The pollinium ofLoroglossum hircinum (Orchidaceae) between pollination and pollen tube emission

The structure of the massulae composing the pollinium ofLoroglossum hircinum was studied before pollination and 12 and 24 hours afterwards. The grains are grouped in tetrads closely packed in massulae. The exine is only present on the outside of the massulae. The intine consists of two layers: a compact layer surrounding the pollen grain and a looser layer surrounding the pollen grain and a looser layer surrounding the tetrad. Twelve hours after pollination, pollen volume and the space between the tetrads increase due to vacuolization. Twenty-four hours after pollination, pollen volume and tetrad spacing are higher due to vacuolization and some grains have emitted pollen tubes. Pollen growth due to vacuole formation, and the absence of common walls between adjacent tetrads lead to crumbling of the massulae. The mature pollen grain does not have apertures: the site of pollen tube emission is determined after pollination. The first grains to germinate are those in the centre of the massula. The vegetative cell nucleus is the first to enter the pollen tube; the generative cell elongates and undergoes the second haploid mitosis shortly after entering the pollen tube.     

Low genetic diversity and high genetic divergence caused by inbreeding and geographical isolation in the populations of endangered species Loropetalum subcordatum (Hamamelidaceae) endemic to China

Loropetalum subcordatum (Hamamelidaceae) is one of the most endangered angiosperm species in China. It is narrowly distributed in a few localities in the evergreen broadleaved forest of southern China. Up to now only a few dozen remnant individuals have been found in the four extant populations. In this project, we studied its genetic diversity and population genetic structure using the high resolution molecular marker of amplified fragment length polymorphism. In total, 47 individuals from all the four populations (including all individuals in three populations) were analyzed. Comparably low genetic diversity within populations was revealed and significantly high genetic differentiation among the populations was detected. Four independent groups were identified which corresponded with their geographical ranges. Autogamy is considered to be the major factor contributing to the low genetic variation and high genetic divergence within this species. In addition, small population size, restricted distribution range, geographical isolation and limited seed dispersal may also contribute to the low genetic diversity and high population genetic differentiation. Clonal reproduction was inferred to occur in the two island populations. Suggestions for conservation strategies are provided to preserve the genetic resources of this species.     

Mycorrhizal diversity and specificity in Lecanorchis (Orchidaceae)

Lecanorchis is a nonphotosynthetic plant genus in Vanilloideae, Orchidaceae. Because of the distribution of many Lecanorchis taxa in various climate conditions, we hypothesized that mycorrhizal diversity and specificity are different among the different taxa of Lecanorchis. In the present study, identities of mycorrhizal fungi were examined for 90 individuals of 10 Lecanorchis taxa at 26 sites from Niigata to Okinawa Prefectures in Japan. Phylogenetic analyses of Lecanorchis taxa based on the internal transcribed spacer (ITS) region of the nuclear ribosomal RNA gene (rDNA) divided the examined Lecanorchis taxa into three groups, groups A, B, and C. ITS rDNA sequences suggested that fungi associating with Lecanorchis were ectomycorrhiza-forming fungi in Lactarius, Russula, Atheliaceae, and Sebacina, with Lactarius and Russula dominant. Our results suggested some degree of mycorrhizal specialization among Lecanorchis taxa. Interestingly, the Lecanorchis group C had some specific relationships with Lactarius, whereas less specificity was found in the relationships with Russula. However, observed specificity results may be biased by geographic opportunity, and we suggest further research to assess whether Lecanorchis species are limited to the associations we observed.     

柞蚕核型多角体病毒(AnpeNPV)三地理株的全基因组比较分析揭示其遗传多样性

[目的]柞蚕核型多角体病毒(Antheraea pernyi nucleopolyhedroviruses,AnpeNPV)能引起柞蚕脓病大面积暴发.尽管之前已完成了两株核型多角体病毒的基因组测序,但基于比较基因组的方法调查AnpeNPV间的遗传变异研究则相对较少.[方法]为了研究AnpeNPV不同地理株系间的遗传多样性,我们测序了1株从中国河南省分离的柞蚕NPV(AnpeNPV-H)基因组,并和之前从辽宁省分离的2株柞蚕NPV(AnpeNPV-L和AnpeNPV-Z)进行了比较基因组学分析.[结果]AnpeNPV-H的全基因组大小为125 605 bp,总共预测了146个开放阅读框(ORF),包括95个功能注释蛋白和51个假定蛋白.我们发现这3株AnpeNPV间的基因组成非常相似.在这3个AnpeNPV株系间,有6个开放阅读框存在碱基变异而导致基因的变短.并鉴定超过200个单核苷酸多态性(single nucleotide variations,SNVs),其中85％位于蛋白编码区.同时,odv-e56,p94-like和egt3个基因的非同义突变较高,表明这3个蛋白质编码基因可能经历了正向选择或纯化选择.我们发现在这3株AnpeNPV间一些基因的氨基酸发生变异,例如编码膜蛋白的基因、抑制凋亡和蜕皮的基因及与DNA复制相关的DNA聚合酶和解旋酶等基因.最后,展示了3株AnpeNPV间遗传重组的证据.[结论]本研究揭示了AnpeNPV种内水平的变异和株系内基因组的动态结构.     

Reproductive isolation in the Aegean Ophrys omegaifera complex (Orchidaceae)

The orchid genus Ophrys operates a system of sexual deception by which high specificity of pollination is attained. Reproductive isolation in Ophrys mainly rests upon prezygotic isolation mechanisms. The level of genetic separateness of Ophrys taxa with different pollinators is therefore likely determined by the fidelity of pollinators. The present study employs genetic fingerprinting to investigate this in the east Aegean Ophrys omegaifera s.l. complex, also including O. dryis, a west Mediterranean species of this complex. Ophrys fleischmannii, O. basilissa, and the west Mediterranean O. dyris, are found to be well-separated genetic entities whereas O. omegaifera s.str. and the putative hybrid taxon, O. sitiaca, are found to be genetically inseparable across their entire range of co-occurrence. This suggests that specific pollinators have high enough fidelity to act as effective isolating factors in east Aegean O. omegaifera s.l. as a whole, but that the situation in the species pair of O. sitiaca and O. omegaifera is likely to be more complex.     

泛希姬蝽不同地理种群的遗传多样性和遗传分化

泛希姬蝽Himacerus apterus(Fabricius)是半翅目姬蝽科中重要的天敌种类,本文旨在分析泛希姬蝽不同地理种群的遗传多样性和遗传分化情况。利用COI作为标记基因,使用DnaSP、Arlequin、MEGA等软件分析了中国4个省12个种群33个体的单倍型多样性、遗传结构分化、系统发育等。共发现19个单倍型,所有单倍型中仅H1为共享单倍型,为宁夏和陕西共有,且出现频率最高。总体单倍型多样性指数Hd=0.913,核苷酸多样性指数π=0.006,平均核苷酸差异数k=4.083。Tajima's D=-0.853,P>0.100,表明泛希姬蝽未经过种群扩张。AMOVA分析表明种群内的分子变异大于种群间分子变异,变异比例分别为45.393%和36.594%,遗传分化指数均大于0.250,差异水平极显著。泛希姬蝽不同地理种群遗传多样性较高,宁夏与内蒙古、山西、陕西省分组间存在极度的遗传分化。种群间遗传距离和地理距离无相关性,表明地理距离不是影响种群间遗传距离的重要因素。通过比较4个省采集点的环境特点,认为地区间基因流受限和气温、猎物的差异可能是影响遗传分化的重要因素。     

Elaiophore diversity in three contrasting members of Oncidiinae (Orchidaceae)

The elaiophores of Trichocentrum cavendishianum (Bateman) M.W. Chase & N.H. Williams, Oncidium loefgrenii Cogn., and Gomesa recurva R. Br. display considerable morphological and anatomical diversity. Oil secretion by flowers of T. cavendishianum and O. loefgrenii can be related to the presence of saddle-like, labellar elaiophores and the labellar callus, respectively, whereas, in G. recurva , although oil is present, no obvious structure appears to be involved in its secretion. In the first two species, the secretory tissue consists of palisade-like cells, whereas, in G. recurva , these cells are oval. Many Oncidiinae are thought to mimic members of the Malpighiaceae, and the elaiophores of that family also contain palisade-like cells that may indicate evolutionary convergence. As oils accumulate below the elaiophore cuticle, that of T. cavendishianum becomes distended, whereas that of the other two species does not. Full discharge of oil from the elaiophores of T. cavendishianum probably occurs only after the cuticle is ruptured by a visiting insect, and this may contribute towards pollinator selection.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 155 , 135–148.     

野生五唇兰根部内生真菌多样性研究

兰科植物根部的内生真菌在兰科植物的整个生活史中起着重要的作用, 为了解不同生境不同类型的兰科植物内生真菌菌群的多样性, 作者于2004年7月至2005年10月, 以海南岛霸王岭自然保护区内的野生五唇兰(Doritis pulcherrima)作为实验材料, 对不同生境、不同形态的五唇兰植株根部的内生真菌群落多样性进行了研究。从附生于石上及生于杂木林或灌丛中、叶背绿色及叶背紫红色的五唇兰植株新鲜营养根段中共分离出83株内生真菌, 鉴定为19个属, 其中包括培养基筛选实验中分离出的30株14属。镰刀菌属(Fusarium)(24.1%)和丝核菌属 (Rhizocto-nia)(14.5%)为优势属。两种叶色的五唇兰内生真菌群落丰富度较为一致; 而两种不同生境中的五唇兰内生真菌群落丰富度则表现出较大的差异: 附生于灌木的五唇兰内生真菌群落Shannon多样性指数远高于附生岩石的。研究结果表明五唇兰内生真菌多样性更多地受生境的影响而不是受植株形态类型的影响。     

Chromosomal diversity in two synchronopatric species of Hoffmannseggella (Orchidaceae)

Hoffmannseggella viridiflora Verola & Semir (Laeliinae, Orchidaceae) is a recently discovered species in the campos rupestres vegetation of the Espinhaço Range, MG, Brazil, in synchronopatry with H. bradei (Pabst) V. P. Castro & Chiron. Both morphological and phenological studies indicate that these species are closely related. To substantiate the differentiation of these two species we examined their chromosome numbers and morphologies. The two species had different chromosome numbers, with H. bradei having 2n = 40 and H. viridiflora having 2n = 44 chromosomes, an aneuploid number not previously documented in the genus. Meiotic behavioral studies undertaken with H. bradei revealed many abnormalities related to bivalent numbers and chromosome migration, suggesting that meiotic abnormalities could generate aneuploid gametes and perhaps aneuploid zygotes. Karyotype formulas and chromosome morphologies are quite different between the species, so H. viridiflora was not directly derived from H. bradei through simple chromosome additions. Complementary analyses are necessary to understand the process and species involved in the origin of H. viridiflora.     

Allozyme variation and genetic integrity of Dactylorhiza incarnata (Orchidaceae)

Eleven Danish populations of the diploid Dactylorhiza incarnata s.lat. have been examined for allozyme variation in DIA, PGD, PGI, PGM, SKD, TP1, and UGPP. The results reveal a deficiency of heterozygotes in several populations. Possible reasons for this deficiency are considered. The results also indicate that no genetic barrier seems to prevent gene flow between D. incarnata var. incarnata , var. dunensis , and var. ochrantha — and some indication exists that a considerable amount of gene exchange takes place between sympatric populations of var. incarnata and var. ochrantha . On the other hand, there is no sign of recent introgression between D. incarnata s.lat. and any of the sympatric tetraploid species ( D. maculata, D. majalis, D. purpurella s.lat.). It is suggested that knowledge on the various degrees of genetic integrity of morphologically recognizable entities should be elaborated and subsequently utilized for a biosystematic approach to Dactylorhiza .     

Extensive variation in the levels of genetic diversity and degree of relatedness among five species of Cypripedium (Orchidaceae)

An electrophoretic analysis of allozyme variation from 14 loci in Cypripedium calceolus, C. candidum, C. arietinum, C. acaule, and C. reginae was conducted to address evolutionary conclusions reached in prior studies on the Orchidaceae. The following specific questions were examined: 1) Do the allozyme data suggest that C. arietinum be transferred to the genus Criosanthes? 2) Do Cypripedium populations contain unusually low levels of genetic variation relative to other angiosperms with comparable life histories? and 3) Is the distribution of genetic variation among populations consistent with the idea that evolutionary processes produce higher levels of among-population differentiation in the Orchidaceae? Very low Nei's genetic identities (0.000–0.285) were found for most species comparisons; however, C. arietinum was not the most genetically distinct taxon and should be retained in the genus Cypripedium. Although most Cypripedium populations contain very low levels of expected heterozygosity, C. calceolus contains unusually high levels in all populations examined. Most species examined here have below average levels of variation distributed among populations. This result indicates that evolutionary processes produce relatively lower, not higher, levels of genetic differentiation among Cypripedium populations compared to other flowering plants. Historical events that could have influenced the observed genetic patterns are discussed.     

Influence of spatial structure on genetic isolation in Plebejus argus populations (Lepidoptera: Lycaenidae)

Populations of Plebejus argus were sampled in southwest Finland, both on the mainland and on islands, and in and around the Do?ana National Park in southwest Spain. A total of 453 individuals coming from 14 locations were investigated using allozyme electrophoresis on a total of 10 polymorphic allozyme loci. Contrary to earlier studies, all conducted in Britain, our samples showed little differentiation between sampled locations. In Spain, the populations of the Dona?a area showed no differentiation despite being up to 36 km apart; only the population to the south of the Guadalquivir river showed a significant difference to the others. In Finland the population on one island showed marked genetic differentiation from all the others, which showed little or no difference from each other. No isolation-by-distance effect could be detected in either system. We hypothesise that emigration-immigration events are more frequent in the Spanish and Finnish populations than in the British ones. We did, however, find two isolated populations, one in Spain and one in Finland; both were small and geographically isolated and shared evident drift.     

Pseudopollen and food-hair diversity in Polystachya Hook. (Orchidaceae)

Labellar food-hairs in Polystachya Hook. exhibit considerable morphological diversity. The commonest type of trichome is uniseriate, two to four-celled, with a clavate or subclavate terminal cell. This type occurs amongst representatives of most sections examined. Other trichomes are bristle-like with tapering or fusiform terminal cells, whereas representatives of section Polystachya have uniseriate, moniliform trichomes that fragment with the formation of rounded or elliptical component cells. Most contain protein and, while some contain starch, lipid is invariably absent. The presence of particular types of labellar trichomes does not coincide with variations in vegetative morphology. Thus, current taxonomic treatment of the genus indicates that trichome types, with perhaps the sole exception of moniliform, pseudopollen-forming hairs found in section Polystachya only, have limited taxonomic value. However, the remarkable similarity between pseudopollen-forming hairs of Polystachya and those of the Neotropical genus Maxillaria in terms of morphology, cellular dimensions and food content indicates that pseudopollen may have arisen several times and evolved in response to similar pollinator pressures.     

Micropropagation and genetic stability of a Dendrobium hybrid (Orchidaceae)

Summary Dendrobium hybrids have great economic importance in a number of countries. Asymbiotic seed germination and the conventional vegetative method have been commonly used by growers to propagate these plants. To overcome somaclonal variation, which is commonly exhibited by Dendrobium (Nobile group) when micropropagated from protocorm-like bodies, a protocol for propagating Dendrobium Second Love in vitro using axillary buds in the presence of thidiazuron was developed. Random amplified polymorphic DNA analysis was also carried out to check for possible genetic alterations in plants originating from six consecutive subcultures. The results revealed that the established protocol was efficient for the in vitro cloning of this orchid hybrid and the plants obtained from the six subcultures did not exhibit any type of polymorphism.     

Patterns of chloroplast diversity among western European Dactylorhiza species (Orchidaceae)

In Europe, the genus Dactylorhiza comprises a bewildering variety of forms that are difficult to sort into discrete species. Most Dactylorhiza species are diploid or tetraploid and contrasting hypotheses have been proposed to explain the complex variation within this group. Using PCR-RFLP analysis in eight putative species, we could identify four highly differentiated chloroplast DNA lineages. The first lineage (clade A) included the unique haplotype found in D. sambucina. Clade B grouped four haplotypes belonging mostly to D. incarnata. Clades C and D included 27 haplotypes detected in diploid D. fuchsii and in all tetraploid species investigated. Eighty percent of the chloroplast variation were consistent with currently accepted species boundaries. The imperfect agreement between chloroplast variation and species boundaries may be ascribed to incomplete lineage sorting and/or reticulation. Our cpDNA results provide strong evidence that the allotetrapolyploids have been formed through asymmetric hybridization with a member of the D. fuchsii / maculata group as the maternal parent.     

棉花遗传多态性研究进展

从系谱分析、形态特征、生化及 DNA分子水平等方面分析了棉花遗传多样性的研究进展 .国内外的研究一致表明陆地棉品种间遗传多态性水平低 ,改进其遗传多样性是今后棉花遗传育种研究的重要内容 .加强对现有栽培品种、野生种质的研究利用和种质引进交流 ,多种育种技术综合运用和合理的植棉区域规划及多育种目标引导 ,是提高育成品种遗传多样性的重要途径 .并提出今后应加强棉花核心种质的研究和从基因组水平对棉花遗传多样性的研究     

Phylogeography of Cycas revoluta Thunb. (Cycadaceae) on the Ryukyu Islands: very low genetic diversity and geographical structure

Variations in the chloroplast and mitochondrial DNA of Cycas revoluta Thunb. (Cycadaceae) were examined in 22 populations distributed across the Ryukyu Islands and southern Kyushu. Among the 14,130 bp of sequence examined, only one site mutation and one indel were polymorphic. The identified polymorphisms were located in the spacers between trnS (UGA) and trnfM (CAU) of the chloroplast DNA and between nad1 exon B and exon C of the mitochondrial DNA, respectively. Three haplotypes were identified from the Ryukyu Islands and southern Kyushu. The areas of distribution of the three haplotypes were highly geographically structured. The boundaries of two of the three haplotypes were demarcated by Okinoerabujima Island in the middle Ryukyus. The northern type and southern types lay north and south of the island, respectively. The third haplotype was almost sympatrically distributed with the southern type. The genetic variation within C. revoluta was estimated to be very low (h = 0.641, π = 0.00071) in comparison to its relative in Taiwan, C. taitungensis, which possesses 97 cpDNA haplotypes and 55 mtDNA haplotypes from two relic populations. A reasonable explanation for the low genetic diversity of the cycad on the Ryukyu Islands could be severe bottleneck effects, resulting from the submersion of low islands and the diminished landmass of islands in the interglacial age in the Quaternary period. The geographically restricted nature of the haplotypes could be attributed to vicariance resulting from the land configuration of the Ryukyu Islands, including changes in geography during the interglacial age in the Quaternary.