濒危植物独花兰的形态变异及其适应意义

采用ANOVA和UPGMA等方法对濒危植物独花兰(Changnieniaamoena)分布于庐山、新宁和神农架3个地点的12个自然居群的形态变异进行了研究,探讨其形态多样性水平和地理变异式样及其可能的适应机制。结果表明,庐山居群13个性状的平均观测值均高于新宁和神农架居群。在物种水平上各个性状存在较丰富的变异,变异系数(CV值)为0.02–0.30。尽管同一性状在不同居群中的变异程度较大,但总体而言,花部器官的变异性比营养器官低。单因素方差分析显示3个地区间多个形态性状存在极显著差异(P<0.01);UPGMA聚类分析也表明这3个地区分别形成明显不同的分支。值得注意的是,神农架地区龙门河和关门山两个地点间存在明显的形态分化,而这种形态分化是以传粉者为媒介自然选择的结果。相关性分析显示,营养器官之间、花部器官之间,以及营养器官与花部器官之间均存在较高的相关性。上述结果对进一步了解独花兰的适应机制以及制定科学的保护策略提供了有益的资料。     

Genome size variation in Macaronesian angiosperms: forty percent of the Canarian endemic flora completed

Genome sizes for 127 Macaronesian endemic angiosperms from 69 genera and 32 families were estimated using propidium iodide flow cytometry. Only about 30-fold variation in 1C-values was found, ranging from 0.32 pg in Echium bonnetii to 9.52 pg in Scilla dasyantha. Taxa with very small DNA amounts (1C 1.4 pg) were the most dominant group (71.7%), whereas the frequency of other categories was much lower (18.9% and 9.4% in taxa with small (1.41–3.50 pg) and intermediate 1C-values (3.51–14.00 pg), respectively). Comparisons of average C- and Cx-values between Macaronesian endemics and non-Macaronesian representatives always revealed significantly smaller amounts in the former group at various taxonomic levels (genus, family, major phylogenetic lineage). Potential relationship between nuclear DNA content and insular burst of speciation is suggested owing to the marked prevalence of very small genomes among angiosperms that underwent rapid adaptive radiation. Merging all the genome size data on Macaronesian angiosperms available shows that this flora represents the best covered plant assemblage from the phytogeographic point of view.     

The considerable genome size variation of Hordeum species (poaceae) is linked to phylogeny, life form, ecology, and speciation rates

Genome size variation in plants is thought to be correlatedwith cytological, physiological, or ecological characters. However,conclusions drawn in several studies were often contradictory.To analyze nuclear genome size evolution in a phylogenetic framework,DNA contents of 134 accessions, representing all but one speciesof the barley genus Hordeum L., were measured by flow cytometry.The 2C DNA contents were in a range from 6.85 to 10.67 pg indiploids (2n = 14) and reached up to 29.85 pg in hexaploid species(2n = 42). The smallest genomes were found in taxa from theNew World, which became secondarily annual, whereas the largestdiploid genomes occur in Eurasian annuals. Genome sizes of polyploidtaxa equaled mostly the added sizes of their proposed progenitorsor were slightly (1% to 5%) smaller. The analysis of ancestralgenome sizes on the base of the phylogeny of the genus revealedlineages with decreasing and with increasing genome sizes. Correlationsof intraspecific genome size variation with the length of vegetationperiod were found in H. marinum populations from Western Europebut were not significant within two species from South America.On a higher taxonomical level (i.e., for species groups or theentire genus), environmental correlations were absent. Thiscould mostly be attributed to the superimposition of life-formchanges and phylogenetic constraints, which conceal ecogeographicalcorrelations.     

Genetic variation in time and space: the use of herbarium specimens to reconstruct patterns of genetic variation in the endangered orchid Anacamptis palustris

Habitat alteration, fragmentation and destruction as a consequence of human impact are a global phenomenon. Here we document changes in genetic variation in the marsh orchid Anacamptis palustris as a consequence of such habitat changes. We examined historical specimens that were collected during the nineteenth and early twentieth centuries, prior to the most recent massive habitat changes affecting this species. Sequences of a hypervariable region in the plastid DNA, located in the tRNA^LEU intron, from herbarium vouchers were compared with those from a near-exhaustive survey of the extant A. palustris populations on the Italian peninsula. It was found that private haplotypes and alleles found in small, extant populations were once widespread and more common in historic populations and that alleles, once present in historic populations, have gone extinct. In addition, genetic differentiation among populations has increased over time and haplotype frequencies significantly differ among historic and extant populations. These results document that human induced habitat changes have reduced genetic diversity and increased the importance of random genetic drift in this species. It is concluded that the analysis of herbarium specimens may provide important insights into changes of genetic diversity over time and may be critical for correct inference of the evolutionary history of rare and endangered species.     

濒危植物盘龙参种子的非共生萌发及种苗的快繁研究

以盘龙参种子为材料,筛选离体条件下适宜种子非共生萌发、种苗快繁的培养基。结果表明:盘龙参种子在无植物生长物质的培养基中能够萌发,但不能发育成苗;在含有1.0mg·L-1 KT、0.1mg·L-1 IAA和0.1mg·L-1 GA3的培养基中萌发,并能进一步发育形成种苗;在较高浓度生长素(1.2mg·L-1 NAA)的培养基中不能萌发。种苗在较高浓度细胞分裂素和较低浓度生长素配比的培养基中能够增殖,最高增殖系数可达到2.8,转入壮苗生长培养基中培养80d后可以移栽温室。最适增殖培养基为1/2MS+12.0mg·L-1 6-BA+0.1mg·L-1 NAA+10.0mg·L-1腺嘌呤;最适壮苗生根培养基为1/2MS+1.0mg·L-1 KT+0.1mg·L-1 IAA+10.0mg·L-1腺嘌呤。     

2C DNA variation and relationships among New World species of the genus Lupinus (Fabaceae)

The 2C DNA values in 38 species and accessions of the genus Lupinus (Fabaceae) from the New World have been analysed using flow cytometry. They are representatives of North and South American species (the Atlantic and the Andean regions). Estimated 2C DNA values ranged from 1.08 pg in L. pusillus to 2.68 pg in L. albicaulis (both from North America), that is a variation of more than 2.5-fold. The variation for North American lupins was much higher than that for South American ones. Statistical analysis of the data resulted in a grouping that showed for North American lupins some correlation with the length of life cycle. Discussion concerns some aspects of the evolution of the genus.     

Genetic diversity in Isoetes yunguiensis, a rare and endangered endemic fern in China

Isoetes yunguiensis is an endangered and endemic fern in China. Field survey indicated that only one population and no more than 50 individuals occur in the wild. The genetic variation of 46 individuals from the population remaining at Pingba (Guizhou Province, China) was assessed by Random Amplified Polymorphic DNA (RAPD) finger-printing. Twelve primers were screened from sixty ten-bp arbitrary primers, and a total of 95 DNA fragments were scored. Of these, 62.1% were polymorphic loci, which indicated that high level genetic variation existed in the natural population. The accumulation of genetic variation in the history of the taxon and the apparent minimal reduction effect on genetic diversity following destruction of habitat might be responsible for the high level genetic diversity presently remaining in the I. yunguiensis population. However, with the continuing decrease of population size, the genetic diversity will gradually be lost. We suggest that the materials from the extant population should be used for re-establishment of the populations. Translated from Journal of Wuhan University (Natural Sciences Edition), 2005, 51(6): 767–770 [译自: 武汉大学学报 (理学版)]     

Taxonomic implications of genome size and pollen colour and vitality for species of Agapanthus L’Héritier (Agapanthaceae)

Nuclear DNA content (2C) and pollen vitality and colour are used as new criteria to investigate all species of the genus Agapanthus LHéritier. The species have the same chromosome number (2n=2x=30), with exception of four triploid plants found. The nuclear DNA content of the diploids, as measured by flow cytometry with propidium iodide, is demonstrated to range from 22.1–31.6 pg. This implies that the largest genome contains roughly 10¹⁰ more base pairs than the smallest. The species could be divided in two groups based on pollen colour and DNA content: a group with lilac pollen and a DNA content between 22.3 and 24.1 pg containing the species A. campanulatus Leighton, A. caulescens Sprenger and the rarer A. coddii Leighton, and a group with yellow/brownish pollen and a DNA content from 25.2–31.6 pg containing the species A. praecox Willd., A. inapertus Beauv. and A. africanus (L.) Hoffmanns. Four other taxa, recognized by Leighton (1965) are treated as follows: A. comptonii Leighton, has a nuclear DNA content similar to A. praecox and is considered to be a synonym of A. praecox subsp. minimus Leighton. A. walshii L. Bol., has with 31.6 pg the same high amount of DNA as A. africanus from the same area and is therefore renamed as a subspecies (A. africanus subsp. walshii (Leighton) Zonn. & Duncan comb. nov.). The nuclear DNA amounts of A. dyeri Leighton, including the geographically isolated plants from Mozambique, are shown to be identical to A. inapertus. Therefore A. dyeri is considered synonymous with A. inapertus subsp. intermedius Leighton. A. nutans Leighton is identical in DNA content to A. caulescens and is considered to be synonymous with that species. Concluding there are six species: A. campanulatus Leighton, A. caulescens Sprenger, A. coddii Leighton, A. praecox Willd., A. inapertus Beauv. and A. africanus (L.) Hoffmanns. Nuclear DNA content as measured by flow cytometry and pollen colour are shown to be relevant traits to throw light on the relationships between Agapanthus species.     

Flow cytometric measurement of nuclear DNA content inCapsicum (Solanaceae)

Nuclei were isolated from leaf tissue of differentCapsicum species and the relative fluorescence intensity was measured by flow cytometry after propidium iodide staining.Pisum sativum nuclei with known nuclear genome size (9.07 pg) were used as internal standard to determine nuclear DNA content of the samples in absolute units. The 2C DNA contents ranged between 7.65 pg inC. annuum and 9.72 pg inC. pubescens, and the general mean of the genus was 8.42 pg. These values correspond, respectively, to 1C genome size of 3.691 (C. annuum), 4.690 (C. pubescens) and 4.063 (general mean) Mbp. In general, white-flowered species proved to have less DNA, with the exception ofC. praetermissum, which displayed a 2C DNA content of 9.23 pg. It was possible to divide the studied species into three main groups according to their DNA content, and demonstrate differences in DNA content within two of the three species complexes established on the basis of morphological traits.     

Isolation and characterization of 24 microsatellite loci in Paphiopedilum rothschildianum, an endangered slipper orchid

This paper describes the characterization of 24 polymorphic microsatellite loci in Paphiopedilum rothschildianum, an endangered slipper orchid endemic to Sabah, Malaysia. A total of 36 clones containing microsatellite repeat motifs yielded 41 dinucleotide, 20 tetranucleotide and 30 cryptic simple repeat sequences. Thirty microsatellite loci were randomly selected to characterize the population, of which 24 were found to be polymorphic. The expected heterozygosity ranged from 0.0813 to 0.7279 (mean 0.4533) and the observed heterozygosity ranged from 0 to 1 (mean 0.3800). The results indicated that there was limited migration between the three subpopulations and a significant degree of genetic differentiation (F_ST = 0.5098) between populations implying that gene flow has been disrupted as a result of habitat fragmentation. The molecular markers have a potential application in population management, CITES enforcement and the forensic detection of specimens in international trade.     

Taxonomic implications of genome size for all species of the genus Gasteria Duval (Aloaceae)

Nuclear DNA content (2C) is used as a new criterion to investigate all species of the genus Gasteria Duval including the three recently described species Gasteria polita van Jaarsv., G. pendulifolia van Jaarsv. and G. glauca van Jaarsv.. The 122 accessions investigated have the same chromosome number (2n=2x=14), with exception of three tetraploid plants found. The nuclear DNA content of the diploids, as measured by flow cytometry with Propidium Iodide, is demonstrated to range from 32.8–43.2 pg. This implies that the largest genome contains roughly 10¹⁰ more base pairs than the smallest. Based on DNA content the species could be divided in five groups: G. rawlinsonii Oberm. with 32.8 pg, 13 mostly inland species with 34.3–36.0 pg, five coastal species with 36.5–39.0 pg and Gasteria batesiana Rowley with 43.2 pg. The thirteen species with 34.3–36.0 pg could be divided further, in a group of eight species occupying mainly very restricted areas with 34.3–35.1 pg and a second group of five species with 35.2–36.0 pg mainly occupying large areas. These five groups did not coincide very well with the two sections and four series of Gasteria based on a cladistic analysis by van Jaarsveld et al. (1994). Based on its long leafy branches, location in the centre of Gasteria species distribution and its by far lowest DNA content, G. rawlinsonii might be the most primitive member of the genus. Nuclear DNA content as measured by flow cytometry is shown to be relevant to provide additional information on the relationships between Gasteria species.     

青藏高原濒危植物唐古特大黄的遗传多样性

唐古特大黄(Rheum tanguticum)是中国传统的中藏药材,近几年由于生境的严重破坏,已濒临灭绝,并被列入濒危植物名单。为了探索唐古特大黄物种濒危的原因并保护其野生资源,本研究采集了9个居群87个个体的唐古特大黄样本,基于该物种的叶绿体基因trn S-G序列对其进行了遗传多样性研究。结果表明,唐古特大黄物种具有较高的遗传多样性水平(Ht=0.694),其中95.97%的遗传分化来自于居群间(G_(ST)=0.960),4.03%的遗传分化来自于居群内(Hs=0.028)。AMOVA分析也显示唐古特大黄居群间基因流较小(N_m=0.01),存在较高的遗传分化(F_(ST)=0.9631)。唐古特大黄较高的遗传多样性水平可能与该物种较长的进化史和生活史有关,居群间较高的遗传分化可能与高山地区特殊的地理环境和人类活动有关。根据研究结果,建议对唐古特大黄所有野生居群进行就地保护,同时收集种质资源开展异地繁殖工作,以保护物种的遗传多样性,维持其进化潜力。     

Genetic diversity of Astragalus nitidiflorus, a critically endangered endemic of SE Spain,and implications for its conservation

Inter-simple sequence repeats (ISSR) markers were used to assess the genetic diversity and population structure in five populations of Astragalus nitidiflorus, a critically endangered species endemic to southeast Spain. Eight primers amplified 78 bands with 40 (51.3%) being polymorphic. Statistical results indicated a low genetic diversity at the population and species level, with percentages of polymorphic bands (PPB) ranging from 28.2 to 37.2% (an average of 31.8%), and means of gene diversity (H_E) of 0.129 and 0.171 respectively. The Shannon’s index (SI) ranged from 0.160 to 0.214 at the population level and was 0.260 at the species level. A low level of genetic differentiation among populations was detected, based on the Shannon’s information index (0.297), the coefficient of genetic differentiation between populations (G_ST = 0.2418) and AMOVA analysis (Φ_ST = 0.255). The estimated gene flow (Nm) was 0.789. The high genetic connectivity found among populations of A. nitidiflorus is an evidence of a recent habitat fragmentation. In addition, a bottleneck event in the past has been revealed, with a subsequent reduction of population size and a loss of genetic variation. Based on these results, the conservation strategy of A. nitidiflorus was proposed.     

Genetic variation in the horsetail Equisetum variegatum Schleich., an endangered species in the Parisian region

Equisetum variegatum Schleicher is a circumboreale species of horsetail. In France, it typically grows at high elevations but is very rare in lowlands. The genetic variation of these populations is described using isozyme electrophoresis and PCR-RFLP of chloroplast DNA. Sampled sites were chosen to represent central vs. marginal and/or endangered parts of the distribution area. Extensive clonal multiplication of plants together with the absence of local recruitment by sexual reproduction seem to be responsible for the low genetic diversity observed within populations. Since adaptive response to environmental changes ultimately relies on the presence of genetic variability, clonal populations of E. variegatum may be particularly vulnerable to disturbance. Moreover, in lowland populations, isolation gives no chance to recover new genotypes through migration events. The preservation of the two endangered populations is proposed by propagation by cuttings of all extant genetic individuals. In the case of a disappearance of one genotype in the field, a replacement will be possible. This plan may be sufficient to preserve E. variegatum in the French lowland for several years.     

Nuclear DNA content in allopolyploid species and synthetic hybrids in the grass genus Paspalum

DNA content was estimated by flow cytometry in seventeen taxa from the Dilatata, Quadrifaria and Paniculata groups of Paspalum and five synthetic hybrids. Results were compared to known genome constitutions and phylogenetic relationships. DNA 2C-values ranged from 1.24 pg in diploid P. juergensii to 3.79 pg in a hexaploid biotype of P. dilatatum. The I genome of three Quadrifaria diploids is 1.2 to 1.5-fold larger than the J genome of P. juergensii (Paniculata). The 2C-values of the IIJJ tetraploids of the Dilatata group are lower than expected based on putative genome donors. Reduction of genome sizes could have occurred after the formation of the allopolyploids of the Dilatata group. The DNA content of all synthetic hybrids is in accordance with the sum of parental C-values. The interactions driving genome downsizing may operate differently during the transition from diploidy to polyploidy than on subsequent increases in ploidy level.     

Genome size variation in the genus Carthamus (Asteraceae, Cardueae): systematic implications and additive changes during allopolyploidization

BACKGROUND AND AIMS: Plant genome size is an important biological characteristic, with relationships to systematics, ecology and distribution. Currently, there is no information regarding nuclear DNA content for any Carthamus species. In addition to improving the knowledge base, this research focuses on interspecific variation and its implications for the infrageneric classification of this genus. Genome size variation in the process of allopolyploid formation is also addressed. METHODS: Nuclear DNA samples from 34 populations of 16 species of the genus Carthamus were assessed by flow cytometry using propidium iodide. KEY RESULTS: The 2C values ranged from 2.26 pg for C. leucocaulos to 7.46 pg for C. turkestanicus, and monoploid genome size (1Cx-value) ranged from 1.13 pg in C. leucocaulos to 1.53 pg in C. alexandrinus. Mean genome sizes differed significantly, based on sectional classification. Both allopolyploid species (C. creticus and C. turkestanicus) exhibited nuclear DNA contents in accordance with the sum of the putative parental C-values (in one case with a slight reduction, frequent in polyploids), supporting their hybrid origin. CONCLUSIONS: Genome size represents a useful tool in elucidating systematic relationships between closely related species. A considerable reduction in monoploid genome size, possibly due to the hybrid formation, is also reported within these taxa.     

中国吊钟花属植物核DNA含量(2C-值)与倍性水平研究

植物核DNA含量(2C-值)与倍性水平是重要的植物学基本特征,是进行种群进化、物种分类和生态学等研究的有力证据.为确定中国吊钟花属(Enkianthus Lour.)各物种的核DNA含量与倍性水平并探究该属植物在种间、种内核DNA含量差异,该研究以6种中国吊钟花属植物共23个居群60个样品为试验材料,以水稻品种'日本晴...     

Genome sizes for all genera of Cycadales

Nuclear DNA content (2C) is reported for all genera of the Cycadales, using flow cytometry with propidium iodide. Nuclear DNA content ranges from 24 to 64 pg in cycads. This implies that the largest genome contains roughly 40 × 10(9) more base pairs than the smallest genome. The narrow range in nuclear DNA content within a genus is remarkable for such an old group. Furthermore, 42 of the 58 plants measured, covering five genera, have 18 chromosomes. They vary from 36.1 to 64.7 pg, covering the whole range of genome sizes (excluding the genome of Cycas). Hence, their does not seem to be a correlation between genome size and the number of chromosomes.     

Genome size variation and evolution in the grape family Vitaceae

Genome size variation is of fundamental biological importance and has been a longstanding puzzle in evolutionary biology. In the present study, the genome size of 61 accessions corresponding to 11 genera and 50 species of Vitaceae and Leeaceae is determined using flow cytometry. Phylogenetically based statistical analyses were used to infer ancestral character reconstructions of nuclear DNA contents. The DNA 1C‐values of 38 species are reported for the first time, with the largest genome (Cyphostemma humile (N. E. Br.) Desc. ex Wild & R. B. Drumm, 1C = 3.25 pg) roughly 10.48‐fold larger than the smallest (Vitis vulpina L., 1C = 0.31 pg). The large genomes are restricted to the tribe Cayratieae, and most other extant species in the family possess relatively small genomes. Ancestral genome size reconstruction revealed that the most recent common ancestor for the family had a relatively small genome (1C = 0.85 pg). Genome evolution in Vitaceae has been characterized by a trend towards genome size reduction, with just one episode of apparent DNA accumulation in the Cayratieae lineage. Such contrasting patterns of genome size evolution probably resulted from transposable elements and chromosome rearrangements, while neopolyploidization seems to contribute to recent genome increase in some species at the tips in the family tree.     

Causes of rarity and range restriction of an endangered, endemic limpet, Siphonaria compressa

The pulmonate limpet Siphonaria compressa is South Africa's most endangered marine mollusc. It is endemic to just two localities: Langebaan Lagoon on the west coast, and Knysna Estuary on the south coast, and occurs only on the eelgrass Zostera capensis. In Langebaan Lagoon, eelgrass has fluctuated substantially over the last 34 years, and S. compressa has twice approached extinction. S. compressa is largely confined to the lower edge of the eelgrass beds there, being replaced higher up by another small gastropod, Assiminea globulus. We explored the physical and biological factors underlying the limpet's narrow habitat, using field observations, translocations, caging and transplant experiments. Abundance of S. compressa was positively correlated with Z. capensis cover and negatively correlated with shore height. When moved to the upper portions of the eelgrass bed, S. compressa had lower rates of persistence and survival than in the lowest zone. The lower limit of zonation for S. compressa was set indirectly by bioturbation by the sandprawn Callianassa kraussi, which excluded eelgrass from intertidal sandbanks. Transplants of eelgrass into the sandbanks proliferated provided C. kraussi was experimentally eliminated, and supported densities of S. compressa 20-fold greater than in control eelgrass beds, suggesting that high-shore eelgrass beds to which S. compressa is normally confined are suboptimal for the limpet. A. globulus showed patterns opposite to those of S. compressa: its persistence and survival were greatest in the upper zone and it actively avoided the lower sections of these beds and never colonised eelgrass transplanted into sandflats lower on the shore. There was no evidence that competition between S. compressa and A. globulus influenced the zonation or abundance of either species. Rarity of S. compressa and its endangered status seem dictated by its extremely narrow and temporally changeable habitat-range, which is defined by physical stress in the high-shore and bioturbation by C. kraussi in the low-shore. Fluctuations in eelgrass abundance and limitation of S. compressa to just two localities add substantially to the risks of extinction for this embattled stenotypic limpet.