Zur vergesellschaftung einiger Nunataker-Taraxaca aus Osttirol (österreich)

Summary The study of the association of the northern Taraxaca-species in the eastern Tyrol was brought up by the publications of Handel-Mazzetti about the occurrence of these species at Nunataker-habitats which had remained free of ice during the glacial period. Proceeding from the division into relics-territories which are topographically given (the ice-free ridges) and the local ecological habitats (corners exposed to the wind resp. resting-places of sheep) the association itself is examined: Taraxacum Reichenbachii and Taraxacum Handlii colonize Drabeto-Saxifragetum, resp. Initial-Elynetum, Taraxacum ceratophorum colonizes sheep-fertilized places in an own community and often on the same ridges in a somewhat lower position.The examination shows that between the closely related T. Handelii and Reichenbachii and the more distant related T. ceratophorum there is a distinct differentiation as to their ecology, their occurrence in higher altitudes, their association, the time and the history of their immigration beside their systematical relationship.In the end a report is given about some new habitats of these species.

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Manuskript eingegangen am 3.XI.1953.     

Molecular differentiation between coexisting species of Taraxacum sect. Erythrosperma (Asteraceae) from populations in south-east and west Germany

The present study focuses on the genetic differentiation between six coexisting species of Taraxacum sect. Erythrosperma . Twenty-six individuals of T. rubicundum , T. brachyglossum , T. tortilobum , T. lacistophyllum , T. parnassicum and T. scanicum were sampled at 14 locations in south-east (Bavaria) and west Germany (Eifel). Using random amplified polymorphic DNA (RAPD) analysis 139 fragments were amplified. Nineteen of these were found to be species specific. The level of polymorphic bands within the different Taraxacum species varied between 0% and 15.8%. An analysis of molecular variance (AMOVA) revealed strong differentiation between the investigated species: 14.3% of the molecular variance were found within the species, while 85.7% of the genetic variability was observed between the species. However, a geographical differentiation between the different regions could not be observed. All analysed species were clearly separated from each other in a cluster analysis using the neighbour joining technique. The observed strong genetic differentiation between the Taraxacum species clearly supports the agamospecies concept of Taraxacum sect. Erythrosperma , which is at present mainly based on morphological and cytological criteria  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 145 , 109–117.     

The potential for genetic assimilation of a native dandelion species, Taraxacum ceratophorum (Asteraceae), by the exotic congener T. officinale

Exotic plant species can threaten closely related native congeners through asymmetric hybridization and subsequent backcrossing, the process known as genetic assimilation. I explore the initial stages of this process in Taraxacum ceratophorum (Asteraceae), the native alpine dandelion, and the invasive apomict T. officinale. In central Colorado, seven T. ceratophorum populations all occur in sympatry with T. officinale. In one large population on Pennsylvania Mountain, surveys further revealed that flowering phenologies and visiting insect taxa overlap almost completely for both Taraxacum species. Together these results indicated that heterospecific pollen transfer is likely. Crossing experiments showed that T. ceratophorum is an obligate outcrosser, and interspecific hand pollinations resulted in 37.3% seed set. However, molecular analysis of the F1 offspring indicated that only 33.2% of germinating seeds were hybrids; the remainder were selfed offspring produced from a breakdown in self-incompatibility (the mentor effect). Although the mentor effect helps reduce the production of hybrids, the asymmetrical direction of hybridization creates the potential for genetic assimilation of T. ceratophorum by T. officinale.     

ON THE OCCURRENCE OF THE PROSOBRANCHS LITTORINA NERITOIDES, L. MARIAE AND L. OBTUSATA IN DENMARK

Littorina neritoides occurs on piers and large stones on thebeaches in northern Jutland, but may not be able to toleratecold winters. L. obtusata and L. mariae are common on Fucus,but only L. mariae penetrates deeply into the fjords and sounds. (Received 10 December 1979;     

Drought tolerance in the alpine dandelion, Taraxacum ceratophorum (Asteraceae), its exotic congener T. officinale, and interspecific hybrids under natural and experimental conditions

We compared water relations and adaptations to drought stress in native and invasive exotic dandelions, Taraxacum ceratophorum and T. officinale. Photosynthesis (A), transpiration (E), and water use efficiency (WUE; carbon gained/water lost) were measured for the two species under extreme drought in the alpine tundra of Colorado, USA. We also subjected both species and F(1) hybrids to a dry-down experiment to determine how relative physiological performance varied with water availability. Photosynthesis and transpiration in the field were low and did not differ between Taraxacum congeners; however, native T. ceratophorum had higher WUE than T. officinale. After 6 days of greenhouse drought, photosynthesis and transpiration were reduced in T. officinale compared to T. ceratophorum. Taraxacum ceratophorum maintained high WUE under control and drought treatments. Conversely, WUE in T. officinale was highly plastic between watered (low WUE) and dry-down (high WUE) treatments. Hybrids did not exhibit heterosis; instead, they were similar to T. officinale in A and E and intermediate to the parental species in WUE. Overall, results suggest that native dandelions are more drought tolerant than invasive congeners or their hybrids, but have less plasticity in WUE. Arid habitats and occasional drought in mesic sites may provide native dandelions with refugia from negative interactions with invasives.     

A comparison of phenotypic plasticity in the native dandelion Taraxacum ceratophorum and its invasive congener T. officinale

We compared plastic responses to variation in the light environment for sympatric populations of native and exotic dandelion species, Taraxacum ceratophorum and Taraxacum officinale. Plasticity in leaf size, inflorescence height, reproductive phenology and dispersal-related traits were measured under experimentally altered light quality (red : far-red light ratio, R : FR) and light intensity (photosynthetically active radiation, PAR). To test whether differences in means and reaction norms of dispersal-related traits between species affected colonization potential, we created seed-dispersal models based on seed-fall rate and release height. Differences in plasticity between species were not systematic, but varied in direction and magnitude among traits. Taraxacum officinale produced larger leaves that exhibited greater plasticity in size under variable light intensity than T. ceratophorum. Plasticity in scape length at flowering occurred in relation to R : FR ratio in both species, but tended to be greater in T. ceratophorum. Seed-bearing scapes of T. officinale were taller and more canalized in height across light regimes than scapes of T. ceratophorum. Seeds of T. officinale were smaller than seeds of T. ceratophorum. Models predict greater dispersal in T. officinale within open and vegetated habitats. In contrast to the idea that plasticity promotes invasiveness, results suggest that the lack of plasticity in dispersal-related traits enhances the colonization potential of T. officinale.     

Responses to internal nitrogen and phosphorus concentrations of two Taraxacum microspecies of contrasting mineral ecology: critical N and P concentrations of whole plants

Of the two Taraxacum microspecies used. Taraxacum sellandii Dahlst. usually occurs in grasslands with a high nutrient level; Taraxacum nordstedtii Dahlst. is generally restricted to undisturbed and mineral-poor habitats. Growth response curves for internal N and P were established, based on relative yield of (whole) plant tissue water and (whole plant) internal mineral concentration on a tissue water basis. Critical nutrient concentrations of N and P were determined from the response curves derived. For both macroelements, T. nordstedtii showed lower critical nutrient concentrations. The difference in critical N concentrations coincided with differences in internal NO₃^-₃ concentrations between the microspecies. Finally, we discuss the use of tissue water as a (whole) plant growth parameter and internal mineral concentration on tissue water basis as a parameter describing the mineral status.     

Neue Taraxacum-Sippen aus dem Kaukasus

In the following work are presented 5 Taraxacum-Taxa as new for science from the Armenian SSR: sect. Ceratophora Dahlst.: Taraxacum glabratum Doll sp. nov., T. papposum Doll sp. nov.; sect. Erythrocarpa (H.-M.) Dahlst. emend. v. Soest: Taraxacum calocephaloides Doll sp. nov., T. pseudo-gracilens Doll sp. nov.; sect. Orientalia H.-M.; Taraxacum wardenium Doll sp. nov. Besides are discussed farther species and microspecies.     

Taxonomic and nomenclatural notes on Taraxacum (Compositae)

Sections Naevosa M. P. Chr., Crocea M. P. Chr. and Macrodonta M. P. Chr. are reduced to subsectional rank in section Spectabilia Dahlst. of the genus Taraxacum. Section Arctica Dahlst. (section Laevia (Hand.-Mazz.) Schischk.) is enlarged by including sections Glabra Dahlst., Antarctica Hand.-Mazz. and Pachera v. Soest.
Taraxacum gurglense A. J. Richards and T. unicoloratum A. J. Richards (section Alpestria v. Soest), T. concucullatum A. J. Richards (section Cucullata v. Soest) and T. venticola A. J. Richards (section Vulgaria Dahlst.) are described as new agamospecies from the Alps; and T. calcifhilum A. J. Richards & J. L. van Soest (section Orientalia Hand.-Mazz.), T. nigricornis A. J. Richards (section Macrocomuta v. Soest) and T. breviscapum A. J. Richards (section Erythrocarpa Hand.-Mazz.) are described as new agamospecies from Afghanistan.     

新疆蒲公英属有性生殖与无融合生殖植物的调查研究

以新疆２２种蒲公英的１８６份腊叶标本为材料,观察统计了每份标本的花粉败育率、花粉粒大小变异的标准方差。标准方差小于３、败育率小于２０％的花粉ＰＲ变异型,是有性生殖植物的特征;标准方差大于３、败育率大于４０％的花粉ＰＳ变异型,是无融合或兼性无融合植物的特征;不产生花粉的ＰＡ变异型,则是雄性不育植物的特征。在所观察的标本中,有４种蒲公英植物出现了有性生殖个体,其余为无融合或兼性无融合类。此外,还就蒲公     

No signature of Y chromosomal resemblance between possible descendants of the Cimbri in Denmark and Northern Italy

Two European populations are believed to be related to the ancient Germanic tribe Cimbri: one living in Northern Italy, the other living in Jutland, Denmark. The people called Cimbri are documented in the ancient Roman historical record. Arriving from the far north their movements can be tracked from successive battles with the Romans. The Cimbri finally entered Italy from the northeast and were defeated at Vercellae (present day Vercelli) in 101 BC by Gaius Marius and his professional legions. Classical sources from the first centuries AD relate the homeland of the Cimbri to the coasts around the Elb estuary (northern Germany) or specifically towards the north (Himmerland in northern Jutland). In the alpine parts of Veneto, northeast of the historical battlefield, local traditions dating back to late medieval time, identify a local population as Cimbri living in Terra dei Cimbri. They are considered the descendents of the Germanic combatants that fled the battlefield at Vercelli. As the defeated Cimbri that possibly fled to the mountains of Northern Italy most likely would have been male (warriors), the present study investigated the possible Y chromosomal diversity of the two present populations using microsatellite markers and single nucleotide polymorphisms. While Cimbri from Himmerland resembled their geographical neighbors from Denmark for the Y-chromosome markers, Cimbri from Italy were significantly differentiated both from Cimbri from Himmerland and from Danes. Therefore, we were not able to show any biological relationship for uniparentally transmitted markers.     

Uniclonal Population Structure in the Pentaploid Obligate Agamosperm Taraxacum albidum Dahlst.

Abstract Electrophoretic data were used to assess levels of clonal diversity within and among populations of Taraxacum albidum Dahlst., a pentaploid obligate agamosperm indigenous to Japan. All specimens sampled from the entire distribution range shared the same 19-locus genotypic profile except for one. This single mutant differed in one allele at one locus only. Contrary to this extreme monomorphism, clonally reproducing species usually consist of multiclonal populations. It is hypothesized that T. albidum recently originated through hybridization between a sexual diploid species of the section Mongolica (most likely T. japonicum Koidz.) and an unknown polyploid Mongolica species.     

Study on nutrient stress tolerance of nine Taraxacum microspecies with a contrasting mineral ecology by cultivation in a low nutrient flowing solution

Growth and mineral status of 9 Taraxacum microspecies were studied under mineral stress conditions, using a flowing solution of low nutrient concentration. Relative growth rate of (whole) plant dry weight, leaf area, and (whole) plant tissue water were used to describe growth. For 4 microspecies, specific uptake rates of NO⁻₃, H₂PO⁻₄, K⁺, Mg²⁺ and Ca²⁺ were investigated.
The applied nutrient condition clearly discriminated between the studied Taraxacum microspecies. With respect to relative growth rate, 3 groups of microspecies could be distinguished: T. nordstedtii > T. lancidens, T. adamii, T. hollandicum, T. taeniatum > T. sellandii, T. eudontum, T. ekmanii, T. ancistrolobum . These categories coincided well with the mineral ecology of the microspecies, going from infertile to fertile sites.
T. nordstedtii , a microspecies of infertile sites, was most efficient in absorbing NO⁻₃, H₂PO⁻₄ and K⁺. T. sellandii and T. eudontum , both occurring in fertile grasslands, showed poor uptake performances for all studied ions. In all Taraxacum microspecies studied, except T. eudontum , internal N concentration appeared to limit growth. Efficiencies in N use, at sub-optimal internal N concentrations, varied with the mineral habitat of the microspecies studied. T. nordstedtii , from infertile sites, and T. sellandii , from fertile sites, were established as high and low extremes, respectively.     

The Holocene vegetation history of northern West Jutland, Denmark

Holocene sediments of three closed Danish lake basins (Solsø, Skånsø, Kragsø) were used for the inference of post-glacial vegetational dynamics in former heathland areas in northern West Jutland, Denmark. The sites were selected to represent the major geomorphological units of West Jutland. The Holocene history of each lake basin was investigated by mapping of sediment distribution, analysis of loss-on-ignition, coarse inorganic matter, humus content, mineral magnetics, δ¹³C, pollen and selected other microfossils. These techniques were supplemented by plant macrofossil analysis at one site. Holocene terrestrial vegetational development was inferred at each site from analyses of pollen and microscopical charred particles. Chronologies were provided by numerous ¹⁴C dates. Stratigraphies of wet ground and terrestrial pollen and spore types were zooned by stratigraphically constrained cluster analysis. Based on the resultant site pollen asemblage zones (site PAZ), regional PAZ were proposed. Using modern analogues, Holocene floristic richness was estimated from pollen richness in the microfossil assemblages. The results support the hypothesis that disturbance is one of the most important mechanisms behind the maintenance of floristic richness. In particular, the response of estimated floristic richness to the intensity of vegetational fires followed the predictions of the Intermediate Disturbance Hypothesis. A period of elevated palynological richness and inferred vegetational disturbance was identified at all sites between 6000 and 5200 BC (calendar years). Using correspondence analysis (CA), the major gradient in the terrestrial pollen sequences was identified as a light-shade gradient, and CA first axis sample scores were used as a supplement to standard AP/NAP pollen ratios as an indicator of the shade-tolerance/light-demand of Holocene terrestrial plant communities. In spite of different vegetational developments since 4000 BC, the timing of major changes towards more light-demanding vegetation types were broadly synchronous at the three sites. Using chord distance as a dissimilarity index, rates of palynological change suggest that the interval between 8000 and 7500 BC (calendar years) was the period of most rapid vegetational change during the Holocene, both in terrestrial as well as lacustrine ecosystems. While climatic forcing of the rapid events around 8000 BC is hypothesised, the synchronous timing of relatively rapid inferred change in lake and terrestrial vegetation around AD 600 may reflect changes in climate as well as in land-use. Reducdancy analysis was used to develop a model between fire intensity (inferred from microscopical charred particles) and vegetational response, as reflected by pollen assemblages. Formulated at one site and tested at the two other sites, the model explains regional Calluna-heathland expansions as a result of vegetational burning. Similarly, declines in heathland cover are explained by lack of maintenance by fire. Regional vegetational development in northern West Jutland is reconstructed and special consideration is given to heathland history. The Holocene heathland development is interpreted as resulting from its importance for grazing. It is hypothesized that on poor soils, Calluna-dominated heathland was a better grazing resource than grass-dominated pasture, due to the winter-grazing offered by Calluna and the low palatibility of dominant grasses on poor soils. This hypothesis is relevant for the explanation of the variation in timing of heathland expansions on the different soil types represented by the study sites.     

Polymorphism of nuclear DNA in selected species of Taraxacum sect. Palustria

This paper presents the results of research on nuclear DNA polymorphism in six apomictic species of marsh dandelions (Taraxacum sect. Palustria): Taraxacum bavaricum, T. belorussicum, T. brandenburgicum, T. paucilobum, T. subdolum and T. vindobonense. The studies demonstrated the existence of clear genetic differences between species and the existence of nuclear DNA polymorphism within each of the studied species.     

Distribution, phenology and demography of sympatric sexual and asexual dandelions (Taraxacum officinale s.l.): geographic parthenogenesis on a small scale

In many plant and animal species, sexual and asexual forms have different geographical distributions ('geographic parthenogenesis'). The common dandelion Taraxacum officinale s.l. provides a particularly clear example of differing distributions: diploid sexuals are restricted to southern and central Europe, while triploid asexuals occur across Europe. To get a better understanding of the factors underlying this pattern, we studied the distribution and demography of sexuals and asexuals in a mixed population that was located at the northern distribution limit of the sexuals. In this population three adjacent, contrasting microhabitats were found: a foreland and south and north slopes of a river dike. Comparative analyses of the distribution, phenology and demography indicated that sexuals had a stronger preference for the south slope than did asexuals. We therefore propose that the large-scale geographic parthenogenesis in T. officinale is shaped by an environmental gradient which acts upon the sexuals.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 82 , 205–218.     

Twelve new native Taraxacum species from the Nordic countries

Eleven native Taraxacum species from Norden are described as new: T. acutilimbatum, T. frondatum, T. latulum, T. thorvaldii, T. wendtii and T. wessbergii (all in T. sect. Erythrosperma), T. danicum (sect. Palustria), T. conspersum and T. lentiginosum (sect. Naevosa), T. pietii‐oosterveldii (sect. Celtica) and T. ovillum (sect. Spectabilia). They are compared with morphologically similar species, and their ecological preferences are outlined. Known distribution areas and lists of paratypes are given. Taraxacum polyschistum Dahlst. forma oelandicum G. E. Haglund (sect. Erythrosperma) is given status of species.     

The Holocene vegetation history of northern West Jutland, Denmark

Holocene sediments of three closed Danish lake basins (Solsø, Skånsø, Kragsø) were used for the inference of post-glacial vegetational dynamics in former heathland areas in northern West Jutland, Denmark. The sites were selected to represent the major geomorphological units of West Jutland. The Holocene history of each lake basin was investigated by mapping of sediment distribution, analysis of loss-on-ignition, coarse inorganic matter, humus content, mineral magnetics, δ¹³C, pollen and selected other microfossils. These techniques were supplemented by plant macrofossil analysis at one site. Holocene terrestrial vegetational development was inferred at each site from analyses of pollen and microscopical charred particles. Chronologies were provided by numerous ¹⁴C dates. Stratigraphies of wet ground and terrestrial pollen and spore types were zooned by stratigraphically constrained cluster analysis. Based on the resultant site pollen asemblage zones (site PAZ), regional PAZ were proposed. Using modern analogues, Holocene floristic richness was estimated from pollen richness in the microfossil assemblages. The results support the hypothesis that disturbance is one of the most important mechanisms behind the maintenance of floristic richness. In particular, the response of estimated floristic richness to the intensity of vegetational fires followed the predictions of the Intermediate Disturbance Hypothesis. A period of elevated palynological richness and inferred vegetational disturbance was identified at all sites between 6000 and 5200 BC (calendar years). Using correspondence analysis (CA), the major gradient in the terrestrial pollen sequences was identified as a light-shade gradient, and CA first axis sample scores were used as a supplement to standard AP/NAP pollen ratios as an indicator of the shade-tolerance/light-demand of Holocene terrestrial plant communities. In spite of different vegetational developments since 4000 BC, the timing of major changes towards more light-demanding vegetation types were broadly synchronous at the three sites. Using chord distance as a dissimilarity index, rales of palynological change suggest that the interval between 8000 and 7500 BC (calendar years) was the period of most rapid vegetational change during the Holocene, both in terrestrial as well as lacustrine ecosystems. While climatic forcing of the rapid events around 8000 BC is hypothesised, the synchronous timing of relatively rapid inferred change in lake and terrestrial vegetation around AD 600 may reflect changes in climate as well as in land-use. Reducdancy analysis was used to develop a model between fire intensity (inferred from microscopical charred particles) and vegetational response, as reflected by pollen assemblages. Formulated at one site and tested at the two other sites, the model explains regional Colluna-heathland expansions as a result of vegetational burning. Similarly, declines in heathland cover are explained by lack of maintenance by fire. Regional vegetational development in northern West Jutland is reconstructed and special consideration is given to heathland history. The Holocene heathland development is interpreted as resulting from its importance for grazing. It is hypothesized that on poor soils, Calluna-dominated heathland was a better grazing resource than grass-dominated pasture, due to the winter-grazing offered by Calluna and the low palatibility of dominant grasses on poor soils. This hypothesis is relevant for the explanation of the variation in timing of heathland expansions on the different soil types represented by the study sites.     

新疆蒲公英属一新种

本文报道了新疆产蒲公英属植物一新种——新源蒲公英Taraxacum xinyuanicum D．T．Zhai et Z. X．An,并对其模式产地种群中其它个体的形态变异做了进一步的说明,同时还指出它与药用蒲公英 T.officinale Wigg．和堆叶蒲公英T．compactum Schischk 的异同;花粉体积变异、败育率和染色体数目的统计表明它是一个二倍体,与后面的两个多倍体种有明显的差别。