Utility of plastid psaB gene sequences for investigating intrafamilial relationships within Orchidaceae

DNA sequences of the plastid gene psaB were completed for 182 species of Orchidaceae (representing 150 different genera) and outgroup families in Asparagales. These data were analyzed using parsimony, and resulting trees were compared to a rbcL phylogeny of Orchidaceae for the same set of taxa after an additional 30 new rbcL sequences were added to a previously published matrix. The psaB tree topology is similar to the rbcL tree, although the psaB data contain less homoplasy and provide greater bootstrap support than rbcL alone. In combination, the two-gene tree recovers the five monophyletic subfamilial clades currently recognized in Orchidaceae, but fails to resolve the positions of Cypripedioideae and Vanilloideae. These new topologies help to clarify some of the anomalous results recovered when rbcL is analyzed alone. Both genes appear to be absent from the plastid genome of several achlorophyllous orchids, but are present in the form of presumably non-functional pseudogenes in Cyrtosia. This study is the first to document the utility of psaB sequences for phylogenetic studies of plants below the family level.     

Further advances in orchid mycorrhizal research

Orchid mycorrhizas are mutualistic interactions between fungi and members of the Orchidaceae, the world’s largest plant family. The majority of the world’s orchids are photosynthetic, a small number of species are myco-heterotrophic throughout their lifetime, and recent research indicates a third mode (mixotrophy) whereby green orchids supplement their photosynthetically fixed carbon with carbon derived from their mycorrhizal fungus. Molecular identification studies of orchid-associated fungi indicate a wide range of fungi might be orchid mycobionts, show common fungal taxa across the globe and support the view that some orchids have specific fungal interactions. Confirmation of mycorrhizal status requires isolation of the fungi and restoration of functional mycorrhizas. New methods may now be used to store orchid-associated fungi and store and germinate seed, leading to more efficient culture of orchid species. However, many orchid mycorrhizas must be synthesised before conservation of these associations can be attempted in the field. Further gene expression studies of orchid mycorrhizas are needed to better understand the establishment and maintenance of the interaction. These data will add to efforts to conserve this diverse and valuable association.     

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.     

兰科植物欺骗性传粉

植物与传粉动物的互利关系在生态系统中非常普遍。然而,有许多植物不为传粉者提供任何报酬,而是利用各种欺骗方式诱骗昆虫拜访,从而实现传粉,即欺骗性传粉。兰科是被子植物大科之一,其高度特化的繁殖器官和适应于昆虫传粉的精巧结构令人称奇。进化论创始人达尔文描述了许多兰花与昆虫精巧的传粉系统,但他忽视了欺骗性传粉的存在。事实上,近1/3的兰科植物都依赖于欺骗性传粉。欺骗性传粉可能是导致兰科植物多样性的重要原因之一。兰花利用或操作昆虫觅食、交配、产卵和栖息等行为,演化出各种各样的欺骗性传粉机制,常见的类型包括泛化的食源性欺骗、Batesian拟态、性欺骗、产卵地拟态和栖息地拟态。花的颜色、形态和气味在欺骗性传粉的成功实现中起到了重要作用。欺骗性兰花与传粉昆虫之间的演化可能是不同步的,兰花追踪昆虫的行为信号而发生分化,然而欺骗性传粉可能对昆虫造成一定的伤害,从而对昆虫也施加选择压力。由于昆虫的学习行为,欺骗性的兰花一般具有低的昆虫拜访率和结实率,其繁殖成功率受各种因素的影响。欺骗性加剧了兰花对传粉昆虫的依赖,使其具有更高的灭绝风险,传粉生物学的研究能为兰科植物的有效保护提供指导。在欺骗性传粉系统中,有报酬的伴生植物、拟态模型和其他拟态信号提供者对传粉成功有重要影响。因此,研究欺骗性传粉兰花、传粉昆虫和相关的生物和生态因子的网状进化关系具有重要理论和实践意义。     

Speciation in the Orchidaceae: confronting the challenges

The Orchidaceae is renowned for its large number of species (19,500) and its many diverse, even bizarre, specialized pollination systems. One unusual feature of orchids is the high frequency of food deception whereby animal pollination is achieved without providing nectar, pollen or other food rewards. Food-deceptive pollination is estimated to occur in approximately one-third of all orchids. Equally intriguing is pollination by sexual deception whereby pollination is achieved by the sexual attraction of male insects to the orchid flower. Sexual deception is found in several hundred species representing multiple lineages. Given their rich species diversity and extraordinary plant-animal interactions, orchids clearly offer exciting research opportunities in pollination biology, reproductive isolation and speciation, yet surprisingly they remain under-represented in scientific investigations both in these fields and more generally. In this special issue of Molecular Ecology, Moccia et al. provide an exemplar study that combine multiple lines of evidence to illuminate the mechanism of reproductive isolation between two closely related food-deceptive orchids. Their study demonstrates that many of the challenges that confront orchid researchers and impede progress in our understanding of speciation in the Orchidaceae can be overcome by the creative application and integration of both old and new tools in ecology and genetics.     

Changing partners in the dark: isotopic and molecular evidence of ectomycorrhizal liaisons between forest orchids and trees

In the mycorrhizal symbiosis, plants exchange photosynthates for mineral nutrients acquired by fungi from the soil. This mutualistic arrangement has been subverted by hundreds of mycorrhizal plant species that lack the ability to photosynthesize. The most numerous examples of this behaviour are found in the largest plant family, the Orchidaceae. Although these non-photosynthetic orchid species are known to be highly specialized exploiters of the ectomycorrhizal symbiosis, photosynthetic orchids are thought to use free-living saprophytic, or pathogenic, fungal lineages. However, we present evidence that putatively photosynthetic orchids from five species which grow in the understorey of forests: (i) form mycorrhizas with ectomycorrhizal fungi of forest trees; and (ii) have stable isotope signatures indicating distinctive pathways for nitrogen and carbon acquisition approaching those of non-photosynthetic orchids that associate with ectomycorrhizal fungi of forest trees. These findings represent a major shift in our understanding of both orchid ecology and evolution because they explain how orchids can thrive in low-irradiance niches and they show that a shift to exploiting ectomycorrhizal fungi precedes viable losses of photosynthetic ability in orchid lineages.     

兰科菌根的生态学研究进展

兰科植物(Orchidaceae)是典型的菌根植物,自然条件下其种子的成功萌发和生长的早期阶段对菌根真菌有绝对的依赖性,在有些成年兰科植物中菌根真菌仍起着重要的作用。目前大部分兰科植物已为濒危物种,鉴于兰科植物天然的菌根共生关系,开展兰科植物和菌根真菌互作的生态学研究不仅具有极高的科研价值,更有助于兰科植物的物种保护和野生种群的生态恢复。近年研究表明,兰科植物对真菌的选择和二者共生关系的建立与菌根真菌的空间分布和丰度密切相关,然而当前对自然环境中兰科菌根真菌的实际分布还了解甚少,因此文章从生态学角度系统分析兰科植物与菌根真菌的关系,探讨该领域的研究热点,旨在为兰科菌根的生态学研究提供参考。     

菌根真菌与兰科植物互作的组学研究进展

兰科植物因其具有丰富的物种多样性和重要的社会经济价值,多年来一直是植物学及生态学界的重点研究对象.菌根真菌对兰科植物的种子萌发、营养吸收和种群动态等多个方面都具有十分重要的作用,因而近年来受到越来越多的关注.探究菌根真菌与兰科植物互作的内在机制是目前兰科菌根研究的一大热点领域,同时也为兰科植物野生资源保护和种群恢复提供...     

东南亚兰科植物的物种多样性、生活习性及其传粉系统（附表）

兰科(Orchidaceae)植物广布于除两极和极端沙漠地区外的各种陆地生态系统,包括5个亚科800多属28 000多种。东南亚地区兰科植物种数约占世界的1/3,是兰科植物生物多样性热点区域之一。通过查阅文献及书籍等资料,该文系统整理了东南亚兰科植物物种种类及其扩散演化历史,并对其生活习性和传粉系统进行了归类。结果表明:(1)东南亚兰科植物8 855种,分属5亚科17族26亚族240属;(2)主要生活型为附生的有127属6 000种以上,地生97属2 000种以上,腐生13属约100种,藤本4属40余种;(3)根据整理出的东南亚79个属的兰科植物传粉系统发现,有44个属含有自动自交的物种,具报酬物的传粉系统有花粉(仅见于拟兰亚科)、芳香类物质(仅见于香荚兰亚科)和花蜜(5个亚科均有)等报酬物类型。欺骗性传粉系统广泛存在于各个亚科,包括食源性欺骗、性拟态、繁殖地拟态和信息素拟态等类型。东南亚兰科植物在物种、生活习性及传粉系统都展现出极高的多样性,对这些生物学特点的总结将为兰科植物的保育提供一定的理论基础和本底资料。     

Fruit set, nectar reward, and rarity in the Orchidaceae

A review of comparative levels of reproductive success among nectariferous and nectarless orchids worldwide was compiled from a comprehensive survey of fruit set from 117 orchid species in the literature and from our own field studies. It confirms the hypothesis that nectariferous orchids are more successful in setting fruit than are nectarless species. Overall fruit set figures for nectarless and nectariferous orchids were 19.5 and 49.3% for North America, 27.7 and 63.1% for Europe, 41.4 and 74.4% for the temperate southern hemisphere, and 11.5 and 24.9% for the tropics, demonstrating that the dichotomy is consistent across all geographical areas. On average, the provision of nectar doubles the probability of fruit set in both temperate and tropical areas, but tropical orchids are remarkable in that all (whether nectarless or nectariferous, or terrestrial or epiphytic) display low fruit productivity (<50%). Fruiting failure in the tropics may be balanced by higher productivity per capsule, since tropical orchid fruits contain on average 150 times more seeds than temperate ones. Hybridization occurs more frequently among nectarless orchids in Britain and Europe than among nectariferous ones, and there is a significant positive association between orchid rarity and lack of nectar reward in the British Isles. Sexual reproduction in the Orchidaceae is predominantly pollinator dependent, but this can sometimes be successfully circumvented by asexual seed production (agamospermy) or, more frequently, by automatic self-pollination (autogamy). The proportion of highly successful nectarless orchids from all geographic areas is very low and comparable with that of orchids offering rewards other than nectar (～14% of species in each case) emphasizing that high reproductive success is only associated with nectar reward (53% of species). It is suggested that the evolution of nectar production within the family has been the most frequent means of escaping the reproductive limitations of low pollinator visitation frequencies.     

中国野生兰科植物资源与保护利用现状*

兰科(Orchidaceae Juss.)是被子植物最大科之一,广泛分布于各种陆地生态系统中,具生态、观赏、药用、食用、文化、科研等多重价值,一直以来都是备受关注的重点保护类群。中国是野生兰科植物资源最为丰富的国家之一,具有从原始类群到高级类群的一系列进化群以及复杂多样的地理分布类型。对中国野生兰科植物资源现状和濒危、保护情况进行综合阐述、分析,并针对未来兰科植物资源的可持续利用进行展望。新版《国家重点保护野生植物名录》的发布打开了我国兰科植物保护新局面,加强对我国源远流长的兰文化和散落民间的相关传统知识的归纳整理及科学普及,重视兰科生物文化多样性的保护工作,并根据传统知识线索,探索兰花新品种和药食新资源,不仅可能成为兰科资源保护和利用的新思路和新动力,也将有助于我国生态文明建设和经济社会可持续发展。     

Evolution and biogeography of the slipper orchids: Eocene vicariance of the conduplicate genera in the Old and New World Tropics

Intercontinental disjunctions between tropical regions, which harbor two-thirds of the flowering plants, have drawn great interest from biologists and biogeographers. Most previous studies on these distribution patterns focused on woody plants, and paid little attention to herbs. The Orchidaceae is one of the largest families of angiosperms, with a herbaceous habit and a high species diversity in the Tropics. Here we investigate the evolutionary and biogeographical history of the slipper orchids, which represents a monophyletic subfamily (Cypripedioideae) of the orchid family and comprises five genera that are disjunctly distributed in tropical to temperate regions. A relatively well-resolved and highly supported phylogeny of slipper orchids was reconstructed based on sequence analyses of six maternally inherited chloroplast and two low-copy nuclear genes (LFY and ACO). We found that the genus Cypripedium with a wide distribution in the northern temperate and subtropical zones diverged first, followed by Selenipedium endemic to South America, and finally conduplicate-leaved genera in the Tropics. Mexipedium and Phragmipedium from the neotropics are most closely related, and form a clade sister to Paphiopedilum from tropical Asia. According to molecular clock estimates, the genus Selenipedium originated in Palaeocene, while the most recent common ancestor of conduplicate-leaved slipper orchids could be dated back to the Eocene. Ancestral area reconstruction indicates that vicariance is responsible for the disjunct distribution of conduplicate slipper orchids in palaeotropical and neotropical regions. Our study sheds some light on mechanisms underlying generic and species diversification in the orchid family and tropical disjunctions of herbaceous plant groups. In addition, we suggest that the biogeographical study should sample both regional endemics and their widespread relatives.     

Identification of putative orthologous genes for the phylogenetic reconstruction of temperate woody bamboos (Poaceae: Bambusoideae)

The temperate woody bamboos (Arundinarieae) are highly diverse in morphology but lack a substantial amount of genetic variation. The taxonomy of this lineage is intractable, and the relationships within the tribe have not been well resolved. Recent studies indicated that this tribe could have a complex evolutionary history. Although phylogenetic studies of the tribe have been carried out, most of these phylogenetic reconstructions were based on plastid data, which provide lower phylogenetic resolution compared with nuclear data. In this study, we intended to identify a set of desirable nuclear genes for resolving the phylogeny of the temperate woody bamboos. Using two different methodologies, we identified 209 and 916 genes, respectively, as putative single copy orthologous genes. A total of 112 genes was successfully amplified and sequenced by next‐generation sequencing technologies in five species sampled from the tribe. As most of the genes exhibited intra‐individual allele heterozygotes, we investigated phylogenetic utility by reconstructing the phylogeny based on individual genes. Discordance among gene trees was observed and, to resolve the conflict, we performed a range of analyses using BUCKy and HybTree. While caution should be taken when inferring a phylogeny from multiple conflicting genes, our analysis indicated that 74 of the 112 investigated genes are potential markers for resolving the phylogeny of the temperate woody bamboos.     

Bioactive Secondary Metabolites from Orchids (Orchidaceae)

The Orchidaceae family is the largest group of flowering plants in the Angiosperm monocotyledons spread on our planet. Its members, called orchids, are herbs or epiphytes with showy flowers distributed mainly in tropical regions. Several classes of phytoconstituents have been so far isolated from therapeutically‐used orchids showing a great chemical diversity. Among them, phenolic derivatives have been studied for their biological activities, especially in the field of cancer, inflammation, and neurodegeneration. On the other hand, limited information has been so far obtained on the numerous alkaloids and terpenoids isolated from several orchid species. Recent articles revealed pronounced effects of some alkaloids on the CNS. Published literature on orchids that are used in traditional medicine has been reviewed in this work indicating a great potential of such organisms as source of chemical entities for the development of new drugs.     

罗霄山脉兰科植物区系及其生态地理学特征

通过对罗霄山脉地区兰科植物的野外调查及文献整理,对该地区兰科植物区系及其生态地理学特征进行研究。结果显示,该地区兰科种类丰富,共有47属124种,其中地生兰、附生兰和腐生兰分别为80、36、8种,占总种数的64.5%、29.0%和6.5%。兰科植物集中分布在海拔400~1200 m,其区系成分复杂,具有较强的热带性质。对该地区兰科植物濒危现状进行了分析并提出了保护建议。本研究对罗霄山脉兰科植物资源的保护和开发利用具有重要意义。     

Strong phylogenetic congruence between Tulasnella fungi and their associated Drakaeinae orchids

The study of congruency between phylogenies of interacting species can provide a powerful approach for understanding the evolutionary history of symbiotic associations. Orchid mycorrhizal fungi can survive independently of orchids making cospeciation unlikely, leading us to predict that any congruence would arise from host-switches to closely related fungal species. The Australasian orchid subtribe Drakaeinae is an iconic group of sexually deceptive orchids that consists of approximately 66 species. In this study, we investigated the evolutionary relationships between representatives of all six Drakaeinae orchid genera (39 species) and their mycorrhizal fungi. We used an exome capture dataset to generate the first well-resolved phylogeny of the Drakaeinae genera. A total of 10 closely related Tulasnella Operational Taxonomic Units (OTUs) and previously described species were associated with the Drakaeinae orchids. Three of them were shared among orchid genera, with each genus associating with 1–6 Tulasnella lineages. Cophylogenetic analyses show Drakaeinae orchids and their Tulasnella associates exhibit significant congruence (p < 0.001) in the topology of their phylogenetic trees. An event-based method also revealed significant congruence in Drakaeinae–Tulasnella relationships, with duplications (35), losses (25), and failure to diverge (9) the most frequent events, with minimal evidence for cospeciation (1) and host-switches (2). The high number of duplications suggests that the orchids speciate independently from the fungi, and the fungal species association of the ancestral orchid species is typically maintained in the daughter species. For the Drakaeinae–Tulasnella interaction, a pattern of phylogenetic niche conservatism rather than coevolution likely explains the observed phylogenetic congruency in orchid and fungal phylogenies. Given that many orchid genera are characterized by sharing of fungal species between closely related orchid species, we predict that these findings may apply to a wide range of orchid lineages.     

Orchid pollination by sexual deception: pollinator perspectives

The extraordinary taxonomic and morphological diversity of orchids is accompanied by a remarkable range of pollinators and pollination systems. Sexually deceptive orchids are adapted to attract specific male insects that are fooled into attempting to mate with orchid flowers and inadvertently acting as pollinators. This review summarises current knowledge, explores new hypotheses in the literature, and introduces some new approaches to understanding sexual deception from the perspective of the duped pollinator. Four main topics are addressed: (1) global patterns in sexual deception, (2) pollinator identities, mating systems and behaviours, (3) pollinator perception of orchid deceptive signals, and (4) the evolutionary implications of pollinator responses to orchid deception, including potential costs imposed on pollinators by orchids. A global list of known and putative sexually deceptive orchids and their pollinators is provided and methods for incorporating pollinator perspectives into sexual deception research are provided and reviewed. At present, almost all known sexually deceptive orchid taxa are from Australia or Europe. A few sexually deceptive species and genera are reported for New Zealand and South Africa. In Central and Southern America, Asia, and the Pacific many more species are likely to be identified in the future. Despite the great diversity of sexually deceptive orchid genera in Australia, pollination rates reported in the literature are similar between Australian and European species. The typical pollinator of a sexually deceptive orchid is a male insect of a species that is polygynous, monandrous, haplodiploid, and solitary rather than social. Insect behaviours involved in the pollination of sexually deceptive orchids include pre‐copulatory gripping of flowers, brief entrapment, mating, and very rarely, ejaculation. Pollinator behaviour varies within and among pollinator species. Deception involving orchid mimicry of insect scent signals is becoming well understood for some species, but visual and tactile signals such as colour, shape, and texture remain neglected. Experimental manipulations that test for function, multi‐signal interactions, and pollinator perception of these signals are required. Furthermore, other forms of deception such as exploitation of pollinator sensory biases or mating preferences merit more comprehensive investigation. Application of molecular techniques adapted from model plants and animals is likely to deliver new insights into orchid signalling, and pollinator perception and behaviour. There is little current evidence that sexual deception drives any species‐level selection on pollinators. Pollinators do learn to avoid deceptive orchids and their locations, but this is not necessarily a response specific to orchids. Even in systems where evidence suggests that orchids do interfere with pollinator mating opportunities, considerable further research is required to determine whether this is sufficient to impose selection on pollinators or generate antagonistic coevolution or an arms race between orchids and their pollinators. Botanists, taxonomists and chemical ecologists have made remarkable progress in the study of deceptive orchid pollination. Further complementary investigations from entomology and behavioural ecology perspectives should prove fascinating and engender a more complete understanding of the evolution and maintenance of such enigmatic plant‐animal interactions.     

北京松山国家级自然保护区兰科植物多样性及其保护评价

选取北京松山国家级自然保护区开展兰科植物多样性调查和分析,评估其保护现状。松山共有兰科植物12属18种,其中北方盔花兰为北京新记录种。在生活型方面,以地生兰为主,计14种（77．78％）,腐生兰4种（22．22％）;在分布区类型方面,属的区系成分以北温带分布为主（6属,5000％）,兼有旧世界温带分布（3属,25．00％）、世界分布（2属,16．67％）和旧世界热带分布（1属,8．33％）;种的区系成分以东亚分布为主（9种,50．00％）,兼有旧世界温带分布（5种,27．78％）和北温带分布（4种,22．22％）。松山兰科植物集中分布于北沟和小海坨山。通过综合分析松山兰科植物保护现状,提出生境评估、种群动态监测、建立迁地保护资源圃和加大宣传等都是切实加强兰科植物保护工作的可行措施。