Selected and annotated chromosome counts inTaraxacum sect.Palustria Dahlst. (Studies inTaraxacum 3.)

Chromosome counts of 9 species ofTaraxacum sect.Palustria are given. Five species were karyologically examined for the first time, viz.T. trilobifolium Hudziok,T. lissocarpum agg.,T. paucilobum Hudziok,T. subalpinum Hudziok andT. mendax, a new pentaploid species. Taxonomic and nomenclatural notes are added.     

Anthropogenic disturbance and habitat differentiation between sexual diploid and apomictic triploidTaraxacum sect.Ruderalia

Co-occurrence of sexual diploid and apomictic triploidTaraxacum sectionRuderalia has been reported frequently. Many suggestions have been put forward with respect to the existence of an ecological differentiation between the cytotypes. In a study of 116Ruderalia populations in the area around Neuchatel (Switzerland) such a habitat differentiation has been proven. Large differences in the diploid/triploid ratio have been found between different field types. Adjacent fields of different types sometimes had significantly different cytotype ratios. In a canonical correspondence analysis significant vegetation differences were found between fields with mainly diploidRuderalia and fields with mainly triploidRuderalia. Two environmental indicators were significantly positively correlated with ploidy levels, altitude with diploids, and the percentage of therophytes in a vegetation with triploids. The percentage of therophytes is thought to be an indicator of the amount of disturbance due to human activities. At lower altitudes, the diploid/triploid ratio is largely determined by the amount of disturbance. Highly-disturbed fields contain mainly triploids whereas relatively stable fields contain mainly diploids. At higher altitudes there are mainly diploids. The presence of triploidTaraxacum sect.Ruderalia in the region around Neuchatel appears to be the result of the high amount of human activities of the last few hundred years. Whether the triploid presence is due to immigration or to local formation from diploids is yet unknown.     

Distribution of diploid sexual plants ofTaraxacum sect.Ruderalia in east-Central Europe,with special reference to Czechoslovakia

Herbarium specimens (c. 1 000) and population samples (76) have been screened for the occurrence of diploid representatives ofTaraxacum sect.Ruderalia (T. sect.Vulgaria, nom. illeg.). The area studied comprises German Democratic Republic, Poland, Czechoslovakia, Hungary and parts of Austria, Yugoslavia, and Rumania. Diploids are common from the Valley of the Moravia river on southwards. Isolated outpost localities are found in S. Poland and extend far to the north: neighbourhood of Berlin. Based on the pattern of distribution in Czechoslovakia, the Pannonian (thermophilous) phytogeographical character of the diploids is discussed. Special attention has been paid to morphological differences between di- and triploids in Czechoslovakia. The study provides a basis for further biosystematical and taxonomic studies in the relationships between diploids and polyploids as well as in the stability of agamospecies.     

Speciation despite gene flow when developmental pathways evolve

Abstract.— Evolutionary biologists assume that species formation requires a drastic reduction in gene exchange between populations, but the rate sufficient to prevent speciation is unknown. To study speciation, we use a new class of population genetic models that incorporate simple developmental genetic rules, likely present in all organisms, to construct the phenotype. When we allow replicate populations to evolve in parallel to a new, shared optimal phenotype, often their hybrids acquire poorly regulated phenotypes: Dobzhansky-Muller incompatibilities arise and postzygotic reproductive isolation evolves. Here we show that, although gene exchange does inhibit this process, it is the proportion of migrants exchanged ( m ) rather than the number of migrants ( Nm ) that is critical, and rates as high as 16 individuals exchanged per generation still permit the evolution of postzygotic isolation. Stronger directional selection counters the inhibitory effect of gene flow, increasing the speciation probability. We see similar results when populations in a standard two-locus, two-allele Dobzhansky-Muller model are subject to simultaneous directional selection and gene flow. However, in developmental pathway models with more than two loci, gene flow is more able to impede speciation. Genetic incompatibilities arise as frequent by-products of adaptive evolution of traits determined by regulatory pathways, something that does not occur when phenotypes are modeled using the standard, additive genetic framework. Development therefore not only constrains the microevolutionary process, it also facilitates the interactions among genes and gene products that make speciation more likely–even in the face of strong gene flow.     

Possible speciation with gene flow in tropical cave snails

In this paper, we present a newly-discovered troglobitic species of the snail genus Georissa from a limestone cave in Borneo. Molecular phylogenetic analysis of 16S mitochondrial DNA sequences shows that its ancestor is the local epigean population of Georissa saulae , living in the rainforest directly at the cave entrances. A multivariate analysis of shell characters reveals that the troglobite has diverged morphologically, but is connected to its epigean ancestor by a population of intermediate morphology in the twilight zone of the cave. The molecular data further indicate ongoing gene flow between the epigean population and the troglobite, via the intermediate population. We suggest that the troglobite may have diverged from its ancestor without prior isolation.     

Modes of speciation and evolution of the sections inTaraxacum

Modes of evolution of species classified within different sections inTaraxacum involve diverse processes, viz. primary divergence of an ancestral sexual diploid, hybridization between a tetraploid apomict and a diploid sexual hybrid, differentiation of an advanced apomictic taxon at one ploidy level, hybridization between a sexual tetraploid and a sexual diploid, formation of a polyploid series from an apomictic ancestor of a lower polyploidy level, and remote hybridization between an autumn-flowering ancestral diploid and a spring-flowering derivative diploid or apomict. Various reproduction systems of the plants involved, different environments and different timing of the processes contribute to a very varied nature of the species groups.     

Clonality as a part of the evolution process inTaraxacum

A review is presented of various ecological and population aspects ofTaraxacum agamospermy. Agamospermy is compared with vegetative clonality, the former differeing in capability to generate variation, seed dispersal and often long evolutionary history. Clonal diversity of agamospermous taxa ranges from almost absolute uniclonality to high diversity of clones. Multiclonality is suggested to represent one of agamospecies' population characteristics. Biological individuality of clones allows coexistence of clones at a locality. Competition and other factors influencing number of clones at a locality are discussed. Geographical and ecological distribution of agamospermous and sexualTaraxacum taxa are evaluated, their coexistence and gene flow are addressed, and a hypothesis is presented concerning the population condition in mixed stands of sexual and asexualTaraxaca. Lastly, agamospermy is shown to significantly reduce recombination processes; it should not be considered an absolute evolutionary “blind alley”.     

Cladistics and Biogeography of Artemisia sect. Viscidipubes and sect. Albiraotea (Compositae)

Twenty-six species and eight varieties of Sect．Viscidipubes & Sect．Albibractea are endemic to Asia．Most species of Sect．Viscidipubes are distributed from low to high altitudes and cold areas in the Hengduan-Himalayan Mountains,with only a few species extending to E or S Asia．Sect．Albibractea is distributed mainly in the subtropics and tropics,lower altitudes and moist areas in S & SE Asia,with a few species extending to the Qinling range of China．Both sections are more advanced than the other sections．They were studied by cladistic analysis and outgroup comparison．Data matrix of 55 characters from stems,leaves,inflorescences,female flowers,bisexual flowers,achenes,pollen grains and chemical constitution was employed in separate and combined studies．Eighteen most parsimonious cladograms were generated with 358 steps,consistency index of 0．72 and retention index of 0．87． 1．Within Artemisia,Sect．Viscidipubes and Sect．Albibractea are sister groups to all the other groups． 2．We support the idea to separate Sect．Viscidipubes (incl．Ser．Viscidipubes,Ser．Erlangshanenses and Ser. Pleiocephalea) and Sect．Albibractea (incl．Ser．Albibractea,Ser．Flaccidae and Ser. Anomalae)．The authors suggest that Ser．Anomalae include A．deversa and Ser．Erlangshanenses include A．zayuensis and A．yadongensis as well as Ser．Viscidipubes include A．gyitangensis and A．boreali-siamensis．As the result of the cladistic analysis,the authors tend to propose a new series, Ser．Tanguticae,incl．A．tangutica in the section． 3．We consider that SW China,especially W Sichuan,is the speciation center and the tration of the present distribution center．4．A．boreali-siamensis,only in N Thailand,is not related to the widely distributed species in Ser．Pleiocephalae,such as A．atrovirens,A．chingii and A．myriantha,but rather closely related to species,such as A．vexans,A．occidentali-sichuanensis,which are endemic to W.Sichuan and E．Xizang．     

Catabolite regulation of the pta gene as part of carbon flow pathways in Bacillus subtilis

In Bacillus subtilis, the products of the pta and ackA genes, phosphotransacetylase and acetate kinase, play a crucial role in the production of acetate, one of the most abundant by-products of carbon metabolism in this gram-positive bacterium. Although these two enzymes are part of the same pathway, only mutants with inactivated ackA did not grow in the presence of glucose. Inactivation of pta had only a weak inhibitory effect on growth. In contrast to pta and ackA in Escherichia coli, the corresponding B. subtilis genes are not cotranscribed. Expression of the pta gene was increased in the presence of glucose, as has been reported for ackA. The effects of the predicted cis-acting catabolite response element (CRE) located upstream from the promoter and of the trans-acting proteins CcpA, HPr, Crh, and HPr kinase on the catabolite regulation of pta were investigated. As for ackA, glucose activation was abolished in ccpA and hprK mutants and in the ptsH1 crh double mutant. Footprinting experiments demonstrated an interaction between CcpA and the pta CRE sequence, which is almost identical to the proposed CRE consensus sequence. This interaction occurs only in the presence of Ser-46-phosphorylated HPr (HPrSer-P) or Ser-46-phosphorylated Crh (CrhSer-P) and fructose-1,6-bisphosphate (FBP). In addition to CcpA, carbon catabolite activation of the pta gene therefore requires at least two other cofactors, FBP and either HPr or Crh, phosphorylated at Ser-46 by the ATP-dependent Hpr kinase.     

铁线莲属尾叶铁线莲组(毛茛科)基于形态学证据的分支系统学

选取铁线莲属 (Clematis) 尾叶铁线莲组(sect. Campanella)中37个种以及西南铁线莲组 (sect. Bebaeanthera) 中的2个种为内类群, 以Clematis alternata作为外类群, 通过对全世界10个标本馆的近2 000份腊叶标本的形态学特征统计, 选取了35个性状进行编码, 利用PAUP 4.0 beta 10 软件进行系统发育重建。通过最简约法(maximum parsimony)分析共得到182棵最简约分支树, 树长为182步, 一致性指数(CI)=0.385, 保持性指数(RI)=0.685。结果表明: (1)尾叶铁线莲组并非是一个单系类群; (2)以花序发生位置这一性状建立的sect. Bebaeanthera不能成立, 应并入尾叶铁线莲组; (3)本研究结果不支持 在尾叶铁线莲组中建立subsect. Henryianae或ser. Henryianae; (4) C. ranunculoides等萼片外面具纵翅的一群植物与本组中萼片红色的种类C. lasiandra和C. dasyandra有较近的亲缘关系; (5)C. otophora、C. pogonandra、C. repens和C.barbellata等几个种聚为一支, 且支持率很高, 它们具有一系列的共衍征, 即萼片质地较厚, 花丝扁平, 宽条形, 被短柔毛, 花药被黄色短毛, 药隔先端凸起, 因此不支持建立Ser. Pogonandrae; (6)本组中非洲分布的2个种无论从形态上还是从地理分布和生境上都十分特殊, 是本组植物的特化类群。     

FTIR spectra of Camellia sect. Oleifera,sect. Paracamellia,and sect. Camellia (Theaceae) with reference to their taxonomic significance

Sixty-five leaf samples in sect. Oleifera H. T. Chang, sect. Paracamellia Sealy, sect. Camellia, and sect. Thea (L.) Dyer of genus Camellia L. were discriminated directly with an OMNI-sampler accessory on the basis of biochemical profiles and a hierarchical dendrogram was finally constructed. The results showed that the infrared spectra of Camellia were fingerprint-like patterns which were highly typical for different taxa. The hierarchical dendrogram based on principal component analysis of Fourier Transform Infrared (FTIR) data confirmed most of morphological classifications of the four sections proposed in previous works. Infrared spectra of leaves are of taxonomic value in genus Camellia, and this technique can be widely used for identification and classification of other taxa when standard spectra are available. The relationships between sect. Oleifera and sect. Paracamellia, subsect. Lucidissima H. T. Chang and subsect. Reticulata H. T. Chang in sect. Camellia, and the species/varieties were also discussed, as many dissensions about the classification exist between Chang’s and Ming’s system.     

山茶属油茶组、短柱茶组和红山茶组植物叶的红外光谱分析及其分类学意义

利用傅立叶红外光谱仪和OMNI采样器直接、迅速、准确地测定山茶属Camellia4组63种2变种植物叶片的红外光谱,结果表明：各分类群（种）的红外光谱具有高度特异性,其红外光谱图的变化可以作为山茶属植物属下的分类依据之一。这也暗示了利用标准红外光谱图库,可以区分和鉴定出山茶属植物的种类。经主成分分析后的红外光谱数据构建的树型聚类图与先前的形态分类结果大体一致,能将油茶组sect.Oleifera和短柱茶组sect.Paracamellia植物明显区分,并且各组中亲缘关系较近的种聚在一起。因此支持它们作为两个独立的组处理。但是,红山茶组sect.Camellia内的滇山茶亚组subsect.Lucidissima和光果红山茶亚组subsect.Reticulata植物在聚类图上很难区分,建议将这两个亚组植物进行归并。最后讨论了张宏达和闵天禄系统中存在分歧的油茶组、短柱茶组和红山茶组内的种间分类关系。     

Molecular clocks and evolutionary relationships: Possible distortions due to horizontal gene flow

Summary This paper discusses recent evidence suggesting that genetic information from one species occasionally transfers to another remotely related species. Besides addressing the issue of whether or not the molecular data are consistent with a wide-spread influence of horizontal gene transfer, the paper shows that horizontal gene flow would not necessarily preclude a linear molecular clock or change the rate of molecular evolution (assuming the neutral allele theory). A pervasive influence of horizontal gene transfer is more than just consistent with the data of molecular evolution, it also provides a unique explanation for a number of possibly conflicting phylogenies and contradictory clocks. This phenomenon might explain why some protein clocks are linear while the superoxide dismutase clock is not, how the molecular data on the phylogeny of apes and Australian song birds are not necessarily in conflict with those based on morphology, and, finally, why the mycoplasmas have an accelerated molecular clock.     

A nonsense mutation in the LDL receptor gene leads to familial hypercholesterolemia in the Druze sect.

Familial hypercholesterolemia (FH) is an autosomal dominant disease caused by mutations in the LDL receptor gene. Here we characterize an LDL receptor mutation that is associated with a distinct haplotype and causes FH in the Druze, a small Middle Eastern Islamic sect with a high degree of inbreeding. The mutation was found in FH families from two distinct Druze villages from the Golan Heights (northern Israel). It was not found neither in another Druze FH family residing in a different geographical area nor in eight Arab and four Jewish FH heterozygote index cases whose hypercholesterolemia cosegregates with an identical LDL receptor gene haplotype. The mutation, a single-base substitution, results in a termination codon in exon 4 of the LDL receptor gene that encodes for the fourth repeat of the binding domain of the mature receptor. It can be diagnosed by allele-specific oligonucleotide hybridization of PCR-amplified DNA from FH patients.     

No evidence of contemporary interploidy gene flow between the closely related European woodland violets Viola reichenbachiana and V. riviniana (sect. Viola,Violaceae)

• Viola reichenbachiana (2n = 4x = 20) and V. riviniana (2n = 8x = 40) are closely related species widely distributed in Europe, often sharing the same habitat throughout their overlapping ranges. It has been suggested in numerous studies that their high intraspecific morphological variability and plasticity might have been further increased by interspecific hybridisation in contact zones, given the sympatry of the species and the incomplete sterility of their hybrid. The aims of this study were to: (i) confirm that V. reichenbachiana and V. riviniana have one 4x genome in common, and (ii) determine the impact of hybridisation and introgression on genetic variation of these two species in selected European populations.
• For our study, we used 31 Viola populations from four European countries, which were analysed using AFLP and sequencing of a variable plastid intergenic spacer, trnH‐psbA.
• Our analysis revealed that V. reichenbachiana exhibited larger haplotype diversity, having three species‐specific haplotypes versus one in V. riviniana. The relationships among haplotypes suggest transfer of common haplotypes into V. riviniana from both V. reichenbachiana and hypothetically the other, now extinct, parental species. AFLP analysis showed low overall genetic diversity of both species, with V. riviniana showing higher among‐population diversity. None of the morphologically designated hybrid populations had additive AFLP polymorphisms that would have indicated recent hybridisation. Also, kinship coefficients between both species did not indicate gene flow. V. riviniana showed significant population subdivision and significant isolation by distance, in contrast to V. reichenbachiana.
• The results indicate lack of gene flow between species, high influence of selfing on genetic variability, as well as probably only localised introgression toward V. riviniana.

     

中国丝膜菌属李玉丝膜菌组一新种：李玉丝膜菌

本研究报道了丝膜菌属的一个新种：李玉丝膜菌,该种采自中国吉林省蒙古栎林中,其主要特征为担子体小型、幼时具蓝紫色调,菌盖强水浸状、具条纹,担孢子近球形。该种在系统发育树中形成一个独立的分支,与斑丝膜菌组形成姐妹关系,但遗传关系较远,属于新组李玉丝膜菌组。本文对新分类单元进行了详细描述,并对其系统发育上相近的物种进行了比较。