Host associations and beta diversity of fungal endophyte communities in New Guinea rainforest trees

Processes shaping the distribution of foliar fungal endophyte species remain poorly understood. Despite increasing evidence that these cryptic fungal symbionts of plants mediate interactions with pathogens and herbivores, there remain basic questions regarding the extent to which dispersal limitation and host specificity might shape fungal endophyte community composition in rainforests. To assess the relative importance of spatial pattern and host specificity, we isolated fungi from a sample of mapped trees in lowland Papua New Guinea. Sequences of the internal transcribed spacer (ITS) region were obtained for 2079 fungal endophytes from three sites and clustered into molecular operational taxonomic units (MOTUs) at 95% similarity. Multivariate analyses suggest that host affinity plays a significant role in structuring endophyte community composition whereas there was no evidence of endophyte spatial pattern at the scale of tens to hundreds of metres. Differences in endophyte communities between sampled trees were weakly correlated with variation in foliar traits but not with tree species relatedness. The dominance of relatively few generalist endophytes and the presence of a large number of rare MOTUs was a consistent observation at three sites separated by hundreds of kilometres and regional turnover was low. Host specificity appears to play a relatively weak but more important role than dispersal limitation in shaping the distribution of fungal endophyte communities in New Guinea forests. Our results suggest that in the absence of strong ecological gradients and host turnover, beta diversity of endophyte communities could be low in large areas of contiguous forest.     

How does the Fungal Endophyte Neotyphodium coenophialum Affect Tall Fescue (Festuca arundinacea) Rhizodeposition and Soil Microorganisms?

The goal of our study was to investigate the impact of fungal endophytes in tall fescue (Festuca arundinacea) on rhizodeposition and in turn, the soil microbial community. Sand-based, aseptic microlysimeter units were constructed for the collection of rhizodeposit solutions for chemical analyses from the roots of endophyte-free (E−) and endophyte-infected (E+) tall fescue plants. E+ plants were infected with Neotyphodium coenophialum, the most common endophyte found in tall fescue. Rhizodeposit solutions collected over nine weeks from E+ grass contained more organic carbon and carbohydrates than E−. These solutions were allowed to percolate through columns of plant-free soils to assess the response of the soil microbial communities. Soils to which solutions from E+ grass were applied had significantly higher respiration rates than those receiving solutions from E− grass, suggesting that microbial activity was stimulated by changes in the rhizodeposits. Culture-based assays of the soil microbial community (plate counts and community-level physiological profiling) suggest that the basic structure of the microbial community was not affected by application of rhizodeposit solutions from E+ plants as compared to E−. Our results indicate that the presence of a fungal endophyte may enhance rhizodeposition by tall fescue and could consequently influence microbial mineralization processes in the soil. In grasslands where nutrients may be limiting, hosting a fungal endophyte has the potential to enhance plant nutrient supply indirectly via a stimulatory effect on the soil microbial biomass. Megan M. Van Hecke and Amy M. Treonis - Both authors contributed equally to this work.     

Fungal endophyte communities in four Rhizophoraceae mangrove species on the south coast of China

This study investigated the taxonomic identities and diversity of fungal endophytes isolated from four Rhizophoraceae mangrove plant species, Ceriops tagal, Rhizophora apiculata, R. stylosa and Bruguiera sexangula var. rhynchopetala, using a combination of morphological and molecular approaches. Two hundred ninety-five isolates were classified into 38 taxa by morphological characteristics. The representative 38 isolates from each taxa were selected for further molecular identification using nuclear ribosomal DNA sequences, including both the internal transcribed spacers (ITS1 and ITS2) and the 5.8S gene region. The 38 representative endophytes were identified to various taxonomic levels. These results suggest that Pestalotiopsis and Phomopsis were the most frequent endophytes in the four host species. Some of the endophytes exhibit host and tissue specificity. The colonization frequencies of endophytic fungi in the stems of the four host plants are evidently higher than in the roots. The four Rhizophoraceae mangrove species have low similarities of endophyte communities.     

Consequences of simultaneous interactions of fungal endophytes and arbuscular mycorrhizal fungi with a shared host grass

Plants simultaneously associate with multiple microbial symbionts throughout their lifetimes. To address the question of whether the effects of simultaneous symbionts are contingent on the specific identities, we conducted a greenhouse experiment manipulating the presence and identities of arbuscular mycorrhizal fungi (AMF) and fungal endophytes on the shared host grass Elymus hystrix. Each plant host was inoculated with one of two AMF species having varying effects on host growth, or a sterile soil control. Further, we used naturally occurring endophyte‐infected (E+) and uninfected (E–) individuals from two populations of the endophyte Epichloë elymi that varied in their interaction with E. hystrix. We then measured responses of plants, AMF, and fungal endophytes. Overall, we found that the combined effects of AMF and fungal endophytes on plant growth were additive, reflecting the mutualistic quality of each symbiont independently interacting with host plants. However, fungal endophyte infection differentially altered hyphal colonization of the two AMF species and the identity of the coinfecting AMF species affected fungal endophyte fitness traits. The results of this study demonstrate that the outcome of interspecific symbiotic interactions varies with partner identity such that the effects of simultaneous symbioses can not be generalized.     

醉马草内生真菌共生体研究进展

有关醉马草(Achnatherum inebrians)内生真菌(Epichloë gansuensis, E. inebrians)共生体的研究, 代表了我国禾草内生真菌研究领域的重要方向, 使中国的醉马草-内生真菌与美国的苇状羊茅(Festuca arundinacea)-内生真菌(E. coenophiana)和新西兰的多年生黑麦草(Lolium perenne)-内生真菌(E. festucae var. lolii)成为禾草内生真菌国际三大研究分支。该文综述了近30年来对醉马草内生真菌共生体的系统研究, 包括: 内生真菌的分布、带菌率、检测方法、多样性, 内生真菌提高宿主的抗旱、耐寒、耐盐碱、耐重金属、抗虫、抗病等抗逆性及其机理, 共生体产生的生物碱等次生代谢物, 对草食动物的毒性, 及其在草地生态系统中的作用等。研究者实验证实了醉马草本身无毒, 只有当内生真菌与醉马草共生并产生麦角新碱和麦角酰胺等麦角类生物碱后才能导致采食醉马草家畜中毒。文章展望了醉马草内生真菌基因组学和功能分析, 利用杀菌剂杀死内生真菌进行醉马草脱毒, 利用无毒内生真菌菌株进行饲用醉马草新品种选育, 利用有毒醉马草内生真菌共生体进行抗虫防鸟的机场绿化新品种选育及生物源农药与医药开发等。     

Advances in research of Achnatherum inebrians-Epichloë endophyte symbionts

有关醉马草(Achnatherum inebrians)内生真菌(Epichloë gansuensis, E. inebrians)共生体的研究, 代表了我国禾草内生真菌研究领域的重要方向, 使中国的醉马草-内生真菌与美国的苇状羊茅(Festuca arundinacea)-内生真菌(E. coenophiana)和新西兰的多年生黑麦草(Lolium perenne)-内生真菌(E. festucae var. lolii)成为禾草内生真菌国际三大研究分支。该文综述了近30年来对醉马草内生真菌共生体的系统研究, 包括: 内生真菌的分布、带菌率、检测方法、多样性, 内生真菌提高宿主的抗旱、耐寒、耐盐碱、耐重金属、抗虫、抗病等抗逆性及其机理, 共生体产生的生物碱等次生代谢物, 对草食动物的毒性, 及其在草地生态系统中的作用等。研究者实验证实了醉马草本身无毒, 只有当内生真菌与醉马草共生并产生麦角新碱和麦角酰胺等麦角类生物碱后才能导致采食醉马草家畜中毒。文章展望了醉马草内生真菌基因组学和功能分析, 利用杀菌剂杀死内生真菌进行醉马草脱毒, 利用无毒内生真菌菌株进行饲用醉马草新品种选育, 利用有毒醉马草内生真菌共生体进行抗虫防鸟的机场绿化新品种选育及生物源农药与医药开发等。     

Do the costs and benefits of fungal endophyte symbiosis vary with light availability?

? Here, we examined whether fungal endophytes modulated host plant responses to light availability. First, we conducted a literature review to evaluate whether natural frequencies of endophyte symbiosis in grasses from shaded habitats were higher than frequencies in grasses occupying more diverse light environments. Then, in a glasshouse experiment, we assessed how four levels of light and the presence of endophyte symbioses affected the growth of six grass species. ? In our literature survey, endophytes were more commonly present in grasses restricted to shaded habitats than in grasses from diverse light environments. ? In the glasshouse, endophyte symbioses did not mediate plant growth in response to light availability. However, in the host grass, Agrostis perennans, symbiotic plants produced 53% more inflorescences than nonsymbiotic plants at the highest level of shade. In addition, under high shade, symbiotic Poa autumnalis invested more in specific leaf area than symbiont-free plants. Finally, shade increased the density of the endophyte in leaf tissues across all six grass species. ? Our results highlight the potential for symbiosis to alter the plasticity of host physiological traits, demonstrate a novel benefit of endophyte symbiosis under shade stress for one host species, and show a positive association between shade-restricted grass species and fungal endophytes.     

Genetic Diversity and Structure of Neotyphodium Species and Their Host Achnatherum sibiricum in a Natural Grass–Endophyte System

Achnatherum sibiricum (Poaceae) is a perennial bunchgrass native to the Inner Mongolia Steppe of China. This grass is commonly infected by epichloë endophytes with high-infection frequencies. Previously, we identified two predominant Neotyphodium spp., N. sibiricum and N. gansuense. In the present study, genetic diversity and structure were analyzed for the two predominant Neotyphodium spp. as well as the host grass. We obtained 103 fungal isolates from five populations; 33 were identified as N. sibiricum and 61 as N. gansuense. All populations hosted both endophytic species, but genetic variation was much higher for N. gansuense than for N. sibiricum. The majority of fungal isolates were haploid, and 13% of them were heterozygous at one SSR locus, suggesting hybrid origins of those isolates. Significant linkage disequilibrium of fungal SSR loci suggested that both fungal species primarily propagate by clonal growth through plant seeds, whereas variation in genetic diversity and the presence of hybrids in both endophytic species revealed that although clonal propagation was prevalent, occasional recombination might also occur. By comparing genetic differentiation among populations, we found around 4–7-fold greater differentiation of endophyte populations than host populations, implying more restricted gene flow of endophytes than hosts. We proposed that endophyte infection of A. sibiricum might confer the host some selective advantages under certain conditions, which could help to maintain high-endophyte-infection frequencies in host populations, even when their gene flows do not match each other. Furthermore, we suggested that the same genotype of endophyte as well as host should be confirmed if the objective of the study is to know the influence of endophyte or host genotype on their symbiotic relationship, instead of just considering whether the plant is infected by an endophyte or not, since endophytes from the same host species could exhibit high levels of genetic diversity, which is likely to influence the outcome of their symbiotic relationship.     

Grass species and their fungal symbionts affect subsequent forage growth

Persistence of forage grasses is enhanced through the deliberate and selective use of symbiotic fungal endophytes that confer benefits, particularly pest resistance. However, they have also been implicated in reduced plant community diversity as a result of directly or indirectly enhancing competitive ability. A relatively underexplored mechanism by which endophytes might influence pasture plant composition is by altering the biotic or abiotic soil conditions. To examine the soil conditioning effects of forage grass species and their fungal symbionts we tested the responses of three pasture plants, perennial ryegrass, prairie grass, and white clover in nine different soils that had been conditioned by monocultures of endophyte-containing (E+), or endophyte-free (E?), perennial ryegrass, tall fescue, or meadow fescue. Conditioning grass species had little effect on the responses of perennial ryegrass and prairie grass regardless of E+ or E? treatments. In contrast, conditioning species had a strong effect on the response of white clover, resulting in reduced biomass when grown in perennial ryegrass conditioned soils. The presence of endophyte also had significant growth consequences for white clover, but was either positive or negative depending on the conditioning grass species. In comparison to their respective E? treatments, E+ tall and meadow fescue conditioned soils resulted in reduced biomass of white clover, whereas E+ perennial ryegrass conditioned soils resulted in increased biomass of white clover. Among the conditioning strains (AR1, AR37, NEA2, WE) of E+ perennial ryegrass, white clover showed significantly different responses, but all responses were positive in comparison to the E? treatment. By examining the effects of several grass species and endophyte strains, we were able to determine the relative importance of grass species vs. fungal symbiont on soil conditioning. Overall, the conditioning effect of grass species was stronger than the effects associated with endophyte, particularly with regard to the response of white clover. We conclude that both grass species and their fungal endophytes can influence pasture plant community composition through plant–soil feedback.     

Genetic diversity in epichloid endophytes of Hordelymus europaeus suggests repeated host jumps and interspecific hybridizations

Epichloid fungal endophytes (Epichloë and Neotyphodium spp.) are excellent model systems for studying speciation processes because of their variable life history traits that are linked to host grass fitness. Presumed jumps to new hosts and subsequent somatic hybridizations appear to be common among epichloid endophytes resulting in increased genetic variation upon which selection can act and speciation be initiated. In this study, we explored the endophyte diversity of a rare European native woodland grass species, Hordelymus europaeus, along a latitudinal transect covering the entire distribution range of H. europaeus. From 28 populations in six countries, isolates were sampled and molecularly characterized. Based on the sequences of tubB and tefA, six distinct epichloid taxa (interspecific hybrid or cryptic haploid species) were found, of which four were novel and two have been previously reported from this host. Of the novel endophytes, two were presumed to be interspecific hybrids and two of nonhybrid origin. While previously known endophytes of H. europaeus are seed‐born and strictly asexual, one of the novel nonhybrid endophytes found in the glacial refugium of the Apennine peninsula reproduced sexually in cultured plants. This is the first case of a seed‐borne, but sexually reproducing endophyte of this host. We discuss the origin, and possible ancestral species, of the six epichloid taxa using phylogenetic analyses. Repeated host jumps and somatic hybridizations characterize the diversity of the endophytes. To date, no other grass species is known to host a larger diversity of endophytes than H. europaeus.     

Fungal endophytes of a forage grass reduce faecal degradation rates

Mutualisms between fungal endophytes and forage grasses can exert broad-reaching effects on grassland communities and ecosystem processes. We hypothesised that endophytes of grasses would retard the process of faecal degradation since grazing animals consume primarily live plant material and excrete a large portion of the herbage they consume as faeces. We examined the degradation rates of faeces from sheep that had consumed pure swards of perennial ryegrass containing a range of unique strains (AR1, AR37, or Wild type) of the fungal endophyte, Neotyphodium lolii, or no endophyte. Ultimately, the presence of endophytes in perennial ryegrass resulted in slower faecal decay rates compared to the nil endophyte treatment, although only consistently for the C concentration decay rates that were approximately 2× to 4× slower in the endophyte-derived faecal matter. The decay rate of dry matter content was significantly slower (ca. 1.5×) in the novel endophyte-derived faeces (AR1 and AR37) compared to the nil endophyte-derived faeces. The N decay rates differed significantly only in the AR1 treatment that was approximately 4× slower than the nil endophyte group. The reduced decay rates are attributed to the presence of endophyte-derived alkaloids in the faeces, and a greater proportion of more easily degraded hemicellulose in faeces from sheep that consumed the endophyte-free grass. There were no significant differences in the faecal carbon and nitrogen decay rates among the three endophyte strain treatments. This suggests that all the strain-specific alkaloids might have similar effects, or that N. lolii has a general effect that is not strain-specific, such as altered fibre composition, as reported here. This is the first report of a fungal endophyte affecting the rate of faecal degradation, and the first report of the alkaloids peramine, lolitrem B and epoxy–janthitrems in faecal matter. This study shows that a common agronomic grass–endophyte mutualism can have effects on ecosystem processes that have not previously been considered.     

Effects of grassland management,endophytic fungi and predators on aphid abundance in two distinct regions

Aims Fungal endophytes of cool-season grass species produce alkaloids toxic to herbivores, affecting food webs in agricultural and natural ecosystems. Field studies about the effects of endophytes on herbivores are rare and show contradictory results, leading to uncertain conclusions about the nature of endophyte–grass symbiosis. We asked whether the environmental contexts of local and regional scales and predation could modify the effects of endophytes on herbivores.Methods In a full factorial field experiment, we quantified the abundance of the aphid species Rhopalosiphum padi on the potted host grass Lolium perenne, which was either infected or uninfected with the endophytic fungus Neotyphodium lolii. Predators were either excluded or had free access to the pots with the aphids. One hundred and sixty grass pots were located in two regions on altogether 40 grassland sites, half of the sites intensively and half extensively managed. We tested the importance of endophyte infection, study region, management intensity of grasslands, predation and all two-way interactions on aphid abundance.Important findings Endophyte infection reduced aphid abundance significantly in one study region only. In both regions, we found that the impacts of aphidophagous predators and grassland management intensity on aphid abundance were substantially stronger and more consistent than that of endophytes on aphid abundance. Pots excluding predators and pots placed on extensive grasslands contained higher aphid abundance. The impact of predators and management on aphid abundance were not modified by the endophyte. We conclude that the effect of endophytes on herbivores can be weak in field experiments and depends on environmental context at a regional scale. Hence, more field research efforts are necessary to detect the relative importance of endophytes and the environmental context on biotic interactions in ecosystems.     

禾草内生真菌的遗传多样性及其共生关系

 近百年的禾草内生真菌研究历经了由浅入深的过程,从最初的家畜中毒事件认识到是一种共生内生真菌存在的缘故,到如今利用分子生物学技术揭示其共生机制,人类发现这类植物内生真菌并非想象中的对生态系统无足轻重。Epichloë及其无性型Neotyphodium与禾本科植物是系统发生的互利共生关系,尤其是Neotyphodium可提高宿主抵抗环境胁迫的能力和抵御动物的取食,增强植物的竞争力。禾草内生真菌有3种生活史：有性生活史、无性生活史和兼性生活史,后者表明真菌在不同的宿主及环境下既能营有性生殖也可营无性繁殖,是一种更灵活而有效的生活史对策。对内生真菌分子系统学、生活史以及与宿主禾草协同进化的研究发现,Neotyphodium起源于禾草致病真菌Epichloë的某些种,或是Epichloë与Neotyphodium的种间杂交后代。植物和内生真菌各异的生活史策略,真菌的种间杂交,两者的协同进化亦或种群间基因流的差异,都促成了共生体多样化的基因组合（Genetic combination ）,也是其共生关系多样化的根源。内生真菌对宿主的有益作用只在特定基因型真菌、宿主和一定环境条件下才起作用,自然生态系统的共生关系要比农业系统复杂得多,是一个从互利共生至寄生关系的连续系统。未来对于更多共生体的遗传背景和基因与环境相互作用的阐明将有助于对禾草内生真菌共生关系本质更加深入的认识。     

禾本科植物内生真菌资源及其物种多样性

植物内生真菌是当代微生物资源研究的一个热门话题,对禾本科植物内生真菌资源研究进行了总结。与冷季型禾本科植物共生的麦角菌科epichlo内生真菌是目前的研究重点,包括偶尔在宿主植物体表形成子座的Epichlo属真菌和几乎完全不形成症状的Neotyphodium属真菌。具体介绍该真菌类群的物种多样性及其地理分布多样性,概括了它们在全球各大区域的分布特征。对近年来中国迅速发展的epichlo内生真菌的研究作了总结,最后展望了国际国内epichlo内生真菌资源探索的发展方向。特别指出:冷季型禾本科植物内生真菌在南美洲和亚洲,暖季型禾本科植物内生真菌在热带亚热带地区的研究还相对薄弱,值得今后继续加强探索和挖掘。     

Vertically transmitted fungal endophytes: different responses of host-parasite systems to environmental conditions

The relationship between vertically transmitted asexual fungal grass endophytes and their hosts is considered to be mutualistic. Results from agronomic field support this line of reasoning but recent studies have shown more variable results in natural systems. We investigated how high and low nutrient and water treatments affected biomass allocation patterns of endophyte‐infected and uninfected Festuca pratensis and F. rubra in greenhouse experiments over two growing seasons. Irrespective of infection status, both grass species showed improved performance on highly fertilized and watered soils. However, infected F. pratensis plants produced larger tillers than endophyte‐free plants on soil low in nutrients and water in the first growing season, although they (E+) otherwise showed decreased performance on nutrient‐poor soil. In low nutrient and water conditions, endophyte‐infected plants produced less tillers and had lower total biomass compared to uninfected plants, and displayed a negative phenotypic correlation between seed production and vegetative growth. The latter indicates costs of reproduction when the plant shares common resources with the fungal endophyte. However, endophyte infection status (E+, E?) interacted significantly with the soil fertilisation in terms of plant growth, having a stronger positive effect on growth in infected F. pratensis plants. In F. rubra, endophyte‐infected plants showed higher vegetative growth in fertilized and watered soils compared to uninfected plants. However, infected plants tended to produce fewer inflorescences. This had no effect on seed production, perhaps because seed production was partly replaced by asexual pseudovivipary. Contrary to the general assumption in the literature that fungal endophytes are plant mutualists, these findings suggest that the costs of endophytes may outweigh their benefits in resource limited conditions. However, the costs of endophyte infections appear to differ among the grass species studied; costs of endophytes were mainly detected in F. pratensis under low nutrient conditions. We propose that differences in response to endophyte infection in these species may depend on the differences in life‐history strategies and environmental requirements of these two fescue and fungal species and may change during the life span of the plant.     

Community analysis of Persian oak fungal microbiome under dust storm conditions

Dust storms have major effects on terrestrial ecosystems through the long-distance transport and deposition of particulate matter. It is unclear how dust deposition affects plant-associated microbiomes in downwind ecosystems. Here we show that dust deposition may negatively influence the isolation, richness, and diversity of endophytic fungal communities of Persian oak. We used culture-based methods paired with Sanger sequencing to examine these effects on fungal assemblages isolated from leaf, branch and deposited dust. Increased amounts of dust deposition led to decreased endophytic fungal diversity in plant tissues but increased fungal diversity in deposited dust layers on leaves. Dust deposition decreased the abundance of a dominant endophyte in branches with promising biocontrol properties. Endophytic fungal communities found in leaves were more similar to fungal assemblages of deposited dust in comparison to branch endophytes. Our results suggest that dust storms may have ecosystem-wide effects by altering the fungal microbiomes of forest-forming trees.     

Endophytic fungal communities in woody perennials of three tropical forest types of the Western Ghats,southern India

Fungal endophytes of tropical trees are expected to be exceptionally species rich as a consequence of high tree diversity in the tropics and the purported host restriction among the endophytes. Based on this premise, endophytes have been regarded as a focal group for estimating fungal numbers because their possible hyperdiverse nature would reflect significantly global fungal diversity. We present our consolidated ten-year work on 75 dicotyledonous tree hosts belonging to 33 families and growing in three different types of tropical forests of the NBR in the Western Ghats, southern India. We conclude that endophyte diversity in these forests is limited due to loose host affiliations among endophytes. Some endophytes have a wide host range and colonize taxonomically disparate hosts suggesting adaptations in them to counter a variety of defense chemicals in their hosts. Furthermore, such polyphagous endophytes dominate the endophyte assemblages of different tree hosts. Individual leaves may be densely colonized but only by a few endophyte species. It appears that the environment (the type of forest in this case) has a larger role in determining the endophyte assemblage of a plant host than the taxonomy of the host plant. Thus, different tropical plant communities have to be studied for their endophyte diversity to test the generalization that endophytes are hyperdiverse in the tropics, estimate their true species richness, and use them as a predictor group for more accurate assessment of global fungal diversity.     

Endophytic fungi increase the processing rate of leaves by leaf‐cutting ants (Atta)

1. Fungal endophytes are microfungi that reside asymptomatically inside of leaf tissues, increasing in density and diversity through time after leaves flush. Previous studies have suggested that the presence of fungal endophytes in the harvest material of leaf‐cutting ants (Atta colombica, Guérin‐Méneville) may negatively affect the ants and their fungal cultivar. 2. In the present study, it was tested whether the presence and diversity of fungal endophytes affected the amount of time necessary for leaf‐cutter ants to cut, process, and plant leaf material in their fungal garden. It was found that ants took 30–43% longer to cut, carry, clean, and plant leaf tissue with high relative to low endophyte abundance, and that the ants responded similarly to leaf tissue with high or low endophyte diversity. 3. It was further investigated whether the fungal cultivars' colonisation rate was greater on leaf material without fungal endophytes. No difference in the ants' cultivar colonisation rate on leaf tissue with high or low endophyte abundance was observed.     

Environmental filtering structures fungal endophyte communities in tree bark

The factors that control the assembly and composition of endophyte communities across plant hosts remains poorly understood. This is especially true for endophyte communities inhabiting inner tree bark, one of the least studied components of the plant microbiome. Here, we test the hypothesis that bark of different tree species acts as an environmental filter structuring endophyte communities, as well as the alternative hypothesis, that bark acts as a passive reservoir that accumulates a diverse assemblage of spores and latent fungal life stages. We develop a means of extracting high‐quality DNA from surface sterilized tree bark to compile the first culture‐independent study of inner bark fungal communities. We sampled a total of 120 trees, spanning five dominant overstorey species across multiple sites in a mixed temperate hardwood forest. We find that each of the five tree species harbour unique assemblages of inner bark fungi and that angiosperm and gymnosperm hosts harbour significantly different fungal communities. Chemical components of tree bark (pH, total phenolic content) structure some of the differences detected among fungal communities residing in particular tree species. Inner bark fungal communities were highly diverse (mean of 117–171 operational taxonomic units per tree) and dominated by a range of Ascomycete fungi living asymptomatically as putative endophytes. Together, our evidence supports the hypothesis that tree bark acts as an environmental filter structuring inner bark fungal communities. The role of these potentially ubiquitous and plant‐specific fungal communities remains uncertain and merits further study.     

Fungal endophyte communities in two tropical forests of southern India: diversity and host affiliation

Fifteen tree species from a tropical dry thorn forest and fifteen tree species from a tropical dry deciduous forest in the Mudumalai Wildlife Sanctuary, Nilgiri Biosphere Reserve, southern India, were surveyed for their foliar endophyte communities during the dry and wet seasons. Surface sterilized leaf segments of uniform dimension were plated on nutrient agar and culturable endophytes growing from the segments were identified. Endophyte diversity was greater in the dry thorn forest than in the dry deciduous forest in the dry season. Although the isolation frequency of culturable endophytes increased for both forests during the wet season, the assemblages were represented not by any unique fungal species but by the commonly occurring ones. Furthermore, although individual leaves were densely colonized by endophytes, only a few species of endophytes colonized the whole leaves; and, only a few fungal species dominated the foliar endophytic communities and were common for both forests during both dry and wet seasons. Thus, even under wet conditions that favour dispersal and infection by fungi, the endophyte diversity increased only marginally, an indication that certain tropical forests are not hyperdiverse with reference to fungal endophytes. This should be considered when using culturable endophyte diversity as a surrogate for estimating global fungal diversity.