哀牢山亚热带中山湿性常绿阔叶林树种beta多样性格局形成的驱动力

Beta多样性通常指群落在时间和空间上物种组成的差异, 包括物种周转组分和物种丰富度差异组分。驱动beta多样性格局形成的生态过程决定了群落的时空动态, 然而关于beta多样性及其两个组分格局形成的驱动力还存在较多争议。以往研究表明, beta多样性的格局存在取样尺度的依赖性, 驱动其形成的生态过程在不同取样尺度下的相对重要性也随之改变。本研究以哀牢山亚热带中山湿性常绿阔叶林20 ha动态监测样地为研究对象, 在不同取样尺度上, 将样方间的Bray-Curtis指数分解为物种周转组分和物种丰富度差异组分, 通过典范冗余分析和方差分解的方法揭示环境过滤和扩散限制对于beta多样性及其两个组分格局形成的相对重要性及其尺度依赖性。结果表明: (1) beta多样性、物种周转组分和物种丰富度差异组分均随取样尺度的增大而减小。在不同取样尺度下, 物种周转组分对于beta多样性的贡献始终占主导地位。(2)随着取样尺度的增大, 环境过滤驱动beta多样性格局形成的相对重要性逐渐增加, 而扩散限制的相对重要性逐渐降低。本研究进一步证实了取样尺度在beta多样性格局形成及其驱动力定量评价中的重要性, 今后的研究需要进一步解析上述尺度效应的形成机制。     

Local and Regional Effects on Community Structure of Dung Beetles in a Mainland-Island Scenario

Understanding the ecological mechanisms driving beta diversity is a major goal of community ecology. Metacommunity theory brings new ways of thinking about the structure of local communities, including processes occurring at different spatial scales. In addition to new theories, new methods have been developed which allow the partitioning of individual and shared contributions of environmental and spatial effects, as well as identification of species and sites that have importance in the generation of beta diversity along ecological gradients. We analyzed the spatial distribution of dung beetle communities in areas of Atlantic Forest in a mainland-island scenario in southern Brazil, with the objective of identifying the mechanisms driving composition, abundance and biomass at three spatial scales (mainland-island, areas and sites). We sampled 20 sites across four large areas, two on the mainland and two on the island. The distribution of our sampling sites was hierarchical and areas are isolated. We used standardized protocols to assess environmental heterogeneity and sample dung beetles. We used spatial eigenfunctions analysis to generate the spatial patterns of sampling points. Environmental heterogeneity showed strong variation among sites and a mild increase with increasing spatial scale. The analysis of diversity partitioning showed an increase in beta diversity with increasing spatial scale. Variation partitioning based on environmental and spatial variables suggests that environmental heterogeneity is the most important driver of beta diversity at the local scale. The spatial effects were significant only at larger spatial scales. Our study presents a case where environmental heterogeneity seems to be the main factor structuring communities at smaller scales, while spatial effects are more important at larger scales. The increase in beta diversity that occurs at larger scales seems to be the result of limitation in species dispersal ability due to habitat fragmentation and the presence of geographical barriers.     

Determinants of beta diversity of spiders in coastal dunes along a gradient of mediterraneity

Aim The Mediterranean Basin is recognized for its high levels of species richness, rarity and endemicity. Our main aim was to evaluate the relative effects of environmental and spatial variables and their scale‐specific importance on beta diversity patterns along a gradient of mediterraneity, using spiders as a model group. Location This study was carried out in 18 coastal dune sites along the Portuguese Atlantic coast. This area encompasses 445 km and comprises two distinct biogeographic regions, Eurosiberian (northern coast) and Mediterranean (centre and south). Methods A forward selection procedure was carried out to select environmental and spatial variables responsible for determining beta diversity patterns. Variation partitioning and principal coordinates of neighbour matrices (PCNM) were used to estimate the contribution of pure environmental and pure spatial effects and their shared influence on beta diversity patterns and to estimate the relative importance of environmental structured variation and pure spatial variation at multiple spatial scales. Results Climate, ground vegetation dune cover and area were selected by a forward selection procedure. The same procedure identified three PCNM variables, all corresponding to large and medium spatial scales. Variation partitioning revealed that 46.1% of the variation of beta diversity patterns was explained by a combination of environmental and PCNM variables. Most of this variation (42.5%) corresponded to spatial variation (environmental spatially structured and pure spatial). Climate and vegetation structure influences were predominant at the PCNM1 and PCNM3 scales, while area was more important at the intermediate PCNM2 scale. Main conclusions Our study revealed that beta diversity of spiders was primarily controlled by a broad‐scale gradient of mediterraneity. The relative importance of environmental variables on the spider assemblage composition varied with spatial scale. This study highlights the need of considering the scale‐specific influence of niche and neutral processes on beta diversity patterns.     

Metacommunity Composition of Web-Spiders in a Fragmented Neotropical Forest: Relative Importance of Environmental and Spatial Effects

The distribution of beta diversity is shaped by factors linked to environmental and spatial control. The relative importance of both processes in structuring spider metacommunities has not yet been investigated in the Atlantic Forest. The variance explained by purely environmental, spatially structured environmental, and purely spatial components was compared for a metacommunity of web spiders. The study was carried out in 16 patches of Atlantic Forest in southern Brazil. Field work was done in one landscape mosaic representing a slight gradient of urbanization. Environmental variables encompassed plot- and patch-level measurements and a climatic matrix, while principal coordinates of neighbor matrices (PCNMs) acted as spatial variables. A forward selection procedure was carried out to select environmental and spatial variables influencing web-spider beta diversity. Variation partitioning was used to estimate the contribution of pure environmental and pure spatial effects and their shared influence on beta-diversity patterns, and to estimate the relative importance of selected environmental variables. Three environmental variables (bush density, land use in the surroundings of patches, and shape of patches) and two spatial variables were selected by forward selection procedures. Variation partitioning revealed that 15% of the variation of beta diversity was explained by a combination of environmental and PCNM variables. Most of this variation (12%) corresponded to pure environmental and spatially environmental structure. The data indicated that (1) spatial legacy was not important in explaining the web-spider beta diversity; (2) environmental predictors explained a significant portion of the variation in web-spider composition; (3) one-third of environmental variation was due to a spatial structure that jointly explains variation in species distributions. We were able to detect important factors related to matrix management influencing the web-spider beta-diversity patterns, which are probably linked to historical deforestation events.     

Different roles of elevational and local environmental factors on abundance‐based beta diversity of the soil Enchytraeidae on the Changbai Mountain

The elevational alpha biodiversity gradient in mountain regions is one of the well‐known ecological patterns, but its beta diversity pattern remains poorly known. Examining the beta diversity and its components could enhance the understanding of community assembly mechanism. We studied the beta diversity pattern of the soil enchytraeids along a distinct elevational gradient (705–2,280 m) on the Changbai Mountain, the best‐preserved mountain in northeastern China. The overall abundance‐based community dissimilarity was relatively high (ca. 0.70), largely due to the balanced‐variation component (85%). The overall dissimilarity and its balanced‐variation (substitution) component were related to both local environmental heterogeneity and elevational distance, with the environmental relationships being stronger. In contrast, the abundance‐gradient (subsets) component was not related to the two gradients. The same important spatial and environmental variables were detected in structuring overall dissimilarity and substitution component, different from that in subsets component. Variation partitioning analysis showed that environmental control played a more important role than spatial (vertical and horizontal) factors in structuring the patterns of overall beta diversity and its two components. The predictive power of multivariate analysis was higher for the substitution component (nearly 50%) and overall dissimilarity (35%), but much lower for subsets components (<4%). These findings implied that abundance‐based beta diversity patterns of the soil enchytraeids were the results of different ecological processes (e.g., environmental sorting and dispersal limitation), operating in the two antithetic components. Our study showed the substitution and loss of individuals reflecting different ecological processes and highlights the importance of partitioning beta diversity in assessing biodiversity patterns and their causes.     

Oribatid mites reveal that competition for resources and trophic structure combine to regulate the assembly of diverse soil animal communities

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Niche versus neutrality in structuring the beta diversity of damselfly assemblages

1. Differences among communities in taxonomic composition – beta diversity – are frequently expected to result from taxon‐specific responses to spatial variation in ecological conditions, through niche partitioning. Such process‐derived patterns are in sharp contrast to arguments from neutral theory, where taxa are ecologically equivalent and beta diversity results primarily from dispersal limitation. 2. Here, we compared beta diversity among assemblages of damselflies (Odonata: Zygoptera), for which previous experiments have shown that niche differences maintain genera within a community, but patterns of relative abundance for species within each genus are shaped primarily by neutral dynamics. 3. Using null‐model and ordination‐based methods, we find that both genera and (in contrast to neutral theory) species assemblage composition vary across the landscape in a deterministic fashion, shaped by environmental and spatial factors. 4. While the observed patterns in species composition conflict with theory, we suggest that this a result of weak ecological filters acting to produce spatial variation in assemblages of ecologically similar species undergoing ecological drift within communities. Such patterns are especially likely in systems of relatively weak dispersers like damselflies.     

Examining residual spatial correlation in variation partitioning of beta diversity in a subtropical forest

Aims The relative roles of ecological processes in structuring beta diversity are usually quantified by variation partitioning of beta diversity with respect to environmental and spatial variables or gamma diversity. However, if important environmental or spatial factors are omitted, or a scale mismatch occurs in the analysis, unaccounted spatial correlation will appear in the residual errors and lead to residual spatial correlation and problematic inferences.     

Scale dependency of processes structuring metacommunities of cladocerans in temporary pools of High‐Andes wetlands

Metacommunity structure can be shaped by a variety of processes operating at different spatial scales. With increasing scale, the compositional variation among local communities (beta diversity) may reflect stronger environmental heterogeneity, but may also reflect reduced exchange of organisms between habitat patches. We analyzed the spatial architecture of a metacommunity of cladoceran zooplankton in temporary pools of High Andes wetlands, with the objective of explaining the spatial dependency of its structure. The spatial distribution of the pools is hierarchical and highly discontinuous: pools are clustered within small wetlands, which lay scattered over valleys that are separated from each other by mountain ridges. We studied a total of 59 pools, belonging to six different wetlands in four different valleys. We assessed pool environmental heterogeneity and sampled active communities and dormant propagule banks of cladoceran zooplankton. Environmental heterogeneity proved very high within wetlands and showed almost no increase with increasing spatial scale. Conversely, diversity partitioning analyses indicated an increase in beta diversity with spatial scale, especially among valleys. Variation partitioning on environmental data and spatial RDA models suggested environmental heterogeneity as the most important generator of beta diversity within wetlands. At the largest spatial scale, beta diversity manifested itself mainly as a differentiation of species occurrence patterns among valleys, which could not be entirely explained by environmental variables. Our study thus presents a case where environmental control seems to be the dominant metacommunity structuring process at the smallest spatial scale, whereas neutral processes and dispersal limitation are the most likely generators of beta diversity at the largest spatial scale.     

西藏横断山区溪流细菌beta多样性组分对气候和水体环境的响应

理解沿环境或空间梯度的群落组成变化(即beta多样性)一直是生态学和保护生物学的中心问题, 且beta多样性的形成机制及其对环境的响应已成为当前生物多样性研究的热点问题。本文以西藏横断山区怒江和澜沧江两个流域入江溪流中的细菌为研究对象, 使用Baselga的beta多样性分解方法, 基于Sørensen相异性指数将细菌的beta多样性分解为周转(turnover)和嵌套(nestedness)两个组分, 探究了细菌beta多样性及其分解组分随海拔距离的分布模式, 并且衡量了环境、气候和空间因子的相对重要性。结果表明, 两个流域中细菌的群落结构显著不同。两个流域的细菌总beta多样性和周转组分随海拔距离的增加而增加, 周转组分占总beta多样性的比例较大。气候和环境因子是两个流域中细菌总beta多样性及周转过程的重要预测因子, 并且所有的显著因子均为正相关, 其中环境因子中相关性最高的为海拔距离(R ²= 0.408, P < 0.001), 而气候因子中相关性最高的为年均温差(R ²= 0.417, P < 0.001)。方差分解结果暗示嵌套组分主要受空间扩散的影响; 总beta多样性和周转组分在环境较恶劣的澜沧江主要受环境过滤的影响, 而在环境较温和的怒江主要受空间扩散和环境过滤的共同影响。此外, 较为恶劣的环境条件会增加细菌的总beta多样性和周转率, 并且会形成更强的环境筛选作用去影响细菌群落的物种组成。我们的研究表明对西藏横断山区水体细菌多样性的保护需要从整个流域入手, 而非少量的生物多样性热点地区。     

Turnover of plant lineages shapes herbivore phylogenetic beta diversity along ecological gradients

Understanding drivers of biodiversity patterns is of prime importance in this era of severe environmental crisis. More diverse plant communities have been postulated to represent a larger functional trait‐space, more likely to sustain a diverse assembly of herbivore species. Here, we expand this hypothesis to integrate environmental, functional and phylogenetic variation of plant communities as factors explaining the diversity of lepidopteran assemblages along elevation gradients in the Swiss Western Alps. According to expectations, we found that the association between butterflies and their host plants is highly phylogenetically structured. Multiple regression analyses showed the combined effect of climate, functional traits and phylogenetic diversity in structuring butterfly communities. Furthermore, we provide the first evidence that plant phylogenetic beta diversity is the major driver explaining butterfly phylogenetic beta diversity. Along ecological gradients, the bottom up control of herbivore diversity is thus driven by phylogenetically structured turnover of plant traits as well as environmental variables.     

Assessing the role of the spatial scale in the analysis of lagoon biodiversity. A case-study on the macrobenthic fauna of the Po River Delta

The analysis of benthic assemblages is a valuable tool to describe the ecological status of transitional water ecosystems, but species are extremely sensitive and respond to both microhabitat and seasonal differences. The identification of changes in the composition of the macrobenthic community in specific microhabitats can then be used as an “early warning” for environmental changes which may affect the economic and ecological importance of lagoons, through their provision of Ecosystem Services. From a conservational point of view, the appropriate definition of the spatial aggregation level of microhabitats or local communities is of crucial importance. The main objective of this work is to assess the role of the spatial scale in the analysis of lagoon biodiversity. First, we analyze the variation in the sample coverage for alternative aggregations of the monitoring stations in three lagoons of the Po River Delta. Then, we analyze the variation of a class of entropy indices by mixed effects models, properly accounting for the fixed effects of biotic and abiotic factors and random effects ruled by nested sources of variability corresponding to alternative definitions of local communities. Finally, we address biodiversity partitioning by a generalized diversity measure, namely the Tsallis entropy, and for alternative definitions of the local communities. The main results obtained by the proposed statistical protocol are presented, discussed and framed in the ecological context.     

A comparative hierarchical analysis of bacterioplankton and biofilm metacommunity structure in an interconnected pond system

It is unknown whether bacterioplankton and biofilm communities are structured by the same ecological processes, and whether they influence each other through continuous dispersal (known as mass effects). Using a hierarchical sampling approach we compared the relative importance of ecological processes structuring the dominant fraction (relative abundance ≥0.1%) of bacterioplankton and biofilm communities from three microhabitats (open water, Nuphar and Phragmites sites) at within‐ and among‐pond scale in a set of 14 interconnected shallow ponds. Our results demonstrate that while bacterioplankton and biofilm communities are highly distinct, a similar hierarchy of ecological processes is acting on them. For both community types, most variation in community composition was determined by pond identity and environmental variables, with no effect of space. The highest β‐diversity within each community type was observed among ponds, while microhabitat type (Nuphar, Phragmites, open water) significantly influenced biofilm communities but not bacterioplankton. Mass effects among bacterioplankton and biofilm communities were not detected, as suggested by the absence of within‐site covariation of biofilm and bacterioplankton communities. Both biofilm and plankton communities were thus highly structured by environmental factors (i.e., species sorting), with among‐lake variation being more important than within‐lake variation, whereas dispersal limitation and mass effects were not observed.     

Contrasting diversity patterns of crenarchaeal, bacterial and fungal soil communities in an alpine landscape

Background

The advent of molecular techniques in microbial ecology has aroused interest in gaining an understanding about the spatial distribution of regional pools of soil microbes and the main drivers responsible of these spatial patterns. Here, we assessed the distribution of crenarcheal, bacterial and fungal communities in an alpine landscape displaying high turnover in plant species over short distances. Our aim is to determine the relative contribution of plant species composition, environmental conditions, and geographic isolation on microbial community distribution.

Methodology/Principal Findings

Eleven types of habitats that best represent the landscape heterogeneity were investigated. Crenarchaeal, bacterial and fungal communities were described by means of Single Strand Conformation Polymorphism. Relationships between microbial beta diversity patterns were examined by using Bray-Curtis dissimilarities and Principal Coordinate Analyses. Distance-based redundancy analyses and variation partitioning were used to estimate the relative contributions of different drivers on microbial beta diversity. Microbial communities tended to be habitat-specific and did not display significant spatial autocorrelation. Microbial beta diversity correlated with soil pH. Fungal beta-diversity was mainly related to soil organic matter. Though the effect of plant species composition was significant for all microbial groups, it was much stronger for Fungi. In contrast, geographic distances did not have any effect on microbial beta diversity.

Conclusions/Significance

Microbial communities exhibit non-random spatial patterns of diversity in alpine landscapes. Crenarcheal, bacterial and fungal community turnover is high and associated with plant species composition through different set of soil variables, but is not caused by geographical isolation.     

美洲森林群落beta多样性的纬度梯度性

Beta多样性度量不同时空尺度物种组成的变化,是生物多样性的重要组成部分;理解其地理格局和形成机制已成为当前生物多样性研究的热点问题。基于Alwyn H. Gentry在美洲收集的131个森林样方数据,采用倍性和加性分配方法度量群落beta多样性,检验beta多样性随纬度的变化趋势,并分析其形成机制。研究表明:(1) 美洲森林群落beta多样性随纬度增加显著下降,热带和亚热带地区beta多样性高于温带地区;此格局可由物种分布范围的纬度梯度性和不同粒度(grain)下物种丰富度与纬度回归斜率的差异推论得出;(2) 加性分配方法表明beta多样性对各个温度带森林群落gamma多样性的相对贡献率平均为78.2%,并且随纬度升高而降低;(3) 美洲南半球森林群落beta多样性高于其北半球,这可能反映了区域间物种进化和环境变迁历史的差异。此外,还探讨了不同beta多样性计算方法的适用情景,首次证实了森林生态系统群落水平beta多样性的纬度梯度性,这对研究生物多样性的形成机制和生物多样性保护都具有重要的意义。     

Defining marine bacterioplankton community assembly rules by contrasting the importance of environmental determinants and biotic interactions

Bacterioplankton communities govern marine productivity and biogeochemical cycling, yet drivers of bacterioplankton assembly remain unclear. Here, we contrast the relative contribution of deterministic processes (environmental factors and biotic interactions) in driving temporal dynamics of bacterioplankton diversity at three different oceanographic time series locations, spanning 15° of latitude, which are each characterized by different environmental conditions and varying degrees of seasonality. Monthly surface samples (5.5 years) were analysed using 16S rRNA amplicon sequencing. The high- and mid-latitude sites of Maria Island and Port Hacking were characterized by high and intermediate levels of environmental heterogeneity, respectively, with both alpha diversity (72%; 24% of total variation) and beta diversity (32%; 30%) patterns within bacterioplankton assemblages explained by day length, ammonium, and mixed layer depth. In contrast, North Stradbroke Island, a sub-tropical location where environmental conditions are less variable, interspecific interactions were of increased importance in structuring bacterioplankton diversity (alpha: 33%; beta: 26%) with environment only contributing 11% and 13% to predicting diversity, respectively. Our results demonstrate that bacterioplankton diversity is the result of both deterministic environmental and biotic processes and that the importance of these different deterministic processes varies, potential in response to environmental heterogeneity.     

Spatio-temporal drivers of different oomycete beta diversity components in Brazilian rivers

Disentangling the role of mechanisms driving metacommunity structure is fundamental for conservation strategies. Several studies have been done in aquatic communities; however, little is known about the factors driving oomycete communities. This research aimed to investigate beta diversity patterns and assess the role of environmental (chemical, physical, and hydrologic), spatial, and temporal (sampling months) factors in driving oomycete beta diversity in a spatial extent of 33 km from two Brazilian rivers. We took water samples in 10 sites quarterly, from August 2017 to May 2018. The partition of beta diversity into its components – species replacement and richness difference – was performed using the Jaccard dissimilarity index. Distance-based redundancy analysis and variation partitioning were used to assess the relationship between explanatory variables and beta diversity. We found that beta diversity was spatially and temporally high, and the replacement component was the main driver of the oomycete metacommunity’s beta diversity. Replacement and total beta diversity were explained mainly by spatial location and the month of sampling, while the richness difference was more associated with the environmental variables chlorophyll a and ammonia. Our findings suggest that dispersal limitation (spatial) and temporal factors are the main drivers of the total beta diversity and replacement in the oomycete metacommunity, while species sorting (environmental factor) influences the richness difference. Accordingly, that taking temporal factors into account in metacommunity studies is important to explain beta diversity patterns, especially in rivers with remarkable variability in hydrological regime and under eutrophic conditions.

     

Partitioning diversity for conservation analyses

Aim  Differentiation of sites or communities is often measured by partitioning regional or gamma diversity into additive or multiplicative alpha and beta components. The beta component and the ratio of within-group to total diversity (alpha/gamma) are then used to infer the compositional differentiation or similarity of the sites. There is debate about the appropriate measures and partitioning formulas for this purpose. We test the main partitioning methods, using empirical and simulated data, to see if some of these methods lead to false conclusions, and we show how to resolve the problems that we uncover.
Location  South America, Ecuador, Orellana province, Rio Shiripuno.
Methods  We construct sets of real and simulated tropical butterfly communities that can be unambiguously ranked according to their degree of differentiation. We then test whether beta and similarity measures from the different partitioning approaches rank these datasets correctly.
Results  The ratio of within-group diversity to total diversity does not reflect compositional similarity, when the Gini–Simpson index or Shannon entropy are used to measure diversity. Additive beta diversity based on the Gini–Simpson index does not reflect the degree of differentiation between N sites or communities.
Main conclusions  The ratio of within-group to total diversity (alpha/gamma) should not be used to measure the compositional similarity of groups, if diversity is equated with Shannon entropy or the Gini–Simpson index. Conversion of these measures to effective number of species solves these problems. Additive Gini–Simpson beta diversity does not directly reflect the differentiation of N samples or communities. However, when properly transformed onto the unit interval so as to remove the dependence on alpha and N , additive and multiplicative beta measures yield identical normalized measures of relative similarity and differentiation.     

Microhabitat partitioning in seagrass mesograzers is driven by consistent species choices across multiple predator and competitor contexts

Explanations for the coexistence of multiple species from the same functional group or taxonomic clade frequently include fine‐scale resource partitioning. However, despite the hypothesized importance of niche partitioning, we know relatively little about the underlying mechanisms. For example, differences in resource use may be fixed consequences of organism traits, or they may be achieved via context‐dependent behaviors. In this study we investigated mechanisms of microhabitat partitioning using eight species of marine mesograzers inhabiting seagrass and algae habitats, using laboratory trials to measure microhabitat use in the presence and absence of both predators and competitors. We found clear evidence for microhabitat partitioning between the species, which account for over 60% of the mesograzers commonly found in this system and vary in both body size and the ability to build tubes on habitat substrates. Species‐specific microhabitat use was poorly predicted by these two traits, but remained remarkably consistent across contexts. Habitat use was not affected by the presence of fish predators common in this system, even though predation pressure is thought to place strong constraints on microhabitat in communities of plant‐associated arthropods. The presence of competing species also did not affect the relative separation of microhabitat use. Behavioral responses to potential competitors did cause significant changes in microhabitat use in all of the smallest species, but these changes did not depend on competitor identity and were relatively small compared to among‐species patterns of microhabitat partitioning. The consistency of species‐specific microhabitat use, regardless of the presence of predators or competitors, should make coexistence most likely among species that differ in these choices. For these species, it appears that the benefits accrued from their selected microhabitats are not affected by species interactions, or that any benefits of alternative microhabitat use are outweighed by risks associated with movement.     

Quantifying Phylogenetic Beta Diversity: Distinguishing between 'True' Turnover of Lineages and Phylogenetic Diversity Gradients

The evolutionary dissimilarity between communities (phylogenetic beta diversity PBD) has been increasingly explored by ecologists and biogeographers to assess the relative roles of ecological and evolutionary processes in structuring natural communities. Among PBD measures, the PhyloSor and UniFrac indices have been widely used to assess the level of turnover of lineages over geographical and environmental gradients. However, these indices can be considered as 'broad-sense' measures of phylogenetic turnover as they incorporate different aspects of differences in evolutionary history between communities that may be attributable to phylogenetic diversity gradients. In the present study, we extend an additive partitioning framework proposed for compositional beta diversity to PBD. Specifically, we decomposed the PhyloSor and UniFrac indices into two separate components accounting for 'true' phylogenetic turnover and phylogenetic diversity gradients, respectively. We illustrated the relevance of this framework using simple theoretical and archetypal examples, as well as an empirical study based on coral reef fish communities. Overall, our results suggest that using PhyloSor and UniFrac may greatly over-estimate the level of spatial turnover of lineages if the two compared communities show contrasting levels of phylogenetic diversity. We therefore recommend that future studies use the 'true' phylogenetic turnover component of these indices when the studied communities encompass a large phylogenetic diversity gradient.