Spatial genetic structure in populations of the terrestrial orchid Cephalanthera longibracteata (Orchidaceae)

Orchid seeds are unusual for being the smallest among flowering plants. These dust-like seeds are wind-borne and, thus, would seem to have the potential for long-distance dispersal (a common perception); this perception has led to a prediction of near-random spatial genetic structure within orchid populations. Mathematical models (e.g., simple ballistic model) for wind-dispersed seeds and wind-tunnel experiments, in contrast, indicate that most seeds of orchids should fall close to the maternal plant (<6 m), supporting a prediction of significant fine-scale genetic structure within populations. In reality we do not know much about seed dispersion in orchids. To determine which of these two predictions is more appropriate, Wright's F statistics and spatial autocorrelation analysis were used to examine the genetic structure within two adult populations of the terrestrial orchid Cephalanthera longibracteata (Orchidaceae) in southern Korea. In results comparable to those of other self-compatible, mixed-mating plant species, C. longibracteata populations exhibited low levels of genetic diversity (mean H(e) = 0.036) and a significant excess of homozygosity (mean F(IS) = 0.330), consistent with substantial inbreeding via selfing and/or mating among close relatives in a spatially structured population. Spatial autocorrelation analysis revealed significant positive genetic correlations among plants located <10 m, with relatedness at <3 m comparable to that expected for half sibs and first cousins. This genetic structure supports the prediction that the majority of seed dispersal occurs over distances of less than 10 m and is responsible for generating substantial overlap in seed shadows within C. longibracteata populations.     

Cephalanthera exigua rediscovered: new insights in the taxonomy,habitat requirements and breeding system of a rare mycoheterotrophic orchid

Five mycoheterotrophic species of Cephalanthera have been proposed from tropical Asia. Until recently, all of them were only known from the type specimens, for which reason it has been difficult to judge if some of them were actually conspecific. The recent discovery of two large populations of C. exigua in Thailand made it possible to describe the range of variation of this species in much more detail, and we then found it to be well distinguished from the others. A phylogenetic analysis based on nuclear rDNA ITS sequences corroborated the systematic position of C. exigua at the generic level. Examination of the previously neglected type of C. pusilla from Myanmar lead to the conclusion that this taxon of disputed generic affinity likewise belongs to Cephalanthera, and that it is a clearly distinct species. Finally, we accept that also C. ericiflora from Laos as well as C. gracilis and C. calcarata from Yunnan are probably distinct species. Cephalanthera exigua grows in hill evergreen forest, but we found little floristic similarity between its two localities in Thailand (IS_S=22.5%). Ectomycorrhizal trees of the families Fagaceae and Ulmaceae are probably the ultimate carbon source for C. exigua at both sites, as the mycorrhizal partners of this orchid (basidiomycetes of the family Thelephoraceae) obtain their carbon nutrition through ectomycorrhizal association with forest trees. Pollination experiments demonstrated that the nectarless flowers of C. exigua are not spontaneously autogamous. Based on the pollination syndrome and previously published observations on other species of the genus, we suggest that C. exigua has an insect‐operated breeding system acting by deceit, and that the pollinators are probably solitary bees.     

The diversity of mycorrhizal fungi in Japanese Cephalanthera species

The diversity of mycorrhizal fungi among four Japanese Cephalanthera (Orchidaceae) species was examined at a total of seven sites, based on sequence variation in nuclear ribosomal DNA. This is the first report to detect mycorrhizal fungi in C. subaphylla. Two patterns of mycorrhizal associations were confirmed from our results. C. falcata has lower fungal specificity, associating with Russulaceae, Sebacinales and Thelephoraceae. By contrast, the three Cephalanthera species C. erecta, C. subaphylla, and C. longifolia were associated mainly with Thelephoraceae fungi. There is no large difference found in mycobionts between green and albino individuals of C. falcata and no distinct preference of Japanese Cephalanthera species for a specific fungal group of Thelephoraceae.     

Infestation of the orchid Cephalanthera spp. by Parallelomma vittatum (Meigen, 1826) (Diptera: Scathophagidae) in Japan

It is important to understand the interactions between orchids and their herbivores, especially considering the rarity of most orchids and the potential negative effects of pests on orchid reproduction. Here, we report the infestation of leaves of Cephalanthera spp. orchids by Parallelomma vittatum (Scathophagidae) in Japan. The present study represents the first report of P. vittatum on orchid hosts in Asia.     

The variability of orchid population size

Orchid population size has long been believed to be highly variable in time and space. Here we present the first quantitative assessment of the variability of orchid population sizes and compare them with plant and animal population data from the literature. Three measures of temporal variation were used (standard deviation of log₁₀ (population size), Hurst exponent and variance in the intrinsic rate of increase). Eight unfertilized plots of Orchis morio in a factorial fertilizer experiment were assessed for variability in population size over a 26 year period. The Hurst exponent across the eight plots gave measures consistent with pink noise well into black noise (0.86 to 1.87). The variation in the intrinsic rate of increase suggested that the expected time to extinction in the plots differed by an order of magnitude. Standard deviation of log₁₀ (population size) across plots was greater than the corresponding temporal variation within plots. Standard deviation of log₁₀ (population size) reached an asymptote between 10 and 20 years. The range of temporal variation between plots in this and other orchid populations was as great as the mean values reported for birds, insects and mammals. These results have highlighted the importance of spatial variation: until we know the relative importance of spatial and temporal variation for more plant species we will be unable to assess whether orchid populations are more variable in size than other species.     

濒危兰科植物再引入技术及其应用

稀有、濒危植物的再引入,是在条件成熟时,把经过迁地保护的人工繁殖体重新放回到它们原来自然和半自然的生态系统或适合它们生存的野外环境中去,重建较为完善的生态系统。再引入技术的目标在于提高生态系统生物多样性及群落稳定性,建立可自我维持种群,它是继就地保护和迁地保护等保护策略之外的一种新兴的珍稀濒危植物保育方式。国际上再引入技术的研究刚起步,高度成功的还不多,目前可借鉴的成熟经验较少。通过分析国内外已经开展的若干珍稀濒危植物再引入技术案例,重点介绍国内外濒危兰科植物再引入的研究现状、技术体系和评价标准,讨论了再引入技术的类型和方法,并总结了可能影响再引入成败的制约性因素,分析了适用于兰科植物的再引入技术要素。由此提出濒危兰科植物再引入的重要现实意义,为今后的规模化人工栽培提供科学依据,同时有利于指导其他濒危植物再引入技术规程的制定。     

The stigma of Cephalanthera (Orchidaceae) provides a link between primitive and derived Epidendroideae

Micromorphological, anatomical and ultrastructural observations of the stigma of several Neottieae ( Cephalanthera damasonium, Epipactis palustris, Neottia nidusavis, Listera ovata ) and a derived epidendroid orchid ( Phaius tankervilliae ) were made. Among these taxa Cephalanthera is the only neottioid orchid possessing a WDc stigma type being typical for the derived Epidendroideae. Further features are a concave, non papillate stigma covered by a specialised cuticle, the arrangement of the anatomical zones, detached cells with conspicuous wall thickenings and the location of lipidic droplets and electron dense material in the stigmatic mucilage. It is suggested that Cephalanthera is more closely related to the derived Epidendroideae than any other neottioid orchid and thereby is a sister group to the derived Epidendroideae.     

The air spora of an orchid greenhouse

The orchid collection of the ELTE Botanical Garden, Budapest, Hungary was monitored for airborne fungi using viable and non-viable air-sampling methods (Hirst-type and a 3-stage Andersen sampler) with three different culture media. A new culture method was also applied to identify fungal spores from Hirst-type samples. The aim of this study was to determine the diversity, human- and phytopathological potential of the air spora. To find out sources of airborne fungi, samples were collected from the air in an adjacent greenhouse and outdoors, and from necrotic plants. A total of 58 genera were found in the air samples. Cladosporium and Penicillium spp. were common members of the airborne biota. A high proportion (27.5%) of identified genera may be presented as a member of microbial consortium associated with the orchids. Airborne fungi potentially pathogenic to humans were also detected. One species, Zygosporium masonii, was new to Hungary. Statistical analysis indicated that conditions of sampling had significant effects. The principal component analysis elucidated the three principal components representing 75.34% of the total variance; the clusters of variables were related to the three types of culture media. Relative abundance of small-sized spores was high, presumably because of the fungal species composition and accelerated sedimentation of large spores in still air. Apparently, in the studied orchid greenhouse, a specific mycobiota developed due to the climate and hosts (Orchideaceae) grown there.     

The structure and function of orchid pollinaria

Cohesive masses of pollen known as pollinia have evolved independently in two plant families — Orchidaceae and Asclepiadaceae. Yet, the bilateral symmetry of orchids has allowed a greater degree of specialization in pollination systems and a much greater diversity in the morphology of pollinaria — units comprising the pollinia(um) together with accessory structures for attachment to the pollinator. Pollinaria differ in the degree of cohesion of pollen in the pollinium, which may be soft, sectile (comprised of sub-units known as massulae) or hard. A single hard pollinium may contain more than a million pollen grains, yet pollen:ovule ratios in orchids are several orders of magnitude lower than in plants with powdery pollen due to the lack of wastage during transport to the stigma. Attachment of pollinia to the pollinator is usually achieved by means of a viscidium that adheres most effectively to smooth surfaces, such as the eyes and mouthparts of insects and beaks of birds. The stalk connecting a pollinium to the viscidium may be comprised of a caudicle (sporogenous in origin) and/or a stipe (derived from vegetative tissue), or be lacking altogether. Caudicles and stipes may undergo a gradual bending movement 20 s to several hours after withdrawal from the flower, the main function of which appears to be to reduce the possibility of geitonogamous pollination. Other mechanisms that promote outcrossing and pollen export in orchids include pollen carryover (achieved by sectile or soft pollinia), temporary retention of the anther cap, protandry and self-incompatibility (rare among orchids). Pollinaria ensure that large pollen loads are deposited on the stigma, thus enabling the fertilization of the large numbers of ovules in the flowers of Orchidaceae. Pollinaria also ensure efficient removal of pollen from the anther, minimal pollen wastage during transit, and a high probability of deposition on conspecific stigmas.     

心启兰属(Chenorchis)——兰科一新属及其蚂蚁传粉的生态策略

在云南的高黎贡山的亚热带区域发现了具热带兰科种类特征的兰科新属心启兰属(Chenorchis)(属模式种心启兰C. singchii).该属种具有附生、单轴生长,花粉团坚硬,粘盘柄存在等兰科较为进化的特征无疑是热带万代兰族(Trib. Vandeae)的成员,与鸟舌兰属(Ascocentrum)和槽舌兰属(Holcoglossum)有亲缘关系.区别点在于新属的唇瓣不具附属物;侧裂片生于中裂片两侧而非距口两侧;柱头腔大;蕊喙甚大,明显宽于蕊柱,向下伸展;花粉团具明显的柄,附着于一个共同的粘盘柄近顶端内弯处.系统学分析结果显示其祖先可能来自热带,因环境改变演化为新属种,体现了被子植物分化的主要动力可能是开拓了更多的生态学机遇;进一步的繁殖生态学特别是传粉机制和繁育系统的检测表明,该物种发展出多个促进自交或近交的机制,如选择有切胸蚁(Temnothorax sp.)栖息的生境,利用蚂蚁近距离传粉;花朵同时开放增加同株异花授粉发生机率;种子有效的就近散播和生长,产生局域拥挤效应以增加近亲繁殖的可能,这些适应性改变成为它们在亚热带生存下来的必要条件,特殊的生活史(繁殖)策略展示了它作为迁移种通过迅速增长抢占生境,自动地将遗传基因传递给后代以保持对当地的适应性,花序进化出大量花并同时开放便于同株异花传粉是成功开拓生境的一种对策,其意义的延伸可能为植物的性的产生是进化上应对生境波动的权衡提供一个证据.     

Utilisation of carbon substrates by orchid and ericoid mycorrhizal fungi from Australian dry sclerophyll forests

The utilisation of a range of cell-wall-related and aromatic carbon substrates by multiple genotypes of three ericoid mycorrhizal fungal taxa was compared with two orchid mycorrhizal fungal taxa. Both groups of fungi catabolised most common substrates, though significant inter- and intraspecific variability was observed in the use of a few carbon substrates. Orchid mycorrhizal fungi had limited access to tannic acid as a carbon source and did not use phenylalanine, while the ericoid mycorrhizal fungi used both. Utilisation of tryptophan was limited to single genotypes of each of the orchid mycorrhizal fungi, and to only two of the three ericoid mycorrhizal fungi examined. Although broadly similar, some significant differences apparently exist in carbon catabolism of ericoid and orchid mycorrhizal fungi from the same habitat. Functional and ecological implications of these observations are discussed.     

The evolution of beetle pollination in a South African orchid

The pollination biology of the orchid Ceratandra grandiflora was investigated in order to determine whether the partial loss of a specialized floral reward (i.e., oil) was the result of an incomplete shift from one specialized pollinator to another. In the three-species clade of section Ceratandra, there has been a progressive loss of the oil-secreting callus. lt is always present in C atrata, sometimes present in C. grandiflora, and never present in C. globosa. Thirty-nine to 67% of individuals in populations of C. grandiflora bear the callus gland, but gland presence has no signifikant effect on the proportion of flowers pollinated. Pollinator observations show that the shift in pollinators is complete and that the oil-secreting callus is a vestige of the ancestral oil-bee pollination system that no longer plays a role in pollination. C grandiflora is pollinated almost exclusively by a single species of hopliine beetle (Scarabaeidae). Experiments with artificial flower traps indicate that color alone can explain the attraction of beetles to C. grandiflora, despite the absence of a floral reward. The proportion of C. grandiflora flowers pollinated (50.2 and 61.1%; N = 524 and 324 flowers, respectively) is unusually high for a plant that relies on generalized food deception and is probably due to the use of inflorescences as mating sites (i.e., rendezvous pollination).