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John A Thomson - One of the best experts on this subject based on the ideXlab platform.
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worldwide relationships in the fern genus Pteridium bracken based on nuclear genome markers
American Journal of Botany, 2019Co-Authors: Paul G Wolf, Joshua P Der, Carol A Rowe, Sylvia P Kinosian, Peter J Lockhart, Lara D Shepherd, Patricia A Mclenachan, John A ThomsonAbstract:Premise Spore-bearing plants are capable of dispersing very long distances. However, it is not known if gene flow can prevent genetic divergence in widely distributed taxa. Here we address this issue, and examine systematic relationships at a global geographic scale for the fern genus Pteridium. Methods We sampled plants from 100 localities worldwide, and generated nucleotide data from four nuclear genes and two plastid regions. We also examined 2801 single nucleotide polymorphisms detected by a restriction site-associated DNA approach. Results We found evidence for two distinct diploid species and two allotetraploids between them. The "northern" species (Pteridium aquilinum) has distinct groups at the continental scale (Europe, Asia, Africa, and North America). The northern European subspecies pinetorum appears to involve admixture among all of these. A sample from the Hawaiian Islands contained elements of both North American and Asian P. aquilinum. The "southern" species, P. esculentum, shows little genetic differentiation between South American and Australian samples. Components of African genotypes are detected on all continents. Conclusions We find evidence of distinct continental-scale genetic differentiation in Pteridium. However, on top of this is a clear signal of recent hybridization. Thus, spore-bearing plants are clearly capable of extensive long-distance gene flow; yet appear to have differentiated genetically at the continental scale. Either gene flow in the past was at a reduced level, or vicariance is possible even in the face of long-distance gene flow.
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taxonomic status of diploid southern hemisphere brackens Pteridium dennstaedtiaceae
Telopea, 2012Co-Authors: John A ThomsonAbstract:Diploid bracken ferns separate morphologically, genetically and reproductively into a predominantly northern hemisphere clade comprising 11 subspecies placed in Pteridium aquilinum (L.) Kuhn and a predominantly southern hemisphere Austral/South American clade of two taxa. Circumscription of Pteridium esculentum (G.Forst.) Cockayne is here emended to include both taxa of the southern clade, respectively P. esculentum subsp. esculentum from Australasia and P. esculentum subsp. arachnoideum (Kaulf.) J.A.Thomson comb. nov. from Central and South America.
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global chloroplast phylogeny and biogeography of bracken Pteridium dennstaedtiaceae
American Journal of Botany, 2009Co-Authors: Joshua P Der, John A Thomson, Jeran K Stratford, Paul G WolfAbstract:Bracken ferns (genus Pteridium) represent an ancient species complex with a natural worldwide distribution. Pteridium has historically been treated as comprising a single species, but recent treatments have recognized several related species. Phenotypic plasticity, geographically structured morphological variation, and geographically biased sampling have all contributed to taxonomic confusion in the genus. We sampled bracken specimens worldwide and used variable regions of the chloroplast genome to investigate phylogeography and reticulate evolution within the genus. Our results distinguish two major clades within Pteridium, a primarily northern hemisphere Laurasian/African clade, which includes all taxa currently assigned to P. aquilinum, and a primarily southern hemisphere Austral/South American clade, which includes P. esculentum and P. arachnoideum. All European accessions of P. aquilinum subsp. aquilinum appear in a monophyletic group and are nested within a clade containing the African P. aquilinum taxa (P. aquilinum subsp. capense and P. aquilinum subsp. centrali-africanum). Our results allow us to hypothesize the maternal progenitors of two allotetraploid bracken species, P. caudatum and P. semihastatum. We also discuss the biogeography of bracken in the context of the chloroplast phylogeny. Our study is one of the first to take a worldwide perspective in addressing variation in a broadly distributed species complex.
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clarification of the taxonomic status and relationships of Pteridium caudatum dennstaedtiaceae in central and south america
Botanical Journal of the Linnean Society, 2002Co-Authors: John A Thomson, Miguel E AlonsoamelotAbstract:Contemporary systematic treatments of the Central and South American bracken ferns in the genus Pteridium Gled. ex Scop. recognize morphotype caudatum as either a full species or a variety of P. aquilinum (L.) Kuhn. Geographically representative sporophytes of morphotype caudatum, including the type in the Linnaean Herbarium, are shown using spore size, guard-cell length and morphology of the cells of the false indusium to be tetraploid (based on 4n = 208). DNA fingerprinting of field-collected Venezuelan samples supports the generalization that morphotype caudatum is a fertile allotetraploid containing genomic elements otherwise distinctive of the southern hemisphere diploid P. arachnoideum (Kaulf.) Maxon, together with elements characteristic of northern hemisphere diploids including the North American P. aquilinum var. pubescens Underw. and P. aquilinum var. pseudocaudatum (Clute) A. Heller. Evidence of genetic isolation from taxa with overlapping distributions, as well as morphological, biochemical and ecological data, validate recognition of P. caudatum (L.) Maxon at species level. Heterogeneity observed within P. caudatum is consistent with multiple origins through independent hybridization events. Pteridium caudatum is strikingly analogous to the tropical Asian/Australasian allotetraploid P. semihastatum (N. Wallich ex J. G. Agardh) S. B. Andrews [=P. yarrabense (Domin) N. A. Wakef.]. © 2002 The Linnean Society of London. Botanical Journal of the Linnean Society, 2002, 140, 237−248.
R H Marrs - One of the best experts on this subject based on the ideXlab platform.
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change to ecosystem properties through changing the dominant species impact of Pteridium aquilinum control and heathland restoration treatments on selected soil properties
Journal of Environmental Management, 2018Co-Authors: Gregg Milligan, E S Cox, Robin J Pakeman, M Le G Duc, K E Booth, Leslie Connor, Sabena Blackbird, R H MarrsAbstract:It is well known that soils are influenced by the plant species that grow in them. Here we consider the effects of management-induced changes to plant communities and their soils during restoration within a 20-year manipulative experiment where the aim was to change a late-successional community dominated by the weed, Pteridium aquilinum, to an earlier-successional grass-heath one. The ecological restoration treatments altered the above- and below-ground components of the community substantially. Untreated plots maintained a dense Pteridium cover with little understory vegetation, cutting treatments produce significant reductions of Pteridium, whereas herbicide (asulam) produced significant immediate reductions in Pteridium but regressed towards the untreated plots within 10 years. Thereafter, all asulam-treated plots were re-treated in year 11, and then were spot-sprayed annually. Both cutting and asulam treatments reduced frond density to almost zero and resulted in a grass-heath vegetation. There was also a massive change in biomass distribution, untreated plots had a large above-ground biomass/necromass that was much reduced where Pteridium was controlled. Below-ground in treated plots, there was a replacement of the substantive Pteridium rhizome mass with a much greater root mass of other species. The combined effects of Pteridium-control and restoration treatment, reduced soil total C and N as and available P concentrations, but increased soil pH and available N. Soil biological activity was also affected with a reduction in soil N mineralization rate, but an increased soil-root respiration. Multivariate analysis showed a clear trend along a pH/organic matter gradient, with movement along it correlated to management intensity from the untreated plots with low pH/high organic matter and treated plots with to a higher pH/lower organic matter in the sequence asulam treatment, cut once per year to cut twice per year. The role that these changed soil conditions might have in restricting Pteridium recovery are discussed.
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a comparative study of resource allocation in Pteridium in different brazilian ecosystems and its relationship with european studies
Brazilian Journal of Biology, 2014Co-Authors: D Silva M Matos, Rafael De Oliveira Xavier, F C S Tiberio, R H MarrsAbstract:Pteridium is a cosmopolitan genus that acts as an invasive species in many parts of the world. Most research on this genus has occurred in Europe, and there is a lack of data on it from South America, in spite of causing considerable conservation problems. We compared the biomass allocation of P. esculentum subsp. arachnoideum in two ecosystems in Brazil - Atlantic forest and Brazilian savanna. We measured the biomass of fronds, rhizomes and above-ground litter. We also compared the density, length and biomass of fronds from this Brazilian study with similar data of P. esculentum subsp. arachnoideum derived from Venezuela and P. aquilinum from Europe. P. esculentum subsp. arachnoideum showed a wide response range. We found a negative relationship between frond and necromass, indicating a negative feedback effect, while a positive relationship was observed between frond and rhizome biomass. The continental comparison of relationships showed that Pteridium responds in a different way in both Brazil and Europe, and that in Brazil fronds tend to be longer and heavier, presumably as a result of the continuous growing season in South America while is shortened in Europe by frost. The paper shows the ability of Pteridium to adapt to different ecosystems.
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effects of experimental restoration on the diaspore bank of an upland moor degraded by Pteridium aquilinum invasion
Land Degradation & Development, 2007Co-Authors: Robin J Pakeman, M Le G Duc, Hugh A Mcallister, J Ghorbani, R H MarrsAbstract:We assessed the effects of a range of experimental restoration treatments on the diaspore bank (seed and spores) on an upland moor infested by dense Pteridium aquilinum, 9 years after implementation. Experimental treatment included both Pteridium control (cutting, spraying and combinations) and restoration treatments (grazing, seeding); both univariate and multivariate analyses of variance were used to assess significant effects. The seed bank was made up largely of Calluna vulgaris, Juncus effusus and Agrostis capillaris with the majority germinating from the litter (38 per cent) and upper soil layer (53 per cent). Soil depth influenced species composition and density, with greatest numbers near the surface, in keeping with a negative exponential response. In the lowest soil depth only ferns were abundant. A. capillaris seed density was greater in the most disturbed treatment (cut twice yearly with grazing), whereas C. vulgaris was greater in the low-disturbance treatment (herbicide application only). The diaspore bank composition response identified that certain treatment combinations had a grass-heath composition in the upper soil layer, which may assist future restoration. There was a significant effect of C. vulgaris seed addition detected in the Pteridium litter layer suggesting that this litter acted as a barrier to seed transfer to the soil. There was little evidence of coupling developing between the diaspore bank and vegetation. The most successful treatment combination was cutting twice per yr with low grazing plus C. vulgaris addition as brash. Where seed is added the Pteridium litter should be disturbed. Copyright © 2007 John Wiley & Sons, Ltd.
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biological flora of the british isles Pteridium aquilinum l kuhn
Journal of Ecology, 2006Co-Authors: R H Marrs, Alex S WattAbstract:Summary 1This account reviews information on all aspects of the biology of bracken Pteridium (mainly aquilinum ssp. aquilinum) that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of the British Isles: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, reproductive characters, herbivores and disease, history, and conservation. 2Pteridium is a complex genus comprising a number of species, subspecies and varieties. The treatment here is based on a recent revision that incorporates both morphological and molecular data, and is related to its geographical distribution. 3Pteridium is thought to be a woodland genus, but it can grow in the open. It is cosmopolitan and occurs on all continents except Antarctica. It responds to human disturbance and is often found in open spaces after forest clearance and cultivation. In some situations it can be a troublesome weed, causing problems for land managers. Moreover, its abundance and distribution in Britain are predicted to increase as a result of global climate change. 4Pteridium aquilinum ssp. aquilinum, the most common taxon in the British Isles, occurs in many plant communities, and it is apparently limited by frost and waterlogging. Its abundance has probably increased in the relatively recent past as a result of changing land management, and this increase impinges on plant communities with a high conservation interest. The changed land management reflects changing use of agricultural land and also a reduction in the use of Pteridium as a resource. Accordingly, in many places Pteridium is viewed as a weed and management is needed to control it and restore more desirable vegetation. These management techniques are summarized.
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the effects of cutting and herbicide treatment on Pteridium aquilinum encroachment
Applied Vegetation Science, 2002Co-Authors: Robin J Pakeman, R H Thwaites, M Le G Duc, R H MarrsAbstract:Abstract Pteridium aquilinum (bracken) encroachment is an important factor in the loss of certain habitats in the United Kingdom. However, no information exists as to whether prevention of encroachment is a cost-effective strategy for Pteridium management. Conventional methods for the control of Pteridium (cutting, asulam application) were tested at one site (Levisham) to quantify their ability to prevent or delay encroachment and to affect the vigour of the Pteridium at the edge of the stand. The effects of encroachment and asulam application on the vegetation present were monitored at a second site (Ramsley), where techniques commonly used for moorland restoration were employed in combination with asulam application. Cutting once per year or a single application of asulam delayed the advance of the Pteridium front. At Levisham, the untreated front advanced 2.7 m in 5 yr, while in the same period the cut front advanced 0.88 m and the sprayed front was 1.5 m behind its initial position. At Ramsley, the un...
Mary T Fletcher - One of the best experts on this subject based on the ideXlab platform.
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norsesquiterpene glycosides in bracken ferns Pteridium esculentum and Pteridium aquilinum subsp wightianum from eastern australia reassessed poisoning risk to animals
Journal of Agricultural and Food Chemistry, 2011Co-Authors: Mary T Fletcher, Ian J Brock, Keith G Reichmann, R A Mckenzie, B J BlaneyAbstract:Austral bracken Pteridium esculentum contains three unstable norsesquiterpene glycosides: ptaquiloside, ptesculento-side, and caudatoside, in variable proportions. The concentration of each of the glycosides was determined in this study as their respective degradation products, pterosin B, pterosin G and pterosin A, by HPLC-UV analysis. Samples of P. esculentum collected from six sites in eastern Australia contained up to 17 mg of total glycoside/g DW, with both ptaquiloside and ptesculentoside present as major components accompanied by smaller amounts of caudatoside. Ratios of ptaquiloside to ptesculentoside varied from 1:3 to 4:3, but in all Australian samples ptesculentoside was a significant component. This profile differed substantially from that of P. esculentum from New Zealand, which contained only small amounts of both ptesculentoside and caudatoside, with ptaquiloside as the dominant component. A similar profile with ptaquiloside as the dominant glycoside was obtained for Pteridium aquilinum subsp. wightianum (previously P. revolutum) from northern Queensland and also P. aquilinum from European sources. Ptesculentoside has chemical reactivity similar to that of ptaquiloside and presumably biological activity similar to that of this potent carcinogen. The presence of this additional reactive glycoside in Australian P. esculentum implies greater toxicity for consuming animals than previously estimated from ptaquiloside content alone.
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ptesculentoside a novel norsesquiterpene glucoside from the australian bracken fern Pteridium esculentum
Tetrahedron Letters, 2010Co-Authors: Mary T Fletcher, P Y Hayes, Michael J Somerville, James J De VossAbstract:A novel norsesquiterpene glucoside ptesculentoside has been isolated from the Australian bracken Pteridium esculentum, together with the known bracken carcinogen ptaquiloside and lesser amounts of caudatoside. The structure of ptesculentoside is determined by analysis of 1D and 2D NMR spectra, and via its conversion into previously known pterosin G.
Silvana Lima Gorniak - One of the best experts on this subject based on the ideXlab platform.
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selenium reverses Pteridium aquilinum induced immunotoxic effects
Food and Chemical Toxicology, 2011Co-Authors: Andreia Oliveira Latorre, B D Caniceiro, H L Wysocki, Mitsue Haraguchi, Dale R Gardner, Silvana Lima GorniakAbstract:We have previously shown that bracken fern (Pteridium aquilinum) has immunomodulatory effects on mouse natural killer (NK) cells by reducing cytotoxicity. Alternatively, it has been demonstrated that selenium can enhance NK cell activity. Therefore, the aims of the present study were to evaluate if ptaquiloside, the main toxic component found in P. aquilinum, is responsible for the immunotoxic effects observed in mice, and if selenium supplementation could prevent or even reverse these effects. Male C57BL/6 mice were administered the P. aquilinum extract by daily gavage for 30 days, and histological analyses revealed a significant reduction in splenic white pulp area that was fully reversed by selenium treatment. In addition, mice administered ptaquiloside by daily gavage for 14 days demonstrated the same reduction of NK cell activity as the P. aquilinum extract, and this reduction was prevented by selenium co-administration. Lastly, non-adherent splenic cells treated in vitro with an RPMI extract of P. aquilinum also showed diminished NK cell activity that was not only prevented by selenium co-treatment but also fully reversed by selenium post-treatment. The results of this study clearly show that the immunosuppressive effects of P. aquilinum are induced by ptaquiloside and that selenium supplementation can prevent as well as reverse these effects.
Miguel E Alonsoamelot - One of the best experts on this subject based on the ideXlab platform.
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clarification of the taxonomic status and relationships of Pteridium caudatum dennstaedtiaceae in central and south america
Botanical Journal of the Linnean Society, 2002Co-Authors: John A Thomson, Miguel E AlonsoamelotAbstract:Contemporary systematic treatments of the Central and South American bracken ferns in the genus Pteridium Gled. ex Scop. recognize morphotype caudatum as either a full species or a variety of P. aquilinum (L.) Kuhn. Geographically representative sporophytes of morphotype caudatum, including the type in the Linnaean Herbarium, are shown using spore size, guard-cell length and morphology of the cells of the false indusium to be tetraploid (based on 4n = 208). DNA fingerprinting of field-collected Venezuelan samples supports the generalization that morphotype caudatum is a fertile allotetraploid containing genomic elements otherwise distinctive of the southern hemisphere diploid P. arachnoideum (Kaulf.) Maxon, together with elements characteristic of northern hemisphere diploids including the North American P. aquilinum var. pubescens Underw. and P. aquilinum var. pseudocaudatum (Clute) A. Heller. Evidence of genetic isolation from taxa with overlapping distributions, as well as morphological, biochemical and ecological data, validate recognition of P. caudatum (L.) Maxon at species level. Heterogeneity observed within P. caudatum is consistent with multiple origins through independent hybridization events. Pteridium caudatum is strikingly analogous to the tropical Asian/Australasian allotetraploid P. semihastatum (N. Wallich ex J. G. Agardh) S. B. Andrews [=P. yarrabense (Domin) N. A. Wakef.]. © 2002 The Linnean Society of London. Botanical Journal of the Linnean Society, 2002, 140, 237−248.
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isoptaquiloside and caudatoside illudane type sesquiterpene glucosides from Pteridium aquilinum var caudatum
ChemInform, 1997Co-Authors: Uvidelio F Castillo, Alistair L Wilkins, D R Lauren, Barry L Smith, N R Towers, Miguel E Alonsoamelot, Ramon JaimesespinozaAbstract:Ptaquiloside and two new illudane-type sesquiterpene glycosides were isolated from Pteridium aquilinum var. caudatum. One- and two-dimensional NMR analyses revealed the new glucosides to be isoptaquiloside and caudatoside. Four pterosins, A, B, K and Z, were also isolated from a base-acid treated extract.
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quantitation of pterosins a and b and ptaquiloside the main carcinogen of Pteridium aquilinum l kuhn by high pressure liquid chromatography
Phytochemical Analysis, 1992Co-Authors: Miguel E Alonsoamelot, Margarita Perezmena, Maria Pia Calcagno, Ramon JaimesespinozaAbstract:A quantitative method for the assessment of ptaquiloside and pterosins A and B in bracken fern has been developed. The technique involves quantitative extraction of fresh plant tissue, base-induced decomposition of ptaquiloside to pterosin B, followed by prepurification of products on a silica gel microcolumn and quantitative high pressure liquid chromatography. The method has been used to estimate the contents of these norsequiter-penes in fronds and rhizomes of Pteridium aquilinum var. caudatum from northern South America.