兰科植物共生胶膜菌:分类学、多样性、专一性和适应性

兰科植物与丝核菌类真菌,包括胶膜菌科、角担菌科和蜡壳菌科等形成菌根共生体。胶膜菌科真菌作为最广泛分布的共生菌根真菌,表现出与兰科植物的协同进化与密切关系。除了形态学特征分析和比较外,分子技术促进了兰科植物胶膜菌的分类学和多样性研究。兰科植物与胶膜菌的特异性可能限制兰科植物的分布和移栽后的生存能力,但有些兰科植物与胶膜菌的共生关系会因为地理分布或环境变化进行调整,使植物更好地生存,这种适应性为实现无菌苗菌根化来促进兰科植物的迁地保护或繁殖提供可能。本文综述了兰科植物共生菌根真菌胶膜菌在分类学、多样性、特异性和适应性等方面的研究。     

Relationships between orchid and fungal biodiversity: Mycorrhizal preferences in Mediterranean orchids

Orchidaceae is one of the most species-rich angiosperm families, and all orchids are fully dependent on fungi for their seed germination and their life cycle. The level of specificity of the association between orchid species and fungi can be related to the number of co-occurring orchid species. To investigate orchid mycorrhizal associations in adult-photosynthetic orchids, 16 Mediterranean orchid species belonging to 4 genera (Anacamptis, Ophrys, Orchis, and Serapias) at 11 different sites were subjected to DNA-based analysis. Eighteen operational taxonomic units representing two fungal families, Tulasnellaceae and Ceratobasidiaceae, were identified. All examined orchid species associated with different mycorrhizal fungi. Interestingly, there was a positive correlation between number of orchid species and number of mycorrhizal. Monospecific populations showed a lower number of fungi, while sympatric populations had a higher number of mycorrhizal fungi. Our results showed that Mediterranean orchid species associated with a higher number of mycorrhizal fungi confirming as photosynthetic orchids are typically generalists toward mycorrhizal fungi. Thus, photosynthetic orchids exhibit low specificity for fungal symbionts showing the potential for opportunistic associations with diverse fungi reducing competition for nutrient. We suggest that these characteristics could confer symbiotic assurance particularly in habitat with resource limitations or prone to stressful conditions.     

Diversity of root-associated fungi of mature Habenaria radiata and Epipactis thunbergii colonizing manmade wetlands in Hiroshima Prefecture,Japan

Throughout the industrialized world, wetland species face the greatest risk of extinction from altered environmental conditions and loss of habitat. Manmade wetlands are often the only feasible strategy to provide habitat for these species. Wetland orchids are particularly susceptible to environmental degradation due to potentially limited availability of specialized pollinators and mycorrhizal symbionts. Here, we assess the fungal symbiont diversity of two orchid species, Habenaria radiata and Epipactis thunbergii, occupying three manmade wetlands in Hiroshima Prefecture, Japan to determine if orchids colonizing reconstructed habitats associate with a phylogenetically diverse or narrow suite of fungal symbionts. We collected three individuals each of H. radiata and E. thunbergii, respectively, growing at the first pond, six H. radiata from a second pond, and two E. thunbergii from a third pond. We identified fungal taxa using PCR and DNA sequencing techniques. Habenaria radiata associated with a phylogenetically diverse suite of fungi; in comparison, E. thunbergii associated with a phylogenetically narrow range of fungi dominated by the Tulasnellaceae. These common wetland orchid species readily colonize manmade wetlands, and we propose sampling soils for the presence of appropriate mycorrhizal fungi to determine limitations on orchid population regeneration due to mycorrhizal specificity.     

3种杓兰属植物菌根真菌系统发育和多样性分析

兰科植物菌根真菌(Orchid mycorrhizal fungi, OrMF)在兰科植物种子萌发和后续生长发育过程中具有重要作用。该研究采用培养(菌丝团分离)和非培养(克隆文库)2种方法获得同一栖息地3种不同杓兰属植物根中菌根真菌ITS序列并划分可操作分类单元(Operational taxonomic units, OTUs),分析其系统发育关系和多样性。结果表明:(1)所有根段中都有菌丝团定植,共分离出菌根真菌64株,其中63株为胶膜菌科(Tulasnellaceae)真菌,1株为角担菌科(Ceratobasidiaceae)真菌;可划分为7个OUT,每个OTU代表菌株的菌丝都能形成OrMF典型的近球形或椭球形链状排列的念珠状细胞;分离出来的菌根真菌均为无性型菌丝且不产生无性孢子。(2) 非培养法得到的3种杓兰属植物的根中OrMF分别隶属于胶膜菌科(Tulasnellaceae),腊壳菌科(Sebacinaceae)、角担菌科(Ceratobasidiaceae)和革菌科(Thelephoraceae),其中胶膜菌科OTU在种类和数量上占有绝对优势,培养和非培养2种方法得到的OrMF OTU类型和数量均为西藏杓兰(Cypripedium tibeticum)>无苞杓兰(C. flavum)>黄花杓兰(C. bardolphianum),但培养法少于非培养法。(3)对胶膜菌进行系统发育分析显示,优势和非优势OTU均分布在系统发育树的3个不同分支上,这种与多种亲缘关系较远的OrMF共生的现象可能与杓兰属植物对环境的适应性有关,且不同杓兰的OrMF物种丰富度没有显著差异,但群落结构存在差异。     

High specificity generally characterizes mycorrhizal association in rare lady's slipper orchids, genus Cypripedium

Lady's slipper orchids (Cypripedium spp.) are rare terrestrial plants that grow throughout the temperate Northern Hemisphere. Like all orchids, they require mycorrhizal fungi for germination and seedling nutrition. The nutritional relationships of adult Cypripedium mycorrhizae are unclear; however, Cypripedium distribution may be limited by mycorrhizal specificity, whether this specificity occurs only during the seedling stage or carries on into adulthood. We attempted to identify the primary mycorrhizal symbionts for 100 Cypripedium plants, and successfully did so with two Cypripedium calceolus, 10 Cypripedium californicum, six Cypripedium candidum, 16 Cypripedium fasciculatum, two Cypripedium guttatum, 12 Cypripedium montanum, and 11 Cypripedium parviflorum plants from a total of 44 populations in Europe and North America, yielding fungal nuclear large subunit and mitochondrial large subunit sequence and RFLP (restriction fragment length polymorphism) data for 59 plants. Because orchid mycorrhizal fungi are typically observed without fruiting structures, we assessed fungal identity through direct PCR (polymerase chain reaction) amplification of fungal genes from mycorrhizally colonized root tissue. Phylogenetic analysis revealed that the great majority of Cypripedium mycorrhizal fungi are members of narrow clades within the fungal family Tulasnellaceae. Rarely occurring root endophytes include members of the Sebacinaceae, Ceratobasidiaceae, and the ascomycetous genus, Phialophora. C. californicum was the only orchid species with apparently low specificity, as it associated with tulasnelloid, ceratobasidioid, and sebacinoid fungi in roughly equal proportion. Our results add support to the growing literature showing that high specificity is not limited to nonphotosynthetic plants, but also occurs in photosynthetic ones.     

Mixotrophy of Platanthera minor, an orchid associated with ectomycorrhiza-forming Ceratobasidiaceae fungi

? We investigated the fungal symbionts and carbon nutrition of a Japanese forest photosynthetic orchid, Platanthera minor, whose ecology suggests a mixotrophic syndrome, that is, a mycorrhizal association with ectomycorrhiza (ECM)-forming fungi and partial exploitation of fungal carbon. ? We performed molecular identification of symbionts by PCR amplifications of the fungal ribosomal DNA on hyphal coils extracted from P. minor roots. We tested for a (13)C and (15)N enrichment characteristic of mixotrophic plants. We also tested the ectomycorrhizal abilities of orchid symbionts using a new protocol of direct inoculation of hyphal coils onto roots of Pinus densiflora seedlings. ? In phylogenetic analyses, most isolated fungi were close to ECM-forming Ceratobasidiaceae clades previously detected from a few fully heterotrophic orchids or environmental ectomycorrhiza surveys. The direct inoculation of fungal coils of these fungi resulted in ectomycorrhiza formation on P. densiflora seedlings. Stable isotope analyses indicated mixotrophic nutrition of P. minor, with fungal carbon contributing from 50% to 65%. ? This is the first evidence of photosynthetic orchids associated with ectomycorrhizal Ceratobasidiaceae taxa, confirming the evolution of mixotrophy in the Orchideae orchid tribe, and of ectomycorrhizal abilities in the Ceratobasidiaceae. Our new ectomycorrhiza formation technique may enhance the study of unculturable orchid mycorrhizal fungi.     

Mycorrhizal fungal community composition in seven orchid species inhabiting Song Mountain,Beijing, China

Mycorrhizal fungi play an important role in the germination and growth of orchids essentially influencing their survival,abundance, and spatial distribution. In this study, we investigated the composition of the mycorrhizal fungal community in seven terrestrial orchid species inhabiting Song Mountain, Beijing, China, using Illumina MiSeq high-throughput sequencing. The mycorrhizal communities in the seven orchids were mainly composed of members of the Ceratobasidiaceae, Sebacinales, and Tulasnellaceae, while a number of ectomycorrhizal fungi belonging to the Russulaceae, Tricholomataceae, Thelephoraceae, and Cortinariaceae were occasionally observed. However, the dominant fungal associates and mycorrhizal community differed significantly among the orchid species as well as subhabitats. These findings confirm the previous observation that sympatric orchid species show different preferences for mycorrhizal fungi, which may drive niche partitioning and contribute to their cooccurrence.     

Two widespread green Neottia species (Orchidaceae) show mycorrhizal preference for Sebacinales in various habitats and ontogenetic stages

Plant dependence on fungal carbon (mycoheterotrophy) evolved repeatedly. In orchids, it is connected with a mycorrhizal shift from rhizoctonia to ectomycorrhizal fungi and a high natural ¹³C and ¹⁵N abundance. Some green relatives of mycoheterotrophic species show identical trends, but most of these remain unstudied, blurring our understanding of evolution to mycoheterotrophy. We analysed mycorrhizal associations and ¹³C and ¹⁵N biomass content in two green species, Neottia ovata and N. cordata (tribe Neottieae), from a genus comprising green and nongreen (mycoheterotrophic) species. Our study covered 41 European sites, including different meadow and forest habitats and orchid developmental stages. Fungal ITS barcoding and electron microscopy showed that both Neottia species associated mainly with nonectomycorrhizal Sebacinales Clade B, a group of rhizoctonia symbionts of green orchids, regardless of the habitat or growth stage. Few additional rhizoctonias from Ceratobasidiaceae and Tulasnellaceae, and ectomycorrhizal fungi were detected. Isotope abundances did not detect carbon gain from the ectomycorrhizal fungi, suggesting a usual nutrition of rhizoctonia‐associated green orchids. Considering associations of related partially or fully mycoheterotrophic species such as Neottia camtschatea or N. nidus‐avis with ectomycorrhizal Sebacinales Clade A, we propose that the genus Neottia displays a mycorrhizal preference for Sebacinales and that the association with nonectomycorrhizal Sebacinales Clade B is likely ancestral. Such a change in preference for mycorrhizal associates differing in ecology within the same fungal taxon is rare among orchids. Moreover, the existence of rhizoctonia‐associated Neottia spp. challenges the shift to ectomycorrhizal fungi as an ancestral pre‐adaptation to mycoheterotrophy in the whole Neottieae.     

Molecular identifications uncover diverse fungal symbionts of Pleione (Orchidaceae)

Fungal mutualisms are essential for the evolution and diversification of Orchidaceae, yet the fungal symbionts of Pleione orchids are poorly understood because molecular data are unavailable for this genus. Based on ITS-rDNA sequencing for mycobionts of 15 Pleione species (both wild and cultivated plants were included), we conducted phylogenetic analyses for the most dominant mycobionts, and compared the operational taxonomic units (OTUs) of mycorrhizal fungi among species within Pleione. Tulasnellaceae, Ceratobasidiaceae, Serendipitaceae (Sebacinales), Atractiellales, and Auriculariales were reported as putative mycobionts of Pleione. In particular, the mycorrhizal associations between subtropical orchids and Atractiellales have not been observed before. For the dominant mycobionts in the roots of Pleione and its related genera, Bletilla and Coelogyne, we detected no fungal OTU that was shared. Within Pleione, species with a sympatric distribution showed preferences for different fungi. Epiphytic and lithophytic individuals of Pleione albiflora shared OTUs of Tulasnellaceae but harbored different OTUs of Sebacinales, indicating some degree of fungal specificity toward certain habitats. These findings provide new insights into the ecological adaptation and evolution of orchids, and will contribute to the conservation and utilization of species resources.     

Specificity and preference of mycorrhizal associations in two species of the genus Dendrobium (Orchidaceae)

Dendrobium is a large genus of tropical epiphytic orchids. Some members of this genus are in danger of extinction across China. To investigate orchid mycorrhizal associations of the genus Dendrobium, plants from two Dendrobium species (Dendrobium officinale and Dendrobium fimbriatum) were collected from two habitats in Guangxi Province, China, and clone libraries were constructed to identify the mycorrhizal fungi of individual plants. A low and high degree of specificity was observed in D. officinale and D. fimbriatum, respectively. Phylogenetic analysis revealed that the majority of Dendrobium mycorrhizal fungi are members of the Tulasnellaceae, but, in some plants, members of the Ceratobasidiaceae and Pluteaceae were also found. In D. officinale, individual plants associated with more than three fungi simultaneously, and, in some cases, associations with five fungi at the same time. One fungus was shared by individual plants of D. officinale collected from the two habitats. In D. fimbriatum, only one fungal partner was found in each population, and this fungus differed between populations. The two species of Dendrobium sampled from the same habitat did not share any fungal taxa. These results provide valuable information for conservation of these orchid species.     

兰科植物种子共生萌发真菌多样性及共生萌发机制研究进展

自然环境下,兰科植物种子细小无胚乳,需要和适宜的真菌共生才能萌发,因而与真菌有天然的共生关系。自身繁殖率低加之近年来栖息地环境破坏导致兰科植物资源更加濒危,而通过筛选适合的真菌进行种子的共生萌发可以有效地实现兰科植物的种质保育及濒危种类野生居群的生态恢复。本文对地生型、附生型以及腐生型等兰科植物已发现的萌发真菌的多样性进行了系统地梳理,发现担子菌门的胶膜菌科、角担菌科以及蜡壳耳目真菌为已报道共生萌发真菌的主要类群;同时对兰科植物种子的共生萌发机制,包括形态学机制、营养机制和分子机制等方面的相关研究进行了归纳论述,但是当前关于兰科植物和真菌互作机制方面的研究还相对较少,许多问题需要进一步明确。本文对共生萌发真菌在兰科植物保育和繁育中的应用以及共生萌发机制的研究等方面具有一定的参考价值。     

High diversity of root-associated fungi isolated from three epiphytic orchids in southern Ecuador

Knowledge of fungal root-associates is essential for effective conservation of tropical epiphytic orchids. We investigated the diversity of root-associated fungi of Cyrtochilum myanthum, Scaphyglottis punctulata and Stelis superbiens from a tropical mountain rainforest in southern Ecuador, using a culture dependent approach. We identified 115 fungal isolates, corresponding to 49 fungal OTUs, based on sequences of the nrDNA ITS and partial 28S region. Members of Ascomycota were unambiguously dominant (37 OTUs), including Trichoderma sp. as the most frequent taxon. Members of Basidiomycota (Agaricales and Polyporales) and Mucoromycota (Umbelopsidales and Mortierellales) were also identified. Four potential mycorrhizal OTUs of Tulasnellaceae and Ceratobasidiaceae were isolated from C. myanthum and S. superbiens. Fungal community composition was examined using Sørensen and Jaccard indices of similarity. Alfa diversity was significantly different between C. myanthum and S. superbiens. No difference in beta diversity of the fungal communities between the 3 orchid species and the collecting sites was detected. The study revealed a high diversity of fungi associated with orchid roots. Our results contribute to a better understanding of specific relationships between epiphytic orchids and their root-associated fungi.     

Mycorrhizal interactions of orchids colonizing Estonian mine tailings hills

Northeastern Estonia is home to extensive oil shale mines. Associated with these are desolate and environmentally damaging hills of ash and semicoke tailings. Interestingly, some of the first plants to colonize these hills are rare orchids. Here, we assess the identities of the mycorrhizal fungi associated with these orchids, in particular Epipactis atrorubens, Orchis militaris, and Dactylorhiza baltica, and compare them with mycorrhizal fungi from orchids from pristine habitat. Epipactis atrorubens associated with the widest breadth of fungi, including unnamed members of the basidiomycete family Tulasnellaceae and the potentially ectomycorrhizal ascomycetes Trichophaea woolhopeia and Geopora cooperi. Orchis militaris also associated with unnamed members of the Tulasnellaceae. Dactylorhiza baltica associated with Ceratobasidium albasitensis. In Epipactis and Orchis, the same fungi associated with plants in the pristine habitat as with those on ash hills. The tulasnelloid and ceratobasidioid fungi mycorrhizal with these orchids appear closely related to common orchid mycorrhizal fungi, while one of the ascomycetes mycorrhizal with E. atrorubens is closely related to a mycorrhizal fungus with E. microphylla. Our results suggest that these orchids and their fungi are not limited to pristine habitats and that environmentally polluted sites may present novel habitats that may be exploited for endangered plant conservation.     

Colonization patterns of mycorrhizal fungi associated with two rare orchids, <Emphasis Type="Italic">Cephalanthera</Emphasis> <Emphasis Type="Italic">falcata</Emphasis> and <Emphasis Type="Italic">C. erecta</Emphasis>

We investigated the spatial distribution and taxonomic identity of mycorrhizal fungi colonizing the root systems of two threatened Cephalanthera species, C. falcata and C. erecta, in naturally regenerated forests. Peloton formation was observed in both plant species, confirming the existence of orchid mycorrhizas. For C. falcata, mycorrhization was significantly different among individuals, ranging from 14 to 63%, and no significant difference among C. erecta individuals was detected (57–68%). Mycorrhization among three growth directions of roots and between orchid species was not significantly different. The spatial distribution of mycorrhizas in both orchids showed significant differences, being most frequent at an apical position. Based on DNA sequencing and phylogenetic analyses, we inferred that the families Thelephoraceae and Sebacinaceae were mycobionts for C. falcata and Thelephoraceae for C. erecta. Our findings indicated that mycorrhizal colonization occurs at a distal position from the base of these orchid root systems and that mycorrhizal fungi are restricted to few ectomycorrhizal fungal families.     

Analysis of network architecture reveals phylogenetic constraints on mycorrhizal specificity in the genus Orchis (Orchidaceae)

The specificity of orchids for their fungi can vary substantially, from highly specialist interactions to more generalist interactions, but little is known about the evolutionary history of the mycorrhizal specificity of orchids. Here, we used a network analysis approach to investigate orchid mycorrhizal associations in 16 species of the genus Orchis sampled across 11 different regions in Europe. We first examined in detail the structure of the network of associations and then tested for a phylogenetic signal in mycorrhizal specificity and identified the fungi with which the orchids associated. We found 20 different fungal lineages that associated with species of the genus Orchis, most of them being related to members of the Tulasnellaceae (84.33% of all identified associations) and a smaller proportion being related to members of the Ceratobasidiaceae (9.97%). Species associations formed a nested network that is built on asymmetric links among species. Evolution of mycorrhizal specificity in Orchis closely resembles a Brownian motion process, and the interaction between Orchis and Tulasnellaceae fungi is significantly influenced by the phylogenetic relationships between the Orchis species. Our results provide evidence of the presence of phylogenetic conservatism in mycorrhizal specificity in orchids and demonstrate that evolutionary processes may be an important factor in generating patterns of mycorrhizal associations.     

The impact of life form on the architecture of orchid mycorrhizal networks in tropical forest

Understanding the processes that determine the architecture of interaction networks represents a major challenge in ecology and evolutionary biology. One of the most important interactions involving plants is the interaction between plants and mycorrhizal fungi. While there is a mounting body of research that has studied the architecture of plant–fungus interaction networks, less is known about the potential factors that drive network architecture. In this study, we described the architecture of the network of interactions between mycorrhizal fungi and 44 orchid species that represented different life forms and co‐occurred in tropical forest and assessed the relative importance of ecological, evolutionary and co‐evolutionary mechanisms determining network architecture. We found 87 different fungal operational taxonomic units (OTUs), most of which were members of the Tulasnellaceae. Most orchid species associated with multiple fungi simultaneously, indicating that extreme host selectivity was rare. However, an increasing specificity towards Tulasnellaceae fungal associates from terrestrial to epiphytic and lithophytic orchids was observed. The network of interactions showed an association pattern that was significantly modular (M = 0.7389, M_random = 0.6998) and nested (NODF = 5.53, p < 0.05). Terrestrial orchids had almost no links to modules containing epiphytic or lithophytic orchids, while modules containing epiphytic orchids also contained lithophytic orchids. Within each life form several modules were observed, suggesting that the processes that organize orchid–fungus interactions are independent of life form. The overall phylogenetic signal for both partners in the interaction network was very weak. Overall, these results indicate that tropical orchids associate with a wide number of mycorrhizal fungi and that ecological rather than phylogenetic constraints determine network architecture.     

High specificity of a rare terrestrial orchid toward a rare fungus within the North American tallgrass prairie

The Orchidaceae are globally distributed and represent a diverse lineage of obligate mycotrophic plants. Given their dependence on symbiotic fungi for germination and/or plant development, fungal community structure in substrates is expected to influence the distribution and persistence of orchid species. Yet, simultaneous characterization of orchid mycorrhizal fungal (OMF) communities in roots and in soil is rarely reported. To explain the co-distributions of OMF in roots, orchid-occupied, and bulk soil, we characterized mycorrhizal fungi associated with Platanthera praeclara over multiple years across its entire natural distribution within the North American tallgrass prairie. Root derived OMF communities included 24 Ceratobasidiaceae and 7 Tulasnellaceae operational taxonomic units (OTUs) though the orchid exhibited high spatio-temporal specificity toward a single Ceratobasidiaceae OTU, which was strongly stable across population sizes and phenological stages of the sampled individuals. The preferred OMF OTUs were primarily restricted to orchid-occupied locations while infrequent or absent in bulk soil. Variation in soil OMF assemblies was explained most by soil moisture, magnesium, manganese, and clay. In this first study of coupled root and soil OMF communities across a threatened grassland ecosystem, we report a strong relationship, further nuanced by soil chemistry, between a rare fungus and a rare orchid.     

Low specificity and nested subset structure characterize mycorrhizal associations in five closely related species of the genus Orchis

Most orchid species rely on mycorrhizae to complete their life cycle. Despite a growing body of literature identifying orchid mycorrhizal associations, the nature and specificity of the association between orchid species and mycorrhizal fungi remains largely an open question. Nonetheless, better insights into these obligate plant–fungus associations are indispensable for understanding the biology and conservation of orchid populations. To investigate orchid mycorrhizal associations in five species of the genus Orchis (O. anthropophora, O. mascula, O. militaris, O. purpurea, and O. simia), we developed internal transcribed spacer‐based DNA arrays from extensive clone library sequence data sets, enabling rapid and simultaneous detection of a wide range of basidiomycetous mycorrhizal fungi. A low degree of specificity was observed, with two orchid species associating with nine different fungal partners. Phylogenetic analysis revealed that the majority of Orchis mycorrhizal fungi are members of the Tulasnellaceae, but in some plants, members of the Thelephoraceae, Cortinariaceae and Ceratobasidiaceae were also found. In all species except one (O. mascula), individual plants associated with more than one fungus simultaneously, and in some cases, associations with ≥3 mycorrhizal fungi at the same time were identified. Nestedness analysis showed that orchid mycorrhizal associations were significantly nested, suggesting asymmetric specialization and a dense core of interactions created by symmetric interactions between generalist species. Our results add support to the growing literature that multiple associations may be common among orchids. Low specificity or preference for a widespread fungal symbiont may partly explain the wide distribution of the investigated species.     

长茎羊耳蒜菌根真菌类群的研究

研究了广西雅长自然保护区和云南西双版纳自然保护区共3个产地的兰科植物羊耳蒜属长茎羊耳蒜Liparis viridiflora的菌根真菌类群区系组成.根内菌根真菌的核糖体基因内转录间隔区序列(rDNA-ITS)采用PCR技术扩增,克隆,测序并构建系统发育树.结果表明,长茎羊耳蒜根内所检测到的真菌大部分为胶膜菌科Tulasnellaceae真菌;根据序列相似性和系统发育分析,所有真菌可归为12个可操作分类单元(OTU),其中胶膜菌科有7个OTUs,达到总数的90.6%,为优势类群.菌根真菌多样性及区系组成在3个不同产地样本之间存在一定的差异;菌根真菌可能和兰科植物的生境适应性存在一定的相关性.     

Phylogenetic constrains on mycorrhizal specificity in eight Dendrobium(Orchidaceae) species

Plant phylogeny constrains orchid mycorrhizal(OrM) fungal community composition in some orchids. Here, we investigated the structures of the OrM fungal communities of eight Dendrobium species in one niche to determine whether similarities in the OrM fungal communities correlated with the phylogeny of the host plants and whether the Dendrobium-OrM fungal interactions are phylogenetically conserved. A phylogeny based on DNA data was constructed for the eight coexisting Dendrobium species,and the OrM fungal communities were characterized by their roots. There were 31 different fungal lineages associated with the eight Dendrobium species. In total, 82.98% of the identified associations belonging to Tulasnellaceae, and a smaller proportion involved members of the unknown Basidiomycota(9.67%). Community analyses revealed that phylogenetically related Dendrobium tended to interact with a similar set of Tulasnellaceae fungi. The interactions between Dendrobium and Tulasnellaceae fungi were significantly influenced by the phylogenetic relationships among the Dendrobium species. Our results provide evidence that the mycorrhizal specificity in the eight coexisting Dendrobium species was phylogenetically conserved.