Population genetics of Matthiola bolleana (Brassicaceae) in the Canary Islands

Genetic variation at 11 isozyme loci was used to explore the levels and apportionment of genetic variation in the eight known populations of Matthiola bolleana, an endemic Brassicaceae to the Eastern Canarian islands of Fuerteventura and Lanzarote. Within islands, ecosystem antiquity and uniformity, lack of evidence for selection or genetic bottlenecks, the high genetic identities between the populations, and the low values of F _ST converge to suggest that the high levels of variation detected have been maintained in a context of prolonged environmental stability through an overall predominance of outbreeding and unrestricted gene flow. Despite the geographical closeness between Fuerteventura and Lanzarote and the long range dispersal features of the propagules of M. bolleana, we detected a striking qualitative genetic differentiation between the two islands. We suggest that wind direction has made seed and pollen flow between Fuerteventura and Lanzarote much less likely than expected, and that the lack of inter-island dispersal has far overriden the influence of stochastic forces and of the reproductive attributes of M. bolleana in shaping the patterns of inter-island genetic differentiation. However, genetic similarity in M. bolleana is within the ranges defined by Canarian taxa for which the extent of genetic differentiation has also been assessed using the values of isozyme genetic identity.     

Two new species of Sisymbrium (Brassicaceae) from coastal Peru

Two new species ofSisymbrium are described from the Department of Arequipa in south-western Peru. Both are annuals from the loma vegetation.Sisymbrium lactucoides has glabrous leaves with clasping bases and is very distinct.Sisymbrium ferreyrae is probably closest toS. llatasii, but it is a much smaller plant with petals and sepals of subequal length (vs. petals longer than sepals inS. llatasii).     

Towards the era of comparative evolutionary genomics in Brassicaceae

The vast genetic diversity, specific genome organization and sequencing of the Arabidopsis thaliana genome made crucifers an ideal group for comparative genomic studies. Arabidopsis genomic resources have greatly expedited comparative genomics within Brassicaceae and fostered the establishment of new Arabidopsis relative model systems (ARMS). The extent of genome colinearity, modes and evolutionary rates of genome alterations are being analyzed by genetic mapping with ever increasing levels of precision. Comparative cytogenetic studies in Brassicaceae are employing various chromosome landmarks and cytogenetic techniques, including localization of rDNA, variation in centromeric satellite repeats, genomic in situ hybridization (GISH), fluorescence ISH using bacterial artificial chromosomes (BAC FISH), and large-scale comparative chromosome painting. Some genome alterations may represent rare genomic changes (RGCs) and thus have the potential to resolve complex/conflicting phylogenetic relationships inferred from DNA sequencing. Comparative genomics should increasingly be integrated with molecular phylogenetics and population genetics to elucidate the processes responsible for genetic variation in Brassicaceae.     

Evolutionary Processes Associated with Biological Invasions in the Brassicaceae

This review highlights evolutionary processes in the Brassicaceae which cause, accompany or are a consequence of biological invasions. Case studies in Capsella and Diplotaxis address the genetics of colonising species. The greatest colonising ability in Capsella bursa-pastoris is associated with polyploidy, predominant selfing, and high genetic diversity. Success of colonial populations seems to be due to the introduction of preadapted genotypes. Colonising species in Diplotaxis reveal contrasting evolutionary patterns. Genetic attributes in D. muralis include annuality, polyploidy, and predominant selfing. Very different from Capsella, D. muralis is nearly devoid of genetic diversity as revealed by molecular markers. In contrast to D. muralis, the colonising D. tenuifolia is perennial, diploid, self-incompatible, and displays high genetic diversity. Hybrid speciation, establishment of the hybrids in man-made habitats, stabilisation of their reproductive system, and reproductive isolation from the parent populations were analysed in Cardamine. The Nasturtium example highlights the importance of hybridisation for the evolution of invasiveness. The last case study concentrates on the evolutionary consequences of hybridisation between native and invading Rorippa species. Introgressive hybridisation between the invasive Rorippa austriaca and native Rorippa species is common and widespread in central Europe, and interspecific gene transfer has led to the formation of a new invasive genotype. Each successful invasion presents new aspects and sound case studies are needed in order to understand the ecology and evolution of the colonisation process and to enable us to assess the evolutionary consequences of biological invasions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Evolution of the monocot gynoecium: evidence from comparative morphology and development in Tofieldia, Japonolirion, Petrosavia and Narthecium

We present new comparative morphological and developmental data on gynoecia of three genera of early-divergent monocots: Tofieldia (Tofieldiaceae, Alismatales), Petrosavia and Japonolirion (Petrosaviaceae, Petrosaviales) and one lilioid monocot: Narthecium (Nartheciaceae, Dioscoreales). Our data show significant differences between the genera examined, and are congruent with the splitting of former Nartheciaceae sensu Tamura (1998) into families Tofieldiaceae, Petrosaviaceae NB-cosistent with later and Nartheciacae (APG II 2003). Our investigation confirms the presence of at least partial carpel fusion in all taxa examined. Previous data indicating apocarpy in Japonolirion, some Petrosavia and Tofieldia could be due to late postgenital carpel fusion in these plants. Syncarpy also characterises other early-divergent monocot lineages such as Acoraceae and Araceae. It is most parsimonious to regard syncarpy as a primitive condition for monocots, but an alternative scenario suggests that apocarpy is plesiomorphic among monocots, involving multiple origins of syncarpy. The latter hypothesis is supported by significant differences between gynoecia of early-divergent monocots, including different modes of carpel fusion.     

Molecules and morphology: Congruence of data inColumnea (Gesneriaceae)

The cladistic analysis and comparison of molecular and morphological data has been the source of much recent debate. In this study, independent analyses of molecular and morphological data fromColumnea L. sects.Pentadenia andStygnanthe (Gesneriaceae) are compared. Comparative methods include consensus, visually comparing trees from independent analyses and combined data analysis. Consensus methods provided little resolution. Comparison of trees obtained from the independent analyses revealed some differences although the trees are highly similar. However, a combined analysis found that the level of incongruence between the two data sets was low. The tree resulting from the combined data has aspects of both the morphological and molecular trees despite the larger number of molecular characters. In addition, the combined data tree has greater resolution than either of the two data sets singly, indicating that the two types of data are congruent, and complementary to each other.     

A new species of Boechera (Brassicaceae) from Utah and Colorado

A new species,Boechera glareosa, is described and a key is provided to separate it from its apparent closest relative,B. gunnisoniana (Rollins) W. A. Weber. Twelve transfers are made fromArabis toBoechera to bring the nomenclature of Rocky Mountain region taxa in line with current DNA data.     

Systematic implications of chloroplast DNA variation inLepidium sectionsCardamon,Lepiocardamon andLepia (Brassicaceae)

Chloroplast DNA restriction site variation was examined amongLepidium taxa usually classified in sects.Lepia, Lepiocardamon andCardamon. By using 15 restriction endonucleases, filter hybridization experiments, and comparative mapping procedures, a total of 119 variable restriction sites was detected. Of these, 56 were phylogenetically informative and were used in a cladistic analysis. The resulting phylogenetic tree agrees with results derived from morphology, isozyme electrophoresis and the analysis of glucosinolates. The data suggest: 1) The recognition of sect.Lepia, and 2) that sect.Lepiocardamon has close relationships to sect.Cardamon and that both should be amalgamated. Low rates of interspecific chloroplast DNA sequence divergence in sect.Lepia correlated well with morphological data and isoelectric focusing analysis of Rubisco, suggesting that taxa of sect.Lepia are closely related and most likely have diversified recently.     

Aspartate aminotransferase isozymes in the genusCapsella (Brassicaceae): Subcellular location,gene duplication,and polymorphism

The subcellular location of aspartate aminotransferase isozymes (EC 2.6.1.1) in the genusCapsella(Brassicaceae) was studied. The diploid speciesC. grandiflora andC. rubella have three AAT isozymes, including one located in the plastids. Each locus is duplicated in the tetraploidCapsella bursa-pastoris. Variation at the plastid-coding locus exceeded that at the other loci.C. bursa-pastoris had some unique alleles not detected in the diploid species. Segregation in open-pollinated families revealed thatCapsella grandiflora was outcrossing, whereasC. rubella was highly inbred, with most populations homozygous or uniform at all three loci. Inheritance in the tetraploid colonizerC. bursa-pastoris is disomic. This species was also predominantly selfing with outcrossing rates between 2% and 10%.Financial support by the German Research Foundation DFG is gratefully acknowledged.     

Colonization of pennycresses (Thlaspi spp.) of the Brassicaceae by arbuscular mycorrhizal fungi

Members of the Brassicaceae are generally believed to be non-mycorrhizal. Pennycress (Thlaspi) species of this family from diverse locations in Slovenia, Austria, Italy and Germany were examined for their colonisation by arbuscular mycorrhizal fungi (AMF). Meadow species (T. praecox, T. caerulescens and T. montanum) were sparsely but distinctly colonised, as indicated by the occurrence of intraradical hyphae, vesicles, coils, and occasionally arbuscules. Species from other locations were poorly colonised, but arbuscules were not discernible. The genus Thlaspi comprises several heavy metal hyperaccumulating species (T. caerulescens, T. goesingense, T. calaminare, T. cepaeifolium). All samples collected from heavy metal soils were at best poorly colonized. Thus the chance is small to find a "hypersystem" in phytoremediation consisting of an AM fungus which prevents the uptake of the major part of the heavy metals and of a Thlaspi species which effectively deposits the residual heavy metals inevitably taken up into its vacuoles. In two different PCR approaches, fungal DNA was amplified from most of the Thlaspi roots examined, even from those with a very low incidence of AMF colonization. Sequencing of the 28S- and 18S-rDNA PCR-products revealed that different Thlaspi field samples were colonized by Glomus intraradices and thus by a common AM fungus. However, none of the sequences obtained was identical to any other found in the present study or deposited in the databanks, which might indicate that a species continuum exists in the G. intraradices clade. An effective colonization of Thlaspi by AMF could not be established in greenhouse experiments. Although the data show that Thlaspi can be colonized by AMF, it is doubtful whether an effective symbiosis with the mutual exchange of metabolites is formed by both partners.     

陕西省十字花科植物新记录

该文报道了陕西省发现的3个新记录属和5个新记录种。新记录属分别是堇叶芥属(Neomartinella Pilger)、皱果荠属(Rapistrum Crantz)和二行芥属(Diplotaxis de Candolle);新记录种分别是永顺堇叶芥［Neomartinella yungshunensis (W. T. Wang) Al Shehbaz］、安徽碎米荠(Cardamine anhuiensis D. C. Zhang et J. Z. Shao)、欧亚蔊菜［Rorippa sylvestris (L.) Bess.］、皱果荠［Rapistrum rugosum (L.) All.］和二行芥［Diplotaxis muralis (L.) DC.］。     

Systematics of AustralianLepidium species (Brassicaceae) and implications for their origin: Evidence from IEF analysis of Rubisco

Variation in subunit polypeptide composition of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) from native AustralianLepidium taxa was analyzed by isoelectric focusing (IEF). Species of grexMonoplocoidea on the one hand, and species of gregesPseudoruderalia andPapillosa on the other, were well separated by Rubisco IEF patterns. The protein data suggest grexMonoplocoidea to be placed in sect.Monoploca whereas gregesPseudoruderalia andPapillosa should be integrated into sect.Dileptium. We suggest that the Rubisco type of American and/or AsianLepidium species was contained in those plants migrating to Australia and evolving into the recent native Australian species. Fossil pollen records and vegetation history indicate that the origin ofLepidium in Australia was restricted to the late Tertiary of Quaternary. Data presented in this study fit best with an immigration by long-distance dispersal of seeds by birds from Asia and/or from South America.     

Seed-coat microsculpturing and its systematic application in Isatis (Brassicaceae) and allied genera in Iran

In order to examine the systematic application of seed-coat microsculpturing in Isatis, seed surfaces of 23 species (41 populations) in four genera of tribe Isatideae were examined using scanning electron microscopy (SEM). Eight types of basic ornamentation patterns were recognized among the studied specimens. Of these, the reticulate–areolate type was the most common and was found in the genera Isatis, Pachypterygium, Samerari and Tauscheria and 15 species (e.g., I. cappodocica, I. kotschyana and I. tinctoria). The reticulate type, the second most frequent, occurred in 7 species while other types each were represented by only one or 2 species. Although different populations of a given species show similar seed-surface sculpturing in most cases, in some polymorphic species like I. cappadocica and I. kotschyana these patterns were variable among populations. To some extent the variation corresponds to infraspecific taxa for some species, but the differences are not significant enough to be useful in the delimitation of the subspecies recognized by previous workers. Moreover, seed-coat characters do not support the separation of genera Isatis, Pachypterygium, Sameraria and Tauscheria.     

The glucosinolate-degrading enzyme myrosinase in Brassicaceae is encoded by a gene family

A full-length cDNA clone (MB3) and three partial clones (MA1, MB1 and MB2) which encode myrosinase (thioglucoside glucohydrolase, EC 3.2.3.1) were isolated from a Sinapis alba (white mustard) cDNA library. Nucleotide sequence analysis of these clones revealed that they are encoded by a gene family. Southern blot analysis with gene-specific probes showed that the gene family consists of a least two subfamilies (MA and MB) each with several members both in S. alba and in Brassica napus (oilseed rape). In Arabidopsis thaliana (wall cress) only three myrosinase genes seem to be present. Northern blot analysis indicated that all the myrosinase mRNA species have the same size, approximately 1.95 kb.     

Functional evolutionary developmental biology (evo-devo) of morphological novelties in plants

The origin of morphological and ecological novelties is a long-standing problem in evolutionary biology.Understanding these processes requires investigation from both the development and evolution standpoints,which promotes a new research field called evolutionary developmental biology (evo-devo).The fundamental mechanism for the origin of a novel structure may involve heterotopy,heterochrony,ectopic expression,or loss of an existing regulatory factor.Accordingly,the morphological and ecological traits cont...     

沙芥属(十字花科)的起源、分类与进化研究进展

沙芥属(PugioniumGaertn.)最初是从匙荠属(Bunias)中分出来单独建立的属,ndhF系统树表明,该属和高河菜属(Megacarpaea)、Farsetia、香雪球属(Lobularia)、屈曲花属(Iberis)和Ionopsidium亲缘关系较近,且和高河菜属构成姐妹关系。自从沙芥属确立以来,先后发表过沙芥[P.cornutum(L.)Gaertn]、斧形沙芥(P.dolabratum Maxim.)、距果沙芥(P.calcaratum Kom.)、鸡冠沙芥(P.cristatum Kom.)、翅果沙芥(P.pterocarpum Kom.)等5个种和宽翅沙芥(P.dolabratumvar.platypterum H.L.Yang)1个变种,但形态统计学和分子生物学的证据表明,沙芥属应该仅包含沙芥(P.cornutum)和斧形沙芥(P.dolabratum)2个形态学物种。基于不同遗传背景的DNA分子标记的研究结果进一步表明,沙芥和斧形沙芥这2个形态学物种间的遗传分化明显,但种间分化的时间并不久远,它们很可能是更新世以来随中亚和中国西北沙漠发展扩张而形成的2个近期分化的姐妹种。该文对沙芥属的系统起源、属下分类和遗传进化方面的研究历史和最新研究进展进行综述,并提出了研究中存在的问题。     

Brassicaceae contain nortropane alkaloids

The report of cochlearine, the 3-hydroxybenzoate ester of tropine found in Cochlearia officinalis, Brassicaceae, initiated a screening for tropane alkaloids in Cochlearia species and for calystegines in further Brassicaceae. All ten Cochlearia species investigated contained cochlearine, tropine, and pseudotropine. Calystegines, nortropane alkaloids deriving from pseudotropine, were also identified in all Cochlearia species and accumulated up to 0.5% dry mass in leaves. Brassicaceae species of all major lineages of the family were analysed for calystegines. Of the 43 species included in the study, 18 accumulated calystegines of various structures. This is the first screening of Brassicaceae for products of the tropane alkaloid pathway, which is known as characteristic for plants of Solanaceae family. The identification of calystegines in all branches of the Brassicaceae family including Aethionema, a species at the basis of the family, suggests tropane alkaloids as secondary compound typical for Brassicaceae.     

Cochlearia macrorrhiza (Brassicaceae): A bridging species between Cochlearia taxa from the Eastern Alps and the Carpathians?

Cochlearia macrorrhiza is one of the most highly endangered species in Central Europe and less than five individuals survived at its natural stand in a lowland area between the Eastern Alps and the Carpathians. Amplified fragment length polymorphisms (AFLPs) confirmed the status of C. macrorrhiza as a distinct taxon. Lowland C. macrorrhiza does not bridge the distribution of montainous and alpine Cochlearia species from the Eastern Alps and the Carpathians genetically, and C. macrorrhiza represents a separate lineage which evolved from diploid Cochlearia as C. excelsa in East Austrian high alpine regions did. Another species considered in this study, the Romanian C. borzaeana is more closely related to C. tatrae from the High Tatra mountains than to C. pyrenaica from Slovakia or Austria and the AFLP results suggest a single origin of alpine 2n=42 taxa. Genetic differentiation within and between populations is highly structured geographically, and the AFLP data favour a former widespread distribution of C. pyrenaica in mountainous regions and a parallel evolution of high alpine taxa in the Eastern Alps and the Carpathians, respectively.