藏北高寒草原针茅属植物AM真菌的物种多样性

基于AMF孢子形态学鉴定,对藏北高寒草原4种针茅菌根际土壤进行了研究,结果表明:(1)高原寒、旱环境下,Glomus属真菌在不同针茅菌根际AM真菌种群构成中的地位和作用非常突出,其孢子密度、种数、相对多度和重要值均显著(P≤0.05)大于Acaulospora、Scutellospora属。(2)针茅属植物种类对AM真菌物种多样性具有重要影响,广布种沙生针茅Shannon-Weiner指数、物种均匀度指数相对最高(分别为1.79和0.72),其次分别为羽柱针茅、紫花针茅和昆仑针茅;青藏高原特有针茅属植物菌根际AMF的繁殖能力相对较强,羽柱针茅、紫花针茅、昆仑针茅孢子密度分别较沙生针茅提高57.8%、48.7%,62.4%。(3)不同针茅菌根际土壤中,同种AM真菌(共有种)和优势种(F>50%)较多、优势种种类差异很大的种群分布特征,体现了AM真菌种群构成的复杂性,以及AMF对高原寒旱环境的高度适应性、协同性。(4)不同针茅菌根际AMF优势种相对多度高达78.2%-92.4%(平均为85.7%),对AM真菌的群落构成具有重要作用。其中,G. claroideum孢子密度即占4类针茅AM真菌优势种的50.2%-71.9%。     

AM真菌与植物共生的生理生化效应研究进展

丛枝菌根真菌是广泛分布的一类土壤微生物,与植物共生后,能够促进宿主对土壤中矿质元素的吸收,调节宿主体内的代谢活动,增强植物的抗逆性,促进植物生长,增加作物产量,改善作物品质,本文综述了上述方面的研究进展和取得的主要成就。     

环境因子和AM真菌分布的关系

由我国东、南沿海七省２７８个土样中的９０８个ＡＭ真菌种次分析了ＡＭ真菌属和种的分布和７种环境因子的关系。球囊霉属在各种环境下均占绝对多数,巨囊霉属＋盾巨囊霉属则为最少,球囊霉属在各ｐＨ水平土壤中分布较均匀;而其它四属主要出现在ｐＨ低于７的土壤中,摩西球囊霉Ｃ．ｍｏｓｓｅａｅ（Ｎｏｃｏｌ．＆Ｇｅｒｄ）Ｇｅｒｄｅｍａｎｎ＆Ｔｒａｐｐｅ在ｐＨ低于５的土壤中仍能发现。所有五属ＡＭ真菌的出现率都随土壤有机质     

AM真菌在植物病虫害生物防治中的作用机制

丛枝菌根(Arbuscular Mycorrhizae,AM)真菌是一类广泛分布于土壤生态系统中的有益微生物,能与大约80%的陆生高等植物形成共生体。由土传病原物侵染引起的土传病害被植物病理学界认定为最难防治的病害之一。研究表明,AM真菌能够拮抗由真菌、线虫、细菌等病原体引起的土传性植物病害,诱导宿主植物增强对病虫害的耐/抗病性。当前,利用AM真菌开展病虫害的生物防治已经引起生态学家和植物病理学家的广泛关注。基于此,围绕AM真菌在植物病虫害生物防治中的最新研究进展,从AM真菌改变植物根系形态结构、调节次生代谢产物的合成、改善植物根际微环境、与病原微生物直接竞争入侵位点和营养分配、诱导植株体内抗病防御体系的形成等角度,探究AM真菌在植物病虫害防治中的作用机理,以期为利用AM真菌开展植物病虫害的生物防治提供理论依据,并对本领域未来的发展方向和应用前景进行展望。     

极旱荒漠植物对AM真菌物种多样性的影响

2015年7月在甘肃安西极旱荒漠国家级自然保护区采集膜果麻黄Ephedra przewalskii、红砂Reaumuria songarica、合头草Sympegma regelii、泡泡刺Nitraria sphaerocarpa和珍珠猪毛菜Salsola passerine 5种典型荒漠植物根区土壤样品,分析了植物种类对arbuscular mycorrhiza(AM)真菌群落组成和生态分布的影响。在分离的7属45种AM真菌中包括无梗囊霉属Acaulospora 17种,球囊霉属Glomus 13种,这两属是5种植物共同优势属;盾巨孢囊霉属Scutellospora 5种,管柄囊霉属Funneliformis 4种,根内根生囊霉属Rhizophagus 3种,近明囊霉属Claroideoglomus 2种,多孢囊霉属Diversispora1种。主成分分析研究说明5种植物根区AM真菌群落组成和物种多样性差异显著。结果表明,植物种类对AM真菌群落组成和分布特征影响显著。     

蒙古沙冬青伴生植物AM真菌的空间分布

进一步探究荒漠植物与AM(arbuscular mycorrhiza)真菌共生关系及其生态适应性,为以蒙古沙冬青为建群种适生区的植被恢复与生态改良提供依据。于2013年6月在内蒙古荒漠带选取以蒙古沙冬青为建群种的3个样地乌海、磴口和阿拉善,从每个样地选择2种主要伴生植物,按0—10、10—20、20—30、30—40、40—50 cm共5个土层采集土样和根样,研究了蒙古沙冬青伴生植物AM真菌空间分布及其与土壤因子的关系。从梭梭(Haloxylon ammodendron)、油蒿(Artemisia ordosica)、柠条锦鸡儿(Caragana korshinskii)和蒙古扁桃(Amygdalus mongolica)4种伴生植物根围土壤共分离鉴定4属25种AM真菌,其中球囊霉属(Glomus)14种,无梗囊霉属(Acaulospora)7种,管柄囊霉属(Funneliformis)3种,盾巨孢囊霉属(Scutellospora)1种,优势菌种为网状球囊霉(Glomus reticulatum),AM真菌属种分布具有不均衡性和地域性。4种伴生植物根系均能与AM真菌形成I-型(intermediate type)丛枝菌根,其共生程度和定殖规律具有明显空间异质性。AM真菌种数随土层深度增加而下降。AM真菌最大定殖率在10—30 cm土层,最大孢子密度在10—20 cm土层。相关性分析表明,AM真菌菌丝与土壤有机C极显著正相关(P0.01),与易提取球囊霉素(EEG)显著负相关(P0.05);孢子密度与有机C、碱性磷酸酶极显著负相关(P0.01),与碱解N极显著正相关(P0.01)。主成分分析表明,土壤有效P、酸性磷酸酶、碱性磷酸酶和总球囊霉素(TEG)等土壤因子能综合反映内蒙古荒漠带营养状况。TEG和EEG平均含量分别为4.76 mg/g和1.62 mg/g,占土壤有机C平均含量为61.26%和20.8%,说明在贫瘠荒漠环境中球囊霉素是土壤有机碳库重要来源和组成部分。     

蒙古沙冬青及其伴生植物AM真菌物种多样性

于2015年7月在内蒙古乌海、磴口2个样地选取蒙古沙冬青(Ammopiptanthus mongolicus)及其伴生植物为研究对象,分别采集0-20 cm和20-40 cm土层根围土样,利用高通量测序方法分析了不同植物AM真菌群落结构和物种多样性,发掘新物种,为补充和完善AM真菌分类体系提供依据。试验共分离鉴定3纲5目6科9属89个AM真菌OTU,属包括Glomus,Funneliformis,Diversispora,Claroideoglomus,Rhizophagus,Septoglomus,Scutellospora,Ambispora和Paraglomus。与形态学研究结果相比,高通量鉴定结果在属水平上更丰富。同一土层不同样地,蒙古沙冬青AM真菌丰度和多样性指数高于伴生植物;同一土层不同植物,AM真菌丰度和多样性指数表现为磴口高于乌海;同一植物不同样地,AM真菌ACE指数和Chao1指数20-40 cm土层高于0-20 cm土层,Simpson指数和Shannon指数0-20 cm土层高于20-40 cm土层。RDA分析表明,AM真菌ACE指数和Chao1指数与土壤碱解N显著正相关,与酸性磷酸酶显著负相关;Simpson指数和Shannon指数与碱性磷酸酶显著正相关,与pH显著负相关。结果表明,蒙古沙冬青AM真菌物种多样性高于伴生植物,同一样地,寄主植物与土壤深度共同作用对AM真菌群落组成有显著影响。     

城市生态系统中AM真菌侵染与群落结构特征

丛枝菌根(AM)真菌作为土壤微生物的重要成员之一,对城市生态系统可持续发展具有重要意义.本文系统总结了城市生态系统中AM真菌着生状况和群落结构特点,探讨了城市生态因子,如人类行为、植被重建与维护、城市土壤状况等对AM真菌着生状况和群落结构的影响,认为今后应加强城市生态系统中AM真菌群落结构与功能的研究,如关键城市生态因子(如水资源匮乏、热岛效应等)改变AM真菌群落结构的效应与机制.     

龙脑香科植物AM真菌的初步研究

对我国云南和海南龙脑香科植物的天然原始林和人工林AM真菌资源进行了调查,对从46处龙脑香林采回的19种龙脑香科树种的根系和根际土壤样品,分别进行显微观察和分离AM真菌的孢子,发现在所调查的19个树种中,所有树种的根系都有不同程度的AM真菌的侵染,高者可达50％平均为21％,其中在大多数根样中发现有泡囊生成;对土壤样品的分析,分离到大量的孢子,其袍子密度从7—132个／20ml土样不等,平均为58个。对所分离到的孢子进行鉴定,发现无梗囊霉属和球囊霉属的孢子占大多数,其频度和相对多度分别为33．25和46．89;18．04和30．80。研究结果表明,龙脑香科不仅仅能够形成外生菌根,而且也能象大多数热带林木一样能够广泛的形成丛枝菌根。     

Phylogenetic trait conservatism and the evolution of functional trade-offs in arbuscular mycorrhizal fungi

The diversity of functional and life-history traits of organisms depends on adaptation as well as the legacy of shared ancestry. Although the evolution of traits in macro-organisms is well studied, relatively little is known about character evolution in micro-organisms. Here, we surveyed an ancient and ecologically important group of microbial plant symbionts, the arbuscular mycorrhizal (AM) fungi, and tested hypotheses about the evolution of functional and life-history traits. Variation in the extent of root and soil colonization by AM fungi is constrained to a few nodes basal to the most diverse groups within the phylum, with relatively little variation associated with recent divergences. We found no evidence for a trade-off in biomass allocated to root versus soil colonization in three published glasshouse experiments; rather these traits were positively correlated. Partial support was observed for correlated evolution between fungal colonization strategies and functional benefits of the symbiosis to host plants. The evolution of increased soil colonization was positively correlated with total plant biomass and shoot phosphorus content. Although the effect of AM fungi on infection by root pathogens was phylogenetically conserved, there was no evidence for correlated evolution between the extent of AM fungal root colonization and pathogen infection. Variability in colonization strategies evolved early in the diversification of AM fungi, and we propose that these strategies were influenced by functional interactions with host plants, resulting in an evolutionary stasis resembling trait conservatism.     

Phylogenetic comparative approaches for studying niche conservatism

Analyses of phylogenetic niche conservatism (PNC) are becoming increasingly common. However, each analysis makes subtly different assumptions about the evolutionary mechanism that generates patterns of niche conservatism. To understand PNC, analyses should be conducted with reference to a clear underlying model, using appropriate methods. Here, we outline five macroevolutionary models that may underlie patterns of PNC (drift, niche retention, phylogenetic inertia, niche filling/shifting and evolutionary rates) and link these to published phylogenetic comparative methods. For each model, we give recent examples from the literature and suggest how the methods can be practically applied. We hope that this will help clarify the niche conservatism literature and encourage people to think about the evolutionary models underlying niche conservatism in their study group.     

真菌内共生细菌研究进展

自真菌内共生细菌在1970年被首次发现以来,各个时期的学者都采用当时流行的研究方法关注宿主真菌及其内共生细菌之间的关联现象。近年来科技手段日益多样,对二者相互作用的探索逐渐成为新的研究热点,随着研究的不断拓展和深入,越来越多的生物学现象和原理被揭示。本文在真菌内共生细菌的研究方法、定殖位置、形态、分类、宿主类群、共生关联的建立、生物学功能、宿主治愈、分离和重新植入等方面进行综述,并在此基础上进行展望,以期为真菌内共生细菌的广泛深入研究提供借鉴。     

Phylogeny,niche conservatism and the latitudinal diversity gradient in mammals

Biologists have long searched for mechanisms responsible for the increase in species richness with decreasing latitude. The strong correlation between species richness and climate is frequently interpreted as reflecting a causal link via processes linked to energy or evolutionary rates. Here, we investigate how the aggregation of clades, as dictated by phylogeny, can give rise to significant climate–richness gradients without gradients in diversification or environmental carrying capacity. The relationship between climate and species richness varies considerably between clades, regions and time periods in a global-scale phylogenetically informed analysis of all terrestrial mammal species. Many young clades show negative richness–temperature slopes (more species at cooler temperatures), with the ages of these clades coinciding with the expansion of temperate climate zones in the late Eocene. In carnivores, we find steeply positive richness–temperature slopes in clades with restricted distributions and tropical origins (e.g. cat clade), whereas widespread, temperate clades exhibit shallow, negative slopes (e.g. dog–bear clade). We show that the slope of the global climate–richness gradient in mammals is driven by aggregating Chiroptera (bats) with their Eutherian sister group. Our findings indicate that the evolutionary history should be accounted for as part of any search for causal links between environment and species richness.