不同纬度植物群落系统发育与功能性状结构研究

研究植物群落系统发育和功能性状结构有助于了解植物多样性维持机制及物种间的亲缘关系。甘肃省地理环境复杂,显著而多变的气候梯度形成了区域植被和环境差异,丰富了栖息地类型,具有显著的纵向连通性和纬度隔离性,以甘肃省典型纬度梯度植物群落为研究对象,通过对其进行群落学调查和功能性状测定,计算净亲缘关系指数(Net relatedness index, NRI)和平均成对性状距离(Mean pairwise trait distance, PW)来分析植物群落系统发育结构和功能性状格局对不同纬度的响应。结果表明：(1) Shannon-Weiner多样性指数,物种丰富度,谱系α多样性指数表现出随纬度增加而显著降低的变化趋势(P<0.05),Pielou均匀度指数随纬度的升高没有显著的变化趋势;(2)系统发育结构在高、低纬度上趋于发散状态(NRI<0),在中纬度上又表现出聚集(NRI>0)的谱系结构,表明种间竞争作用减弱,环境过滤作用逐渐增强,随纬度继续升高相似性限制作用在物种聚集过程中占优势;而群落的功能性状结构随着纬度增加表现出与谱系结构相反的状态,因此植物群落的系统发育和功能...     

沿海拔梯度变化的哀牢山亚热带森林群落系统发育结构

为揭示森林群落系统发育结构在海拔梯度上的变化及其驱动因素, 本研究以云南哀牢山西坡的亚热带森林群落为研究对象, 以APG III系统为基础框架, 结合DNA条形码序列信息解决末端分类单元亲缘关系的方法, 构建了哀牢山森林群落系统发育进化树, 采用净亲缘指数(net relatedness index, NRI)和最近亲缘指数(nearest taxon index, NTI), 探讨了不同植被类型的森林群落系统发育结构和沿海拔梯度的变化规律。结果表明, 从整体的海拔变化趋势上来看, 哀牢山森林群落系统发育结构随海拔上升由系统发育聚集(phylogenetic clustering)走向发散(phylogenetic overdispersion)或聚集程度降低。在低海拔地区, 群落表现为系统发育聚集, 表明生态位理论中的生境过滤作用在群落构建和生物多样性的维持中起着主导作用; 在中海拔地区, 出现了聚集与发散两种群落系统发育结构并存的现象, 推测可能是生境过滤和竞争排斥两种生态过程共同作用的结果; 在高海拔地区, 群落的系统发育结构因选择的指数不同而出现相反的结果, NRI表现出系统发育聚集, 而NTI却表现为随机或发散, 考虑到高海拔地区的环境胁迫可能促使植物发生趋同进化, 推测其群落构建的生态学过程需要更为综合的研究。本研究揭示群落系统发育结构沿海拔梯度确实存在显著的变化, 证明在生态群落的构建过程中非随机过程起到促进乃至关键作用。     

戴云山物种多样性与系统发育多样性海拔梯度分布格局及驱动因子

生物多样性的海拔分布格局是生态学研究的热点。海拔作为综合性因子驱动着植物群落的物种、系统发育与功能多样性的空间分布。以戴云山南坡900-1600 m森林植物群落为研究对象,探讨物种多样性、系统发育指数与环境驱动因子的相互关系以及环境因子在群落构建与多样性维持中的重要意义。结果表明：（1）森林植物群落的系统发育多样性与物种多样性沿海拔均呈现中间高度膨胀格局。（2）物种多样性Margalef指数、Shannon-Wiener指数与系统发育多样性指数呈显著正相关,表明物种多样性越高,系统发育多样性也越高。Shannon-Wiener指数与物种多样性指数（Margalef、Pielou、Simpson指数）、系统发育多样性及系统发育结构都存在显著相关性,一定程度上Shannon-Wiener指数可以代替其他指数。Pielou指数、Simpson指数、Shannon-Wiener指数与系统发育结构NRI （Net relatedness index）指数、NTI （Net nearest taxa index）指数存在显著正相关,表明群落优势度、均匀度与系统发育结构相关性较强。（3）土壤全磷含量是影响系统发育多样性和物种多样性的主要驱动因子,土壤含水量是影响Shannon-Wiener、Pielou、Simpson指数的最显著因子,海拔是影响群落系统发育结构的主要因素。海拔是影响系统发育结构变化的主要环境因子,而土壤因子是影响物种多样性与系统发育多样性的主要因素,进一步验证了物种多样性与系统发育多样性的高度相关,结果旨在揭示物种群落空间分布规律。     

乌鲁木齐达坂城山区地衣生态位特征的研究

为揭示达坂城山区地衣对生境资源的利用状况及竞争程度,该研究在野外设置30个样方并调查其物种盖度数据,利用生态位宽度、生态位重叠指数及排序分析,探讨达坂城山区地衣的生态位特征及环境影响因子。结果表明:(1)达坂城山区生态位最宽的为丽黄鳞衣(Rusavskia elegans)和内卷野粮衣(Circinaria contorta),对不同环境具有较强的适应性,其他地衣物种生态位宽度较窄,对环境资源利用程度低。(2)物种间生态位重叠值整体偏低,生态位重叠值较高的物种对极少,地衣物种生态位分化程度高,物种间竞争不激烈。(3)生态位较宽的物种与多数物种之间都存在生态位重叠,但重叠值较低; 一些生态位较窄的物种与其他物种之间的生态位重叠值较高; 生态位重叠和生态位宽度之间并无直接的线性关系。(4)地衣物种沿海拔梯度分布具有差异,海拔、光照强度、湿度、风速和人为干扰是本地区地衣群落物种生态位特征差异的主导环境因子。综上所述,达坂城山区地衣物种由于生境资源的竞争占据各自独特的生态位,形成了生态位的分化,群落较为稳定,沿海拔梯度的生境条件差异是物种差异分布的重要原因。该研究可为地衣群落构建研究提供理论依据,并对该地区地衣物种的多样性和生境保护具有重要意义。     

太行山北段地区荆条灌丛和三裂绣线菊灌丛群落谱系结构

灌丛是太行山地区最重要的生态系统类型之一, 灌丛群落生物多样性的维持及其生态系统服务功能对京津冀地区的生态安全具有重要作用。本研究选择太行山最具代表性的两种灌木群落——荆条(Vitex negundo var. heterophylla)灌丛和三裂绣线菊(Spiraea trilobata)灌丛为研究对象, 利用净亲缘关系指数(net relatedness index, NRI)和多元回归等方法探究了两种灌丛群落构建机制的异同及主要的环境影响因子, 同时还利用谱系结构主坐标分析(principal coordinates of phylogenetic structure, PCPS)对决定群落谱系结构的关键系统发育节点进行了探究。结果表明: 两种灌丛群落内灌木植物的物种多样性没有显著差异, 但谱系结构差异显著。三裂绣线菊群落表现出显著的谱系发散趋势, 而荆条群落谱系聚集程度高于三裂绣线菊群落, 但未表现出显著的谱系结构。三裂绣线菊灌丛群落构建的驱动机制是生态位分化, 荆条灌丛中生境过滤作用有所增加, 与生态位分化共同驱动其群落构建过程。与干旱胁迫相关的生境过滤因素增加是荆条灌丛群落谱系聚集程度增加的重要原因。PCPS二维排序结果表明: 荆条灌丛群落谱系趋向聚集与其群落内缺乏蔷薇目、壳斗目等亲缘关系较远的类群有关, 而三裂绣线菊灌丛群落内物种则包含较多的演化分支。总体而言, 环境过滤不是决定太行山地区灌丛群落构建的主要驱动因素, 但水分条件仍然是影响区域群落谱系结构的重要因素。     

物种多度和径级尺度对于评价群落系统发育结构的影响: 以尖峰岭热带山地雨林为例

研究不同径级尺度群落系统发育多样性有助于了解不同年龄模式下物种的亲缘关系及其群落系统发育结构; 但是关于物种多度对群落系统发育结构影响的研究较少。以海南尖峰岭热带山地雨林群落为例, 首先在不同径级尺度比较物种多度加权与否分别对4个广泛采用的系统发育指数的影响, 继而利用其中2个经过标准化处理的系统发育多样性指数: 净种间亲缘关系指数(net relatedness index, NRI)和净最近种间亲缘关系指数(nearest taxon index, NTI), 结合群落的生境类型来量度不同局域生境条件下不同径级尺度木本植物系统发育关系。结果发现: (1)未考虑物种多度加权的系统发育平均成对距离(mean pairwise distance, MPD)指数比考虑物种多度加权的MPD指数显著地高估了群落整体系统发育多样性, 且这种现象在小径级尺度(1 cm≤DBH<5 cm)最为明显。因此, 在森林监测样地中对于中、小径级群落系统发育结构研究中建议考虑物种多度信息。(2) 从群落组成整体系统发育结构来看, 尖峰岭热带山地雨林在几乎所有径级尺度和生境下均倾向于系统发育发散, 且随着径级的递增发散程度趋于明显(NRI<0)。(3)从群落组成局部系统发育结构来看, 尖峰岭热带山地雨林在中、小径级倾向于系统发育聚集(NTI>0), 而在大径级(DBH≥15 cm)则倾向于系统发育发散(NTI<0)。总之, 研究群落系统发育结构时应考虑物种多度的影响以及径级尺度效应。     

长白山针阔混交林不同演替阶段群落系统发育和功能性状结构

群落构建一直是生态学研究的热点,基于系统发育和功能性状量化生境过滤、竞争排斥以及随机过程在群落构建中的作用,能够深入理解群落构建机制。本研究以长白山针阔混交林不同演替阶段的3个5.2 hm~2样地(次生杨桦林、次生针阔混交林、原始椴树红松林)为平台,基于被子植物分类系统Ⅲ(Angiosperm Classification System,APGⅢ)构建的系统发育树和7个关键功能性状(叶面积、比叶面积、叶片厚度、叶片氮含量、叶片磷含量、氮磷比、最大树高),结合环境数据,分析不同演替阶段群落系统发育和功能性状结构。研究表明:(1)各演替阶段7个植物功能性状都表现出显著的系统发育信号,表明植物功能性状受系统发育历史影响;(2)系统发育和功能性状结构在不同演替阶段和不同径级均为非随机状态。随着演替的推进群落系统发育和功能性状结构由聚集走向发散;随着径级的增加,系统发育和功能性状结构的聚集程度减小,表明随着演替阶段的进行和径级增大,竞争性排斥的作用逐渐明显;(3)各演替阶段系统发育和功能性状的周转都为非随机且不同因子对两者的解释力度存在差异。演替早期空间距离的解释力度小于环境距离,说明生境过滤在群落构建中的重要性,而在演替后期空间距离的解释力度大于环境距离,验证了扩散限制在群落构建中的重要性。     

暖湿化气候情景下喀斯特木本植物群落构建机制

云南喀斯特区域是滇桂黔岩溶石漠化重点治理区之一,探讨气候暖湿化下植物群落演替阶段的构建特征是生态恢复和森林管理可持续的关键。以气候暖湿化为背景,将喀斯特天坑作为天然“开顶式气室”,天坑南坡地下森林为群落演替顶极。联合系统发育和功能性状探讨演替序列(坑外针阔混交林,坑外常绿阔叶林,坑内常绿阔叶林)的群落构建机制。结果发现：(1)演替前期植物性状的系统发育信号较弱,叶长宽比、叶面积、叶厚度和比叶面积的系统发育信号显著,但功能性状的保守性较弱;演替后期植物性状转为趋同进化,系统发育信号均不显著。(2)演替阶段植物群落的系统发育多样性逐渐降低,并与物种丰富度显著正相关。(3)系统发育指数NRI(净亲缘指数)和NTI(最近种间亲缘指数)由小于0转为大于0,功能性状结构指数TraitSESMPD(标准化平均配对性状距离指数)和TraitSESMNTD(标准化平均最近相邻性状距离指数)均大于0。演替阶段的群落构建过程由生境过滤和物种间相互作用所主导。(4)系统发育和功能性状结构指数主要与土壤含水量、全磷和速效钾含量显著负相关。演替阶段下土壤水分和养分受限时群落趋于聚集,群落构建过程支持生态位假说。研...     

山西陵川南方红豆杉自然保护区鹅耳枥植物群落谱系结构特征

分析植物群落谱系结构,可以探究乔木层、灌木层和草本层物种对环境变化的响应情况。以山西陵川南方红豆杉自然保护区鹅耳枥群落为研究对象,采用样方法,分别从不同径级和不同坡向对鹅耳枥群落净谱系亲缘关系指数(Net relatedness index,NRI)和净最近种间亲缘关系指数(Nearest taxon index,NTI)进行研究,探讨了鹅耳枥群落沿着径级梯度形成群落谱系结构特征,进而分析了鹅耳枥群落构建的历史进程。结果表明:(1)该保护区鹅耳枥群落乔木层(26种)、灌木层(32种)和草本层(39种)谱系结构树可分为5个类群、5个类群和4个类群;乔木层(86.67%的样地,下同)和灌木层(73.33%)物种群落谱系结构呈谱系发散格局(NRI0,NTI0),但草本层(86.67%)物种群落谱系结构呈谱系聚集格局(NRI0,NTI0)。(2)鹅耳枥群落乔木层中,DBH在Ⅰ级至Ⅱ级间,NRI指数随着DBH的增大而减小,NTI指数随着DBH的增大而增大;在Ⅱ级至Ⅴ级之间,随着植物DBH增大NRI指数和NTI指数值均呈下降趋势;而且在不同DBH水平上群落NRI和NTI指数均差异显著(P0.05),说明随着径级的增大,群落谱系结构由谱系聚集变为谱系发散。(3)灌木层物种谱系结构在阴坡和阳坡均呈聚集型,乔木层阴坡物种的谱系结构呈发散型(NRI0,NTI0),乔木层阳坡和草本层阴阳坡群落均无法判定群落谱系结构是聚集还是发散。     

基于功能性状及系统发育的亚高寒草甸群落构建北大核心CSCD

为了解甘南藏族自治州亚高寒草甸植物群落在坡向梯度上的构建机制,该文选取5个坡向的样地,构建了植物群落系统发育树,测定了各坡向土壤环境因子和植物叶片的功能性状,检验了叶片功能性状的系统发育信号。结果表明:坡向变化对土壤含水量、土壤养分含量影响显著。大部分植物的叶片特征在不同坡向的差异显著,叶片干物质含量在南坡、西南坡较高,比叶面积和叶片氮、磷含量在北坡和西北坡较高。叶片的磷含量具有微弱的系统发育信号,而叶片干物质含量、比叶面积、叶片的氮含量均没表现出显著的系统发育信号。从南坡到北坡,群落的系统发育结构由发散到聚集。生境过滤作用是南坡、西南坡群落构建的驱动因素,种间竞争是北坡和西北坡群落构建的主要驱动力。西坡系统发育指数相反,其构建机制比较复杂,可能是几种机制共同作用的结果。     

放牧干扰梯度下川西亚高山植物群落的组合机理

为了阐明放牧干扰对川西亚高山区域植物群落的组合过程以及群落结构的影响, 研究了放牧干扰梯度下的功能群均匀度和群落谱系结构的变化趋势。结果显示: 在干扰较轻的阔叶林与针叶林样地, 部分样方的功能群均匀度显著高于无效模型, 随着干扰梯度的增强, 功能群均匀度呈线性下降, 样方平均值从0.930降至0.840, 其高于无效模型的次数也逐渐降低, 干扰程度较大的草甸中出现部分样方的功能群均匀度显著低于无效模型。随着干扰程度的增强, 群落的谱系结构指数也呈逐渐上升趋势, 净关联指数平均值由-0.634逐渐增加至2.360, 邻近类群指数由-0.158上升至2.179。草甸与低矮灌丛受干扰较为严重, 其大部分样方的谱系结构指数显著高于随机群落, 表明干扰群落的谱系结构呈聚集分布。功能群均匀度与谱系结构的变化趋势一致, 表明生境筛滤效应与种间竞争作用的平衡决定着群落的组合过程。干扰降低了竞争作用, 促进了少数耐干扰功能群的优势地位, 造成功能群均匀度下降, 同时通过生境筛滤作用, 使群落的谱系结构呈现出聚集分布; 而未干扰的群落中由于竞争作用的效应, 功能群均匀度较高, 谱系结构也更加分散。研究区域植物群落的功能群均匀度与物种丰富度呈负相关, 表明物种间特别是相似物种间的竞争限制了群落的物种多样性。研究结果说明, 生态位分化和物种间的相互竞争在物种共存与群落组合中具有重要作用。     

Using phylogeny and functional traits for assessing community assembly along environmental gradients: A deterministic process driven by elevation

Community assembly processes is the primary focus of community ecology. Using phylogenetic‐based and functional trait‐based methods jointly to explore these processes along environmental gradients are useful ways to explain the change of assembly mechanisms under changing world. Our study combined these methods to test assembly processes in wide range gradients of elevation and other habitat environmental factors. We collected our data at 40 plots in Taibai Mountain, China, with more than 2,300 m altitude difference in study area and then measured traits and environmental factors. Variance partitioning was used to distinguish the main environment factors leading to phylogeny and traits change among 40 plots. Principal component analysis (PCA) was applied to colligate other environment factors. Community assembly patterns along environmental gradients based on phylogenetic and functional methods were studied for exploring assembly mechanisms. Phylogenetic signal was calculated for each community along environmental gradients in order to detect the variation of trait performance on phylogeny. Elevation showed a better explanatory power than other environment factors for phylogenetic and most traits’ variance. Phylogenetic and several functional structure clustered at high elevation while some conserved traits overdispersed. Convergent tendency which might be caused by filtering or competition along elevation was detected based on functional traits. Leaf dry matter content (LDMC) and leaf nitrogen content along PCA 1 axis showed conflicting patterns comparing to patterns showed on elevation. LDMC exhibited the strongest phylogenetic signal. Only the phylogenetic signal of maximum plant height showed explicable change along environmental gradients. Synthesis. Elevation is the best environment factors for predicting phylogeny and traits change. Plant's phylogenetic and some functional structures show environmental filtering in alpine region while it shows different assembly processes in middle‐ and low‐altitude region by different trait/phylogeny. The results highlight deterministic processes dominate community assembly in large‐scale environmental gradients. Performance of phylogeny and traits along gradients may be independent with each other. The novel method for calculating functional structure which we used in this study and the focus of phylogenetic signal change along gradients may provide more useful ways to detect community assembly mechanisms.     

Disturbance regime changes the trait distribution,phylogenetic structure and community assembly of tropical rain forests

A rapidly increasing effort to merge functional community ecology and phylogenetic biology has increased our understanding of community assembly. However, studies using both phylogenetic‐ and trait‐based methods have been mainly conducted in old‐growth forests, with fewer studies in human‐disturbed communities, which play an increasingly important role in providing ecosystem services as primary forests are degraded. We used data from 18 1‐ha plots in tropical old‐growth forests and secondary forests with different disturbance histories (logging and shifting cultivation) and vegetation types (tropical lowland and montane forests) on Hainan Island, southern China. The distributions of 11 functional traits were compared among these six forest types. We used a null model approach to assess the effects of disturbance regimes on variation in response and effect traits and community phylogenetic structure across different stem sizes (saplings, treelets, and adult trees) and spatial scales (10–50 m). We found significant differences in the distribution of functional traits in highly disturbed lowland sites versus other forest types. Many individuals in highly disturbed lowland sites were deciduous, spiny, with non‐fleshy fruits and seeds dispersed passively or by wind, and low SLA. The response traits of coexisting species were clustered in all sites except for highly disturbed lowland sites where evenness was evident. There were different distributions of effect traits for saplings and treelets among different forest types but adult trees showed stronger clustering of trait values with increasing spatial scale among all forest types. Phylogenetic clustering predominated across all size classes and spatial scales in the highly disturbed lowland sites, and evenness in other forest types. High disturbance can lead to abiotic filtering, generating a community dominated by closely related species with disturbance‐adapted traits, where biotic interactions play a relatively minor role. In lightly disturbed and old growth forests, multiple processes simultaneously drive the community assembly, but biotic processes dominate at the fine scale.     

Multi-scale phylogenetic structure in coastal dune plant communities across the globe

Aims Studies integrating phylogenetic history and large-scale community assembly are few, and many questions remain unanswered. Here, we use a global coastal dune plant data set to uncover the important factors in community assembly across scales from the local filtering processes to the global long-term diversification and dispersal dynamics. Coastal dune plant communities occur worldwide under a wide range of climatic and geologic conditions as well as in all biogeographic regions. However, global patterns in the phylogenetic composition of coastal dune plant communities have not previously been studied.Methods The data set comprised vegetation data from 18463 plots in New Zealand, South Africa, South America, North America and Europe. The phylogenetic tree comprised 2241 plant species from 149 families. We calculated phylogenetic clustering (Net Relatedness Index, NRI, and Nearest Taxon Index, NTI) of regional dune floras to estimate the amount of in situ diversification relative to the global dune species pool and evaluated the relative importance of land and climate barriers for these diversification patterns by geographic analyses of phylogenetic similarity. We then tested whether dune plant communities exhibit similar patterns of phylogenetic structure within regions. Finally, we calculated NRI for local communities relative to the regional species pool and tested for an association with functional traits (plant height and seed mass) thought to vary along sea–inland gradients.Important findings Regional species pools were phylogenetically clustered relative to the global pool, indicating regional diversification. NTI showed stronger clustering than NRI pointing to the importance of especially recent diversifications within regions. The species pools grouped phylogenetically into two clusters on either side of the tropics suggesting greater dispersal rates within hemispheres than between hemispheres. Local NRI plot values confirmed that most communities were also phylogenetically clustered within regions. NRI values decreased with increasing plant height and seed mass, indicating greater phylogenetic clustering in communities with short maximum height and good dispersers prone to wind and tidal disturbance as well as salt spray, consistent with environmental filtering along sea–inland gradients. Height and seed mass both showed significant phylogenetic signal, and NRI tended to correlate negatively with both at the plot level. Low NRI plots tended to represent coastal scrub and forest, whereas high NRI plots tended to represent herb-dominated vegetation. We conclude that regional diversification processes play a role in dune plant community assembly, with convergence in local phylogenetic community structure and local variation in community structure probably reflecting consistent coastal-inland gradients. Our study contributes to a better understanding of the globally distributed dynamic coastal ecosystems and the structuring factors working on dune plant communities across spatial scales and regions.     

Exploring the community phylogenetic structure along the slope aspect of subalpine meadows in the eastern Qinghai–Tibetan Plateau,China

Exploring the community assembly has been important for explaining the maintenance mechanisms of biodiversity and species coexistence, in that it is a central issue in community ecology. Here, we examined patterns of the community phylogenetic structure of the subalpine meadow plant community along the slope gradient in the Qinghai–Tibetan Plateau of China. We surveyed all species and constructed the phylogenetic tree of the plant community based on data from the Angiosperm Phylogeny Group III. We selected the net relative index (NRI) and evaluated the community phylogenetic structure along the five slope plants communities. We found that the phylogenetic structure varied from phylogenetic clustering to phylogenetic overdispersion with the slope aspect from north to south. In the north slope, the community phylogenetically cluster indicated that the limiting similarity played a leading role in the community assembly and the maintenance of biodiversity. Community phylogenetic overdispersion in the east, southeast, and south slopes indicated that habitat filtration was the driving force for community assembly. The NRI index of the northeast slope was close to zero, implying random dispersion. But it may be driven by the neutral process or limiting similarity, in that the community assembly process was the result of a combination of several ecological factors and thus required further study.     

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

The relative importance of environmental filtering, biotic interactions and neutral processes in community assembly remains an openly debated question and one that is increasingly addressed using phylogenetic approaches. Closely related species may occur together more frequently than expected (phylogenetic clustering) if environmental filtering operates on traits with significant phylogenetic signal. Recent studies show that phylogenetic clustering tends to increase with spatial scale, presumably because greater environmental variation is encompassed at larger spatial scales, providing opportunities for species to sort across environmental gradients. However, if environmental filtering is the cause of species sorting along environmental gradients, then environmental variation rather than spatial scale per se should drive the processes governing community assembly. Using species abundance and light availability data from a long‐term experiment in Minnesota oak savanna understory communities, we explicitly test the hypothesis that greater environmental variation results in greater phylogenetic clustering when spatial scale is held constant. Concordant with previous studies, we found that phylogenetic community structure varied with spatial extent. At the landscape scale (~1000 ha), communities were phylogenetically clustered. At the local scale (0.375ha), phylogenetic community structure varied among plots. As hypothesized, plots encompassing the greatest environmental variation in light availability exhibited the strongest phylogenetic clustering. We also found strong correlations between species functional traits, particularly specific leaf area (SLA) and perimeter per area (PA), and species light availability niche. There was also a phylogenetic signal in both functional traits and species light availability niche, providing a mechanistic explanation for phylogenetic clustering in relation to light availability. We conclude that the pattern of increased phylogenetic clustering with increased environmental variation is a consequence of environmental filtering acting on phylogenetically conserved functional traits. These results indicate that the importance of environmental filtering in community assembly depends not on spatial scale per se, but on the steepness of the environmental gradient.     

The Impact of Anthropogenic Disturbance on Assembly Patterns of Termite Communities

Intensification of land‐use threatens biodiversity, especially in tropical ecosystems that harbor the planet's highest species richness. This negative impact of anthropogenic disturbance on species numbers is well established, but the mechanisms underlying the community assembly processes are less well understood. Termites are of fundamental importance in tropical ecosystems where they are critical for nutrient recycling and species diversity. We tested the impact of anthropogenic disturbance on termite species diversity and assembly processes in a West African savanna applying the newest techniques of phylogenetic community analyses. Species richness dropped in areas of intensive land‐use and compositional similarity between intensive land‐use areas was high. This contrasted with a protected National Park where communities were characterized by high species richness and intermediate species turnover between sites. Slightly disturbed areas in the buffer zone surrounding the park were intermediate, they still had high species richness but similarity between sites increased. Strikingly, the assembly pattern also changed with disturbance from more phylogenetic overdispersion to more clustering (coexisting species became phylogenetically more similar), but only when the fungus‐growing termite Macrotermes bellicosus was absent. Our data suggest that the major forces structuring termite communities depend: (1) on the presence of this dominant mound‐building termite; and (2) that they change to more environmental filtering with disturbance. Anthropogenic disturbance seems to function as a filter that allows only a specific subset of species to occur. Such an effect might be widespread in ecology but it is difficult to document quantitatively. Phylogenetic community analyses can help to contribute such evidence.     

Exploring the community assembly of subalpine meadow communities based on functional traits and community phylogeny

Aims The community assembly has been a prominent issue in community ecology. This work was intended to explore the mechanisms of the species coexistence and biodiversity in communities. Our objective was to explore the mechanisms of community assembly in subalpine meadow plant communities along slope gradients in Gannan Tibetan Autonomous Prefecture, Gansu Province, Northwest China.Methods We selected five slope-oriented plots to construct a super-tree representing the species pool. We surveyed the leaf functional traits and soil environmental factors in different slopes. Then we tested the phylogenetic signal of leaf dry matter content (LDMC), specific leaf area (SLA), leaf nitrogen content (LNC) and leaf phosphorus content (LPC).Important findings The changes of slope aspect had significant influence on soil water content (SWC) and soil nutrient content. Most of the plants leaf functional traits had significant difference along different slope aspects. The LDMC was higher in south and southwest slope than north slope, while SLA, LNC and LPC were relatively high in north and northwest slope. The LPC showed feeble phylogenetic signal, while LDMC, SLA, LNC did not have a significant phylogenetic signal. With changes in the slope aspect from south to north, community phylogenetic structure shifted from over-dispersion to clustered dispersion. In south and southwest slope, habitat filtering was the driving force for community assembly. Interspecific competition was the main driving factor for community assembly in north and northwest slope aspects. But in west slope, two indices showed contrary consequence. This means the process of community assembly in west slope was more complicated and its phylogenetic index may be the result of several mechanisms working together.     

Plant traits determine the phylogenetic structure of arbuscular mycorrhizal fungal communities

Functional diversity in ecosystems has traditionally been studied using aboveground plant traits. Despite the known effect of plant traits on the microbial community composition, their effects on the microbial functional diversity are only starting to be assessed. In this study, the phylogenetic structure of arbuscular mycorrhizal (AM) fungal communities associated with plant species differing in life cycle and growth form, that is, plant life forms, was determined to unravel the effect of plant traits on the functional diversity of this fungal group. The results of the 454 pyrosequencing showed that the AM fungal community composition differed across plant life forms and this effect was dependent on the soil collection date. Plants with ruderal characteristics tended to associate with phylogenetically clustered AM fungal communities. By contrast, plants with resource‐conservative traits associated with phylogenetically overdispersed AM fungal communities. Additionally, the soil collected in different seasons yielded AM fungal communities with different phylogenetic dispersion. In summary, we found that the phylogenetic structure, and hence the functional diversity, of AM fungal communities is dependent on plant traits. This finding adds value to the use of plant traits for the evaluation of belowground ecosystem diversity, functions and processes.