Evidence for phylogenetic correlation of plant–AMF assemblages?

Background and Aims Specificity in biotic interactions is mediated'' by functional traits inducing shifts in the community species composition. Functional traits are often evolutionarily conserved, resulting in closely related species tending to interact with similar species. This tendency may initially shape the phylogenetic composition of coexisting guilds, but other intraguild ecological processes may either blur or promote the mirroring of the phylogenetic compositions between guilds. The roles of intra- and interguild interactions in shaping the phylogenetic community composition are largely unknown, beyond the mere selectivity in the interguild interactions. Plant facilitation is a phylogenetically structured species-specific process involving interactions not only between the same guild of plants, but also between plants and other guilds such as arbuscular mycorrhizal fungi (AMF). In this study it is hypothesized that reciprocal plant–AMF interactions will leave an interdependent phylogenetic signal in the community composition of both plants and AMF.Methods A correlation was used to test for a relationship between the phylogenetic composition of plant and AMF assemblages in a patchy xeric shrubland environment shaped by plant facilitation. In addition, a null model was used to test whether this correlation can be solely explained by selectivity in plant–AMF interactions.Key Results A significant correlation was observed between the phylogenetic composition of plant and AMF assemblages. Plant phylogenetic composition in a patch was related to the predominance of plant species with high nursery quality that can influence the community assembly. AMF phylogenetic composition was related to the AMF phylogenetic diversity in each patch.Conclusions This study shows that shifts in the phylogenetic composition of plants and AMF assemblages do not occur independently. It is suggested that besides selectivity in plant–AMF interactions, inter-related succession dynamics of plants and AMF within patches could be an ecological mechanism driving community assembly. Future lines of research might explore whether interlinked above- and below-ground dynamics could be occurring across multiple guilds simultaneously.     

太白山森林样地系统发育多样性格局及其影响因素

太白山森林样地系统发育多样性格局及其影响因素 系统发育多样性指数常被用作区分植物群落构建过程中生态和演化过程的相对作用。系统发育多样性格局的推断方法(如系统树的构建和不同的系统发育多样性指数)、演化历史(如生活型)以及环境梯度都可能影响系统发育多样性格局的估计值,进而可能影响我们对植物群落构建过程的认知。因此,有必要区分这些因素如何作用于系统发育多样性格局的估计值,但其相对重要性及其交互作用仍不清楚。本研究利用位于太白山北坡沿海拔分布的20个森林样地(整体高差2800 m左右)的野外调查数据,包括274种木本植物和581种草本植物。对于上述样地内所有植物,我们构建了当前广泛采用的合成树和分子树以比较系统树的构建,特别是合成树末端的多歧分支结构,及其对系统发育多样性格局估计值的可能影响。同时,我们计算了每个样地的3种不同的系统发育多样性指数,包括Faith’s PD, 平均成对距离(MPD)和平均最近类群距离(MNTD),并分别对木本和草本植物进行计算。多模型比较分析系统发育多样性格局的估计值与系统树重建方法、多样性指数、生活型、海拔及其交互作用的最简约关系。研究结果表明,基于合成树和分子树所得到的系统发育多样性格局之间没有显著差异。海拔和多样性指数与生活型在解释系统发育多样性格局方面存在强烈的交互作用,并且能够解释44%以上的变异。系统发育多样性格局的估计值总体随海拔升高而降低,但草本植物相比木本植物变化更平缓。对于木本植物,3种系统发育多样性指数表现出一致的海拔分布格局(即系统发育聚集),而草本植物的平均成对距离指数则表现为随机的海拔分布格局。因此,分析沿环境梯度的系统发育多样性格局需要考虑系统发育格局的推断方法和演化历史的影响,以帮助我们更好地理解植物群落的构建过程。     

Environment differentially affects the functional and phylogenetic structures of plant communities in a dry evergreen Afromontane tropical forest

Testing how local environmental conditions influence plant community assembly is important to understand the underlying mechanisms that promote and/or maintain biodiversity. Functional traits are used to find the broad spectrum of resource use strategies that plants use to respond to environmental variation. The patterns and drivers of plant community assembly through the lens of traits and phylogeny; however, remain to be studied in a uniquely biodiversity rich but poorly known fragmented dry Afromontane forest of Ethiopia. Here, we combined trait and community phylogenetic data from thirty sampling plots of 20 × 20 m size to determine the functional and phylogenetic structures and their drivers in a fragmented, human-dominated dry evergreen Afromontane forest. We found phylogenetic and functional clustering of plants in which the effect of environment was found to be trait specific. A weak phylogenetic signal for traits was detected suggesting that species resource use strategies may not be inferred using species phylogenetic distance. Additionally, we found functional traits to be weak in predicting species abundance distribution. Overall, while this study shows a non-random community assembly pattern, it also highlights the importance of deterministic processes being trait specific.     

Phylogenetic turnover during subtropical forest succession across environmental and phylogenetic scales

Although spatial and temporal patterns of phylogenetic community structure during succession are inherently interlinked and assembly processes vary with environmental and phylogenetic scales, successional studies of community assembly have yet to integrate spatial and temporal components of community structure, while accounting for scaling issues. To gain insight into the processes that generate biodiversity after disturbance, we combine analyses of spatial and temporal phylogenetic turnover across phylogenetic scales, accounting for covariation with environmental differences. We compared phylogenetic turnover, at the species‐ and individual‐level, within and between five successional stages, representing woody plant communities in a subtropical forest chronosequence. We decomposed turnover at different phylogenetic depths and assessed its covariation with between‐plot abiotic differences. Phylogenetic turnover between stages was low relative to species turnover and was not explained by abiotic differences. However, within the late‐successional stages, there was high presence‐/absence‐based turnover (clustering) that occurred deep in the phylogeny and covaried with environmental differentiation. Our results support a deterministic model of community assembly where (i) phylogenetic composition is constrained through successional time, but (ii) toward late succession, species sorting into preferred habitats according to niche traits that are conserved deep in phylogeny, becomes increasingly important.     

A taxonomic and phylogenetic perspective on plant community assembly along an elevational gradient in subtropical forests

亚热带森林植物群落沿海拔梯度的分类与系统发育研究 生物多样性沿海拔梯度的分布格局已受到广泛关注。然而,生物多样性格局沿海拔梯度的变异及其潜在机制尚不清楚。整合生物多样性的多维度信息为理解群落构建机制提供了新思路。本研究在我国东部亚热带森林沿海拔270–1470 m的梯度上设置了17个木本植物固定样地,分析了沿海拔梯度植物群落 构建的生态和进化驱动力。基于样地内物种出现(0–1数据)和多度信息,计算群落内被子植物的物种和系统发育alpha和beta多样性、系统发育结构等,并量化多样性指标与微气候和地形之间的关系。研究发现,不论多度加权与否,物种alpha多样性均沿海拔升高而增加,物种和系统发育的相似性随海拔距离的增加而呈衰减趋势。然而,多度加权与否会形成不同的系统发育alpha多样性格局。对于系统发育结构而言,沿海拔增加并无明显趋势。地形和微气候是多样性格局和系统发育结构的主要驱动力。与未考虑物种多度的多样性指标相比,多度加权的指标与坡度和胸高断面积相关性更高。这些结果表明,由局域物种多度介导的确定性过程对沿海拔梯度的植物群落构建具有一定影响。     

Plastome-based phylogeny improves community phylogenetics of subtropical forests in China

Phylogenetic trees have been extensively used in community ecology. However, how the phylogeny construction affects ecological inferences is poorly understood. In this study, we constructed three different types of phylogenetic trees (a synthetic-tree generated using V.PhyloMaker, a barcode-tree generated using rbcL+matK+trnH-psbA, and a plastome-tree generated from plastid genomes) that represented an increasing level of phylogenetic resolution among 580 woody plant species from six forest dynamic plots in subtropical evergreen broadleaved forests of China. We then evaluated the performance of each phylogeny in estimations of community phylogenetic structure, turnover and phylogenetic signal in functional traits. As expected, the plastome-tree was most resolved and most supported for relationships among species. For local phylogenetic structure, the three trees showed consistent results with Faith's PD and MPD; however, only the synthetic-tree produced significant clustering patterns using MNTD for some plots. For phylogenetic turnover, contrasting results between the molecular trees and the synthetic-tree occurred only with nearest neighbor distance. The barcode-tree agreed more with the plastome-tree than the synthetic-tree for both phylogenetic structure and turnover. For functional traits, both the barcode-tree and plastome-tree detected phylogenetic signal in maximum height, but only the plastome-tree detected signal in leaf width. This is the first study that uses plastid genomes in large-scale community phylogenetics. Our results highlight the improvement of plastome-trees over barcode-trees and synthetic-trees for the analyses studied here. Our results also point to the possibility of type I and II errors in estimation of phylogenetic structure and turnover and detection of phylogenetic signal when using synthetic-trees.     

Plant–mycorrhizal fungus co‐occurrence network lacks substantial structure

The interactions between plants and arbuscular mycorrhizal fungi (AMF) maintain a crucial link between macroscopic organisms and the soil microbial world. These interactions are of extreme importance for the diversity of plant communities and ecosystem functioning. Despite this importance, only recently has the structure of plant–AMF interaction networks been studied. These recent studies, which used genetic data, suggest that these networks are highly structured, very similar to plant–animal mutualistic networks. However, the assembly process of plant–AMF communities is still largely unknown, and an important feature of plant–AMF interactions has not been incorporated: they occur at an extremely localized scale. Studying plant–AMF networks in a spatial context seems therefore a crucial step. This paper studies a plant–AMF spatial co‐occurrence network using novel methodology based on information theory and a unique set of spatially explicit species‐level data. We apply three null models of which only one accounts for spatial effects. We find that the data show substantial departures from null expectations for the two non‐spatial null models. However, for the null model considering spatial effects, there are few significant co‐occurrences compared with the other two null models. Thus, plant–AMF spatial co‐occurrences seem to be mostly explained by stochasticity, with a small role for other factors related to plant–AMF specialization. Furthermore, we find that the network is not significantly nested or modular. We conclude that this plant–AMF spatial co‐occurrence network lacks substantial structure and, therefore, plants and AMF species do not track each other over space. Thus, random encounters seem more important in the first step of the assembly of plant–AMF communities. Synthesis The symbiotic interaction between plants and arbuscular mycorrhizal fungi (AMF) is crucial for ecosystem functioning. However, the factors affecting the assembly of plant‐AMF communities are poorly understood. An important factor of the assembly of plant‐AMF communities has been overlooked: plant‐AMF interactions occur at a localized spatial scale. Our study investigated the importance of space in the structure of plant‐AMF communities. We studied a plant‐AMF spatial co‐occurrence network using a unique set of spatially explicit data and applied three null models. We found that plant‐AMF spatial co‐occurrences seem to be mostly explained by stochasticity. In particular, our study shows that this plant‐AMF spatial co‐occurrence network lacks substantial structure and, therefore, plants and AMF species do not track each other over space. Thus, random encounters seem to drive the assembly of plant‐AMF communities.     

An exotic invader drives the evolution of plant traits that determine mycorrhizal fungal diversity in a native competitor

The symbiosis between land plants and arbuscular mycorrhizal fungi (AMF) is one of the most widespread and ancient mutualisms on the planet. However, relatively little is known about the evolution of these symbiotic plant–fungal interactions in natural communities. In this study, we investigated the symbiotic AMF communities of populations of the native plant species Pilea pumila (Urticaceae) with varying histories of coexistence with a nonmycorrhizal invasive species, Alliaria petiolata (Brassicaceae), known to affect mycorrhizal communities. We found that native populations of P. pumila with a long history of coexistence with the invasive species developed more diverse symbiotic AMF communities. This effect was strongest when A. petiolata plants were actively growing with the natives, and in soils with the longest history of A. petiolata growth. These results suggest that despite the ancient and widespread nature of the plant–AMF symbiosis, the plant traits responsible for symbiotic preferences can, nevertheless, evolve rapidly in response to environmental changes.     

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.     

Flowering and Fruiting Patterns in a Subtropical Rain Forest,Taiwan

Reproductive patterns of tropical and temperate plants are usually associated with climatic seasonality, such as rainfall or temperature, and with their phylogeny. It is still unclear, however, whether plant reproductive phenology is influenced by climatic factors and/or phylogeny in aseasonal subtropical regions. The plant reproductive phenology of a subtropical rain forest in northern Taiwan (24°45′ N, 121°35′ E) was monitored at weekly intervals during a 7‐yr period (2002–2009). The flowering patterns of 46 taxa and fruiting patterns of 26 taxa were examined and evaluated in relation to climatic seasonality, phylogenetic constraints, and different phenophases. Our results indicated that most of the studied species reproduced annually. Additionally, both community‐wide flowering and fruiting patterns exhibited distinct annual rhythms and varied little among years. The community flowering peak matched seasonal changes in day length, temperature, and irradiance; while the community fruiting peak coincided with an increase in bird richness and the diet‐switching of resident omnivorous birds. In addition, phylogenetically closely related species tended to reproduce during the same periods of a year. Neither the mean flowering dates nor seasonal variation in solar radiation, however, was related to the fruit development times. Our results indicate the importance of abiotic, biotic, and evolutionary factors in determining the reproductive phenology in this subtropical forest.     

浙江古田山亚热带常绿阔叶林开花物候:气候因素、系统发育关系和功能性状的影响

植物的开花物候受气候因素、植物系统发育关系和功能性状的影响。然而当前植物开花物候研究中未见同时考虑这3个因素的报道。为了解它们相互之间的影响, 本研究利用中国东部地区浙江省古田山国家级自然保护区亚热带常绿阔叶林24 ha大样地(GTS; 118°03′50′′-118°11′12.2′′ E, 29°10′19′′-29°17′41′′ N)设置的130个种子雨收集器5年的开花数据检验这3个因素对开花的影响。结果表明, 古田山植物的开花高峰期集中在5月, 群落开花格局明显受温度和降雨的影响。利用植物DNA条形码数据研究发现, 植物间系统发育关系对古田山植物开花时间有显著影响, 亲缘关系近的物种开花时间更相近。植物的平均开花时间受最大树高的影响, 但不受传粉方式、花色、种子质量和扩散方式的影响。该研究结果说明气候因素、植物系统发育关系和功能性状都可能影响植物开花物候格局, 同时考虑这3个因素能够帮助我们更好地理解开花物候格局。     

Phylogenetic structure and phylogenetic diversity of angiosperm assemblages in forests along an elevational gradient in Changbaishan,China

Aims Understanding what drives the variation in species composition and diversity among local communities can provide insights into the mechanisms of community assembly. Because ecological traits are often thought to be phylogenetically conserved, there should be patterns in phylogenetic structure and phylogenetic diversity in local communities along ecological gradients. We investigate potential patterns in angiosperm assemblages along an elevational gradient with a steep ecological gradient in Changbaishan, China.Methods We used 13 angiosperm assemblages in forest plots (32×32 m) distributed along an elevational gradient from 720 to 1900 m above sea level. We used Faith's phylogenetic diversity metric to quantify the phylogenetic alpha diversity of each forest plot, used the net relatedness index to quantify the degree of phylogenetic relatedness among angiosperm species within each forest plot and used a phylogenetic dissimilarity index to quantify phylogenetic beta diversity among forest plots. We related the measures of phylogenetic structure and phylogenetic diversity to environmental (climatic and edaphic) factors.Important findings Our study showed that angiosperm assemblages tended to be more phylogenetically clustered at higher elevations in Changbaishan. This finding is consistent with the prediction of the phylogenetic niche conservatism hypothesis, which highlights the role of niche constraints in governing the phylogenetic structure of assemblages. Our study also showed that woody assemblages differ from herbaceous assemblages in several major aspects. First, phylogenetic clustering dominated in woody assemblages, whereas phylogenetic overdispersion dominated in herbaceous assemblages; second, patterns in phylogenetic relatedness along the elevational and temperature gradients of Changbaishan were stronger for woody assemblages than for herbaceous assemblages; third, environmental variables explained much more variations in phylogenetic relatedness, phylogenetic alpha diversity and phylogenetic beta diversity for woody assemblages than for herbaceous assemblages.     

A phylogenetic and trait‐based analysis of community assembly in a subtropical forest in central China

Despite several decades of study in community ecology, the relative importance of the ecological processes that determine species co‐occurrence across spatial scales remains uncertain. Some of this uncertainty may be reduced by studying the scale dependency of community assembly in the light of environmental variation. Phylogenetic information and functional trait information are often used to provide potentially valuable insights into the drivers of community assembly. Here, we combined phylogenetic and trait‐based tests to gain insights into community processes at four spatial scales in a large stem‐mapped subtropical forest dynamics plot in central China. We found that all of the six leaf economic traits measured in this study had weak, but significant, phylogenetic signal. Nonrandom phylogenetic and trait‐based patterns associated with topographic variables indicate that deterministic processes tend to dominate community assembly in this plot. Specifically, we found that, on average, co‐occurring species were more phylogenetically and functionally similar than expected throughout the plot at most spatial scales and assemblages of less similar than expected species could only be found on finer spatial scales. In sum, our results suggest that the trait‐based effects on community assembly change with spatial scale in a predictable manner and the association of these patterns with topographic variables, indicates the importance of deterministic processes in community assembly relatively to random processes.     

Effects of Alliaria petiolata (garlic mustard; Brassicaceae) on mycorrhizal colonization and community structure in three herbaceous plants in a mixed deciduous forest

Herbaceous plant species are important components of forest ecosystems, and their persistence in forests may be affected by invasive plant species that reduce mycorrhizal colonization of plant roots. I examined the effect of the invasive plant Alliaria petiolata on arbuscular mycorrhizal fungi (AMF) colonizing the roots of three forest plant species. AMF root colonization and community structure was examined from plants that were growing either in the absence or presence of Alliaria under natural forest conditions. AMF root colonization varied among the plant species but was not significantly affected by Alliaria. With molecular methods, ～12 different taxa of AMF could be distinguished among the root samples, and these taxa belonged to the genera Acaulospora and Glomus, with Glomus dominating AMF communities. There were significant differences between the community of AMF colonizing roots of Maianthemum racemosum and Trillium grandiflorum, but only AMF communities of Maianthemum roots were significantly affected by Alliaria. Indicator species analysis found that an Acaulospora species type was a significant indicator of Maianthemum plants grown in the absence of Alliaria. These results suggest invasive plants like Alliaria may selectively suppress AMF fungi, and this suppression can affect AMF communities colonizing the roots of some native plant species.     

Plant identity strongly structures the root-associated fungal community in a diverse subtropical forest

Revealing the relationship between plants and root-associated fungi is very important in understanding diversity maintenance and community assembly in ecosystems. However, the community assembly of root-associated fungi of focal plant species along a subtropical plant species diversity gradient is less documented. Here, we examined root-associated fungal communities associated with five ectomycorrhizal (EM) plant species (Betula luminifera, Castanea henryi, Castanopsis fargesii, C. sclerophylla, and Quercus serrate) in a Chinese subtropical woody plant species diversity (1, 2, 4, 8, 16 and 24 species) experiment, using paired-end Illumina MiSeq sequencing of the ITS2 region. In total, we detected 1933 root-associated fungal operational taxonomic units (OTUs) at a 97% sequence similarity level. Plant identity had a significant effect on total and saprotrophic fungal OTU richness, but plant species diversity level had a significant effect on saprotrophic and pathogenic fungal OTU richness. The community composition of total, saprotrophic and EM fungi was structured by plant identity and plant species diversity level. However, the community composition of pathogenic fungi was only shaped by plant identity. This study highlights that plant identity has a stronger effect on the root-associated fungal community than plant species diversity level in a diverse subtropical forest ecosystem.     

Functional traits of tree species with phylogenetic signal co-vary with environmental niches in two large forest dynamics plots

Aims While using phylogenetic and functional approaches to test the mechanisms of community assembly, functional traits often act as the proxy of niches. However, there is little detailed knowledge regarding the correlation between functional traits of tree species and their niches in local communities. We suggest that the co-varying correlation between functional traits and niches should be the premise for using phylogenetic and functional approaches to test mechanisms of community assembly. Using functional traits, phylogenetic and environmental data, this study aims to answer the questions: (i) within local communities, do functional traits of co-occurring species co-vary with their environmental niches at the species level? and (ii) what is the key ecological process underlying community assembly in Xishuangbanna and Ailaoshan forest dynamic plots (FDPs)?Methods We measured seven functional traits of 229 and 36 common species in Xishuangbanna and Ailaoshan FDPs in tropical and subtropical China, respectively. We also quantified the environmental niches for these species based on conditional probability. We then analyzed the correlations between functional traits and environmental niches using phylogenetic independent contrasts. After examining phylogenetic signals of functional traits using Pagel's λ, we quantified the phylogenetic and functional dispersion along environmental gradients within local tree communities.Important findings For target species, functional traits do co-vary with environmental niches at the species level in both of the FDPs, supporting that functional traits can be used as a proxy for local-scale environmental niches. Functional traits show significant phylogenetic signals in both of the FDPs. We found that the phylogenetic and functional dispersion were significantly clustered along topographical gradients in the Ailaoshan FDP but overdispersion in the Xishuangbanna FDP. These patterns of phylogenetic and functional dispersion suggest that environmental filtering plays a key role in structuring local tree assemblages in Ailaoshan FDP, while competition exclusion plays a key role in Xishuangbanna FDP.     

Species richness and phylogenetic diversity of seed plants across vegetation zones of Mount Kenya,East Africa

Mount Kenya is of ecological importance in tropical east Africa due to the dramatic gradient in vegetation types that can be observed from low to high elevation zones. However, species richness and phylogenetic diversity of this mountain have not been well studied. Here, we surveyed distribution patterns for a total of 1,335 seed plants of this mountain and calculated species richness and phylogenetic diversity across seven vegetation zones. We also measured phylogenetic structure using the net relatedness index (NRI) and the nearest species index (NTI). Our results show that lower montane wet forest has the highest level of species richness, density, and phylogenetic diversity of woody plants, while lower montane dry forest has the highest level of species richness, density, and phylogenetic diversity in herbaceous plants. In total plants, NRI and NTI of four forest zones were smaller than three alpine zones. In woody plants, lower montane wet forest and upper montane forest have overdispersed phylogenetic structures. In herbaceous plants, NRI of Afro‐alpine zone and nival zone are smaller than those of bamboo zone, upper montane forest, and heath zone. We suggest that compared to open dry forest, humid forest has fewer herbaceous plants because of the closed canopy of woody plants. Woody plants may have climate‐dominated niches, whereas herbaceous plants may have edaphic and microhabitat‐dominated niches. We also proposed lower and upper montane forests with high species richness or overdispersed phylogenetic structures as the priority areas in conservation of Mount Kenya and other high mountains in the Eastern Afro‐montane biodiversity hotspot regions.     

功能多样性和谱系多样性对热带云雾林群落构建的影响

近年来, 功能多样性和谱系多样性为探究群落构建机制提供了新方法。为了更准确地了解海南岛高海拔热带云雾林群落构建机制, 该研究以海南岛霸王岭热带云雾林为对象, 测定7个环境因子和13个植物功能性状。利用主成分分析(PCA)筛选环境因子, 以霸王岭、尖峰岭和黎母山热带云雾林分布物种建立区域物种库, 结合模型, 分析Rao二次熵(RaoQ)和平均成对谱系距离(MPD)变化对植物群落构建的影响。结果表明: 林冠开阔度、土壤全磷含量和坡度是影响植物群落构建的关键环境因子。多数功能性状的系统发育信号很低且不显著, 说明热带云雾林群落的系统发育关系与功能性状随历史进程变化不一致。RaoQ和MPD的实际观测值都显著低于期望值, 且其标准效应值与土壤磷含量显著相关, 说明生境过滤是驱动热带云雾林群落构建的关键因子, 土壤磷含量是群落构建的关键环境筛。     

The composition of arbuscular mycorrhizal fungal communities in the roots of a ruderal forb is not related to the forest fragmentation process

Land‐use changes and forest fragmentation have strong impact on biodiversity. However, little is known about the influence of new landscape configurations on arbuscular mycorrhizal fungal (AMF) community composition. We used 454 pyrosequencing to assess AMF diversity in plant roots from a fragmented forest. We detected 59 virtual taxa (VT; phylogenetically defined operational taxonomic units) of AMF – including 10 new VT – in the roots of Euphorbia acerensis. AMF communities were mainly composed of members of family Glomeraceae and were similar throughout the fragmented landscape, despite variation in forest fragment size (i.e. small, medium and large) and isolation (i.e. varying pairwise distances). AMF communities in forest fragments were phylogenetically clustered compared with the global, but not regional and local AMF taxon pools. This indicates that non‐random community assembly processes possibly related to dispersal limitation at a large scale, rather than habitat filtering or biotic interactions, may be important in structuring the AMF communities. In this system, forest fragmentation did not appear to influence AMF community composition in the roots of the ruderal plant. Whether this is true for AMF communities in soil and the roots of other ecological groups of host plants or in other habitats deserves further study.     

Arbuscular mycorrhizal fungal communities in plant roots are not random assemblages

We investigated whether arbuscular mycorrhizal fungal (AMF) communities in plant roots are random subsets of the local taxon pool or whether they reflect the action of certain community assembly rules. We studied AMF small subunit rRNA gene sequence groups in the roots of plant individuals belonging to 11 temperate forest understorey species. Empirical data were compared with null models assuming random association. Distinct fungal species pools were present in young and old successional forest. In both forest types, the richness of plant-AMF associations was lower than expected by chance, indicating a degree of partner selectivity. AMF communities were generally not characteristic of individual plant species, but those associated with ecological groups of plant species - habitat generalists and forest specialists - were nonrandom subsets of the available pool of fungal taxa and differed significantly from each other. Moreover, these AMF communities were the least distinctive in spring, but developed later in the season. Comparison with a global database showed that generalist plants tend to associate with generalist AMF. Thus, the habitat range of the host and a possible interaction with season played a role in the assembly of AMF communities in individual plant root systems.