青藏高原毛茛科3种特有植物核型和进化研究

对青藏高原高山冰缘地区毛茛科3 种特有植物的核型进行了分析。它们的核型公式(K)、染色体相对长度组成(C. R. L. ) 和核型不对称系数(A s. K% ) 分别为: 青藏金莲花 T rollius pumilus var. tangu ticus: K (2n) = 6m + 8sm (2SA T ) + 2st, C. R. L. = 4L + 4M 2+ 4M 1+ 4S,A s. K% = 63. 57, 核型属2B型; 甘青乌头A conitum tanguticum 为K (2n) = 6m + 10sm ,C. R. L. = 4L + 8M 1+ 4S,A s. K% = 62. 54, 2B 型; 单花翠雀花Delphinium candelabrum var.monanthum 为K (2n) = 6m + 8sm + 2st, C. R. L. = 4L + 4M 2+ 4M 1+ 6S,A s. K% = 64. 34, 属3B 型。经同相关近缘种核型资料比较, 青藏金莲花核型不对称性和进化程度比金莲花T.ch inensis 低; 甘青乌头的核型不对称性和进化程度在其近缘类群(乌头组Sect. Aconitum ) 已报道的种之内最低; 单花翠雀花核型不对称性和进化水平比翠雀组(Sect. Delphinastrum ) 已报道的展毛翠雀花D. kamaoense var. glabrescens、多枝翠雀花D. maxim owiczii 和蓝翠雀花D. caeruleum 都低。这与该3 种植物在王文采先生(1979) 中国毛茛分类系统中的位置是一致的。

鬼灯檠属的系统发育、分类和地理分布

本文对鬼灯檠属Rodgersia Gray的染色体数、花粉体积和纹饰、萼片数目、萼片脉序和脉型、萼片腹面毛被、花梗和花序轴毛被、叶的类型等关键性状进行了分析,确定了其进化顺序;依据性状的系统发生,绘制了鬼灯檠属的瓦格勒尔系统树;确认本属有5种和3变种,其中以R.podophylla为最原始, R.nepalensis为最进化,而R.aesculifolia,R.sambucifolia和R.pinnata则居于两者之间。本属分两组Sect.Rodgersia,仅含R.podophylla;Sect.Sambuclfolia J.T.Pan,含R.aesculifolia,R.sambucifolia,R.pinnata,R.nepalensis。依据种的主要分布区,划本属植物为4个分布类型,即:日本-朝鲜间断分布,秦岭-大巴山分布,横断山分布和东喜马拉雅分布。笔者认为, 本属的起源地在日本一朝鲜一带, 横断山地区是其现代分布中心和分化中心本属的散布路线是自日本一朝鲜, 经秦岭一大巴山, 通过横断山地区而进入东喜马拉雅本属的起源时间, 当在晚第三纪以前晚白要世至早第三纪。此外, 还报道了鬼灯集属植物的花粉形态。

橐吾属的起源、演化与地理分布

橐吾属Ligularia Cass.是菊科千里光族款冬亚族的一个大属。在款冬亚族中本属与大吾风草属Farfugium Lindl.亲缘关系最近,但进化程度较高。本属包括6组、11系129种。所有种类均分布在亚洲,仅2种扩散至欧洲。在东亚地区有119种,占该属总种数的96％。高度集中在横断山区的有4组、6系67种,其中61种为特有种,占该属总组数的66％,总系数的54.5％,总种数的52％。这个事实表明了横断山区是该属的多度中心和多样化中心。通过性状分析,伞房组伞房系Sect.Corymbosae,Ser.Calthifoliae叶肾形,具掌状叶脉,头状花序大而少,排列呈伞房状,总苞半球形,被认为是该属的原始类群。原始种齿叶橐吾L.dentata和鹿蹄橐吾L.hodgsonii的分布区从我国四川东部经过湖北、湖南、安徽、福建等省至日本。这个分布格局与近缘属...

Two new species of Saxifraga (Saxifragaceae) from Southwestern China

Two new species, Saxifraga xiaozhongdianensis J. T. Pan and S. ludingensis J. T. Pan, from the Saxifragaceae in China are described and illustrated. Of these, S. xiaozhongdianensis is endemic to Zhongdian, Yunnan, and is related to S. brachyphylla Franchet. It differs from S. brachyphylla in the sepals adaxially dark brown glandular-villose and the petals basally subauriculate. Saxifraga ludingensis occurs in Luding, Sichuan, and is very similar to S. egregioides J. T. Pan and S. stellariifolia Franchet. It differs from S. egregioides in the stems brown glandular-villose, the cauline leaves adaxially brown glandular-villose, the sepals spreading in anthesis and abaxially brown glandular-villose, and the petals 5-veined. It differs from S. stellariifolia in the leaves cordate and abaxially glabrous, the sepals abaxially brown glandular-villose, and the petals 4-callose and 5-veined. Saxifraga xiaozhongdianensis and S. ludingeasis are apparently endemic to western China and belong to Saxifraga sect. Ciliatae Haworth, emend. J. T. Pan.

Origin of the Qinghai-Tibetan Plateau endemic Milula (Liliaceae): further insights from karyological comparisons with Allium

Milula, a monotypic genus endemic to the Qinghai-Tibetan Plateau, was found to be nested deeply within Allium by the molecular phylogeny despite the aberrant morphology. It remains unknown what had contributed to the rapid evolution of morphology and origin of this exceptional species. In contrast to a previous report of its karyotypes with 2n = 16 = 8M+8SM (2SAT), similar to most species of Allium, a rather different karyotype, 2n = 20 = 4M +10SM+6T (2SAT), was found in examined 31 individuals from 6 populations of M. spicata distributed in the central Tibet. Karyotypes of 7 Allium species occurring in the Qinghai-Tibetan Plateau were further reported. The basic number x = 8 was confirmed for all of them and their karyotypes consist mainly of metacentric and submetacentric chromosomes with rare subterminal and terminal chromosomes. The karyotype of M. spicata is distinctly different from that of most Allium species occurring in the plateau through a complete comparison of all available species in this region and adjacent areas. However, the same chromosome number and similar karyotypic structure were found in A. fasciculatum of Sect. Bromatorrhiza, indicating a possible close relationship between them. But this similarity is contradictory to the preliminary molecular phylogenetic analysis that Milula was closely related to A. cyathophorum of Sect. Bromatorrhiza with x=8, but the other species with x=10 and 11 in this section were clearly placed in the other clade. We therefore suggested that the paralleling evolution from x=8 to x=9, 10 and 11 with increasing asymmetry of karyotype possibly due to the chromosomal Robertsonian translocation might occur separately in the two recognized phylogenetic lineages of Allium. In addition to aneuploidy and following change of the chromosomal structures, the habitat isolation due to the recent uplift of the Qinghai-Tibetan Plateau and the Quaternary climatic oscillation, plays a greater role in origin of Milula and other endemic species (genera) with aberrant morphology from their progenitors.

Molecular phylogeny, recent radiation and evolution of gross morphology of the rhubarb genus Rheum (Polygonaceae) inferred from chloroplast DNA trnL-F sequences

Background and Aims Rheum, a highly diversified genus with about 60 species, is mainly confined to the mountainous and desert regions of the Qinghai-Tibetan plateau and adjacent areas. This genus represents a good example of the extensive diversification of the temperate genera in the Qinghai-Tibetan plateau, in which the forces to drive diversification remain unknown. To date, the infrageneric classification of Rheum has been mainly based on morphological characters. However, it may have been subject to convergent evolution under habitat pressure, and the systematic position of some sections are unclear, especially Sect. Globulosa, which has globular inflorescences, and Sect. Nobilia, which has semi-translucent bracts. Recent palynological research has found substantial contradictions between exine patterns and the current classification of Rheum. Two specific objectives of this research were (1) to evaluate possible relationships of some ambiguous sections with a unique morphology, and (2) to examine possible occurrence of the radiative speciation with low genetic divergence across the total genus and the correlation between the extensive diversification time of Rheum and past geographical events, especially the recent large-scale uplifts of the Qinghai-Tibetan Plateau.Methods The chloroplast DNA trnL-F region of 29 individuals representing 26 species of Rheum, belonging to seven out of eight sections, was sequenced and compared. The phylogenetic relationships were further constructed based on the sequences obtained.Key Results Despite the highly diversified morphology, the genetic variation in this DNA fragment is relatively low. The molecular phylogeny is highly inconsistent with gross morphology, pollen exine patterns and traditional classifications, except for identifying all samples of Sect. Palmata, three species of Sect. Spiciformia and a few species of Sect. Rheum as corresponding monophyletic groups. The monotypic Sect. Globulosa showed a tentative position within the clade comprising five species of Sect. Rheum. All of the analyses revealed the paraphyly of R. nobile and R. alexandrae, the only two species of Sect. Nobilia circumscribed by the possession of large bracts. The crude calibration of lineages based on trnL-F sequence differentiation implied an extensive diversification of Rheum within approx. 7 million years.Conclusions Based on these results, it is suggested that the rich geological and ecological diversity caused by the recent large-scale uplifts of the Qinghai-Tibetan Plateau since the late Tertiary, coupled with the oscillating climate of the Quaternary stage, might have promoted rapid speciation in small and isolated populations, as well as allowing the fixation of unique or rare morphological characters in Rheum. Such a rapid radiation, combined with introgressive hybridization and reticulate evolution, may have caused the transfer of cpDNA haplotypes between morphologically dissimilar species, and might account for the inconsistency between morphological classification and molecular phylogeny reported here.

A new species of Saussurea (Asteraceae) from Tibet and its systematic position based on ITS sequence analysis

A new species of Saussurea, S. erecta S. W Liu, J. T Pan A J. Q. Liu sp. nov., is described from Tibet. It resembles S. kingii but may be distinguished by having distinct stems and glabrous achenes. Saussurea kingii was placed in sect. Pseudoeriocoryne of subgen. Eriocoryne; this section was circumscribed by acaulescence and an inflorescence with congested capitula surrounded by a rosette of leaves. The discovery of S. erecta with distinct stems, cauline leaves and corymbose capitula blurred the delimitation of sect. Pseudoeriocoryne and suggested that the section may be polyphyletic. Both the close relationship and the significant difference between S. erecta and S. kingii were confirmed by analyses of nrDNA ITS sequences. The resulting phylogenies based on ITS data further suggest that Saussurea sect. Pseudoeriocoryne, as traditionally defined, does not constitute a monophyletic group. The rapid radiation and speciation of Saussurea in the Qinghai-Tibetan Plateau, as inferred from ITS phylogeny, are discussed. (c) 2005 The Linnean Society of London.

Metagentiana, a new genus of Gentianaceae

The evidence from cross morphology, floral anatomy, chromosomes, palynology, and embryology all indicates that sect. Stenogyne is discordant within the genus Gentiana and is as distinct from the other sections of Gentiana as are other genera, such as Tripterospermum and Crawfurdia. In light of these characters, sect. Stenogyne is removed from Gentiana and given generic rank as the new genus Metagentiana. It is more related to Tripterospermum and Crawfurdia than to Gentiana, though it is more primitive than the first two genera. Together with Tripterospermum and Crawfurdia the new genus forms a monophyletic group, which is the sister group to the genus Gentiana. Fourteen new combinations required at specific rank are proposed.