1,721,020 research outputs found
Rivisiting Phragmites australis variation in the Danube Delta with DNA molecular techniques
No full textHeteroplasmy due to chloroplast paternal leakage: another insight into Phragmites haplotypic diversity in North America
No full textChloroplasts contain several copies of their DNA, and intra-individual haplotypic variation (heteroplasmy) is common in plants, but unexplored in the cosmopolitan genus Phragmites. The aims of this study were to assess if heteroplasmy due to paternal leakage of the chloroplast occurs in Phragmites and which new insights into the evolutionary history of Phragmitesaustralis in North America can be identified from the heteroplasmic variation. Eight non-native P. australis haplotypes occur in North America and can interbreed with P. australis ssp. americanus and P. australis var. berlandieri, creating opportunities for biparental inheritance of distinctive haplotypes. The polymorphism in the trnT-trnL sequence length revealed seventeen cases of heteroplasmy worldwide, in contact zones of distantly related haplotypes and in known hybrid populations, nine of which occurred in North America. In America, the cloned sequences, combined with nuclear markers, identified recombined haplotypes between native P. australis ssp. americanus and invasive P. australis haplotype M, and between the species P. mauritianus and P. australis, due to chloroplast paternal leakage. The occurrence of heteroplasmy and recombined haplotypes suggest a local origin for some of the rare non-native haplotypes occurring in North America, and plastid leakage events in the evolutionary histories of P. australis ssp. americanus and P. australis var. berlandieri
Mowing regime has different effects on reed stands in relation to habitat
No full textReed (Phragmites australis) is widespread in aquatic habitats in Europe where it plays an important ecological role, especially as stabilizer of lake and river shores and as filter against pollutants. Reed is also abundant in ecotones towards terrestrial habitats, especially fen meadows, where its expansion can out-compete rare slowly-growing fen species. Therefore, defining appropriate guidelines for managing reed in wetlands has to consider differences in the ecological roles that reed plays in different wetland habitats. In a small pre-alpine lake in N Italy, we mowed reed stands in three plant communities located along a transect from the lake shore to the periphery. In each community, three areas were subjected to reed mowing in late winter, as traditionally done in the past. Three additional areas were subjected to mowing in winter and summer, while three areas served as un-treated controls. Summer mowing was carried out in August, when the nesting period of birds was concluded. Mowing in winter did not affect reed aboveground biomass (RAB) in any community but enhanced the efficiency of removing nutrients by reducing litter accumulation in the soil. Mowing in winter and summer only slightly decreased RAB in the riparian community, not at all in the intermediate community but significantly diminished RAB in fen meadows. Phosphorus deficiency and/or reduced competition with other species probably accounted for RAB reduction in fen meadows. In conclusion, winter mowing can be overall recommended for preventing eutrophication of littoral habitats while summer mowing is advisable for preventing reed expansion in fen meadows. However, the timing of summer mowing has to be defined considering all requirements needed for optimal management of each individual site. © 2014
Herbarium specimens as a source of DNA for AFLP fingerprinting of Phragmites (Poaceae): Possibilities and limitations
No full textHerbarium collections are a valuable source of genetic information. Even though the DNA obtained from the specimens is often highly fragmented and present in small quantities, it has been successfully used particularly for DNA sequencing and microsatellite analysis. The present study shows that the quality is often sufficient for use also for AFLPs. With this technique, a considerable number of DNA fragments with unknown sequence from the entire genome of the plant are amplified, often with the purpose of phylogeographic studies or analyses of interrelationships of closely related species. In order to avoid the effects of potential artefacts resulting from DNA degradation, such as "false polymorphisms", it is suggested that fresh samples should always be included for comparison, and that AFLP chromatograms based on herbarium specimens should be included in analyses only when they contain AFLP fragments monomorphic among the fresh samples, and when signal quality is comparable to that of fresh samples. © 2008 Springer-Verlag
Phylogeography reveals a potential cryptic invasion in the Southern Hemisphere of Ceratophyllum demersum, New Zealand's worst invasive macrophyte
Full text linkCeratophyllum demersum (common hornwort) is presently considered the worst invasive submerged aquatic macrophyte in New Zealand. We explored the global phylogeographic pattern of the species, based on chloroplast and nuclear DNA, in order to identify the origin of the invasive populations in New Zealand and to clarify if there were multiple introductions. The phylogeographic study identified geographically differentiated gene pools in North America, tropical Asia, Australia, and South Africa, likely native to these regions, and a recent dispersal event of a Eurasian-related haplotype to North America, New Zealand, Australia, and South Africa. At least two different invasive genotypes of this Eurasian-related haplotype have been found in New Zealand. One genotype is closely related to genotypes in Australia and South Africa, while we could not trace the closest relatives of the other genotype within our C. demersum sample set. Contrasting spectra of genetic distances in New Zealand and in a region within the native range (Denmark), suggest that the invasive population was founded by vegetative reproduction, seen as low genetic distances among genotypes. We also discovered the introduction of the same Eurasian-related haplotype in Australia and South Africa and that a cryptic invasion may be occurring in these continents
Genetic structure of the submersed Ranunculus baudotii (sect. Batrachium) population in a lowland stream in Denmark
No full textUnidirectional hydrochory, reproduction mode and mating system have different impacts on the ecology of stream plants, and variation in the combination of these processes shapes unique genetic patterns which can have different consequences for the fitness of stream populations.
We studied the genetic structure inferred by AFLPs, ITS SNPs and matK sequences of three populations of the common clonal macrophyte Ranunculus baudotii in River Aarhus in order to understand the role of vegetative and sexual reproduction in the stream and how genetic variation is distributed along the stream. We also explored the genetic relationships of the R. baudotii population in River Aarhus with other species of sect. Batrachium, because hybrids have been identified in the stream and they might affect the structure of the populations.
The three studied populations were genetically distinct despite low genetic diversity and plant fragmentation is likely the main form of reproduction in the river system. The establishment of a few seeds, sexual recombination, the occurrence of putative hybrids and genetic drift in the establishment of fragments and seeds dramatically changed the genetic diversity of the populations along the stream and led to differentiation among populations. Further research is needed to understand the conditions favoring sexual reproduction and gene flow distances
The value of repetitive sequences in chloroplast DNA for phylogeographic inference: A comment on Vachon & Freeland 2011
No full textIn a recent Technical Advance article, Vachon and Freeland (2011, Molecular Ecology Resources, 11, 279-285.) evaluate the utility of repetitive and non-repetitive variation in the chloroplast genome for phylogeographic inference, using variation in Phragmites australis as an example. While we agree that repetitive and nonrepetitive regions evolve at different rates and homoplasy can impact results, we disagree with the conclusion that repetitive regions are inappropriate for large-scale phylogeographic studies. Here we describe limitations to the study dataset and analysis, and provide an alternative viewpoint on the utility of repetitive regions for phylogeographic studies. © 2012 Blackwell Publishing Ltd
Salinity effects on germination, seedlings and full-grown plants of upland and lowland switchgrass cultivars
Full text linkSoil salinization is one of the major threats affecting crop production, in particular in the Mediterranean basin where over 1 Mha are salt-affected. Growing lignocellulosic crops, such as switchgrass (Panicum virgatum L.), in marginal saline soils could represent a valuable opportunity to mitigate land abandonment while producing feedstock for biofuels. However, little is still known about salt tolerance of upland and lowland switchgrass cultivars. This study addressed the morphological and physiological responses of Shawnee (upland) and Alamo (lowland) to a range of salinity levels from 0 to 14 dS m−1. Two consecutive experiments were carried out: one in petri dish to test the response to salinity at germination and early growth stages, the other in pot to evaluate the response to salinity until flowering stage (full-grown plants). Both upland and lowland cultivars were able to grow until “critical” salinity levels (14 dS m−1) but their tolerance differed depending on growth stage. Alamo showed a higher tolerance to salinity than Shawnee at very early growth stages (germination/emergence), presenting a germination rate more than double that of Shawnee (60 vs. 19%, main effect cultivar). Nevertheless, Shawnee resulted in a higher tolerance at a full-grown stage likely due to a more efficient salt exclusion capacity, as indicated by the higher residual soil electric conductivity at the end of the experiment detected in Shawnee pots. Final biomass production was anyhow considerably significantly higher in Alamo than Shawnee under any tested salinity level, which demonstrated the improved ability of lowland cultivar to produce biomass compared to Shawnee which otherwise might have invested resources into exclusion mechanisms
Increased invasive potential of non-native Phragmites australis: Elevated CO2 and temperature alleviate salinity effects on photosynthesis and growth
No full textThe prospective rise in atmospheric CO2 and temperature may change the distribution and invasive potential of a species; and intraspecific invasive lineages may respond differently to climate change. In this study, we simulated a future climate scenario with simultaneously elevated atmospheric CO2 and temperature, and investigated its interaction with soil salinity, to assess the effects of global change on the ecophysiology of two competing haplotypes of the wetland grass Phragmites australis, that are invasive in the coastal marshes of North America. The two haplotypes with the phenotypes 'EU-type' (Eurasian haplotype) and 'Delta-type' (Mediterranean haplotype), were grown at 0‰ and 20‰ soil salinity, and at ambient or elevated climatic conditions (700 ppm CO2, +5 °C) in a phytotron system. The aboveground growth of both phenotypes was highest at the elevated climatic conditions. Growth at 20‰ salinity resulted in declined aboveground growth, lower transpiration rates (E), stomata conductance (gs), specific leaf area, photosynthetic pigment concentrations, and a reduced photosynthetic performance. The negative effects of salinity were, however, significantly less severe at elevated CO2 and temperature than at the ambient climatic conditions. The Delta-type P. australis had higher shoot elongation rates than the EU-type P. australis, particularly at high salinity. The Delta-type also had higher maximum light-saturated rates of photosynthesis (Asat), maximum carboxylation rates of Rubisco (Vcmax), maximum electron transport rates (Jmax), triose phosphate utilization rates (Tp), stomata conductance (gs), as well as higher Rubisco carboxylation-limited, RuBP regeneration-limited and Tp-regeneration limited CO2 assimilation rates than the EU-type under all growth conditions. Our results suggest that the EU-type will not become dominant over the Delta-type, since the Delta-type has superior ecophysiological traits. However, the projected rise in atmospheric CO2 and temperature will alleviate the effects of salinity on both phenotypes and facilitate their expansion into more saline areas. © 2013 John Wiley & Sons Ltd
Expansive reed populations – alien invasion or disturbed wetlands?
Full text linkThe tall statured grasses in the genus Phragmites are dominant vegetation in wetlands worldwide and thus play a vital role in ecosystem functioning. As a result, Phragmites spp. are some of the most widely studied plants; particularly in areas where changes to their abundances have occurred, most notably in Europe and North America. In southern Africa a pattern of reed expansion has occurred in recent decades that has shown a similar trend to cryptic invasions reported in North America. This study used molecular techniques to explore the phylogeography of P. australis and P. mauritianus in the region to investigate whether the expansion is due to an alien invasion or local factors such as wetland disturbance. Three haplotypes were found and all haplotypes are presently considered African haplotypes (Haplotype K for P. australis and Haplotype V and AP for P. mauritianus). Both Phragmites spp. were found to have high genetic diversity. Microsatellite and grass-waxy analysis also found evidence of hybridisation between the two species. No evidence was found for a recent cryptic invasion of non-native haplotypes in southern Africa. The expansion of P. australis and P. mauritianus is therefore most likely a result of anthropogenic activity. Identifying and mitigating the human-mediated factors that may be contributing to reed growth, such as eutrophication and sedimentation, should be the focus of future management protocols
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