量多个群落的谱系距离, 结合环境梯度分析或生态位模型等, 从局域过程和区域过程两方面共同揭示现有生物多样性格局。因此, 分析环境因素对谱系结构的影响, 要特别注意大尺度下区域物种库的影响。我们需要先消除种库效应, 或者直接选择种库一致的群落进行研究, 寻找引起选择作用加强的关键环境因子。

4 群落谱系与其他群落生态学机制

关于群落构建成因的理论和假说非常多, 分析群落谱系还有助于探讨其他群落生态学机制。中性理论所认为的群落构建是在随机作用下等价个体的随机生态漂变过程(Hubbell, 2001), 而谱系结构研究的零假设是指研究群落由从物种库随机选取的同实际物种数目相等的物种构成, 类似中性理论的内涵: 群落内物种组成是随机构建的。而在生态位保守假说的前提下, 谱系聚集或者发散揭示的生境过滤或者竞争排斥作用则强调了物种的非等价性, 承认了生态位理论。所以群落谱系结构为验证中性理论, 甚至为解决两个理论之争议提供了一个新的途径(Cavender-Bares et al., 2009b)。但在实际应用中需要注意, 谱系随机可能是生境过滤和竞争排斥的中和产物(Mayfield & Levine, 2010), 因此不能简单地将谱系随机确认为中性理论, 而应该考虑环境因素等作进一步细致分析。

密度制约假说认为生物在种群密度较高的生境中存活率较低。以往研究常常集中于目标物种的种群动态, 但是其邻体并不只是同种个体, 特别是在热带雨林地区, 聚集程度最高的物种, 其最近邻体常常是其他物种(祝燕等, 2009)。将谱系关系引入种群动态研究, 可以分析亲缘距离不同的其他物种对研究物种种群的影响。Webb等(2006)研究了婆罗洲热带雨林, 发现提高邻体的谱系多样性能降低幼苗的死亡率, 说明密度制约也会发生在近缘种之间。

外界干扰作用会直接影响群落动态, 因此平行比较物种库一致的群落谱系结构, 有助于了解干扰作用对群落影响的后果。Verdu和Pausas(2007)以及Ojeda等(2010)研究地中海植物群落发现, 野火发生频率高的植物群落内谱系聚集; 相反, 野火发生频率低的群落中大多谱系发散。这说明火的干扰会影响群落谱系结构, 或者说火是构建地中海植物群落的关键进化驱动力和重要环境因素。Lessard等(2009)研究发现, 没有被入侵的本地蚂蚁群落表现为谱系发散, 入侵后的群落转为谱系聚集, 说明生物入侵导致生境对物种的选择作用加强。另外, Dinnage(2009)也发现没受到干扰作用的撂荒地内, 植物群落没有显著谱系结构, 但是近期受到人为干扰的撂荒地, 群落谱系结构表现为更加聚集。

从以上的研究结果我们发现, 尽管各种干扰形式不同, 但是对群落谱系结构的作用结果是一致的, 即都会导致群落谱系聚集, 其可能原因是相同的物种对干扰的敏感度相似, 干扰作为一种环境过滤器, 可引起群落形成显著谱系结构(Helmus et al., 2010)。

5 结语与展望

5.1 基于生态特征、环境变量和谱系结构的共同分析, 深入探讨群落构建成因

群落谱系结构研究对了解群落构建、群落动态有着重要作用, 将会成为群落生态学中一项重要手段。由于谱系结构受到尺度、生态特征以及环境因子等的影响, 我们不能盲目地从谱系结构结果来判断群落构建原因, 而是需要全面考虑这几方面因素, 共同揭示其成因(Pausas & Verdu, 2010)。例如, 如果发现群落谱系聚集, 应该尽量寻找导致这种结构的环境因子, 测定适应该环境因子的植物功能性状是否保守进化, 最后才能确定环境过滤作用的地位。值得注意的是, 现有的森林大型固定样地的建立, 为研究植物群落构建提供了非常好的平台, 样地内环境因子和植物生态特征等基础资料已较为详实, 而且长期的定位监测更利于从动态的角度了解群落构建(马克平, 2008; 叶万辉等, 2008)。因此, 与生态特征、环境变量等相结合的群落谱系结构研究将会在大样地的平台下发挥重要的作用。

5.2 结合研究群落谱系结构和多种生态过程, 正确分析群落构建成因

在生态位理论中, 生境过滤和竞争排斥作用一直被认为是群落构建的两个重要因素, 现有的研究主要用这两个生态过程来解释群落物种多样性格局。但是, 其他生态过程也会影响群落构建, 如生物之间捕食作用、促进作用、互利共生等, 尤其捕食作用可能是物种生存于某一群落的第二层过滤筛(Pausas & Verdu, 2010)。一些研究已经发现, 捕食者相似度和被捕食者的谱系距离之间存在着显著的负相关关系, 即随着植物谱系距离的增大, 同时被一种病原体侵染或同一类昆虫捕食的可能性变小(Weiblen et al., 2006; Gilbert & Webb, 2007)。另外, 周围物种的改变, 特别是生物入侵, 也可能成为一种过滤器, 引起群落谱系结构的改变(Lessard et al., 2009)。因此, 通过群落谱系结构判断群落构建原因, 不应仅仅考虑竞争排斥和生境过滤作用, 还需要分析其他生态过程。为了避免各种复杂因素的影响, 适当地进行一些生态控制实验, 来确认群落构建的关键因素将是以后的重要方向, 例如可通过控制性地增加湿度、降低光照、改变土壤营养等来确认生境对群落的影响(Pausas & Verdu, 2010)。

现有的谱系结构研究主要是针对一个群落, 侧重从小尺度上(群落的微环境或者群落内部物种间相互作用等)来分析其群落构建成因。但是进化常发生在大的空间和时间尺度上, 大尺度生态过程(物种形成等)也会影响群落物种多样性, 特别是物种库的大小对其有着直接的限制作用(Eriksson, 1993)。很多研究已经发现在区域尺度上生物多样性本身有很大的差异, 甚至呈现出随纬度增大, 物种多样性降低的格局(Molles, 2008)。因此, 今后的研究还需要增加多个群落的谱系结构分析, 这样不仅为小尺度群落里物种多样性的维持机制提供更为准确的解释, 而且有助于揭示现有区域尺度上的物种多样性格局。

5.3 群落谱系结构的研究方法和手段的进一步完善

群落谱系结构研究中, 首先需要建立一个超级谱系树, 因而谱系树的准确程度关系着下一步的结果。植物群落内物种系统发育关系主要是基于APG分类系统(Angiosperm Phylogeny Group)(APGIII, 2009), 通过在Phylomatic程序中输入物种名录来获得(如Kembel & Hubbell, 2006; Letcher, 2010)。但是该方法存在一些弊端: 对物种的分辨率不高, 往往只解决到属的水平(Kress et al., 2009); 所含信息不完整, 只包含了被子植物的信息。随着测序技术的成熟和测序费用的降低, 分辨率高的DNA条形码技术逐渐受到大家的青睐。它可以提高和改善解析谱系树末端分支的能力, 同时增加了拒绝零假设的统计能力(Kress et al., 2009), 比APG方法获得的谱系树更加准确(详见本期裴男才等(2011)关于植物DNA条形码的介绍)。但是, DNA条形码识别物种仍无法达到100%的效果。今后的研究应该首先通过选择合适的基因片段建立系统树, 然后通过生态特征来校正系统树, 这样才能更加准确地反映物种间的亲缘距离(Grandcolas et al., 2001), 便于下一步的 研究。

获得谱系树后, 统计方法的选择尤为重要。目前检测群落内物种亲缘关系最为常用的指数是Webb(2000)提出的NRI和NTI。但是这两个指数并不完美, 例如NTI对检测竞争具有更大的统计能力, 而NRI对检测环境过滤更为有效(Swenson et al., 2007)。另外, 零模型的建立对统计结果具有比较重要的作用, 然而现有的零模型还没有考虑全面, 一个更逼真的模型应该是考虑群落中的物种丰富度, 且将进化特征和群落结合起来(Kraft et al., 2007)。因此, 将来需要更多的研究来验证这些指数的准确性并寻找更加合理的模型, 增加统计分析和解决问题的能力。

总之, 由于谱系结构研究刚刚开展起来, 在方法和手段上还有一些不足, 需要进一步的修正和 完善。

5.4 利用谱系结构研究对群落演化趋势进行预测

群落谱系结构研究将进化和生态学联系起来, 是从进化的角度研究群落内物种组成的历史和起源, 分析群落构建的原因。通过了解群落构建的规律, 将有可能利用现有的条件预测群落将来的动态变化, 如受到干扰后群落内物种组成的改变等。特别是随着全球变化(包括生境退化、生物入侵、气候变化等)速度的加快, 了解群落的响应和动态显得至关重要(Cavender-Bares & Pahlich, 2009)。

此外, 了解群落内不同营养级的谱系结构之间的相关性, 就可以通过一个营养级群落的大小来预测另一个营养级群落的动态变化。特别是了解植物与病原体之间的关系, 将有助于预测病原体的危害范围(Cavender-Bares et al., 2009a), 这在实际应用中有重要意义。

由此可见, 群落谱系结构研究不仅能够通过了解群落现状来推测其形成的历史原因, 还可能通过现状推测群落以后的发展方向, 该研究将会成为群落生态学研究的一个重要手段。

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Phylogenetic structure of floridian plant communities depends on taxonomic and spatial scale

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DOI:10.1890/0012-9658(2006)87[109:psofpc]2.0.co;2      URL     PMID:16922307      [本文引用: 2]

Consideration of the scale at which communities are defined both taxonomically and spatially can reconcile apparently contradictory results on the extent to which plants show phylogenetic niche conservatism. In plant communities in north central Florida, we collected species abundances in 55 0.1-ha plots in several state parks. When communities were defined narrowly to include a single phylogenetic lineage, such as Quercus, Pinus, or Ilex, neighbors tended to be less related than expected (phylogenetic overdispersion) or there was no pattern. If the same communities were defined more broadly, such as when all seed plants were included, neighbors tended to be more related than expected (phylogenetic clustering). These results provide evidence that species interactions among close relatives influence community structure, but they also show that niche conservatism is increasingly evident as communities are defined to include greater phylogenetic diversity. We also found that, as the spatial scale is increased to encompass greater environmental heterogeneity, niche conservatism emerges as the dominant pattern. We then examined patterns of trait evolution in relation to trait similarity within communities for 11 functional traits for a single phylogenetic lineage (Quercus) and for all woody plants. Among the oaks, convergent evolution of traits important for environmental filtering contributes to the observed pattern of phylogenetic overdispersion. At the broader taxonomic scale, traits tend to be conserved, giving rise to phylogenetic clustering. The shift from overdispersion to clustering can be explained by the increasing conservatism of traits at broader phylogenetic scales.

Cavender-Bares J, Kozak KH, Fine PVA, Kembel SW (2009b)

The merging of community ecology and phylogenetic biology

Ecology Letters, 12, 693-715.

DOI:10.1111/j.1461-0248.2009.01314.x      URL     PMID:19473217      [本文引用: 1]

The increasing availability of phylogenetic data, computing power and informatics tools has facilitated a rapid expansion of studies that apply phylogenetic data and methods to community ecology. Several key areas are reviewed in which phylogenetic information helps to resolve long-standing controversies in community ecology, challenges previous assumptions, and opens new areas of investigation. In particular, studies in phylogenetic community ecology have helped to reveal the multitude of processes driving community assembly and have demonstrated the importance of evolution in the assembly process. Phylogenetic approaches have also increased understanding of the consequences of community interactions for speciation, adaptation and extinction. Finally, phylogenetic community structure and composition holds promise for predicting ecosystem processes and impacts of global change. Major challenges to advancing these areas remain. In particular, determining the extent to which ecologically relevant traits are phylogenetically conserved or convergent, and over what temporal scale, is critical to understanding the causes of community phylogenetic structure and its evolutionary and ecosystem consequences. Harnessing phylogenetic information to understand and forecast changes in diversity and dynamics of communities is a critical step in managing and restoring the Earth's biota in a time of rapid global change.

Cavender-Bares J, Pahlich A (2009)

Molecular, morphological and ecological niche differentiation of sympatric sister oak species, Quercus virginiana and Q. geminata (Fagaceae)

American Journal of Botany, 96, 1690-1702.

DOI:10.3732/ajb.0800315      URL     PMID:21622355      [本文引用: 1]

The genus Quercus (the oaks) is notorious for interspecific hybrization, generating questions about the mechanisms that permit coexistence of closely related species. Two sister oak species, Quercus virginiana and Q. geminata, occur in sympatry in Florida and throughout the southeastern United States. In 11 sites from northern and southeastern regions of Florida, we used a leaf-based morphological index to identify individuals to species. Eleven nuclear microsatellite markers significantly differentiated between the species with a high correspondence between molecular and morphological typing of specimens. Nevertheless, Bayesian clustering analysis indicates interspecific gene flow, and six of 109 individuals had mixed ancestry. The identity of several individuals also was mismatched using molecular markers and morphological characters. In a common environment, the two species performed differently in terms of photosynthetic performance and growth, corresponding to their divergent ecological niches with respect to soil moisture and other edaphic properties. Our data support earlier hypotheses that divergence in flowering time causes assortative mating, allowing these ecologically distinct sister species to occur in sympatry. Limited gene flow that permits ecological differentiation helps to explain the overdispersion of oak species in local communities.

Chazdon RL, Careaga S, Webb C, Vargas O (2003)

Community and phylogenetic structure of reproductive traits of woody species in wet tropical forests

Ecological Monographs, 73, 331-348.

DOI:10.1890/02-4037      URL     [本文引用: 1]

Darwin C (1859)

On the Origin of Species by Means of Natural Selection

John Murray, London.

[本文引用: 2]

Dinnage R (2009)

Disturbance alters the phylogenetic composition and structure of plant communities in an old field system

PloS ONE, 4, e7071.

DOI:10.1371/journal.pone.0007071      URL     PMID:19763265      [本文引用: 1]

The changes in phylogenetic composition and structure of communities during succession following disturbance can give us insights into the forces that are shaping communities over time. In abandoned agricultural fields, community composition changes rapidly when a field is plowed, and is thought to reflect a relaxation of competition due to the elimination of dominant species which take time to re-establish. Competition can drive phylogenetic overdispersion, due to phylogenetic conservation of 'niche' traits that allow species to partition resources. Therefore, undisturbed old field communities should exhibit higher phylogenetic dispersion than recently disturbed systems, which should be relatively 'clustered' with respect to phylogenetic relationships. Several measures of phylogenetic structure between plant communities were measured in recently plowed areas and nearby 'undisturbed' sites. There was no difference in the absolute values of these measures between disturbed and 'undisturbed' sites. However, there was a difference in the 'expected' phylogenetic structure between habitats, leading to significantly lower than expected phylogenetic diversity in disturbed plots, and no difference from random expectation in 'undisturbed' plots. This suggests that plant species characteristic of each habitat are fairly evenly distributed on the shared species pool phylogeny, but that once the initial sorting of species into the two habitat types has occurred, the processes operating on them affect each habitat differently. These results were consistent with an analysis of correlation between phylogenetic distance and co-occurrence indices of species pairs in the two habitat types. This study supports the notion that disturbed plots are more clustered than expected, rather than 'undisturbed' plots being more overdispersed, suggesting that disturbed plant communities are being more strongly influenced by environmental filtering of conserved niche traits.

Elton C (1946)

Competition and the structure of ecological communities

Journal of Animal Ecology, 15, 54-68.

DOI:10.2307/1625      URL     [本文引用: 1]

Eriksson O (1993)

The species-pool hypothesis and plant community diversity

Oikos, 68, 371-374.

DOI:10.2307/3544854      URL     [本文引用: 2]

Fang JY (方精云), Wang XP (王襄平), Tang ZY (唐志尧) (2009)

Local and regional processes control species richness of plant communities: the species pool hypothesis

Biodiversity Science (生物多样性), 17, 605-612. (in Chinese with English abstract)

DOI:10.3724/SP.J.1003.2009.09141      URL     [本文引用: 2]

Exploring the mechanisms underlying community species richness is a key issue in ecology and conservation biology, and many hypotheses based on small-scale, local processes have traditionally been used as explanations. The species pool hypothesis developed by Zobel et al. suggests that the variation in community species richness is not only associated with contemporary environmental factors and ecological processes (e.g. competition and predation), but also limited by the regional species pool. The regional species pool is the set of species in a certain region that are capable of coexisting in a target community, which is shaped by historical (e.g. glaciation and geological age) and regional processes (e.g. speciation, immigration, dispersion, and extinction). The species pool hypothesis suggests that the larger the area of a habitat type and the greater its geological age, the greater the opportunity for speciation and hence the larger the number of available species adapted to that particular habitat, which will in turn lead to higher community diversity. The species pool is generally studied at two spatial scales: the regional and the actual scales. While the regional species pool is primarily determined by biogeographic processes, the actual species pool (species present in the target community) is determined by both ecological processes (e.g. competition) and the regional pool. In this review, we introduce and discuss the concepts relating to, and evidence for the species pool hypothesis, together with methods for estimating the species pool.

Fine PVA, Miller ZJ, Mesones I, Irazuzta S, Appel HM, Stevens MHH, Saaksjarvi I, Schultz JC, Coley PD (2006)

The growth-defense trade-off and habitat specialization by plants in Amazonian forests

Ecology, 87, S150-S162.

DOI:10.1890/0012-9658(2006)87[150:tgtahs]2.0.co;2      URL     PMID:16922310      [本文引用: 1]

Tropical forests include a diversity of habitats, which has led to specialization in plants. Near Iquitos, in the Peruvian Amazon, nutrient-rich clay forests surround nutrient-poor white-sand forests, each harboring a unique composition of habitat specialist trees. We tested the hypothesis that the combination of impoverished soils and herbivory creates strong natural selection for plant defenses in white-sand forest, while rapid growth is favored in clay forests. Recently, we reported evidence from a reciprocal-transplant experiment that manipulated the presence of herbivores and involved 20 species from six genera, including phylogenetically independent pairs of closely related white-sand and clay specialists. When protected from herbivores, clay specialists exhibited faster growth rates than white-sand specialists in both habitats. But, when unprotected, white-sand specialists outperformed clay specialists in white-sand habitat, and clay specialists outperformed white-sand specialists in clay habitat. Here we test further the hypothesis that the growth defense trade-off contributes to habitat specialization by comparing patterns of growth, herbivory, and defensive traits in these same six genera of white-sand and clay specialists. While the probability of herbivore attack did not differ between the two habitats, an artificial defoliation experiment showed that the impact of herbivory on plant mortality was significantly greater in white-sand forests. We quantified the amount of terpenes, phenolics, leaf toughness, and available foliar protein for the plants in the experiment. Different genera invested in different defensive strategies, and we found strong evidence for phylogenetic constraint in defense type. Overall, however, we found significantly higher total defense investment for white-sand specialists, relative to their clay specialist congeners. Furthermore, herbivore resistance consistently exhibited a significant trade-off against growth rate in each of the six phylogenetically independent species-pairs. These results confirm theoretical predictions that a trade-off exists between growth rate and defense investment, causing white-sand and clay specialists to evolve divergent strategies. We propose that the growth-defense trade-off is universal and provides an important mechanism by which herbivores govern plant distribution patterns across resource gradients.

Gilbert GS, Webb CO (2007)

Phylogenetic signal in plant pathogen-host range

Proceedings of the National Academy of Sciences, USA, 104, 4979-4983.

DOI:10.1073/pnas.0607968104      URL     [本文引用: 1]

Goldberg DE, Miller TE (1990)

Effects of different resource additions on species diversity in an annual plant community

Ecology, 71, 213-225.

DOI:10.2307/1940261      URL     [本文引用: 1]

Graham CH, Fine PVA (2008)

Phylogenetic beta diversity: linking ecological and evolutionary processes across space in time

Ecology Letters, 11, 1265-1277.

URL     PMID:19046358      [本文引用: 1]

Graham CH, Parra JL, Rahbek C, McGuire JA (2009)

Phylogenetic structure in tropical hummingbird communities

Proceedings of the National Academy of Sciences, USA, 106, 19673-19678.

DOI:10.1073/pnas.0901649106      URL     [本文引用: 1]

Grandcolas P, Deleporte P, Desutter-Grandcolas L, Daugeron C (2001)

Phylogenetics and ecology: as many characters as possible should be included in the cladistic analysis

Cladistics, 17, 104-110.

DOI:10.1006/clad.2000.0149      URL     [本文引用: 1]

AbstractAs many data as possible must be included in any scientific analysis, provided that they follow the logical principles on which this analysis is based. Phylogenetic analysis is based on the basic principle of evolution, i.e., descent with modification. Consequently, ecological characters or any other nontraditional characters must be included in phylogenetic analyses, provided that they can plausibly be postulated heritable. The claim of Zrzavý (1997, Oikos 80, 186–192) or Luckow and Bruneau (1997, Cladistics 13, 145–151) that any character of interest should be included in the analysis is thus inaccurate. Many characters, broadly defined or extrinsic (such as distribution areas), cannot be considered as actually heritable. It is argued that we should better care for the precise definition and properties of characters of interest than decide a priori to include them in any case in the analysis. The symmetrical claim of de Queiroz (1996, Am. Nat. 148, 700–708) that some characters of interest should better be excluded from analyses to reconstruct their history is similarly inaccurate. If they match the logical principles of phylogenetic analysis, there is no acceptable reason to exclude them. The different statistical testing strategies of Zrzavý (1997) and de Queiroz (1996) aimed at justifying inclusion versus exclusion of characters are ill-conceived, leading respectively to Type II and Type I errors. It is argued that phylogenetic analyses should not be constrained by testing strategies that are downstream of the logical principles of phylogenetics. Excluding characters and mapping them on an independent phylogeny produces a particular and suboptimal kind of secondary homology, the use of which can be justified only for preliminary studies dealing with broadly defined characters.]]>

Helmus MR, Keller W, Paterson MJ, Yan ND, Cannon CH, Rusak JA (2010)

Communities contain closely related species during ecosystem disturbance

Ecology Letters, 13, 162-174.

DOI:10.1111/j.1461-0248.2009.01411.x      URL     PMID:20015255      [本文引用: 1]

Predicting community and species responses to disturbance is complicated by incomplete knowledge about species traits. A phylogenetic framework should partially solve this problem, as trait similarity is generally correlated with species relatedness, closely related species should have similar sensitivities to disturbance. Disturbance should thus result in community assemblages of closely related species. We tested this hypothesis with 18 disturbed and 16 reference whole-lake, long-term zooplankton data sets. Regardless of disturbance type, communities generally contained more closely related species when disturbed. This effect was independent of species richness, evenness, and abundance. Communities already under stress (i.e., those in acidic lakes) changed most when disturbed. Species sensitivities to specific disturbances were phylogenetically conserved, were independent of body size, and could be predicted by the sensitivities of close relatives within the same community. Phylogenetic relatedness can effectively act as a proxy for missing trait information when predicting community and species responses to disturbance.

Huang JX (黄建雄), Zheng FY (郑凤英), Mi XC (米湘成) (2010)

Influence of environmental factors on phylogenetic structure at multiple spatial scales in an evergreen broad-leaved forest of China

Chinese Journal of Plant Ecology (Chinese Version) (植物生态学报), 34, 309-315. (in Chinese with English abstract)

DOI:10.3773/j.issn.1005-264x.2010.03.008      URL     [本文引用: 3]

Aims Phylogenetic structure of a community is a synthetical indicator reflecting underlying ecological processes. Understanding of the phylogenetic structure of a community will provide insights into the relative importanceof different processes structuring the community. Our objectives are 1) examine the effects of environmental factors on phylogenetic structure; 2) test the prediction of neutral theory that the community is randomly assembled and the prediction of niche theory that the community is mainly determined by niche differentiation; and 3) determine the relative importance of neutral theory and niche theory in biodiversity maintenance in subtropicalevergreen broadleaved forest.Methods Gutianshan forest dynamic plot is located in the Gutianshan National Nature Reserve at Kaihua County, Zhejian Province of China. We randomly chose 1 000 subplots at five spatial scales of radii 5, 25, 50, 75 and 100 m in the Gutianshan forest dynamic plot and analyzed phylogenetic structure of subplots at these scales with net relatedness index (NRI). We analyzed the effect of environmental factors, including topographical factors, such as altitude, slope, aspect and convexity, and edaphic factors such as soil moisture, pH and 16 soil nutrients, on the community phylogenetic structure with multivariate regression.Important findings Communities were phylogenetically clustered at all spatial scales, indicating that trees were more closely related to their neighbors than expected by chance. With increasing scale, the strength of clustering increased and then deceased. Multiple linear regression showed that environmental factors had almost no effect on phylogenetic structure at smaller scales, but strongly affected the community structure at larger scales (radius of 100 m). At the radius of 100 m, two types of different phylogenetic structure emerged: some of subplots kept clustering, yet others became overdispersed. The difference of phylogenetic community structures at scale of 100 m was mainly determined by altitude. Our results support the prediction of niche theory that the community phylogenetic structure is structured by niche differentiation, and do not support the prediction that the community phylogenetic structure is randomly assembled by ecological drift and dispersal limitation.]]>

Hubbell SP (2001) The Unified Neutral Theory of Biodiversity and Biogeography. Princeton University Press, Princeton, NJ.

[本文引用: 1]

Kembel SW, Hubbell SP (2006)

The phylogenetic structure of a neotropical forest tree community

Ecology, 87, S86-S99.

DOI:10.1890/0012-9658(2006)87[86:tpsoan]2.0.co;2      URL     PMID:16922305      [本文引用: 4]

Numerous ecological and evolutionary processes are thought to play a role in maintaining the high plant species diversity of tropical forests. An understanding of the phylogenetic structure of an ecological community can provide insights into the relative importance of different processes structuring that community. The objectives of this study were to measure the phylogenetic structure of Neotropical forest tree communities in the Forest Dynamics Plot (FDP) on Barro Colorado Island, Panama, to determine how the phylogenetic structure of tree communities varied among spatial scales and habitats within the FDP, and to study the effects of null-model choice on estimates of community phylogenetic structure. We measured community phylogenetic structure for tree species occurring together in quadrats ranging in size from 10 x 10 m to 100 X 100 m in the FDP. We estimated phylogenetic structure by comparing observed phylogenetic distances among species to the distribution of phylogenetic distances for null communities generated using two different null models. A null model that did not maintain observed species occurrence frequencies tended to find nonrandom community phylogenetic structure, even for random data. Using a null model that maintained observed species frequencies in null communities, the average phylogenetic structure of tree communities in the FDP was close to random at all spatial scales examined, but more quadrats than expected contained species that were phylogenetically clustered or overdispersed, and phylogenetic structure varied among habitats. In young forests and plateau habitats, communities were phylogenetically clustered, meaning that trees were more closely related to their neighbors than expected, while communities in swamp and slope habitats were phylogenetically overdispersed, meaning that trees were more distantly related to their neighbors than expected. Phylogenetic clustering suggests the importance of environmental filtering of phylogenetically conserved traits in young forests and plateau habitats, but the phylogenetic overdispersion observed in other habitats has several possible explanations, including variation in the strength of ecological processes among habitats or the phylogenetic history of niches, traits, and habitat associations. Future studies will need to include information on species traits in order to explain the variation in phylogenetic structure among habitats in tropical forests.

Kraft NJB, Cornwell WK, Webb CO, Ackerly DD (2007)

Trait evolution, community assembly, and the phylogenetic structure of ecological communities

The American Naturalist, 170, 271-283.

DOI:10.1086/519400      URL     PMID:17874377      [本文引用: 4]

Taxa co-occurring in communities often represent a nonrandom sample, in phenotypic or phylogenetic terms, of the regional species pool. While heuristic arguments have identified processes that create community phylogenetic patterns, further progress hinges on a more comprehensive understanding of the interactions between underlying ecological and evolutionary processes. We created a simulation framework to model trait evolution, assemble communities (via competition, habitat filtering, or neutral assembly), and test the phylogenetic pattern of the resulting communities. We found that phylogenetic community structure is greatest when traits are highly conserved and when multiple traits influence species membership in communities. Habitat filtering produces stronger phylogenetic structure when taxa with derived (as opposed to ancestral) traits are favored in the community. Nearest-relative tests have greater power to detect patterns due to competition, while total community relatedness tests perform better with habitat filtering. The size of the local community relative to the regional pool strongly influences statistical power; in general, power increases with larger pool sizes for communities created by filtering but decreases for communities created by competition. Our results deepen our understanding of processes that contribute to phylogenetic community structure and provide guidance for the design and interpretation of empirical research.

Kress WJ, Erickson DL, Jones FA, Swenson NG, Perez R, Sanjur O, Bermingham E (2009)

Plant DNA barcodes and a community phylogeny of a tropical forest dynamics plot in Panama

Proceedings of the National Academy of Sciences, USA, 106, 18621-18626.

DOI:10.1073/pnas.0909820106      URL     [本文引用: 2]

Leibold MA, Holyoak M, Mouquet N, Amarasekare P, Chase JM, Hoopes MF, Holt RD, Shurin JB, Law R, Tilman D, Loreau M, Gonzalez A (2004)

The metacommunity concept: a framework for multi-scale community ecology

Ecology Letters, 7, 601-613.

DOI:10.1111/ele.2004.7.issue-7      URL     [本文引用: 1]

Lessard JP, Fordyce JA, Gotelli NJ, Sanders NJ (2009)

Invasive ants alter the phylogenetic structure of ant communities

Ecology, 90, 2664-2669.

DOI:10.1890/09-0503.1      URL     PMID:19886475      [本文引用: 2]

Invasive species displace native species and potentially alter the structure and function of ecological communities. In this study, we compared the generic composition of intact and invaded ant communities from 12 published studies and found that invasive ant species alter the phylogenetic structure of native ant communities. Intact ant communities were phylogenetically evenly dispersed, suggesting that competition structures communities. However, in the presence of an invasive ant species, these same communities were phylogenetically clustered. Phylogenetic clustering in invaded communities suggests that invasive species may act as strong environmental filters and prune the phylogenetic tree of native species in a nonrandom manner, such that only a few closely related taxa can persist in the face of a biological invasion. Taxa that were displaced by invasive ant species were evenly dispersed in the phylogeny, suggesting that diversity losses from invasive ant species are not clustered in particular lineages. Collectively, these results suggest that there is strong phylogenetic structuring in intact native ant communities, but the spread of invasive species disassembles those communities above and beyond the effect of simple reductions in diversity.

Letcher SG (2010)

Phylogenetic structure of angiosperm communities during tropical forest succession

Proceedings of the Royal Society B: Biological Sciences, 277, 97-104.

DOI:10.1098/rspb.2009.0865      URL     PMID:19801375      [本文引用: 2]

The phylogenetic structure of ecological communities can shed light on assembly processes, but the focus of phylogenetic structure research thus far has been on mature ecosystems. Here, I present the first investigation of phylogenetic community structure during succession. In a replicated chronosequence of 30 sites in northeastern Costa Rica, I found strong phylogenetic overdispersion at multiple scales: species present at local sites were a non-random assemblage, more distantly related than chance would predict. Phylogenetic overdispersion was evident when comparing the species present at each site with the regional species pool, the species pool found in each age category to the regional pool or the species present at each site to the pool of species found in sites of that age category. Comparing stem size classes within each age category, I found that during early succession, phylogenetic overdispersion is strongest in small stems. Overdispersion strengthens and spreads into larger size classes as succession proceeds, corroborating an existing model of forest succession. This study is the first evidence that succession leaves a distinct signature in the phylogenetic structure of communities.

Losos JB, Leal M, Glor RE, de Queiroz K, Hertz PE, Schettino LR, Lara AC, Jackman TR, Larson A (2003)

Niche lability in the evolution of a Caribbean lizard community

Nature, 424, 542-545.

DOI:10.1038/nature01814      URL     PMID:12891355      [本文引用: 1]

Niche conservatism--the tendency for closely related species to be ecologically similar--is widespread. However, most studies compare closely related taxa that occur in allopatry; in sympatry, the stabilizing forces that promote niche conservatism, and thus inhibit niche shifts, may be countered by natural selection favouring ecological divergence to minimize the intensity of interspecific interactions. Consequently, the relative importance of niche conservatism versus niche divergence in determining community structure has received little attention. Here, we examine a tropical lizard community in which species have a long evolutionary history of ecological interaction. We find that evolutionary divergence overcomes niche conservatism: closely related species are no more ecologically similar than expected by random divergence and some distantly related species are ecologically similar, leading to a community in which the relationship between ecological similarity and phylogenetic relatedness is very weak. Despite this lack of niche conservatism, the ecological structuring of the community has a phylogenetic component: niche complementarity only occurs among distantly related species, which suggests that the strength of ecological interactions among species may be related to phylogeny, but it is not necessarily the most closely related species that interact most strongly.

Loya Y (1972)

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Marine Biology, 13, 100-123.

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Ma KP (马克平) (2008)

Large scale permanent plots: important platform for long term research on biodiversity in forest ecosystem

Journal of Plant Ecology (Chinese Version)(植物生态学报), 32, 237. (in Chinese)

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Mayfield MM, Levine JM (2010)

Opposing effects of competitive exclusion on the phylogenetic structure of communities

Ecology Letters, 13, 1085-1093.

DOI:10.1111/j.1461-0248.2010.01509.x      URL     PMID:20576030      [本文引用: 1]

Though many processes are involved in determining which species coexist and assemble into communities, competition is among the best studied. One hypothesis about competition's contribution to community assembly is that more closely related species are less likely to coexist. Though empirical evidence for this hypothesis is mixed, it remains a common assumption in certain phylogenetic approaches for inferring the effects of environmental filtering and competitive exclusion. Here, we relate modern coexistence theory to phylogenetic community assembly approaches to refine expectations for how species relatedness influences the outcome of competition. We argue that two types of species differences determine competitive exclusion with opposing effects on relatedness patterns. Importantly, this means that competition can sometimes eliminate more different and less related taxa, even when the traits underlying the relevant species differences are phylogenetically conserved. Our argument leads to a reinterpretation of the assembly processes inferred from community phylogenetic structure.

Molles MC (2008)

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Moreau RE (1948)

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Ojeda F, Pausas JG, Verdu M (2010)

Soil shapes community structure through fire

Oecologia, 163, 729-735.

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Pausas JG, Verdu M (2010)

The jungle of methods for evaluating phenotypic and phylogenetic structure of communities

BioScience, 60, 614-625.

DOI:10.1525/bio.2010.60.8.7      URL     [本文引用: 3]

Pei NC (裴男才), Zhang JL (张金龙), Mi XC (米湘成), Ge XJ (葛学军) (2011)

Plant DNA barcodes promote the development of phylogenetic community ecology

Biodiversity Science (生物多样性), 19, 284-294. (in Chinese with English abstract)

DOI:10.3724/SP.J.1003.2011.11250      URL     [本文引用: 1]

rbcL+matK+trnH-psbA) for fast species discrimination and community phylogenetic reconstruction. We also explore the utilization of well-resolved phylogenies to understand community ecology. We discuss the limitations of core plant DNA barcodes (rbcL+matK) when identifying congeners, and propose an improved sequencing strategy suitable for studies at the community level. We expect that plant DNA barcodes will prove very useful for the study of species diversity, mechanisms of biodiversity maintenance, phylogenetic beta diversity and functional trait evolution.]]>

Peterson AT, Soberon J, Sanchez-Cordero V (1999)

Conservatism of ecological niches in evolutionary time

Science, 285, 1265-1267.

DOI:10.1126/science.285.5431.1265      URL     PMID:10455053      [本文引用: 1]

Theory predicts low niche differentiation between species over evolutionary time scales, but little empirical evidence is available. Reciprocal geographic predictions based on ecological niche models of sister taxon pairs of birds, mammals, and butterflies in southern Mexico indicate niche conservatism over several million years of independent evolution (between putative sister taxon pairs) but little conservatism at the level of families. Niche conservatism over such time scales indicates that speciation takes place in geographic, not ecological, dimensions and that ecological differences evolve later.

Pillar VD, Duarte LDS (2010)

A framework for metacom- munity analysis of phylogenetic structure

Ecology Letters, 13, 587-596.

URL     PMID:20337699      [本文引用: 1]

Prinzing A, Durka W, Klotz S, Brandl R (2001)

The niche of higher plants: evidence for phylogenetic conservatism

Proceedings of the Royal Society of London Series B: Biological Sciences, 268, 2383-2389.

URL     PMID:11703879      [本文引用: 2]

Ricklefs RE (1987)

Community diversity: relative roles of local and regional process

Science, 235, 167-171.

DOI:10.1126/science.235.4785.167      URL     PMID:17778629      [本文引用: 1]

The species richness (diversity) of local plant and animal assemblages-biological communities-balances regional processes of species formation and geographic dispersal, which add species to communities, against processes of predation, competitive exclusion, adaptation, and stochastic variation, which may promote local extinction. During the past three decades, ecologists have sought to explain differences in local diversity by the influence of the physical environment on local interactions among species, interactions that are generally believed to limit the number of coexisting species. But diversity of the biological community often fails to converge under similar physical conditions, and local diversity bears a demonstrable dependence upon regional diversity. These observations suggest that regional and historical processes, as well as unique events and circumstances, profoundly influence local community structure. Ecologists must broaden their concepts of community processes and incorporate data from systematics, biogeography, and paleontology into analyses of ecological patterns and tests of community theory.

Silva IA, Batalha MA (2009)

Phylogenetic overdispersion of plant species in southern Brazilian savannas

Brazilian Journal of Biology, 69, 845-851.

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Silvertown J, Dodd M, Gowing D, Lawson C, McConway K (2006a)

Phylogeny and the hierarchical organization of plant diversity

Ecology, 87, S39-S49.

URL     PMID:16922301      [本文引用: 1]

Silvertown J, McConway K, Gowing D, Dodd M, Fay MF, Joseph JA, Dolphin K (2006b)

Absence of phylogenetic signal in the niche structure of meadow plant communities

Proceedings of the Royal Society B: Biological Sciences, 273, 39-44.

DOI:10.1098/rspb.2005.3288      URL     PMID:16519232      [本文引用: 1]

A significant proportion of the global diversity of flowering plants has evolved in recent geological time, probably through adaptive radiation into new niches. However, rapid evolution is at odds with recent research which has suggested that plant ecological traits, including the beta- (or habitat) niche, evolve only slowly. We have quantified traits that determine within-habitat alpha diversity (alpha niches) in two communities in which species segregate on hydrological gradients. Molecular phylogenetic analysis of these data shows practically no evidence of a correlation between the ecological and evolutionary distances separating species, indicating that hydrological alpha niches are evolutionarily labile. We propose that contrasting patterns of evolutionary conservatism for alpha- and beta-niches is a general phenomenon necessitated by the hierarchical filtering of species during community assembly. This determines that species must have similar beta niches in order to occupy the same habitat, but different alpha niches in order to coexist.

Simberloff DS (1970)

Taxonomic diversity of island biotas

Evolution, 24, 23-47.

DOI:10.1111/j.1558-5646.1970.tb01738.x      URL     PMID:28563004      [本文引用: 1]

Slingsby JA, Verboom GA (2006)

Phylogenetic relatedness limits co-occurrence at fine spatial scales: evidence from the schoenoid sedges (Cyperaceae: Schoeneae) of the Cape Floristic Region, South Africa

The American Naturalist, 168, 14-27.

URL     PMID:16874612      [本文引用: 1]

Swenson NG, Enquist BJ, Pither J, Thompson J, Zimmerman JK (2006)

The problem and promise of scale dependency in community phylogenetics

Ecology, 87, 2418-2424.

URL     PMID:17089650      [本文引用: 4]

Swenson NG, Enquist BJ, Thompson J, Zimmerman JK (2007)

The influence of spatial and size scale on phylogenetic relatedness in tropical forest communities

Ecology, 88, 1770-1780.

DOI:10.1890/06-1499.1      URL     PMID:17645023      [本文引用: 7]

The relative importance of biotic, abiotic, and stochastic processes in structuring ecological communities continues to be a central focus in community ecology. In order to assess the role of phylogenetic relatedness on the nature of biodiversity we first quantified the degree of phylogenetic niche conservatism of several plant traits linked to plant form and function. Next we quantified the degree of phylogenetic relatedness across two fundamental scaling dimensions: plant size and neighborhood size. The results show that phylogenetic niche conservatism is likely widespread, indicating that closely related species are more functionally similar than distantly related species. Utilizing this information we show that three of five tropical forest dynamics plots (FDPs) exhibit similar scale-dependent patterns of phylogenetic structuring using only a spatial scaling axis. When spatial- and size-scaling axes were analyzed in concert, phylogenetic overdispersion of co-occurring species was most important at small spatial scales and in four of five FDPs for the largest size class. These results suggest that phylogenetic relatedness is increasingly important: (1) at small spatial scales, where phylogenetic overdispersion is more common, and (2) in large size classes, where phylogenetic overdispersion becomes more common throughout ontogeny. Collectively, our results highlight the critical spatial and size scales at which the degree of phylogenetic relatedness between constituent species influences the structuring of tropical forest diversity.

Tunnicliffe V (1981)

High species diversity and abundance of the epibenthic community in an oxygen-deficient basin

Nature, 294, 354-356.

DOI:10.1038/294354a0      URL     [本文引用: 1]

Vamosi SM, Heard SB, Vamosi JC, Webb CO (2009)

Emerging patterns in the comparative analysis of phylogenetic community structure

Molecular Ecology, 18, 572-592.

DOI:10.1111/j.1365-294X.2008.04001.x      URL     PMID:19037898      [本文引用: 3]

The analysis of the phylogenetic structure of communities can help reveal contemporary ecological interactions, as well as link community ecology with biogeography and the study of character evolution. The number of studies employing this broad approach has increased to the point where comparison of their results can now be used to highlight successes and deficiencies in the approach, and to detect emerging patterns in community organization. We review studies of the phylogenetic structure of communities of different major taxa and trophic levels, across different spatial and phylogenetic scales, and using different metrics and null models. Twenty-three of 39 studies (59%) find evidence for phylogenetic clustering in contemporary communities, but terrestrial and/or plant systems are heavily over-represented among published studies. Experimental investigations, although uncommon at present, hold promise for unravelling mechanisms underlying the phylogenetic community structure patterns observed in community surveys. We discuss the relationship between metrics of phylogenetic clustering and tree balance and explore the various emerging biases in taxonomy and pitfalls of scale. Finally, we look beyond one-dimensional metrics of phylogenetic structure towards multivariate descriptors that better capture the variety of ecological behaviours likely to be exhibited in communities of species with hundreds of millions of years of independent evolution.

Verdu M, Pausas JG (2007)

Fire drives phylogenetic clustering in Mediterranean Basin woody plant communities

Journal of Ecology, 95, 1316-1323.

DOI:10.1111/jec.2007.95.issue-6      URL     [本文引用: 1]

Webb CO (2000)

Exploring the phylogenetic structure of ecological communities: an example for rain forest trees

The American Naturalist, 156, 145-155.

DOI:10.1086/303378      URL     PMID:10856198      [本文引用: 3]

Because of the correlation expected between the phylogenetic relatedness of two taxa and their net ecological similarity, a measure of the overall phylogenetic relatedness of a community of interacting organisms can be used to investigate the contemporary ecological processes that structure community composition. I describe two indices that use the number of nodes that separate taxa on a phylogeny as a measure of their phylogenetic relatedness. As an example of the use of these indices in community analysis, I compared the mean observed net relatedness of trees (>/=10 cm diameter at breast height) in each of 28 plots (each 0.16 ha) in a Bornean rain forest with the net relatedness expected if species were drawn randomly from the species pool (of the 324 species in the 28 plots), using a supertree that I assembled from published sources. I found that the species in plots were more phylogenetically related than expected by chance, a result that was insensitive to various modifications to the basic methodology. I tentatively infer that variation in habitat among plots causes ecologically more similar species to co-occur within plots. Finally, I suggest a range of applications for phylogenetic relatedness measures in community analysis.

Webb CO, Ackerly DD, McPeek MA, Donoghue MJ (2002)

Phylogenies and community ecology

Annual Review of Ecology and Systematics, 33, 475-505.

DOI:10.1146/annurev.ecolsys.33.010802.150448      URL     [本文引用: 6]

Webb CO, Gilbert GS, Donoghue MJ (2006)

Phylodiversity-dependent seedling mortality, size structure, and disease in a bornean rain forest

Ecology, 87, S123-S131.

DOI:10.1890/0012-9658(2006)87[123:psmssa]2.0.co;2      URL     PMID:16922308      [本文引用: 1]

Density-dependent models that partition neighbors into conspecifics and heterospecifics ignore the great variation in effect of heterospecifics on focal plants. Both evolutionary theory and empirical results suggest that the negative effect of other plants on a focal plant should be higher for closely related neighbors than for less related neighbors. Using community-wide seedling mortality data from a forest where density dependence has previously been found, we searched for significant phylogenetic neighborhood effects (the

Weiblen GD, Webb CO, Novotny V, Basset Y, Miller SE (2006)

Phylogenetic dispersion of host use in a tropical insect herbivore community

Ecology, 87, S62-S75.

DOI:10.1890/0012-9658(2006)87[62:pdohui]2.0.co;2      URL     PMID:16922303      [本文引用: 1]

Theory has long predicted that insect community structure should be related to host plant phylogeny. We examined the distribution of insect herbivore associations with respect to host plant phylogeny for caterpillars (Lepidoptera), beetles (Coleoptera), and grasshoppers and relatives (orthopteroids) in a New Guinea rain forest. We collected herbivores from three lineages of closely related woody plants and from more distantly related plant lineages in the same locality to examine the phylogenetic scale at which host specificity can be detected in a community sample. By grafting molecular phylogenies inferred from three different genes into a supertree, we developed a phylogenetic hypothesis for the host community. Feeding experiments were performed on more than 100 000 live insects collected from the 62 host species. We examined patterns of host use with respect to the host plant phylogeny. As predicted, we found a negative relationship between faunal similarity, defined as the proportion of all herbivores feeding on two hosts that are shared between the hosts, and the phylogenetic distance between hosts based on DNA sequence divergence. Host phylogenetic distance explained a significant fraction of the variance (25%) in herbivore community similarity, in spite of the many ecological factors that probably influence feeding patterns. Herbivore community similarity among congeneric hosts was high (50% on average) compared to overlap among host families (20-30% on average). We confirmed this pattern using the nearest taxon index (NTI) and net relatedness index (NRI) to quantify the extent of phylogenetic clustering in particular herbivore associations and to test whether patterns are significantly different from chance expectations. We found that 40% of caterpillar species showed significant phylogenetic clustering with respect to host plant associations, somewhat more so than for beetles or orthopteroids. We interpret this as evidence that a substantial fraction of tropical forest insect herbivores are clade specialists.

Wiens JJ, Ackerly DD, Allen AP, Anacker BL, Buckley LB, Cornell HV, Damschen EI, Davies TJ, Grytnes JA, Harrison SP, Hawkins BA, Holt RD, McCain CM, Stephens PR (2010)

Niche conservatism as an emerging principle in ecology and conservation biology

Ecology Letters, 13, 1310-1324.

DOI:10.1111/j.1461-0248.2010.01515.x      URL     PMID:20649638      [本文引用: 1]

The diversity of life is ultimately generated by evolution, and much attention has focused on the rapid evolution of ecological traits. Yet, the tendency for many ecological traits to instead remain similar over time [niche conservatism (NC)] has many consequences for the fundamental patterns and processes studied in ecology and conservation biology. Here, we describe the mounting evidence for the importance of NC to major topics in ecology (e.g. species richness, ecosystem function) and conservation (e.g. climate change, invasive species). We also review other areas where it may be important but has generally been overlooked, in both ecology (e.g. food webs, disease ecology, mutualistic interactions) and conservation (e.g. habitat modification). We summarize methods for testing for NC, and suggest that a commonly used and advocated method (involving a test for phylogenetic signal) is potentially problematic, and describe alternative approaches. We suggest that considering NC: (1) focuses attention on the within-species processes that cause traits to be conserved over time, (2) emphasizes connections between questions and research areas that are not obviously related (e.g. invasives, global warming, tropical richness), and (3) suggests new areas for research (e.g. why are some clades largely nocturnal? why do related species share diseases?).

Wiens JJ, Graham CH (2005)

Niche conservatism: integrating evolution, ecology, and conservation biology

Annual Review of Ecology, Evolution, and Systematics, 36, 519-539.

[本文引用: 1]

Willis CG, Halina M, Lehman C, Reich PB, Keen A, McCarthy S, Cavender-Bares J (2010)

Phylogenetic community structure in Minnesota oak savanna is influenced by spatial extent and environmental variation

Ecography, 33, 565-577.

[本文引用: 1]

Ye WH (叶万辉), Cao HL (曹洪麟), Huang ZL (黄忠良), Lian JY (练琚愉), Wang ZG (王志高), Li L (李林), Wei SG (魏识广), Wang ZM (王章明) (2008)

Community structure of a 20 hm2 lower subtropical evergreen broadleaved forest plot in Dinghushan, China

Journal of Plant Ecology (Chinese Version) (植物生态学报), 32, 274-286. (in Chinese with English abstract)

[本文引用: 1]

Zhu Y (祝燕), Mi XC (米湘成), Ma KP (马克平) (2009)

A mechanism of plant species coexistence: the negative density-dependent hypothesis

Biodiversity Science (生物多样性), 17, 594-604. (in Chinese with English abstract)

DOI:10.3724/SP.J.1003.2009.09183      URL     [本文引用: 1]

The negative density-dependent hypothesis focuses mainly on conspecific interactions to explain the coexistence of diverse species in natural communities. The hypothesis describes the impairment of per-formance among conspecific individuals due to resource competition, predation of pests (e.g., pathogen, her-bivore) and so on. Impairment of conspecific individuals decreases growth and increases mortality, thereby freeing space for other species, and thus promotes coexistence of diverse species. There are three main kinds of density dependent effects including distance-dependence of mortality and abundance of offspring near parents (Janzen-Connell hypothesis), density dependent thinning (random-mortality hypothesis), and com-munity compensatory trends (CCT). Research has shown that density dependence among phylogenetically closely-related species results partially from competition for similar resources. This fact led to the proposal of species herd protection and phylodiversity dependence models. Density dependence has long history of study and the recent establishment of a global network of large-scale forest dynamic plots facilitates the detection of density dependence in natural communities. However, there are many challenges when testing for density dependence. For example, some previous studies can not disentangle density dependence from other con-founding effects, and most studies focus exclusively on the tropical zone, seldom considering other zones. Therefore, though strong evidence to contrary does not exist, debate continues on the importance of density dependence in maintaining diverse-species coexistence.

Zobel K (2001)

On the species-pool hypothesis and on the quasi-neutral concept of plant community diversity

Folia Geobotanica, 36, 3-8.

DOI:10.1007/BF02803133      URL     [本文引用: 1]

5.1. According to the results from studying a broad variety of Estonian herbaceous communities (4.11) the question in 1.14 should be answered as:selection from a regional species pool into an actual species pool and selection from actual species pool into a microsite are mostly random and neutral processes and they are not directed significantly by interspecific competition. 5.2. Yet, the formation of a diversity pattern should be called aquasi-neutral process,mainly because the exclusion of species from communities due to asymmetric light competition is common during succession (when taller species outcompete shorter ones).]]>

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