利用微卫星遗传标记探讨达氏鳇的多倍体倍性

鲟形目(Acipenseriformes)鱼类是一类多倍体起源的鱼类,种问易于杂交,且由于存在大量微型染色体,其染色体数目和倍性也难于确定.到目前为止包括达氏鳇(Huso dauricus)在内的一些鲟鱼物种基因组大小和染色体倍性仍旧存在争议.本实验采用微卫星遗传标记技术,通过观察9个微卫星位点的等位基因数目,发现达氏鳇在大部分位点中显示的倍性大于二倍性,同时利用多倍体分析软件POLYSAT推断了26尾达氏鳇的个体倍性.结果表明,26尾达氏鳇中有20尾显示为六倍体,占总数的76.92％;4尾显示为八倍体,占总数的15.38％;2尾显示为四倍体,占总数的7.79％.因此,我们认为达氏鳇应该为八倍体物种,结果中出现的四倍体和六倍体个体,是由于这些个体在我们选取的微卫星位点中存在部分纯合等位基因,导致了多数个体显示为六倍体.这一结论与近年来支持达氏鳇为进化性八倍体物种的研究结果一致.     

Ploidy level and origin of the European invasive weed Senecio inaequidens (Asteraceae)

Native to South-Africa, species of the Senecio inaequidens complex are presently invasive in Europe, Australia and South-America. Previously, different ploidy levels have been found in these different areas, with only tetraploid individuals reported in Europe, and only diploids in South-Africa and Australia. In the present study chromosome counts and flow cytometry were used to survey DNA ploidy levels in a large sample of 66 native and 21 European invasive populations. One Mexican individual was also added to the study. We found only tetraploid individuals occurring in Europe, whereas both ploidy levels, diploid and tetraploid, were found in South-Africa. Moreover, based on genome size, we suggest that two largely allopatric varieties of diploids exist in South-Africa. The Mexican individual was diploid. We suggest that European tetraploid individuals come from South-Africa and hypothesize that a hybridization event between the two DNA types of diploids occurred in the Lesotho area. The taxonomic difficulties surrounding species of theS. inaequidens complex are briefly discussed.     

Association of ploidy and sexual system in Lycium californicum (Solanaceae)

In North American Lycium (Solanaceae), the evolution of gender dimorphism has been proposed as a means of restoring outcrossing after polyploidization causes the loss of self-incompatibility. Previous studies of this process in Lycium focused on comparisons between species that differ in ploidy. We examined intraspecific variation in floral morphology and DNA content in populations of L. californicum to determine correlations between sexual system and cytotype. We also used nuclear ITS and GBSSI sequence data to determine whether diploid and polyploid forms represent the same phylogenetic species, and the phylogeographic relationships among populations and ploidy levels. Within populations, no variation in ploidy was found, although among populations there was a perfect correspondence between sexual system and cytotype. Diploid populations were all hermaphroditic, whereas tetraploid populations were all gender dimorphic. There was no clear geographic pattern to the occurrence of diploid and tetraploid forms. Phylogenetic analysis confirms that L. californicum, regardless of ploidy, forms a monophyletic group within the genus Lycium. Sequences from diploid and polyploid individuals did not form reciprocally monophyletic clades, indicating either multiple gains of polyploidy, ongoing gene flow between cytotypes, or lack of lineage sorting since the evolution of polyploidy. The correspondence between ploidy and sex expression is consistent with the hypothesis that polyploidization triggers the evolution of gender dimorphism in this and other Lycium species.     

Polyploidy determines the stage of invasion: clues from Kashmir Himalayan aquatic flora

Invasive species pose a major threat to native biodiversity and ecosystem integrity in many ecologically sensitive parts of the globe. Many research efforts have so far been made mainly with a focus on morphology, physiology and reproductive biology of invasive species to explain what determines the patterns of invasion. Recently, polyploidy has been reported to significantly influence plant invasiveness. Notwithstanding the profound management and conservation implications, determining the genetic basis of plant invasiveness is a challenging task for ecologists. Variation in ploidy levels of species promises to yield some useful insights in this direction and we, therefore, aimed to test the relation between polyploidy and species invasiveness. We documented chromosome number and ploidy level of 118 alien aquatic plant species including 50 alien non-invasive and 70 alien invasive species, belonging to 64 genera and 39 families distributed across various aquatic habitats of the Kashmir Himalaya at different stages of invasion. Results yielded 47 (39.83%) diploid species, 53 (44.91%) polyploids and the remaining 18 (15.25%) species were reported to have mixed ploidy, i.e., both diploids and polyploids. The invasive plant species exhibited about 40% of intraspecific ploidy polymorphism in contrast to about 28% found in non-invasive plant species. Alien invasive species (at stage IVa, IVb and V senso Colautti and MacIsaac 2004) were found to have more polyploidy (60%) than non-invasive species (at stage II and III) having only 45.23% polyploidy. Our results depict a clear pattern that non-invasive species are disproportionately more diploids with lower ploidy ratios, while invasive plant species on the contrary exhibit higher chromosome counts, thereby being predominantly polyploids. Invasion stage III with 17 diploid species represents by far the highest relative proportion of diploid species, while invasion stage V having 16 polyploid species is highest in terms of polyploid species. Regression analysis based on the stage of invasion and the ploidy status revealed that the relative proportion of polyploids on progressing stage of invasion increases significantly (p < 0.01). These results indicate that polyploidy may be one of the potential determinants of plant invasion. The implications of these results in timely prediction and better management of invasive species are discussed.     

利用整合分类学方法进行蕨类植物复合体的物种划分: 以线裂铁角蕨复合体为例

广泛的杂交和多倍化使得铁角蕨属(Asplenium)下存在着许多分类困难的物种复合体, 针对这些类群进行整合分类学的研究, 有助于我们更加全面和深入地理解物种的界限以及形成机制。线裂铁角蕨复合体(Asplenium coenobiale complex)是铁角蕨属下一个形态多样性较高的类群, 由于缺乏全面取样和系统研究, 该复合体的物种划分长期存在争议。本研究选取线裂铁角蕨复合体中形态变异和地理分布具有代表性的个体, 通过孢粉学研究确定该类群的生殖特性, 运用流式细胞分析获取倍性信息, 同时结合叶绿体和核基因组片段系统发生分析的证据, 对该类群的系统演化关系和起源方式进行了探讨。结果表明: (1)虽然部分孢子囊败育的情况在线裂铁角蕨复合体中十分普遍, 但正常孢子囊内形成的64个孢子说明该类群植物仍能进行正常的有性生殖; (2)该复合体中存在着倍性变异, 其中多角铁角蕨(A. cornutissimum)是二倍体, 而其他成员均为四倍体; (3)依据母系遗传的叶绿体序列所构建的系统发生关系将该类群划为4个分支, 与基于核基因序列构建的系统树存在冲突, 这暗示杂交可能在该复合体的形成过程中起到了重要的推动作用。综上所述, 我们建议将线裂铁角蕨复合体划分为4个物种, 即同源四倍体新种马关铁角蕨(A. maguanense sp. nov.), 二倍体多角铁角蕨, 以及两个由同一对亲本正反交产生的异源四倍体线裂铁角蕨(A. coenobiale)和叶基宽铁角蕨(A. pulcherrimum)。     

A review of ploidy in the genus Prosopis (Leguminosae)

The genus Prosopis contains 44 species of trees and shrubs, the majority of which originate in the Americas. Most species are reported to be diploid, with a somatic chromosome number of 2 n  = 28. There are rare reports of polyploidy, although it is thought that these may represent polysomaty in root tissues. However, flow cytometry has recently indicated that P. juliflora is entirely tetraploid with a somatic chromosome number of 2 n  = 56. In order to clarify the situation, an extensive review of ploidy in Prosopis was undertaken, the first of its kind. The ploidy levels of 124 samples of Prosopis from 21 countries, including both the natural and introduced ranges, were analysed using flow cytometry. In addition, a comprehensive literature review was carried out, examining 305 published ploidy values and covering 32 of the 44 species of Prosopis . Flow cytometry analysis suggests that P. juliflora is the only tetraploid species, with a somatic chromosome number of 2 n  = 4 x  = 56, whilst the remainder of the species analysed are diploid with 2 n  = 2 x  = 28, including the first report for P. articulata (2 n  = 28). A critical review of published ploidy values shows that all species of Prosopis are reported to be entirely diploid, except P. glandulosa , P. juliflora , and P. koelziana , for which both diploid and tetraploid values have been recorded. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 156 , 425–438.     

Foliar flavonoid aglycones of Phoebanthus

The diploid Phoebanthus tenuifolius and the tetraploid P. grandiflorus yielded identical complements of foliar flavonoid aglycones, including the compounds nepetin, jaceosidin, and hymenoxin. Flavonoid data do not resolve the origin of the tetraploid species. The similarity between the flavonoids of Phoebanthus and those earlier reported for Helianthus would support a merger of the two genera.     

Species diversity and ecological range in relation to ploidy level in the flora of the Pyrenees

Polyploidy is a major process in plant evolution. Surprisingly, no study has examined its role in species diversification and ecological distribution in relation to other life history traits. In this study, we examine to what extent polyploidy and the other traditionally examined biological traits (pollination mode, dispersal mode and growth form) account for ecological and taxonomic diversity in the flora of the Pyrenees. Fifty genera (in 22 angiosperm families) were classified according to ploidy level, growth form, pollination mode and dispersal mode, and 451 species and/or subspecies in these 50 genera were classified according to ploidy level and growth form. We examined the contribution of ploidy level, pollination and dispersal modes and growth form to (i) the ecological range of species and genera, i.e., the number of natural habitats (defined by a combination of ecological characteristics) where they occur, and (ii) the taxonomic diversity of the 50 genera. Ploidy level and dispersal mode had significant effects on the taxonomic diversity of the 50 genera. Taxonomic diversity, but not polyploidy per se, was significantly correlated with ecological range of genera. For individual species, diploids had a larger ecological range than polyploids, and herbaceous growth forms had wider ecological distributions than other growth forms. Our results indicate that polyploidisation may be a source of ecological diversification of genera, not by increasing the ecological range of particular polyploid species compared to diploids, but rather by creating taxonomic diversity that leads in some genera to a diversification of the habitats occupied by different ploidy levels. This observation is consistent with previous observations of ecological divergence of chromosomal races in some species in the Alps and in the Pyrenees. As found in other studies, species diversification in the studied flora appears to be greatly influenced by the occurrence of multiple dispersal modes, while ecological range of species or subspecies is significantly increased by the presence of herbaceous species.     

Ploidy variation in Buddleja L. (Buddlejaceae) in the Sino-Himalayan region and its biogeographical implications

The chromosome numbers of 27 populations of Buddleja , comprising 14 species, were counted. The basic chromosome number of all species was x  = 19, confirming previous reports. Different ploidy levels (2 n  = 38, 76, 114, 228) were observed in these taxa, representing diploids, tetraploids, hexaploids, and dodecaploids, respectively. The chromosome numbers of B. yunnanensis , B. brachystachya , and B. macrostachya are reported for the first time. The tetraploid 2 n  = 76 is a new ploidy level for B. myriantha . Particular attention was given to B. macrostachya , because of the variation in morphology and ploidy level between isolated populations of this species. Two types of interphase nuclei were recognized: the complex chromocentre type in B. macrostachya and the simple chromocentre type in the other species. Biogeographically, most of the polyploidy in the Asiatic species occurs in the Sino-Himalayan region. It seems to be associated with the uplift of the Himalayan Mountains, the orogeny of this region playing an important role in the evolution of polyploidy in these taxa.  © 2007 The Linnean Society of London. Botanical Journal of the Linnean Society , 2007, 154 , 305–312.     

Phylogenetic position of Mediterranean Astereae and character evolution of daisies (Bellis,Asteraceae) inferred from nrDNA ITS sequences

Phylogenetic analyses of nrITS sequences of Asteraceae revealed that the Bellis group is a natural assemblage comprising all the species of Bellis and Bellium, but not Rhynchospermum. In contrast, we propose to include the genera Bellis, Bellium, and Bellidastrum in the subtribe Bellidinae in the interest of circumscribing natural groups. Our results also suggest an early diversification in the western Mediterranean Basin of two monophyletic lineages, Bellis and Bellium. Three major groups can be distinguished within BELLIS: (1) the B. perennis group, containing five annual and perennial species with three ploidy levels (diploid, octoploid, and decaploid), which are distributed throughout the Mediterranean Basin despite lack of pappus; (2) the Bellis sylvestris group, with five annual and perennial species primarily from the western Mediterranean, in which there are five ploidy levels (diploid, tetraploid, hexaploid, octoploid, and decaploid); and (3) a basal grade consisting of three diploid, perennial species which displays remarkable diversification of morphologies. Striking characteristics, such as an annual life form, polyploidy, and loss of pappus, seem to have occurred in parallel several times and in different geographical areas during the early diversification of Bellis species in the western Mediterranean. Character evolution reconstructions allow us to describe a putative ancestor of the genus Bellis (proto-Bellis).     

Ploidy level of the invasive weed Rubus alceifolius (Rosaceae) in its native range and in areas of introduction

 A change in ploidy level could increase invasiveness of introduced plants in insular plant communities. To examine this question for R. alceifolius, we compared its ploidy level in its Asian native range and in the Indian Ocean islands where it has been introduced. We first counted chromosomes on root tips from a Vietnamese individual, which proved to be tetraploid (2n=4x=28). The nuclear DNA content of other individuals from the native range and areas of introduction was estimated using the flow cytometry method. The Vietnamese individual on which chromosomes were counted was added to the sample, to enable deduction of the ploidy level of all individuals from their nuclear DNA content. All individuals were found to be tetraploid, except 10 individuals from a single clone collected in a Vietnamese population, estimated to be triploid, and morphologically different of other individuals of this study. We showed that while polyploidy of the source population may have predisposed this plant to become a successful invader, its introduction into Indian Ocean islands was not associated with any change in ploidy level. Received January 23, 2001 Accepted May 22, 2001     

三江源地区刺柏属植物群落类型特征

三江源地区位于青藏高原的腹地, 是典型的生态脆弱区, 刺柏属(Juniperus)植物群落是该地区天然林资源的重要组分, 在维持生物多样性与水生态安全方面发挥着重要作用。该研究调查了刺柏属植物群落的主要植被类型, 通过对53个样地的样方数据分析, 量化描述了其各个群落类型的主要特征。结果表明: (1)根据生活型和优势度原则, 该区刺柏属植物群落可划分为祁连圆柏(J. przewalskii)林、大果圆柏(J. tibetica)林、密枝圆柏(J. convallium)林、塔枝圆柏(J. komarovii)林、大果圆柏灌丛和密枝圆柏灌丛, 进一步分为15个群丛。(2)调查所得维管植物共有142种, 隶属34科90属, 其中菊科种数最多, 占总种数的16.20%。(3)群落垂直结构明显, 其中乔木层优势种单一, 灌木层优势种主要有鲜黄小檗(Berberis diaphana)、银露梅(Potentilla glabra)及灌木状的大果圆柏, 草本层以薹草属(Carex)和马先蒿属(Pedicularis)占优势。(4)该区种子植物种的地理成分中, 温带成分占总种数的52.59%, 温带亚洲分布、东亚分布和中亚分布等为本区分布占比较大的分布区类型; 中国特有种占47.41%; 区系成分呈现横断山植物区系和唐古特植物区系成分互相交融的特点。     

Pollen and stomata morphometrics and polyploidy in Eriotheca (Malvaceae‐Bombacoideae)

Approximately 70% of the angiosperm species are polyploid, an important phenomenon in the evolution of those plants. But ploidy estimates have often been hindered because of the small size and large number of chromosomes in many tropical groups. Since polyploidy affects cell size, morphometric analyses of pollen grains and stomata have been used to infer ploidy level. Polyploidy is present in many species of the Cerrado, the Neotropical savanna region in Central Brazil, and has been linked to apomixis in some taxa. Eriotheca gracilipes and Eriotheca pubescens are common tree species in this region, and present cytotypes that form reproductive mosaics. Hexaploid individuals (2n = 6x = 276) are polyembryonic and apomictic, while tetraploid and diploid individuals (2n = 2x = 92, 2n = 4x = 184) are sexual and monoembryonic. We tested whether morphometric analysis can be used to estimate ploidy levels in E. gracilipes and E. pubescens individuals. Pollen material from diploid and hexaploid individuals of E. gracilipes, and tetraploid and hexaploid individuals of E. pubescens, were fixed in 50% FAA, and expanded leaves were dried in silica gel. Pollen grains and stomata of at least five individuals from each population were measured. The results demonstrate that all measures were significantly different among cytotypes. Individuals with higher levels of ploidy (hexaploid) all presented measurements that were higher than those with lower levels (diploid and tetraploid). There was no overlap between ploidy levels in each species at 95% confidence interval. Thus, the size of the pollen grains and stomata are effective parameters for analysis of ploidy levels in E. gracilipes and E. pubescens.     

CHROMOSOME NUMBERS IN SPHAERALCEA SECTION FENDLERIANAE

Chromosome numbers are reported for ten taxa in Sphaeralcea section Fendlerianae (Malvaceae). New ploidy levels are reported for six taxa, with one species not previously reported, and extensive polyploidy at all taxonomic levels is documented. The geographic and taxonomic distribution of polyploids suggests that polyploidy arose many times in the taxa of Sphaeralcea. Sphaeralcea fendleri var. venusta, S. polychroma, and S. wrightii populations have yielded exclusively tetraploid counts. Tetraploidy is correlated with taxa having lavender petals. Polyploidy has also allowed the taxa to expand their distributions without resulting in speciation.     

Terpenes of leaf oils from Cupressaceae

The components of the leaf oils from twelve species in the four genera (Thuja, Thujopsis, Juniperus and Chamaecyparis) of the Cupressaceae have been studied quantitatively. Some chemotaxonomical feature on the components are discussed.     

钱江源国家公园叶附生苔类植物的物种多样性

本文报道钱江源国家公园叶附生苔类植物4科9属19种, 较之前记录增加3科8属17种。与钱江源处于同纬度的我国其他地区相比, 钱江源叶附生苔类植物的种数仅次于西藏墨脱, 排名第二。鳞叶疣鳞苔(Cololejeunea longifolia)和尖叶薄鳞苔(Leptolejeunea subacuta)是钱江源国家公园最常见的2种叶附生苔类植物。丰富的叶附生苔类植物表明钱江源国家公园具有较合适的叶附生苔类植物生长环境, 这可能与该地区长期有效的保护密切相关。     

赛罕乌拉自然保护区蝶类多样性及其影响因素

为了解赛罕乌拉自然保护区蝶类多样性及其影响因素, 我们于2017年5-9月分别对保护区的典型草原、湿地、山地沟谷草甸、退化草原、农田、山地旱生灌丛、山地中生灌丛等7种生境中的蝴蝶进行观测调查。共记录和采集蝴蝶2,290只, 隶属5科42属63种。蛱蝶科的种类数(34种)和个体数(991只)最多。柑橘凤蝶(Papilio xuthus)、云粉蝶(Pontia daplidice)、绢粉蝶(Aporia crataegi)、荨麻蛱蝶(Aglais urticae)、银斑豹蛱蝶(Speyeria aglaja)等5种为保护区的优势种。保护区蝶类群落的种-多度曲线呈正态分布模式, 表明保护区生态环境良好, 生境相互重叠, 蝶类活动范围在不同生境中可以延伸。不同生境中蝶类群落种类及数量存在一定差异, 其中山地中生灌丛蝶类群落的多样性指数最高, 优势度指数最低; 退化草原的多样性指数和物种丰富度指数均为最低, 优势度指数最高; 山地沟谷草甸的科、属、种、个体数最多; 退化草原的科、属、种、个体数都是最少。区系组成分析表明广布种占63.49%, 古北种占36.51%。保护区不同生境中蝶类群落多样性特征指数在各月份间有明显差异, 蝴蝶种类及个体数与温度之间呈显著正相关, 与降雨量无显著相关性。综上, 我们认为适当的干扰有利于蝶类多样性发展, 而强烈的人为干扰会严重破坏草场环境, 影响蝶类生存和繁衍, 降低蝶类多样性。     

Polyploidy: a missing link in the conversation about seed transfer of a commonly seeded native grass in western North America

The use of local, native plant materials is now common in restoration but testing for polyploidy in seed sources is not. Diversity in cytotypes across a landscape can pose special seed transfer challenges, because the methods used to determine genetically appropriate materials for seed transfer do not account for cytotypic variation. This lack of consideration may result in mixing cytotypes through revegetation, which could reduce long‐term population viability. We surveyed nine populations of a native bunchgrass, Pseudoroegneria spicata, in three EPA Level III Ecoregions in the western United States to determine the frequency of polyploidy, whether there are differences in traits (phenotype, fecundity, and mortality) among plants of different cytotypes, and whether cytotype frequency varies among ecoregions. We assessed trait variation over 2 years in a common garden and determined ploidy using flow cytometry. Polyploidy and mixed cytotype populations were common, and polyploids occurred in all ecoregions. Four of the nine populations were diploid. The other five had tetraploids present: three had only tetraploid individuals whereas two had mixed diploid/tetraploid cytotypes. There was significant variation in traits among cytotypes: plants from tetraploid populations were larger than diploid or mixed populations. The frequency and distribution of cytotypes make it likely that seed transfer in the study area will inadvertently mix diploid and polyploid cytotypes in this species. The increasing availability of flow cytometry may allow ploidy to be incorporated into native plant materials sourcing and seed transfer.     

Morphology and Genetic Diversity of Phragmites australis in Beijing

为探明北京地区芦苇(Phragmites australis)的资源状态和多样性, 实地考察北京主要河流、湿地和水库, 发现北京地区芦苇总生长面积已超过600 hm²。芦苇染色体倍性以八倍体为主, 四倍体次之。在面积较大的湿地内, 八倍体单一芦苇群落占据优势地位; 而在城市的浅河内有形态和遗传性多样的混合种群。研究表明, 植物性状和倍性水平之间无显著相关性。在小清河发现了6种形态各异的芦苇克隆, 均属于叶绿体DNA片段的P单倍型; 其单倍体基因组大小为(0.499±0.019) pg, 变异系数为3.8%。这表明表型与单倍型之间也不具相关性。此外, 发现1个具有变叶特性的芦苇, 将其命名为金条芦苇。北京地区芦苇形态和遗传多样性为研究芦苇基因型与环境适应性之间的关系提供了珍贵的资源。     

One plus one makes seven: Intricate phylogeographic patterns in Odontites vernus (Orobanchaceae: Rhinantheae) in the Iberian Peninsula

The Odontites vernus group is the most widespread of the genus Odontites, occupying the temperate regions of Eurasia and northern Morocco. The group contains three species, all inhabiting the Iberian Peninsula, where O. vernus s.l. (sensu lato) exhibits remarkable morphological variability and includes diploid and tetraploid individuals corresponding to the two subspecies that occur there. We collected 301 individuals from 100 sampling sites covering the entire distribution of O. vernus in the Iberian Peninsula and genotyped them using 12 simple sequence repeat (SSR) markers. Their ploidy level was estimated by flow cytometry, and two cpDNA regions (rps16 intron and trnK-rps16) were sequenced. We found 129 diploids and 172 tetraploids distributed following a mosaic parapatry model, while only two mixed-ploidy populations were discovered. The 20 haplotypes found fit two well-defined haplogroups, to some extent correlated with estimated ploidy levels. The frequencies of the SSR alleles shared by both cytotypes, as well as those of the private alleles corresponding to the tetraploid cytotype, indicate that tetraploids likely originated at least twice through autopolyploidy. Additionally, the results from SSR markers were structured in a higher number of groups than did the cpDNA sequences. Thus, the genetic distance analysis detected four groups, but the Bayesian analysis of population structure identified seven, with only low levels of gene flow detected among groups. The distributions of the seven genetic groups coincide with well-known refugium areas within the Iberian Peninsula during the climatic oscillations of the Quaternary. Thus, the results give additional support to the “refugia within refugia” hypothesis.