2007

Invasion of giant hogweed (Heracleum mantegazzianum) in Europe

Giant hogweed (Heracleum mantegazzianum), native to Caucasus, is a serious invasive species in Europe. Since 2002, various aspects of this species’ biology, ecology, genetics, biogeography and management were addressed within the GIANT ALIEN project of the 5th Framework Programme of EU. In 2007, the results were summarized in a monograph reviewing current knowledge of the invasion of this species in Europe (Pyšek et al. 2007). Three species of large hogweeds (H. mantegazzianum, H. sosnowskyi, H. persicum) invade in Europe and their distribution in the continent reflects different germination requirements and seed bank characteristics; Central Europe is invaded by Heracleum mantegazzianum. A high genetic variation was found in the invaded range, most likely due to repeated introductions of all three species to Europe (Jahodová et al., Diversity & Distributions 2007). Genetic studies identified suitable markers for Heracleum mantegazzianum (Henry et al. 2007). The invasive success of this species is determined by a combination of several traits, mostly related to reproduction: high fecundity, extremely high germination rate, short-term persistent seed bank, reproductive assurance through self-pollination, efficient dispersal and high regeneration ability); these traits are described, quantified and analysed in the monograph chapters (Pyšek et al. 2007). A comparison of theoretical simulations of population dynamics with real data, obtained from aerial photographs, suggests that about 2.5% of seed are subject to long-distance dispersal, which results in a dynamic spread and colonization of new sites (Nehrbass et al. 2007). Because of extremely high regeneration of giant hogweed plants, control measures aimed at preventing it from seed production need to be based on appropriate timing. If conducted too early, plants regenerate, if too late, seeds ripe on cut umbels (Pyšek et al., Biological Invasions 2007). The results are important for control and management of giant hogweed in Europe.

Pyšek, P., Cock, M. J. W., Nentwig, W. & Ravn, H. P. (2007): Ecology and management of Giant Hogweed (Heracleum mantegazzianum). – CAB International, Wallingford, 331 pp.

Jahodová, Š., Trybush, S., Pyšek, P., Wade, M., Karp, A.: Invasive species of Heracleum in Europe: an insight into genetic relationships and invasion history. – Diversity and Distributions 13: 99–114.

Pyšek, P., Krinke, L., Jarošík, V., Perglová, I., Pergl, J., Moravcová, L. (2007): Timing and extent of tissue removal affect reproduction characteristics of an invasive species Heracleum mantegazzianum. – Biological Invasions 9: 335–351.

Nehrbass, N., Winkler, E., Müllerová, J., Pergl, J., Pyšek, P., Perglová, I. (2007): A simulation model of plant invasion: long-distance dispersal determines the pattern of spread. – Biological Invasions 9: 383–395 (2007).

Henry, P., Provan, J., Goudet, J., Guisan, A., Jahodová, Š., Besnard, G. (2008): A set of primers for plastid indels and nuclear microsatellites in the invasive plant Heracleum mantegazzianum (Apiaceae) and their transferability to Heracleum sphondylium. – Molecular Ecology Resources 8: 161–1633.

Jahodová, Š., Fröberg, L., Pyšek, P., Geltman, D., Trybush, S., Karp, A. (2007): Taxonomy, identification, genetic relationships and distribution of large Heracleum species in Europe. – In: Pyšek P. et al. (eds), Ecology and management of giant hogweed (Heracleum mantegazzianum), CAB International, Wallingford, p. 1–19; Pyšek, P., Müllerová, J., Jarošík, V.: Historical dynamics of Heracleum mantegazzianum invasion on regional and local scales. – Ibid., p. 42–54; Perglová, I., Pergl, J., Pyšek, P.: Reproductive ecology of Heracleum mantegazzianum. – Ibid., p. 55–73; Moravcová, L., Pyšek, P., Krinke, L., Pergl, J., Perglová, I., Thompson, K.: Seed germination, dispersal and seed bank in Heracleum mantegazzianum. – Ibid., p. 74–91; Pyšek, P., Perglová, I., Krinke, L., Jarošík, V., Pergl, J., Moravcová, L.: Regeneration ability of Heracleum mantegazzianum and implication for control. – Ibid., p. 112–125; Moravcová, L., Gudžinskas, Z., Pyšek, P., Pergl, J., Perglová, I.: Seed ecology of Heracleum mantegazzianum and H. sosnowskyi, two invasive species with different distributions in Europe. – Ibid., p. 157–169; Pyšek, P., Cock, M. J. W., Nentwig, W., Ravn, H. P.: Master of all traits: Can we successfully fight giant hogweed? – Ibid., p. 297–312.

Diversity and evolution of Hieracium (Asteraceae)

The genus Hieracium belongs to most diverse and taxonomically intricate plant groups in Europe. The extreme diversity is caused by a combination of various breeding systems (sexuality, apomixis, vegetative spreading), common hybridization and polyploidy. Just study of groups with different modes of reproduction is an important contemporary issue. A series of papers comprising various new approaches was published in 2007. Phylogenetic reconstruction of Hieracium subgen. Pilosella based on selected molecular traits is of crucial importance for assessment of evolution in this group. Sequencing of selected segments of chloroplast DNA revealed two groups of haploide genotypes (haplotypes), incongruent with the recently accepted classifications. On the other hand, result of nuclear DNA (ITS) sequencing correspond with morphology and most likely reflect the real evolution (Fehrer et al. 2007). A review summarizing the sources of variation in Hieracium subgen. Pilosella appeared in 2000. Due to accelerated development in this field, research team of IB summarized recently gathered data, scattered in many publications (Fehrer et al. 2007). Recent development of flow cytometry allowed the estimation of genome size (DNA content) in a large set of basic species and both field and experimental hybrids of Hieracium subgen. Pilosella. Considerable interspecific differences were detected, which enable, besides others, to infer genome constitution (putative parental combination) in hybrids (Suda et al. 2007). Within Hieracium subgen. Hieracium, taxonomic treatment of a mountain apomictic group Hieracium nigrescens was finished. Morphological and geographical approaches were accompanied by isozyme analysis and a relation between isozyme phenotypes and morphologically defined types was confirmed (Chrtek et al. 2007, Chrtek & Mráz 2007).

Fehrer J., Gemeinholzer B., Chrtek J. Jr & Bräutigam S. (2007): Incongruent plastid and nuclear DNA phylogenies reveal ancient intergeneric hybridization in Pilosella hawkweeds (Hieracium, Cichorieae, Asteraceae). – Molecular Phylogenetics and Evolution 42: 347–361.

Circulation of cyanobacteria, algae and bacteria in the catchment area of Werenskoilbreen glacier, Svalbard

The succession of the algae, cyanobacteria and bacteria was studied in the catchment area of the Weresnkoildbreen glacier at Svalbard. The study was performed in four different habitats- subglacial sediments, proglacial sediments, in deglaciated soil and in wetlands. The main focus was laid on the circulation of the microorganisms among these different habitats, and their ability to survive the transfer to the subglacial systems and if they can participate on the primary colonization of newly deglaciated soils. It was found that the phototropic microorganisms can survive in the sediments under the glacier (subglacial systems) and that they can participate on the colonization of deglaciated soil. The most important sources of the inoculum for colonization are cryoconite sediments from proglacial area and microorganisms from wetlands. The transport is done by water in the summer season and by wind in the late autumn.
Other part of study was the seasonal and diurnal dynamics of the physiological state and photosynthetic activity of the snow alga Chlamydomonas nivalis. Photosynthetic activity was measured using pulse amplitude modulation fluorometry. Three types of cell (green biflagellate vegetative cells, orange spores clustered by means of mucilaginous sheaths, and purple spores with thick cell walls) were found, all of them photosynthetically active. The photosynthetic activity had seasonal and diel dynamics. The Fv/Fm values ranged between 0.4 and 0.7, and generally declined over the course of the season. A dynamic response of Fv/Fm to the irradiance was recorded.

Stibal, M., Elster, J., Šabacká, M., Kaštovská, K.: Seasonal and dial changes in photosynthetic activity of the snow algae Chlamydomonas nivalis (Chlorophyceae) from Svalbard determined by PAM fluorometry. – FEMS Microbioloy Ecology 59: 265–273 (2007).

Applications of flow cytometry to plant biosystematics, ecology, and population biology

Flow cytometry (FCM), a method of rapidly characterizing optical properties of isolated particles, is advancing research in several areas of cellular biology. However, its routine use in plant sciences was markedly delayed due to methodological difficulties and only the last decade has seen significant increase of FCM applications in plant biosystematics, ecology, and population biology. One of the recent landmarks is the first comprehensive book “Flow Cytometry with Plant Cells” (Doležel et al. 2007). Elucidation of causes and consequences of genome duplication, variation in nuclear genome size and modes of reproduction rank among the most promising research avenues (Kron et al. 2007). FCM offers many advantages over other methods of detecting ploidy, which paves the way for large-scale surveys at the landscape and population levels. Representative sampling allowed gaining novel insights into the extent of intra- and inter-population ploidy variation, niche differentiation, and ecological preferences of particular cytotypes (Suda et al., Amer. J. Bot. 2007). Synergistic use of FCM and molecular analyses proved suitable for unravelling complex low-level taxonomies, detection of cryptic biodiversity (Schönswetter et al. 2007) and colonization history of species/cytotypes (Eidesen et al. 2007). Genome size, another key character of living systems, was used as a species-specific character in plant groups with complex evolutionary history (Leong-Škorničková et al. 2007; Suda et al., Ann. Bot. 2007). A prerequisite of reliable FCM studies is the meticulous methodology (Doležel et al., Nature Protocols 2007). The data obtained will help better understanding of frequency and dynamics of polyploidy and genome evolution in populations of wild plants.

Doležel, J., Greilhuber, J., Suda, J.: Flow cytometry with plant cells: Analysis of genes, chromosomes and genomes. – Wiley-VCH, Weinheim, 455 pp. (2007).