Patterns of nucleotide substitution in angiosperm cpDNA trnL (UAA)-trnF (GAA) regions

Patterns of substitution in chloroplast encoded trnL_F regions were compared between species of Actaea (Ranunculales), Digitalis (Scrophulariales), Drosera (Caryophyllales), Panicoideae (Poales), the small chromosome species clade of Pelargonium (Geraniales), each representing a different order of flowering plants, and Huperzia (Lycopodiales). In total, the study included 265 taxa, each with > 900-bp sequences, totaling 0.24 Mb. Both pairwise and phylogeny-based comparisons were used to assess nucleotide substitution patterns. In all six groups, we found that transition/transversion ratios, as estimated by maximum likelihood on most-parsimonious trees, ranged between 0.8 and 1.0 for ingroups. These values occurred both at low sequence divergences, where substitutional saturation, i.e., multiple substitutions having occurred at the same (homologous) nucleotide position, was not expected, and at higher levels of divergence. This suggests that the angiosperm trnL-F regions evolve in a pattern different from that generally observed for nuclear and animal mtDNA (transitional/transversion ratio > or = 2). Transition/transversion ratios in the intron and the spacer region differed in all alignments compared, yet base compositions between the regions were highly similar in all six groups. A>-C transversions were significantly less frequent than the other four substitution types. This correlates with results from studies on fidelity mechanisms in DNA replication that predict A<->T and G<->C transversions to be least likely to occur. It therefore strengthens confidence in the link between mutation bias at the polymerase level and the actual fixation of substitutions as recorded on evolutionary trees, and concomitantly, in the neutrality of nucleotide substitutions as phylogenetic markers.

绣球族的系统学研究

绣球科绣球族包含9属：草绣球属、叉叶蓝属、Broussaisia、常山属、绣球属、蛛网萼属、赤壁木属、冠盖藤属和钻地风属。到目前为止，绣球族内的属间关系还不清楚，族内的系统发育关系还有争论。本研究的目的是在前人研究的基础上，进一步发现新的系统学性状，为绣球族乃至绣球科补充新的证据;并综合多学科的研究结果进行分析，探讨绣球族的系统学关系。 本文研究了绣球族的外部形态学、花发育形态学、解剖学、分子系统学和分支系统学。 主要内容包括： 1. 形态学 通过标本室研究和野外观察，对绣球族植物的形态分化进行了分析。发现习性、地上茎的生存期限、花冠卷叠式、花瓣联合与否、花柱的联合程度、雄蕊的数目及排列具有系统学价值;放射花和果实是很好的分类性状，但并非可靠的系统学性状。 2. 花发育形态学 在扫描电子显微镜下，研究了绣球族常山属、绣球属、冠盖藤属、蛛网萼属共4种植物花器官发生和发育的全过程。发现它们的花萼均为螺旋式相继发生，花瓣的发生近乎同时。冠盖藤、马桑绣球及常山具两轮雄蕊，第一轮雄蕊发生于花瓣内轮正对萼片中部的位置，随后第二轮雄蕊发生于正对花瓣中部的位置。在第一轮雄蕊略靠内的位置形成第二轮雄蕊的时候，多数情况下，相邻的对萼雄蕊之间只形成1个对瓣雄蕊，但有时却形成2个对瓣雄蕊，使雄蕊群的数目略多于花被的数目。对萼雄蕊与对瓣雄蕊的分化方式基本一致，但它们在花芽中空间取向不同。 蛛网萼雄蕊数目极多，雄蕊群的发生式样较为独特，并不始于对萼三联体。最早的雄蕊于杯状体近基部发生，之后雄蕊的发生大致沿杯状体壁向上，具离心趋势。在雄蕊发生过程中杯状体继续伸长，为众多雄蕊的发生提供了空间。蛛网萼雌蕊的发生明显早于雄蕊，其它3种植物雌蕊的发生晚于雄蕊。4种植物的雌蕊在发生上较为相似，发育却不同。在常山、马桑绣球和蛛网萼中，花柱从开始到发育成熟始终分离，柱头在每个花柱的顶端形成;而冠盖藤属的花柱裂片从开始就是联合的，最终形成单一的花柱，柱头从合生花柱顶端远轴面分化形成。 3. 解剖学 在光学显微镜和扫描电子显微镜下，观察了绣球族9属42种1变种及近缘8属11种共53种1变种的叶表皮特征。发现气孔的分布、气孔器的类型、表皮细胞的形状及其垂周壁式样、毛被等具有一定的系统学意义和分类价值。绣球族各属的气孔仅散生于下表皮;而在绣球族的几个近缘属中，上下表皮均有气孔分布。气孔器在多数类群中为无规则型，仅常山属和绣球属离瓣组的成员为平列型。气孔多为椭圆形，稀近圆形;外拱盖表面通常光滑，仅在钻地风属中具条状纹饰;外拱盖内缘具环状加厚，近全缘、不规则波状或浅波状。表皮细胞在多数种中为不规则形，垂周壁波状、浅波状或深波状;在有些种中为（近）多边形，垂周壁平直或弓形。叶表皮细胞形状、垂周壁式样在绣球族寡种属属级水平比较稳定，但在绣球属中变化较大。表皮角质膜纹饰形态多样，有网纹、粗网纹、浅波状条纹、波状条纹、条纹、粗条纹及丝状条纹;在钻地风属及绣球属的少数种中，角质膜条纹有时汇集呈球形或玫瑰型。表皮毛状附属物有单细胞2分枝毛（黄山梅属）、多细胞星状毛（星毛冠盖藤）、单细胞星状毛（溲疏属）和单细胞不分枝毛四种。对钻地风属所有种的观察结果表明，仅在椭圆钻地风的下表皮细胞中央观察到乳突状结构，而在白背钻地风和圆叶钻地风中并未观察到前人描述的附属物。 4. 叶绿体DNA trnL-F序列的分析 首次对绣球族9属23种及近缘类群3属3种的trnL-F序列进行了测定。序列长度在860 bp~970 bp范围内变化。在以山梅花属、溲疏属和黄山梅属为外类群，基于trnL-F序列构建的系统树上，绣球族作为一个单系群得到很高的支持率。绣球属的种出现在不同的分支上，表明该属不是一个单系群。绣球族被分为两大支：第一支由绣球属离瓣组的中国绣球、绣球、以及常山和Broussaisia arguta组成;第二支由绣球属另外的9个种与草绣球属、叉叶蓝属、蛛网萼属、赤壁木属、冠盖藤属以及钻地风属组成。在第二支中，下列类群的近缘关系得到支持：① 草绣球与叉叶蓝属;② 绣球属挂苦子组的东陵绣球、圆锥绣球和挂苦绣球。③ 钻地风属、赤壁木属和冠盖藤属;④ 蜡莲绣球、莼兰绣球、马桑绣球、粗枝绣球。 5. 分支分析 以山梅花属为外类群，基于形态、解剖、花发育、孢粉等32个性状（或性状状态）对绣球族9属的系统发育关系进行了分支分析。结果表明：草绣球属和叉叶蓝属为基出类群，这两个属有多个共同特征;绣球族其余的成员聚成一支，该支又有5个分支。其中蛛网萼属和绣球属冠盖组各为单独的分支，它们有多个自衍征，可能有各自独立的演化线;绣球属离瓣组与常山属聚成一分支，二者的密切关系得到解剖学证据的支持;绣球属绣球组和星毛组聚成一分支，这两个组包含了绣球属的多数种类;钻地风属、赤壁木属、冠盖藤属、Broussaisia和绣球属挂苦子组聚成一分支。其中钻地风属、赤壁木属与冠盖藤属具多个近裔衍征，表明它们是绣球族的晚出类群。 通过对绣球族植物外部形态、花器官发生、叶表皮微形态特征、叶绿体DNA trnL-F区的研究以及基于形态性状的分支分析，并综合已有的研究结果，我们认为： 1. 绣球族是一个单系群;绣球属不是一个单系群。 2. 在绣球族中，草绣球属和叉叶蓝属关系密切，它们可能是绣球族其余成员的姐妹群。 3. 绣球组和星毛组可能是绣球属的核心成员;离瓣组和常山属关系密切;冠盖组有单独的演化线。 4. 赤壁木属、冠盖藤属和钻地风属为单系群，它们在绣球族处于较高的演化位置。 5. 绣球属需重新界定。

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.

Phylogeny of South American Pogonieae (Orchidaceae, Vanilloideae) based on sequences of nuclear ribosomal (ITS) and chloroplast (psaB, rbcL, rps16, and trnL-F) DNA, with emphasis on Cleistes and discussion of biogeographic implications

Tribe Pogonieae (Orchidaceae), as Currently known, comprises live genera distributed from South to North America and Eastern Asia. Phylogenetic inferences within Cleistes and among genera of tribe Pogonieae were made based oil nrDNA (ITS) and cpDNA (trnL-F, rps16, rbcL, and psaB) Sequence data and maximum parsimony. Eighteen species of Cleistes, members of all other genera of Pogonieae, and outgroups were sampled. Analyses based oil individual DNA regions provided similar topologies. All evidence indicates that Cleistes is paraphyletic. The North American C. divaricata and C bifaria are more closely related to the temperate genera Isotria and Pogonia than to their Central and South American congeners, the latter Constituting a monophyletic group characterized by the production of nectar as reward, tuberous roots, and their distribution in Central and South America. The Amazonian Duckeella is sister to the remainder of Pogonieae. Taxonomic and biogeographic implications are discussed, and morphological synapomorphies are given For clades obtained in the inferred molecular phylogeny. (C) 2008 Gesellschaft fur Biologische Systematik. Published by Elsevier GmbH. All rights reserved.

Phylogeny of Pelargonium (Geraniaceae) based on DNA sequences from three genomes

Phylogenetic hypotheses for the largely South African genus Pelargonium L'Hér. (Geraniaceae) were derived based on DNA sequence data from nuclear, chloroplast and mitochondrial encoded regions. The datasets were unequally represented and comprised cpDNA trnL-F sequences for 152 taxa, nrDNA ITS sequences for 55 taxa, and mtDNA nad1 b/c exons for 51 taxa. Phylogenetic hypotheses derived from the separate three datasets were overall congruent. A single hypothesis synthesising the information in the three datasets was constructed following a total evidence approach and implementing dataset specific stepmatrices in order to correct for substitution biases. Pelargonium was found to consist of five main clades, some with contrasting evolutionary patterns with respect to biogeographic distributions, dispersal capacity, pollination biology and karyological diversification. The five main clades are structured in two (subgeneric) clades that correlate with chromosome size. One of these clades includes a "winter rainfall clade" containing more than 70% of all currently described Pelargonium species, and all restricted to the South African Cape winter rainfall region. Apart from (woody) shrubs and small herbaceous rosette subshrubs, this clade comprises a large "xerophytic" clade including geophytes, stem and leaf succulents, harbouring in total almost half of the genus. This clade is considered to be the result of in situ proliferation, possibly in response to late-Miocene and Pliocene aridification events. Nested within it is a radiation comprising c. 80 species from the geophytic Pelargonium section Hoarea, all characterised by the possession of (a series of) tunicate tubers.

Nomenclature in the dock. Overclassification leads to instability: a case study in the horticulturally important genus Cyclamen (Myrsinaceae)

Nine different classifications have been produced in the last 70 years for the horticulturally valuable genus Cyclamen, a small genus with fewer than 30 species. These classifications, generated by intuitive methods and cladistic analyses, incorporated a total of four infrageneric ranks above that of species and were based on data from morphology, cytology and DNA sequencing. Our results, based on cladistic analyses of three independent data sources − nrDNA ITS, cpDNA trnL intron and morphological data − reveal good resolution only in nrDNA sequence data. However, when these three data sources are combined they provide stronger resolution and support for three major clades, only one of which, subgenus Psilanthum, has been consistently supported in previous classifications. The differing infrageneric classifications produced in Cyclamen result from varying taxon sampling, differing interpretation of morphological data, changes in the sources and analysis of data, and inconsistent application of names. Extensive subdivision of small genera in the absence of adequate data that could provide evidence for consistent patterns of relationship is premature and leads to a proliferation of names.© 2004 The Linnean Society of London, Botanical Journal of the Linnean Society, 2004, 146, 339-349.

Is there such a thing as Kalmia x Rhododendron?

Two putative hybrids between Kalmia and Rhododendron, their suspected progenitor species and related taxa were submitted to DNA sequencing of cpDNA trnL-F and nrDNA ITS regions in order to test whether there was DNA sequence evidence both for hybridization per se and for the direction of the cross should one be evident. Comparison of eight DNA sequences from these putative hybrids with Rhododendron and Kalmia species showed clear evidence of origin within Rhododendron. No evidence of Kalmia DNA was detected. These putative intergeneric hybrids appear to be mutants of Rhododendron and not of hybrid origin.

中国郁金香属(广义)的系统学研究

郁金香属（Tulipa L.）是世界著名的观赏植物，广泛分布于欧洲、亚洲的温带地区以及非洲的西北部，中亚地区是其分布和多样化中心。该属包括老鸦瓣组、长柱组、郁金香组、毛蕊组、扭药组、鸡冠组和无毛组共七个组，40至150种。老鸦瓣组是东亚特有类群。中国共有郁金香属植物16种，主要分布于西北（新疆）以及中东部地区，其中老鸦瓣组有4个种，占该组全部种类的4/5。长期以来，由于对老鸦瓣组的生物学特性及其地理分布缺乏了解，该类群的归属问题一直都是该属系统学研究中争论的焦点之一。因此，本文以分布于我国的郁金香属作为主要研究对象，通过对其形态学、胚囊发育的比较胚胎学以及分子系统学研究，对老鸦瓣组的系统位置以及上述特征在该属分类中的意义进行了探讨。主要结果如下 1)通过对该属18种植物（包括土耳其的3个种）28个形态性状数据的分支分析，表明广义郁金香属并不是一个单系类群。Tulipa sect. Amana与该属其他四个组（sect. Orithyia、sect. Eriostemones、sect. Leiostemones和sect. Tulipanum）在分支树上各成一支，它们与Lloydia属构成一个大支的三个分支。同时，sect. Amana具有与子房近等长的花柱以及2-3（-4）个苞片等与郁金香属不同的形态特征。因此，我们认为sect. Amana应从广义郁金香属中独立出来，恢复其老鸦瓣属Amana Honda作为属的分类地位。 2)发现了一个新种：Amana kuocangshanica D.Y. Tan et D. Y. Hong。该种与A. erythronioides 和A. anhuiensis近缘，区别在于鳞茎皮内侧光滑无毛，下部叶披针形，自基部向上2/3处最宽，果喙长0.64±0.08 cm。 3）对16种植物叶表皮形态观察的结果表明，老鸦瓣属4个种的叶上表皮细胞为矩形或矩圆形、下表皮为菱形或矩形，垂周壁为直线形或波形，上表皮无气孔或气孔密度较小，这些特征与狭义郁金香属的种差异显著。在狭义郁金香属中，叶表皮特征在种间差异明显，可以作为分种及种间亲缘关系探讨的依据，但在组间没有明显的差异。 4）对19种植物的花粉形态观察表明，Amana属的4种为近椭球形、舟形和肾形， 外壁纹饰网状，网脊浅皱波状，与狭义郁金香属的15种具明显不同。在狭义郁金香属中，花粉外壁纹饰虽然在种间存在一定程度的差异，但对组的划分意义不大。 5）从种皮形态及微形态特征看，在所观察的16种植物中，Amana属的种子小，呈半月形，较厚，种柄明显，胚不易见;种皮纹饰为皱波状或不规则，与狭义郁金香属存在显著的差异。狭义郁金香属的12种在种皮纹饰、网眼大小及形状、网脊宽窄等方面均存在明显的差异，但组间无明显差别，说明这些特征在种的划分上具有一定的分类学意义。 6）对16种植物的胚囊发育过程观察表明：共有6种胚囊发育类型，即Fritillaria type、Drusa type、Tulipa iliensis type、Tulipa tetraphylla type、 Adoxa type和Eriostemones type。其中Tulipa iliensis type为所发现的一种新的胚囊发育类型。Tulipa iliensis、T. heterophylla和T. heteropetala3个种具有两种胚囊类型。在郁金香属中，胚囊的发育类型具有一定的系统学意义。 7）通过对21种郁金香以及猪牙花属2种植物基于nrDNA ITS区和cpDNA trnL-F 区的序列分析，发现广义郁金香属并非一单系类群，老鸦瓣属为猪牙花属的姐妹群。在狭义郁金香属中，sect. Orithyia、sect. Tulipanum以及sect. Eriostemones得到了该分子系统学分析的支持，而sect. Leiostemones是否成立及其系统关系问题尚有待于进一步研究。

花楸属的系统学初步研究

花楸属隶属于蔷薇科苹果亚科，全世界约有100种左右，主要分布在北半球的亚洲、欧洲和北美洲。广义的花楸属包括下述六个亚属，即Subg. Aria, Subg. Chamaemespilus, Subg. Micromeles, Subg. Torminalis, Subg. Cormus, Subg. Sorbus。由于缺乏野外工作和标本不够丰富等原因，部分亚属的分类处理尚不能令人满意。同时，该属的范围及其属下部分类群的系统位置存在一定的争议。本文对广义花楸属的属下类群进行了研究，通过分支分析和表征分析以及分子系统学两方面的研究，对该属的属下类群的系统位置进行了探讨。 1、分支分析和表征分析 选取了广义花楸属（Sorbus L.）属下6个亚属的34种植物作为研究对象，并以Pyrus, Crataegus, Photinia, Malus和Cotoneaster作为外类群来研究花楸属属下类群的分类关系，对该属典型的30个形态性状数据进行编码，进行了分支分析和表征分析。结果表明，广义花楸属是一个非单系类群，外类群完全镶嵌于其中。广义花楸属属下的6个亚属各自也不能形成单系，只有花楸亚属（Subg. Sorbus）形成不严格的单系。因此，我们初步认为，花楸属应该仅包含复叶类群（Subg. Sorbus），或者还会有Subg. Cormus。由于其余的4个亚属尚不能形成规则的单系或聚类，因此进一步的研究宜采用分类群的更多性状或运用分子系统学的途径。 2、分子系统学 通过对花楸属23个种类的两个DNA片段：核nrDNA的ITS和叶绿体cpDNA的trnL-F进行简约分析，构建了广义花楸属5个亚属及其与近缘属的系统发育树。结果显示，由于外类群大多镶嵌于广义花楸属中，故花楸属不能形成一个单系。其中单叶类群Subg. Aria聚类较明显，并且得到了很高的支持率，而且该亚属与外类群Crataegus和Cotoneaster的关系要比它与其它亚属的关系更近，至于其是否是独立的属还有待进一步的研究。该属中的复叶类群Subg. Sorbus在图中并不能形成严格的单系，其分类位置值得重新考虑。

Cyclamen: time, sea and speciation biogeography using a temporally calibrated phylogeny

Aim The Mediterranean region is a species-rich area with a complex geographical history. Geographical barriers have been removed and restored due to sea level changes and local climatic change. Such barriers have been proposed as a plausible mechanism driving the high levels of speciation and endemism in the Mediterranean basin. This raises the fundamental question: is allopatric isolation the mechanism by which speciation occurs? This study explores the potential driving influence of palaeo-geographical events on the speciation of Cyclamen (Myrsinaceae), a group with most species endemic to the Mediterranean region. Cyclamen species have been shown experimentally to have few genetic barriers to hybridization. Location The Mediterranean region, including northern Africa, extending eastwards to the Black Sea coast. Methods A generic level molecular phylogeny of Myrsinaceae and Primulaceae is constructed, using Bayesian approximation, to produce a secondary age estimate for the stem lineage of Cyclamen. This estimate is used to calibrate temporally an infrageneric phylogeny of Cyclamen, built with nrDNA ITS, cpDNA trnL-F and cpDNA rps16 sequences. A biogeographical analysis of Cyclamen is performed using dispersal-vicariance analysis. Results The emergence of the Cyclamen stem lineage is estimated at 30.1-29.2 Ma, and the crown divergence at 12.9-12.2 Ma. The average age of Cyclamen species is 3.7 Myr. Every pair of sister species have mutually exclusive, allopatric distributions relative to each other. This pattern appears typical of divergence events throughout the evolutionary history of the genus. Main conclusions Geographical barriers, such as the varying levels of the Mediterranean Sea, are the most plausible explanation for speciation events throughout the phylogenetic history of Cyclamen. The genus demonstrates distributional patterns congruent with the temporally reticulate palaeogeography of the Mediterranean region.

Evolutionary tendencies in African Marantaceae

Die Marantaceae (550 Arten) sind eine weltweit verbreitete Familie von Stauden und Lianen aus dem Unterwuchs tropischer Tieflandregenwälder. Der morphologisch-ökologische Vergleich des basal abzweigenden Sarcophrynium-Astes mit dem in abgeleiteter Position stehenden Marantochloa-Ast, soll beispielhaft evolutionäre Muster in der Familie beleuchten. So wird in der Doktorarbeit zum ersten Mal ein Überblick über die Blütenbiologie und Phylogenie von rund 30 der 40 afrikanischen Marantaceae Arten präsentiert. Die Analysen basieren auf Daten von drei mehrmonatigen Feldaufenthalten in Gabun jeweils zwischen September und Januar. Vier Blütentypen werden beschrieben, die jeweils mit einer spezifischen Bestäubergilde verbunden sind (kleine, mittlere, große Bienen bzw. Vögel). Bestäubungsexperimente belegen, dass 18 Arten selbstkompatibel, aber nur zwei Arten autogam sind, also keine Bestäubungsvermittler benötigen. Der Fruchtansatz ist generell gering (10 -30 %). Die komplexe Synorganisation der Blüte ermöglicht in den Marantaceae einen explosiven Bestäubungsmechanismus. Um dessen ökologische Funktionalität zu verstehen, werden die Blüten von 66 Arten, alle wichtigen Äste der Marantaceae abdeckend, unter einem morphologisch-funktionalen Gesichtspunkt untersucht. Es gibt große Übereinstimmungen zwischen allen untersuchten Arten im Zusammenspiel (Synorganisation) der wichtigsten Bauelemente (Griffel, Kapuzenblatt, Schwielenblatt), die eine präzise Pollenübertragung ermöglichen. Basierend auf Daten von nrDNA (ITS, 5S) und cpDNA (trnL-F) wird für ein nahezu komplettes Artenspektrum die Phylogenie der zwei afrikanischen Äste erstellt. Hierauf werden morphologische und ökologische Merkmale sowie geographischer Verbreitungsmuster nach dem Parsimonieprinzip rekonstruiert, um so deren evolutionäre Bedeutung für die Marantaceae abschätzen zu können. Die Ergebnisse weisen auf die Beteiligung einer Vielzahl verschiedener Artbildungsfaktoren hin.

Phylogenetic relationships withinPelargonium sect. Peristera (Geraniaceae) inferred from nrDNA and cpDNA sequence comparisons

Phylogenetic analysis of nrDNA ITS and trnL (UAA) 5′ exon-trnF (GAA) chloroplast DNA sequences from 17 species ofPelargonium sect.Peristera, together with nine putative outgroups, suggests paraphyly for the section and a close relationship between the highly disjunct South African and Australian species of sect.Peristera. Representatives fromPelargonium sectt.Reniformia, Ligularia s. l. andIsopetalum (the St. Helena endemicP. cotyledonis) appear to be nested within thePeristera clade. The close relationship between the South African and AustralianPeristera is interpreted as being caused by long-range dispersal to Australia, probably as recent as the late Pliocene.

Cucumber chloroplast trnL(CAA) gene: nucleotide sequence and in vivo expression analysis in etiolated cucumber seedlings treated with benzyladenine and light.

The nucleotide sequence of a 714 bp BamHI-EcoRI fragment of cucumber chloroplast DNA was determined. The fragment contained a gene for tRNA(Leu) together with its flanking regions. The trnL(CAA) gene sequence is about 99% in similarity to broad bean, cauliflower, maize, spinach and tobacco corresponding genes. The relative expression level of the gene was determined by Northern (tRNA) gel blot and Northern (total cellular RNA) slot-blot analyses using the trnL gene probe in 6-day old etiolated cucumber seedlings and the seedlings that had been kept in the dark (dark-grown), treated with benzyladenine (BA) and kept in the dark (BA-treated dark-grown), illuminated (light-grown), and treated with BA and illuminated (BA-treated light-grown), for additional 4, 8 or 12 hr. The trnL transcripts and tRNA(Leu) levels in BA-treated dark-grown seedlings were 5 and 3 times higher, respectively after 4 hr BA treatment, while in the BA treated light-grown seedlings the level of trnL transcripts was only 3 times higher and had no detectable effect on mature tRNA(Leu) when compared to the time-4 hr dark-grown seedlings. However, the level of mature tRNA(Leu) did not show marked changes in the light-grown seedlings, whereas the level of trnL transcripts increases 3 times after 8 hr illumination of dark-grown seedlings. These data indicate that both light and cytokinin can signal changes in plastid tRNA gene expression. The possible regulatory mechanisms for such changes are discussed.

Cucumber chloroplast trnL(CAA) gene: nucleotide sequence and in vivo expression analysis in etiolated cucumber seedlings treated with benzyladenine and light

The nucleotide sequence of a 714 bp BamHI-EcoRI fragment of cucumber chloroplast DNA was determined. The fragment contained a gene for tRNA(Leu) together with its flanking regions. The trnL(CAA) gene sequence is about 99% in similarity to broad bean, cauliflower, maize, spinach and tobacco corresponding genes. The relative expression level of the gene was determined by Northern (tRNA) gel blot and Northern (total cellular RNA) slot-blot analyses using the trnL gene probe in 6-day old etiolated cucumber seedlings and the seedlings that had been kept in the dark (dark-grown), treated with benzyladenine (BA) and kept in the dark (BA-treated dark-grown), illuminated (light-grown), and treated with BA and illuminated (BA- treated light-grown), for additional 4, 8 or 12 hr. The trnL transcripts and tRNA(Leu) levels in BA-treated dark-grown seedlings were 5 and 3 times higher, respectively after 4 hr BA treatment, while in the BA treated light-grown seedlings the level of trnL transcripts was only 3 times higher and had not detectable effect on mature tRNA(Leu) when compared to the time-4 hr dark-grown seedlings. However, the level of mature tRNA(Leu) did not show marked changes in the light-grown seedlings, whereas the level of trnL transcripts increases 3 times after 8 hr illumination of dark-grown seedlings. These date indicate that both light and cytokinin can signal changes in plastid tRNA gene expression. The possible regulatory mechanisms for such changes are discussed.