Spatial patterns of fungal endophytes in a subtropical montane rainforest of northern Taiwan

Fungal endophytes of plants are ubiquitous and important to host plant health. Wood-inhabiting and foliar endophyte communities from multiple tree hosts were sampled at multiple spatial scales across the Fushan forest dynamics plot in northern Taiwan, using culture-free, community DNA amplicon sequencing methods. Fungal endophyte communities were distinct between leaves and wood, but the mycobiomes were highly variable across and within tree species. Despite this, host tree species was an important predictor of mycobiome community-composition. Within a single common tree species, “core” mycobiomes were characterized using co-occurrence analysis. The spatial co-occurrence patterns of these few species of fungal endophytes appear to explain the strong host effect. For wood endophytes, a consistent core mycobiome coexisted with the host across the extent of the study. For leaf endophytes, the core fungi resembled a more dynamic, “gradient” model of the core microbiome, changing across the topography and distance of the study.     

Rare taxa maintain the stability of crop mycobiomes and ecosystem functions

Plants harbour highly diverse mycobiomes which sustain essential functions for host health and productivity. However, ecological processes that govern the plant–mycobiome assembly, interactions and their impact on ecosystem functions remain poorly known. Here we characterized the ecological role and community assembly of both abundant and rare fungal taxa along the soil–plant continuums (rhizosphere, phyllosphere and endosphere) in the maize–wheat/barley rotation system under different fertilization practices at two contrasting sites. Our results indicate that mycobiome assembly is shaped predominantly by compartment niche and host species rather than by environmental factors. Moreover, crop-associated fungal communities are dominated by few abundant taxa mainly belonging to Sordariomycetes and Dothideomycetes, while the majority of diversity within mycobiomes are represented by rare taxa. For plant compartments, the abundant sub-community is mainly determined by stochastic processes. In contrast, the rare sub-community is more sensitive to host selection and mainly governed by deterministic processes. Furthermore, our results demonstrate that rare taxa play an important role in fungal co-occurrence network and ecosystem functioning like crop yield and soil enzyme activities. These results significantly advance our understanding of crop mycobiome assembly and highlight the key role of rare taxa in sustaining the stability of crop mycobiomes and ecosystem functions.     

Changes in hydraulic traits of nine vascular plants from different evolutionary lineages北大核心CSCD

Aims As vascular plants evolve from ferns to gymnosperms and angiosperms, their physiological structures and functions are assumed more adaptable to arid environment. Whether the three plant groups from early to late evolved lineages have improved their water transport and use efficiency has been studied on the basis of the morphological structure of leaf veins and stomata.Moreover, the water transportation rate was directly measured in the angiosperms. Therefore, we measured structural and functional traits related to water relations in all three plant groups simultaneously, to test the hypothesis on the evolutionary process of plant hydraulics. Methods We selected three species in each group grown in South China Botanical Garden, Guangzhou, China, including ferns (Dicranopteris pedata, Cyclosorus parasiticus and Blechnum orientale), gymnosperms (Podocarpus macrophyllus, Podocarpus nagi and Taxodium distichum) and angiosperms (Manglietia fordiana var. hainanensis, Sindora tonkinensis and Bauhinia purpurea). Important findings Sapwood and leaf specific hydraulic conductivities (KS and KL, respectively), and leaf conductance (Kleaf) significantly increased from ferns, gymnosperms to angiosperms. However, no significant trends were found in transpiration rate (E) and intrinsic water use efficiency. Meanwhile, neither the size and density of stomata nor wood density showed significant difference among three plant groups. The hydraulic functional traits (KS, KL and Kleaf) had significantly positive correlations with each other, but had no relationships with the two measured structural traits. Phylogenetic independent contrasts analyses showed that the coordination between KS and Kleaf, and between KS and E were independent of the phylogeny. Based on the nine vascular species, this study demonstrated that water transport related traits are improved as vascular plants evolved, and the co-evolution between water transport and transpiration traits were identified. For further study, it is necessary to consolidate our data with investigations of more detailed water-transport structures in more species from different evolutionary lineages. © 2018 Editorial Office of Chinese Journal of Plant Ecology. All rights reserved.     

Are correlations among foliar traits in ferns consistent with those in the seed plants?

Broad-based studies of gymnosperms and angiosperms reveal consistent and functionally significant correlations among foliar traits such as leaf mass per area (LMA), maximum photosynthetic rate (A(area)), foliar nitrogen (N(area)), foliar chlorophyll (Chl) and leaf longevity. To assess the generality of these relationships, we studied 20 fern species growing in the understorey of a temperate deciduous forest. We found that foliar N(area) increases with LMA, and that foliar N(area) and A(area) are positively correlated with one another, as are foliar N(area) and Chl. The ferns in general have very low LMA compared with most seed plants; A(area), N(area) and Chl are below median values for seed plants but are not extreme. Species with overwintering fronds have significantly higher LMA than species with fronds that senesce at the end of the growing season, as well as a significantly higher C : N ratio in frond tissue and relatively high foliar N on an areal basis. Correlations among foliar traits associated with gas exchange in these forest understorey ferns are in accordance with patterns reported for seed plants, suggesting a high degree of functional constraint on the interrelationships among key elements in foliar design.     

Paleoclimatic Analysis of Paleogene Flora in Yilan County,Heilongjiang

Plant fossils were collected from the sand-shale above the lower coal seam and the upper oil shale above the upper coal seam in the Yilan coal mine, Heilongjiang. The floras contained 2 species of pteridophytes, 10 species of gymnosperms and over 58 species of angiosperms assigned to 46 genera and 34 families. The fossils were divided into two floras, one of which was in lower sand-shale beds, with the age assigned to the Eocene, and the other was in the upper part of oil shales considered to belong to the Oligocene. The floras were complicated in composition and rich in species, and were studied by means of floristic analysis, foliar architectural and physiognomical analysis. The Eocene flora consisted of many evergreen broad-leaved species, which indicated that the flora belonged to north subtropical evergreen broad-leaved forest or subtropical coniferous and broad-leaved mixed forest. The foliar physiognomical analysis of the floristic composition showed that the species with entire leaf margines made up 38.3 percent of the total. The climate in the Eocene was estimated by means of climatic nomogram as follow: The mean annual temperature was 13.2 ℃ and annual temperature deviancy was 20℃. In the Oligocene flora, deciduous broadleaved trees were dominant, which indicated that the vegetation was of temperate deciduous broad-leaved forest or warm temperate coniferous and deciduous broad-leaved mixed forest. The species with entire leaf margines were 30. 8 percent with an estimated mean annual temperature of 11 ℃ and mean annual temperature deviancy of 25 ℃. The floristic aspect and climate in the Paleogene of Yilan region were very different from the present ones.     

A global analysis of plant recovery performance from water stress

Plant post‐drought recovery performance is essential to predict shifts in ecosystem dynamics and production during frequent climate change‐driven drought events. Yet, it is not clear how post‐drought recovery is related to evolutionary and geographic variations in plants. In this study, we generated a global data set of post‐drought recovery performance in 140 plant species from published studies. We quantified the plant post‐drought recovery performance by calculating a recovery index for multiple plant physiological and hydraulic parameters, including leaf water potential, net photosynthetic rate, leaf hydraulic conductance and shoot biomass. The magnitude of recovery among four plant functional types (deciduous angiosperms, evergreen angiosperms, gymnosperms, and crops), two plant growth forms (shrubs and trees), two water management strategies (isohydric and anisohydric), four xylem porosity types (diffuse, ring, semi‐ring and tracheid), and four major biomes (dry sclerophyll forest, boreal forest, temperate forest and tropical/subtropical forest) were compared. We found the inability to completely recover immediately after severe water stress is ubiquitous across all plant functional types and growth forms, while the rate and magnitude of post‐drought recovery varied greatly across different plant taxonomic categories and geographic ranges. In general, plant hydraulic architecture, leaf anatomy and physiology affect plants’ propensity towards recovery, and reflect evolutionary consequences of plant adaptation to their habitat. Due to the essential role of plant functional traits in regulating carbon storage in each biome, a better understanding plant post‐drought recovery performance could improve our predictions on ecosystem productivity in a rapidly changing climate.     

Nitrogen use strategy drives interspecific differences in plant photosynthetic CO2 acclimation

Rising atmospheric CO₂ concentration triggers an emergent phenomenon called plant photosynthetic acclimation to elevated CO₂ (PAC). PAC is often characterized by a reduction in leaf photosynthetic capacity (A_sat), which varies dramatically along the continuum of plant phylogeny. However, it remains unclear whether the mechanisms responsible for PAC are also different across plant phylogeny, especially between gymnosperms and angiosperms. Here, by compiling a dataset of 73 species, we found that although leaf A_sat increased significantly from gymnosperms to angiosperms, there was no phylogenetic signal in the PAC magnitude along the phylogenetic continuum. Physio-morphologically, leaf nitrogen concentration (N_m), photosynthetic nitrogen-use efficiency (PNUE), and leaf mass per area (LMA) dominated PAC for 36, 29, and 8 species, respectively. However, there was no apparent difference in PAC mechanisms across major evolutionary clades, with 75% of gymnosperms and 92% of angiosperms regulated by the combination of N_m and PNUE. There was a trade-off between N_m and PNUE in driving PAC across species, and PNUE dominated the long-term changes and inter-specific differences in A_sat under elevated CO₂. These findings indicate that nitrogen-use strategy drives the acclimation of leaf photosynthetic capacity to elevated CO₂ across terrestrial plant species.     

九种维管植物水力性状的演化趋势

维管植物从蕨类植物、裸子植物到被子植物的演化过程中, 生理结构和功能都被认为更趋向于适应干旱的环境。但是关于3类植物是否提升了水分传导和水分利用效率的研究目前多基于叶脉和气孔的形态结构推断, 而对水分传导速率的直接测量则集中于被子植物内部。因此, 同时测定3类植物叶片和枝条尺度的水力性状, 可以研究维管植物水力性状的演化趋势和协同演化关系。该研究测定了中国科学院华南植物园内的蕨类植物(芒萁(Dicranopteris pedata)、华南毛蕨(Cyclosorus parasiticus)、乌毛蕨(Blechnum orientale)), 裸子植物(罗汉松(Podocarpus macrophyllus)、竹柏(Podocarpus nagi)、落羽杉(Taxodium distichum))和被子植物(海南木莲(Manglietia fordiana var. hainanensis)、东京油楠(Sindora tonkinensis)、羊蹄甲(Bauhinia purpurea))共9种植物的水力结构与功能的相关性状。发现9种植物从原始到更演化物种的枝条比导水率(K_S)、叶片比导水率(K_L)和叶片水力导度(K_leaf)依次升高; 叶片蒸腾速率(E)和潜在水分利用效率(WUE_i)升高趋势不显著; 气孔面积指数(SPI)和木材密度(WD)在3个类群间无明显变化趋势。水力功能性状在枝条(K_S)和叶片(K_L、K_leaf和E)尺度显著相关, 但和两个结构性状并无显著相关性。对显著相关的性状进行系统发育独立差分析发现相关性依然存在, 表明枝条导水和叶片导水、叶片失水的协同性独立于系统发育而存在。该文以9种维管植物为例, 发现演化过程中水分传导相关的功能性状有显著提升, 且导水和失水的性状存在着协同演化关系。上述维管植物水力性状演化趋势的结论需要对更多物种、更精细的水力结构性状的进行测定验证。     

Changes in hydraulic traits of nine vascular plants from different evolutionary lineages

维管植物从蕨类植物、裸子植物到被子植物的演化过程中, 生理结构和功能都被认为更趋向于适应干旱的环境。但是关于3类植物是否提升了水分传导和水分利用效率的研究目前多基于叶脉和气孔的形态结构推断, 而对水分传导速率的直接测量则集中于被子植物内部。因此, 同时测定3类植物叶片和枝条尺度的水力性状, 可以研究维管植物水力性状的演化趋势和协同演化关系。该研究测定了中国科学院华南植物园内的蕨类植物(芒萁(Dicranopteris pedata)、华南毛蕨(Cyclosorus parasiticus)、乌毛蕨(Blechnum orientale)), 裸子植物(罗汉松(Podocarpus macrophyllus)、竹柏(Podocarpus nagi)、落羽杉(Taxodium distichum))和被子植物(海南木莲(Manglietia fordiana var. hainanensis)、东京油楠(Sindora tonkinensis)、羊蹄甲(Bauhinia purpurea))共9种植物的水力结构与功能的相关性状。发现9种植物从原始到更演化物种的枝条比导水率(K_S)、叶片比导水率(K_L)和叶片水力导度(K_leaf)依次升高; 叶片蒸腾速率(E)和潜在水分利用效率(WUE_i)升高趋势不显著; 气孔面积指数(SPI)和木材密度(WD)在3个类群间无明显变化趋势。水力功能性状在枝条(K_S)和叶片(K_L、K_leaf和E)尺度显著相关, 但和两个结构性状并无显著相关性。对显著相关的性状进行系统发育独立差分析发现相关性依然存在, 表明枝条导水和叶片导水、叶片失水的协同性独立于系统发育而存在。该文以9种维管植物为例, 发现演化过程中水分传导相关的功能性状有显著提升, 且导水和失水的性状存在着协同演化关系。上述维管植物水力性状演化趋势的结论需要对更多物种、更精细的水力结构性状的进行测定验证。     

Species richness of sawfly–host plant associations at higher taxonomic levels

Insect–plant interactions are important to understanding the evolutionary mechanisms responsible for most of the diverse plant‐feeding insects. We aggregated data on sawfly–host plant associations and other resource associations from existing sources to address the following questions: (i) Is there a general correlation between host diversity and sawfly species richness? (ii) Is the pattern of host plant use consistent across sawfly lineages? and (iii) Is there a phylogenetically significant shift in species richness among sawflies? Our analysis comprised 8567 sawfly species, including 2087 species with host plant and other records. In total, there were 2126 records of host usage for sawflies, the overwhelming majority of which were sawflies using angiosperms as resources. Rosales are used by most of the species in sawfly families or subfamilies. We found that there was a strong correlation between the number of host plant orders and the species richness of sawfly families and subfamilies. To examine the points at which sawflies have experienced significant shifts in species richness, we compared sister taxon species richness. Several positive and negative shifts in species richness among sawflies were related to their range of host plant usage and specialized niche, respectively. In general, we found that most of the sawfly families and subfamilies used several orders as host plants, but mainly core eudicots, although some families or subfamilies were specialized on pteridophytes or gymnosperms.     

Trait syndromes among North American trees are evolutionarily conserved and show adaptive value over broad geographic scales

Adaptive syndromes and their evolutionary constraints represent a powerful construct for understanding plant distributions. However, it is unclear how the species requirements to face multiple stressors promotes syndrome formation and to which abiotic stressors these syndromes show adaptive value over broad geographic scales. We combined local occurrence data from the U.S. Forest Inventory and Analysis (FIA) of 219 angiosperm and 85 gymnosperm species living across the conterminous US with phylogenies and trait data to identify tree syndromes, their evolutionary conservatism, and their adaptive value over broad scales. Factor analyses and evolutionary model selection revealed that trees possess functional trait syndromes that are strongly conserved. Major syndromes at the species level differed between angiosperms and gymnosperms. While the two main syndromes in angiosperms were related to cold and drought‐waterlogging tolerance, in gymnosperms a trade‐off between shade and drought tolerance was the main syndrome followed by a growth‐fire resistance syndrome. Additional RLQ and fourth‐corner approaches revealed that trait syndromes at the community level were broadly similar to those observed at the species level for angiosperms, although this was less clear for gymnosperms. This suggests that syndrome evolution has played an important role on angiosperm distributions, whereas additional ecological factors explain gymnosperm distributions. Importantly, syndromes show adaptive value, as they were geographically associated with several environmental variables showing structure from continental to local scales, being temperature the main abiotic stressor. Our results indicate that across the conterminous US tree species possess clear syndromes that are subjected to strong evolutionary constraints driving tree species and forest community distribution.     

Oral Colonization of Fungi

Opportunistic microbes are able to exist as commensals or pathogens depending on local environmental conditions. The bacterial microbiome at mucosal sites (gut, oral and vaginal) has been well characterized but there has been less focus on the fungal component of the microbiome, the “mycobiome”, especially of the oral mucosa. Genomic characterization studies have shown that Candida species are the most prevalent fungal species in the mycobiomes of the murine gut and human oral cavity, with C. albicans being the most abundant fungal species in the oral cavity. In this review, we outline recent advances in the characterization of the oral mycobiome, how different Candida species colonize, invade and infect the oral cavity, and how epithelial surfaces play a key role in antifungal activity and discriminate between commensal and pathogenic Candida.     

Are functional traits and litter decomposability coordinated across leaves,twigs and wood? A test using temperate rainforest tree species

Synthesis This study compared the decomposability of leaf, twig and wood litter from 27 co‐occurring temperate rainforest tree species in New Zealand. We found that interspecific variation in decomposition was not coordinated across the three litter types. Analysis of the relationships between functional traits and decomposition revealed that traits predictive of wood decomposition varied among the species independently from traits predictive of the decomposition of leaf and twig litter. We conclude that efforts to understand how tree species influence C, N and P dynamics in forested ecosystems through the decomposition pathway need to consider the functional traits of multiple plant structures. Plant functional traits are increasingly used to evaluate changes in ecological and ecosystem processes. However our understanding of how functional traits coordinate across different plant structures, and the implications for trait‐driven processes such as litter decomposition, remains limited. We compared the functional traits of green leaves and leaf, twig and wood litter among 27 co‐occurring tree species from New Zealand, and quantified the loss of mass, N and P from the three litter types during decomposition. We hypothesised that: a) the functional traits of green leaves, and leaf, twig and wood litter are co‐ordinated so that species which produce high quality leaves and leaf litter will also produce high quality twig and wood litter, and b) the decomposability of leaf, twig and wood litter is coordinated because breakdown of all three litter types is driven by similar combinations of traits. Trait variation across species was co‐ordinated between leaves, twigs and wood when angiosperm and gymnosperm species were considered in combination, or when angiosperms were considered separately, but trait coordination was poor for gymnosperms. There was little coordination among the three litter types in their decomposability, especially when angiosperms and gymnosperms were considered separately; this was caused by the decomposability of each of the three litter types, at least partially, being driven by different functional traits or trait combinations. Our findings indicate that although interspecific variation in the functional traits of trees can be coordinated among leaves, twigs and wood, different or unrelated traits predict the decomposition of these different structures. Furthermore, leaf‐level analyses of functional traits are not satisfactory proxies for function of whole trees and related ecological processes. As such, efforts to understand how tree species influence C, N and P dynamics in forested ecosystems through the decomposition pathway need to consider functional traits of other plant structures.     

The relationship between nuclear DNA content and leaf strategy in seed plants

BACKGROUND AND AIMS: Species' 2C-values (mass of DNA in G(1) phase 2n nuclei) vary by at least four orders of magnitude among seed plants. The 2C-value has been shown to be co-ordinated with a number of other species traits, and with environmental variables. A prediction that species 2C-values are negatively related to leaf life span (LL) and leaf mass per area (LMA) is tested. These leaf traits are components of a major dimension of ecological variation among plant species. METHODS: Flow cytometry was used to measure the 2C-values for 41 Australian seed plant species, 40 of which were new to the literature. Where possible, LL and LMA data from the global literature were combined with 2C-values from our data set and online C-value databases. KEY RESULTS: Across all species, weak positive relationships were found between 2C-values and both LL and LMA; however, these did not reflect the relationships within either angiosperms or gymnosperms. Across 59 angiosperm species, there were weak negative relationships between 2C-values and both LL (r2 = 0.13, P = 0.005) and LMA (r2 = 0.15, P = 0.002). These relationships were the result of shifts to longer LL and greater LMA in woody compared with herbaceous growth forms, with no relationships present within growth forms. It was not possible to explain a positive relationship between 2C-values and LMA (r2 = 0.30, P = 0.024) across 17 gymnosperm species. The 2C-value was not related to LL or LMA either across species within orders (except for LMA among Pinales), or as radiation divergences in a model phylogeny. CONCLUSIONS: Gymnosperms appear to vary along a spectrum different from angiosperms. Among angiosperms, weak negative cross-species relationships were associated with growth form differences, and traced to a few divergences deep in the model phylogeny. These results suggest that among angiosperms, nuclear DNA content and leaf strategy are unrelated.     

Universal primers for amplification of three non-coding regions of chloroplast DNA

Six primers for the amplification of three non-coding regions of chloroplast DNA via the polymerase chain reaction (PCR) have been designed. In order to find out whether these primers were universal, we used them in an attempt to amplify DNA from various plant species. The primers worked for most species tested including algae, bryophytes, pteridophytes, gymnosperms and angiosperms. The fact that they amplify chloroplast DNA non-coding regions over a wide taxonomic range means that these primers may be used to study the population biology (in supplying markers) and evolution (inter- and probably intraspecific phylogenies) of plants.     

Community structure of ectomycorrhizal fungi across an alpine/subalpine ecotone

In order to assess changes in the community structure of ectomycorrhizal fungi across the tree line, data on distributions of fungi and their host plants, as well as on edaphic factors and stand age, were collected at two montane sites in the Front Range of the Canadian Rockies. Canonical correspondence analysis (CCA) was used to explore relationships between fungal species composition and environmental factors. Richness and diversity of ectomycorrhizal fungi decreased with elevation, in spite of the fact that host plant diversity was highest at the ecotone between the subalpine forest and the alpine zone. Both host plant distribution and edaphic factors were important in explaining the observed changes in fungal species diversity and composition. The majority of ectotnycorrhizal fungi found in the subalpine forest and at the ecotone were conifer associates, while a large proportion of those in the alpine zone were non-host specific and able to form mycorrhizae with both angiosperms and gymnosperms. The abundance of non-host specific fungi in the alpine zone is expected to provide a favorable environment for the establishment of conifer seedlings above the present tree line.     

Leaf energy balance modelling as a tool to infer habitat preference in the early angiosperms

Despite more than a century of research, some key aspects of habitat preference and ecology of the earliest angiosperms remain poorly constrained. Proposed growth ecology has varied from opportunistic weedy species growing in full sun to slow-growing species limited to the shaded understorey of gymnosperm forests. Evidence suggests that the earliest angiosperms possessed low transpiration rates: gas exchange rates for extant basal angiosperms are low, as are the reconstructed gas exchange rates for the oldest known angiosperm leaf fossils. Leaves with low transpirational capacity are vulnerable to overheating in full sun, favouring the hypothesis that early angiosperms were limited to the shaded understorey. Here, modelled leaf temperatures are used to examine the thermal tolerance of some of the earliest angiosperms. Our results indicate that small leaf size could have mitigated the low transpirational cooling capacity of many early angiosperms, enabling many species to survive in full sun. We propose that during the earliest phases of the angiosperm leaf record, angiosperms may not have been limited to the understorey, and that some species were able to compete with ferns and gymnosperms in both shaded and sunny habitats, especially in the absence of competition from more rapidly growing and transpiring advanced lineages of angiosperms.     

Mycorrhizal status of epiphytes in Malaysian oil palm plantations

Epiphytic plants were collected from four oil palm plantations in Peninsular Malaysia and their mycorrhizal status determined. Conspecific plants with a terrestrial habit (16 species) and rhizosphere soils were also examined for mycorrhizal colonization and glomalean fungi, respectively. Twelve species of glomalean fungi were recovered from the four oil palm plantation soils. Of the 29 epiphytic species in 16 families belonging to the bryophytes, pteridophytes and angiosperms, only four species of angiosperms that were facultative epiphytes and a hemiepiphyte growing within 0.4 m of ground level had vesicular-arbuscular mycorrhizal (VAM) fungi. Bioassays of organic debris from oil palm trunks did not produce vesicular-arbuscular mycorrhizas on maize. Six epiphytic species grown in the greenhouse in pots containing oil palm rhizosphere soils rooted and had VAM fungi and thus may be facultative epiphytes. Five other epiphyte species failed to grow in pots and are probably obligate epiphytes. Seven epiphyte species that established themselves in pots failed to form vesicular-arbuscular mycorrhizas.     

Correlation analysis between arbuscular mycorrhizal fungal community and host plant phylogeny

 为弄清丛枝菌根(arbuscular mycorrhiza, AM)真菌群落随宿主植物演化的变异规律,通过对MaarjAM数据库进行数据挖掘, 根据每个分子虚拟种(virtual taxa, VT)包含的DNA序列不少于5条的标准, 筛选出188种菌根植物。通过分析植物与其根内AM真菌的关系发现: AM真菌的物种丰富度随着寄主植物的分化而增加; 在不同的植物系统类群中, AM真菌的物种丰富度显著不同; 在起源时间较晚的被子植物和裸子植物中, AM真菌的物种丰富度显著高于起源较早的苔类、角苔类和蕨类植物类群, 而与寄生植物共生的AM真菌物种丰富度与早期植物无显著差异; 不同寄主植物进化类群间AM真菌组成差异显著。以上结果表明: AM真菌群落随着寄主植物进化而发生变化。在进化过程中, 寄主植物倾向于选择保留共生效率较高的AM真菌。     

Nuclear DNA Amounts in Pteridophytes

DNA amounts (C-value and genome size) are much-used biodiversitycharacters. A workshop held at Kew in 1997 identified majorgaps in our knowledge of plant DNA amounts, recommending targetsfor new work to fill them. Murray reviewed non-angiosperm plantsnoting that representation of pteridophyte species (approx.0.42%) was poor, while locating C-value data for them was verydifficult. The workshop confirmed the need to make data forother groups besides angiosperms accessible for reference purposes.This paper pools DNA C-values for 48 pteridophyte species fromeight original sources into one reference source, and fulfilsa key workshop recommendation for this group. Comparing thesedata shows that nuclear 1C-values in pteridophytes vary approx.1000-fold, from 0.055 pg in Selaginella species to about 55pg in Ophioglossum petiolatum. Genome size estimates for 25pteridophytes vary approx. 200-fold from 0.055 to 10.7 pg, andthe mean genome sizes in diploids and polyploids (5.15 and 4.59pg, respectively) are not significantly different. Wider comparisonsshow that ranges of genome sizes in the major groups of landplants are very different. Those in bryophytes and pteridophytesare narrow compared with those in gymnosperms and angiosperms.The data indicate that the origin of land plants possibly involveda first major increase in genome size in the evolution of vascularplants, while a second such increase occurred later in gymnosperms.C-values for pteridophytes remain very few, but conversely opportunitiesfor new work on them are many. Copyright 2001 Annals of BotanyCompany Pteridophyte DNA amounts, DNA C-values, nuclear genome sizes