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P. Australis (p + australi)
Selected AbstractsMethane efflux in relation to plant biomass and sediment characteristics in stands of three common emergent macrophytes in boreal mesoeutrophic lakesGLOBAL CHANGE BIOLOGY, Issue 1 2005Paula Kankaala Abstract Methane efflux was studied in stands of three emergent macrophyte species (Equisetum fluviatile, Schoenoplectus lacustris and Phragmites australis) commonly found in the littoral zone of boreal lakes. In vegetation stands with relatively low methane (CH4) emissions (<0.3 mol m,2 (ice-free period),1), the seasonal variation of CH4 efflux was better correlated with the dynamics of plant growth than variation in sediment temperature. In dense and productive vegetation stands that released high amounts of CH4 (2.3,7.7 mol m,2 (ice-free period),1), the seasonal variation in CH4 efflux was correlated with sediment temperature, indicating that methanogens were more limited by temperature than substrate supply. The bottom type at the growth site of the emergent plants significantly influenced the ratio of CH4 efflux to aboveground biomass of plants (Eff : B). The lowest Eff : B ratio was found in E. fluviatile stands growing on sand bottom under experimental conditions and the highest in P. australis -dominated littoral areas accumulating detritus from external sources. The future changes expected in the hydrology of boreal lakes and rivers because of climatic warming may impact the growth conditions of aquatic macrophytes as well as decomposition and accumulation of detritus and, thus, CH4 effluxes from boreal lakes. [source] Mechanisms of exclusion of native coastal marsh plants by an invasive grassJOURNAL OF ECOLOGY, Issue 2 2006TODD E. MINCHINTON Summary 1Determining the mechanisms by which invasive species exclude natives is critical for conserving and restoring native populations in impacted habitats. In recent decades the grass Phragmites australis has been aggressively invading coastal marshes of North America, with monocultures often replacing diverse assemblages of plants. 2Our objective was to quantify how P. australis modifies the abiotic (soil and light conditions) and biotic (litter and shoots) environment and to determine the mechanisms by which it excludes two common forbs, the annual chenopod Atriplex patula var. hastata and the perennial aster Solidago sempervirens, from the highest tidal elevations of a brackish marsh in southern New England, USA. 3In a 3-year field experiment we added seeds of both forb species to stands of P. australis, where we manipulated shoots and litter in an orthogonal design, and to uninvaded marsh areas dominated by the rush Juncus gerardi, where we manipulated the shoots of the marsh vegetation. In general, seedling establishment and the number of plants surviving until the end of the growing season were substantially greater in areas not invaded by P. australis, and both shoots and litter limited the abundance of forbs within stands. 4Forbs surviving within stands of P. australis grew larger and produced more seeds than those in uninvaded areas, indicating that changes to the soil resulting from invasion do not preclude the survival of established forbs. This was confirmed by a glasshouse study where the performance of forbs in soil collected from within stands of P. australis was better than in soil from areas dominated by J. gerardi. 5Similar to many invasive grasses in terrestrial communities, P. australis excludes native forbs through competition, modifying the biotic environment of the marsh at both the ground (litter) and above-ground (shoots) levels. Our results suggest that successful invaders, such as P. australis, are likely to be the ones that can engineer habitats in multiple ways and limit populations of native species across several critical stages of their life history. [source] DOMOIC ACID PRODUCTION By PSEUDO-NITZSCHIA SERIATA (BACILLARIOPHYCEAE) IN SCOTTISH WATERS,JOURNAL OF PHYCOLOGY, Issue 4 2004Johanna Fehling In 1999, a 49,000 km2 area in western Scottish waters was closed to shellfish harvesting due to the amnesic shellfish poisoning (ASP) toxin domoic acid (DA). The only previously confirmed DA producer identified had been Pseudo-nitzschia australis Frenguelli. The toxin has appeared every year since and has led to more harvesting closures. We isolated and cultured two strains of Pseudo-nitzschia seriata f. seriata (P. T. Cleve) H. Peragallo from western Scottish waters in 2001 and 2002. They were identified using TEM analysis of their morphological fine structure and sequencing of the internal transcribed spacer (ITS)1, 5.8S, ITS2, and partial large subunit (LSU) rDNA. The morphology of the Scottish P. seriata f. seriata strains differed slightly, for example, in the number of poroid rows, from descriptions in identification keys. Comparison of P. seriata sequences with those of two co-occurring Pseudo-nitzschia australis isolates showed an overall divergence of only 0.012. Sequence divergence between both species was highest in the ITS1 region (0.036). Combined morphological and genetic approaches are needed to identify closely related Pseudo-nitzschia species. The P. seriata strains grew successfully at 15°C, suggesting that although seen as a psychrophilic species, it may also occur at higher water temperatures. All isolates produced DA in stationary phase (measured on day 25): 0.16,0.23 pg DA·cell,1 in P. seriata and 0.15,1.68 pg DA·cell,1 in P. australis. Our study is the first to identify P. seriata f. seriata as a DA producer in Scottish waters and indicates that at least it and P. australis can be responsible for ASP toxicity in that region. [source] Clonal genetic diversity and populational genetic differentiation in Phragmites australis distributed in the Songnen Prairie in northeast China as revealed by amplified fragment length polymorphism and sequence-specific amplification polymorphism molecular markersANNALS OF APPLIED BIOLOGY, Issue 1 2009M. Li Abstract Genetic variation within and between four naturally occurring Phragmites australis land populations, DBS, QG, SS1 and SS2 (named after locality), which colonise distinct habitats (different edaphic conditions) in the Songnen Prairie in northeast China, were investigated by amplified fragment length polymorphism (AFLP) and sequence-specific amplification polymorphism (S-SAP) markers. It was found that the selected primer combinations of both markers were highly efficient in revealing the inter-clonal genetic diversity and inter-populational genetic differentiation in P. australis from a molecular ecological perspective. Cluster analysis categorised the plants into distinct groups (DBS, QG and SS groups), which were in line with their localities, albeit the two SS group populations (SS1 and SS2) showed a lower degree of inter-populational differentiation. These results were strongly supported by multiple statistical analysis including Mantel's test, principal coordinate analysis, allocation test and analysis of molecular variance, which further suggested that gene flow, genetic drift and differences in as yet unidentified edaphic factors may all underpin the inter-clonal genetic diversity and inter-populational differentiation at the nucleotide sequence level. Analysis of intra-population clonal diversity also revealed that the QG population harboured a strikingly lower amount of within-population variation compared with those of the other three populations, presumably being caused by genetic drift and followed by physical and/or biological isolation. Homology analysis of a subset of population-specific or population-private AFLP and S-SAP bands suggested that regulatory genes and retroelements might play important roles in the ecological adaptation and differentiation of the P. australis populations. Possible causes for and implications of the extensive genetic variability in P. australis were discussed for its future genetic conservation and use in ecological revegetation. [source] | ||||||||||