| cellular protein receptors of maculosin, a host specific phytotoxin of spotted knapweed (centaurea maculosa l.). | maculosin (the diketopiperazine, cyclo (l-pro-l-tyr)) is a host specific phytotoxin produced by alternaria alternata on spotted knapweed (centaurea maculosa l.). receptors for this phytotoxin have been isolated from spotted knapweed. knapweed leaves possess most of the maculosin-binding activity in the cytosolic fraction. however, activity was also observed in the whole membrane fraction of the leaf. the binding component of the cytosolic fraction was identified as a protein(s) because of its he ... | 1994 | 8280748 |
| evaluation of the growth response of six invasive species to past, present and future atmospheric carbon dioxide. | the response of plant species to future atmospheric carbon dioxide concentrations [co(2)] has been determined for hundreds of crop and tree species. however, no data are currently available regarding the response of invasive weedy species to past or future atmospheric [co(2)]. in the current study, the growth of six species which are widely recognized as among the most invasive weeds in the continental united states, canada thistle (cirsium arvense (l.) scop.), field bindweed (convolvulus arvens ... | 2003 | 12493868 |
| allelopathy and exotic plant invasion: from molecules and genes to species interactions. | here we present evidence that centaurea maculosa (spotted knapweed), an invasive species in the western united states, displaces native plant species by exuding the phytotoxin (-)-catechin from its roots. our results show inhibition of native species' growth and germination in field soils at natural concentrations of (-)-catechin. in susceptible species such as arabidopsis thaliana, the allelochemical triggers a wave of reactive oxygen species (ros) initiated at the root meristem, which leads to ... | 2003 | 12958360 |
| maculosin, a host-specific phytotoxin for spotted knapweed from alternaria alternata. | several diketopiperazines have been isolated from liquid cultures of alternaria alternata, the causal agent of black leaf blight of spotted knapweed, centaurea maculosa lam. one of these compounds, maculosin [the diketopiperazine cyclo(-l-pro-l-tyr-)], was active in the nicked-leaf bioassay at 10(-5) m; synthetic maculosin possessed chemical and biological activities identical to those of the natural product. other diketopiperazines isolated from the fungus possessed either less activity or none ... | 1988 | 16593989 |
| biological control agents elevate hantavirus by subsidizing deer mouse populations. | biological control of exotic invasive plants using exotic insects is practiced under the assumption that biological control agents are safe if they do not directly attack non-target species. we tested this assumption by evaluating the potential for two host-specific biological control agents (urophora spp.), widely established in north america for spotted knapweed (centaurea maculosa) control, to indirectly elevate sin nombre hantavirus by providing food subsidies to populations of deer mice (pe ... | 2006 | 16623730 |
| chemical facilitation and induced pathogen resistance mediated by a root-secreted phytotoxin. | the flavonol (+/-)-catechin is an allelochemical produced by the invasive weed centaurea maculosa (spotted knapweed). the full effects of (+/-)-catechin on plant communities in both the native and the introduced ranges of c. maculosa remain uncertain. here, by supplementing plant growth media with (+/-)-catechin, we showed that low (+/-)-catechin concentrations may induce growth and defense responses in neighboring plants. doses of the allelochemical lower than the minimum inhibitory concentrati ... | 2007 | 17286833 |
| native plant diversity resists invasion at both low and high resource levels. | human modification of the environment is causing both loss of species and changes in resource availability. while studies have examined how species loss at the local level can influence invasion resistance, interactions between species loss and other components of environmental change remain poorly studied. in particular, the manner in which native diversity interacts with resource availability to influence invasion resistance is not well understood. we created experimental plant assemblages tha ... | 2007 | 18027767 |
| mitigating exotic impacts: restoring deer mouse populations elevated by an exotic food subsidy. | the threat posed by exotic organisms to native systems has led to extensive research on exotic invaders, yet management of invasives has progressed relatively slowly. this is partly due to poor understanding of how exotic species management influences native organisms. to address this shortfall, we experimentally evaluated the efficacy of an invasives management tool for restoring native deer mouse (peromyscus maniculatus) populations elevated by exotic species. the exotic insects, urophora spp. ... | 2008 | 18488599 |
| weed-biocontrol insects reduce native-plant recruitment through second-order apparent competition. | small-mammal seed predation is an important force structuring native-plant communities that may also influence exotic-plant invasions. in the intermountain west, deer mice (peromyscus maniculatus) are prominent predators of native-plant seeds, but they avoid consuming seeds of certain widespread invasives like spotted knapweed (centaurea maculosa). these mice also consume the biological-control insects urophora spp. introduced to control c. maculosa, and this food resource substantially increase ... | 2008 | 18767624 |
| shift in cytotype frequency and niche space in the invasive plant centaurea maculosa. | polyploidy is often assumed to increase the spread and thus the success of alien plant species, but few empirical studies exist. we tested this hypothesis with centaurea maculosa lam., a species native to europe and introduced into north america approximately 120 years ago where it became highly invasive. we analyzed the ploidy level of more than 2000 plants from 93 native and 48 invasive c. maculosa populations and found a pronounced shift in the relative frequency of diploid and tetraploid cyt ... | 2009 | 19537556 |
| impact of (+/-)-catechin on soil microbial communities. | catechin is a highly studied but controversial allelochemical reported as a component of the root exudates of centaurea maculosa. initial reports of high and consistent exudation rates and soil concentrations have been shown to be highly inaccurate, but the chemical has been found in root exudates at and much less frequently in soil but sporadically at high concentrations. part of the problem of detection and measuring phytotoxicity in natural soils may be due to the confounding effect of soil m ... | 2009 | 19704908 |
| phytotoxic effects of (+/-)-catechin in vitro, in soil, and in the field. | exploring the residence time of allelochemicals released by plants into different soils, episodic exposure of plants to allelochemicals, and the effects of allelochemicals in the field has the potential to improve our understanding of interactions among plants. | 2008 | 18648546 |
| invasive plant architecture alters trophic interactions by changing predator abundance and behavior. | as primary producers, plants are known to influence higher trophic interactions by initiating food chains. however, as architects, plants may bypass consumers to directly affect predators with important but underappreciated trophic ramifications. invasion of western north american grasslands by the perennial forb, spotted knapweed (centaurea maculosa), has fundamentally altered the architecture of native grassland vegetation. here, i use long-term monitoring, observational studies, and field exp ... | 2009 | 19082630 |
| oxalate contributes to the resistance of gaillardia grandiflora and lupinus sericeus to a phytotoxin produced by centaurea maculosa. | centaurea maculosa lam. is a noxious weed in western north america that produces a phytotoxin, (+/-)-catechin, which is thought to contribute to its invasiveness. areas invaded by c. maculosa often result in monocultures of the weed, however; in some areas, north american natives stand their ground against c. maculosa and show varying degrees of resistance to its phytotoxin. two of these resistant native species, lupinus sericeus pursh and gaillardia grandiflora van houtte, were found to secrete ... | 2006 | 16395587 |
| long-term population dynamics of seeded plants in invaded grasslands. | in recent decades, dozens of studies have involved attempts to introduce native and desirable nonnative plant species into grasslands dominated by invasive weeds. the newly introduced plants have proved capable of establishing, but because they are rarely monitored for more than four years, it is unknown if they have a high likelihood of persisting and suppressing invaders for the long-term. beyond invaded grasslands, this lack of long-term monitoring is a general problem plaguing efforts to rei ... | 2012 | 22827138 |
| simulated warming differentially affects the growth and competitive ability of centaurea maculosa populations from home and introduced ranges. | climate warming may drive invasions by exotic plants, thereby raising concerns over the risks of invasive plants. however, little is known about how climate warming influences the growth and competitive ability of exotic plants from their home and introduced ranges. we conducted a common garden experiment with an invasive plant centaurea maculosa and a native plant poa pratensis, in which a mixture of sand and vermiculite was used as a neutral medium, and contrasted the total biomass, competitiv ... | 2012 | 22303485 |
| trait- and density-mediated indirect interactions initiated by an exotic invasive plant autogenic ecosystem engineer. | indirect interactions are important for structuring ecological systems. however, research on indirect effects has been heavily biased toward top-down trophic interactions, and less is known about other indirect-interaction pathways. as autogenic ecosystem engineers, plants can serve as initiators of nontrophic indirect interactions that, like top-down pathways, can involve both trait-mediated indirect interactions (tmiis) and density-mediated indirect interactions (dmiis). using microcosms, i ex ... | 2010 | 20715973 |
| plant neighbor identity influences plant biochemistry and physiology related to defense. | chemical and biological processes dictate an individual organism's ability to recognize and respond to other organisms. a small but growing body of evidence suggests that plants may be capable of recognizing and responding to neighboring plants in a species specific fashion. here we tested whether or not individuals of the invasive exotic weed, centaurea maculosa, would modulate their defensive strategy in response to different plant neighbors. | 2010 | 20565801 |
| species-specific effects of polyploidisation and plant traits of centaurea maculosa and senecio inaequidens on rhizosphere microorganisms. | invasive plant species represent a threat to terrestrial ecosystems, but their effects on the soil biota and the mechanisms involved are not yet well understood. many invasive species have undergone polyploidisation, leading to the coexistence of various cytotypes in the native range, whereas, in most cases, only one cytotype is present in the introduced range. since genetic variation within a species can modify soil rhizosphere communities, we studied the effects of different cytotypes and rang ... | 2010 | 20229242 |
| novel weapons and invasion: biogeographic differences in the competitive effects of centaurea maculosa and its root exudate (+/-)-catechin. | recent studies suggest that the invasive success of centaurea maculosa may be related to its stronger allelopathic effects on native north american species than on related european species, one component of the "novel weapons" hypothesis. other research indicates that c. maculosa plants from the invasive range in north america have evolved to be larger and better competitors than conspecifics from the native range in europe, a component of the "evolution of increased competitive ability" hypothe ... | 2009 | 19219462 |
| predicting current and future biological invasions: both native and invaded ranges matter. | the classical approach to predicting the geographical extent of species invasions consists of training models in the native range and projecting them in distinct, potentially invasible areas. however, recent studies have demonstrated that this approach could be hampered by a change of the realized climatic niche, allowing invasive species to spread into habitats in the invaded ranges that are climatically distinct from those occupied in the native range. we propose an alternative approach that i ... | 2008 | 18664415 |
| effects of native species diversity and resource additions on invader impact. | theory and empirical work have demonstrated that diverse communities can inhibit invasion. yet, it is unclear how diversity influences invader impact, how impact varies among exotics, and what the relative importance of diversity is versus extrinsic factors that themselves can influence invasion. to address these issues, we established plant assemblages that varied in native species and functional richness and crossed this gradient in diversity with resource (water) addition. identical assemblag ... | 2008 | 18554141 |
| an invader differentially affects leaf physiology of two natives across a gradient in diversity. | little is known about how exotics influence the ecophysiology of co-occurring native plants or how invader impact on plant physiology may be mediated by community diversity or resource levels. we measured the effect of the widespread invasive forb spotted knapweed (centaurea maculosa) on leaf traits (leaf dry matter content, specific leaf area, leaf nitrogen percentage, leaf c:n ratios, and delta13c as a proxy for water use efficiency) of two co-occurring native perennial grassland species, mona ... | 2008 | 18543627 |
| bioavailability of allelochemicals as affected by companion compounds in soil matrices. | multicompound allelochemical interactions were studied using centaurea maculosa as a model source to understand how the bioavailability of complex allelochemical mixtures is modified in soil-microbial systems. litter decomposition of c. maculosa in sandy loam soil yielded five phenolic acids, namely, hydroxybenzoic, vanillic, protocatechuic, p-coumaric, and ferulic acids. the degradation studies were conducted by exogenous application of catechin, the primary allelochemical exuded by c. maculosa ... | 2008 | 18435537 |
| soil fungal abundance and diversity: another victim of the invasive plant centaurea maculosa. | interactions between plants and soil microbes are important determinants of both above- and belowground community composition, and ultimately ecosystem function. as exotic plants continue to invade and modify native plant communities, there has been increasing interest in determining the influence of exotic invasives on native soil microbial communities. here, using highly sensitive molecular techniques, we examine fungal abundance and diversity in the soil surrounding a particularly aggressive ... | 2007 | 18059499 |
| concentrations of the allelochemical (+/-)-catechin in centaurea maculosa soils. | the phytotoxin (+/-)-catechin has been proposed to mediate invasion and autoinhibition by the eurasian plant centaurea maculosa (spotted knapweed). the importance of (+/-)-catechin to c. maculosa ecology depends in part on whether sufficient catechin concentrations occur at appropriate times and locations within c. maculosa soil to influence neighboring plants. previous research on catechin in c. maculosa soils has yielded conflicting results, with some studies finding high soil catechin concent ... | 2007 | 18030533 |
| grassland invader responses to realistic changes in native species richness. | the importance of species richness for repelling exotic plant invasions varies from ecosystem to ecosystem. thus, in order to prioritize conservation objectives, it is critical to identify those ecosystems where decreasing richness will most greatly magnify invasion risks. our goal was to determine if invasion risks greatly increase in response to common reductions in grassland species richness. we imposed treatments that mimic management-induced reductions in grassland species richness (i.e., r ... | 2007 | 17913143 |
| allocating nitrogen away from a herbivore: a novel compensatory response to root herbivory. | centaurea maculosa, an invasive north american plant species, shows a high degree of tolerance to the root-boring biocontrol herbivore, agapeta zoegana. for example, infested individuals of c. maculosa often exhibit more rigorous growth and reproduction compared with their non-infested counterparts. compensatory responses to aboveground herbivores often involve increases in leaf area and/or photosynthetic capacity, but considerably less is known about root system compensatory responses to belowg ... | 2007 | 17619205 |
| a first step in understanding an invasive weed through its genes: an est analysis of invasive centaurea maculosa. | the economic and biological implications of plant invasion are overwhelming; however, the processes by which plants become successful invaders are not well understood. limited genetic resources are available for most invasive and weedy species, making it difficult to study molecular and genetic aspects that may be associated with invasion. | 2007 | 17524143 |
| can plant biochemistry contribute to understanding of invasion ecology? | ecologists have long searched for an explanation as to why some plant invaders become much more dominant in their naturalized range than in their native range, and, accordingly, several non-exclusive ecological hypotheses have been proposed. recently, a biochemical explanation was proposed--the "novel weapons hypothesis"--based on findings that centaurea diffusa and centaurea maculosa produce bioactive compounds (weapons) that are more active against naïve plant species in the introduced range t ... | 2006 | 17092763 |
| invasion of an exotic forb impacts reproductive success and site fidelity of a migratory songbird. | although exotic plant invasions threaten natural systems worldwide, we know little about the specific ecological impacts of invaders, including the magnitude of effects and underlying mechanisms. exotic plants are likely to impact higher trophic levels when they overrun native plant communities, affecting habitat quality for breeding songbirds by altering food availability and/or nest predation levels. we studied chipping sparrows (spizella passerina) breeding in savannas that were either domina ... | 2006 | 16685510 |
| plant-derived natural products exhibiting activity against formosan subterranean termites (coptotermes formosanus). | the formosan subterranean termite, coptotermes formosanus shiraki, is among the most devastating termite pests. natural products derived from plant extracts were tested in a discovery programme for effective, environmentally friendly termite control agents. among the natural products tested, vulgarone b (isolated from artemisia douglasiana besser), apiol (isolated from ligusticum hultenii (fern.) calder & taylor) and cnicin (isolated from centaurea maculosa lam.) exhibited significantly higher m ... | 2006 | 16625680 |
| phytotoxic and antimicrobial activities of catechin derivatives. | (+/-)-catechin is a potent phytotoxin, with the phytotoxicity due entirely to the (-)-catechin enantiomer. (+)-catechin, but not the (-)-enantiomer, has antibacterial and antifungal activities. tetramethoxy, pentaacetoxy, and cyclic derivatives of (+/-)-catechin retained phytotoxicity. the results indicate that antioxidant properties of catechins are not a determining factor for phytotoxicity. a similar conclusion was reached for the antimicrobial properties. centaurea maculosa (spotted knapweed ... | 2004 | 14995101 |
| soil biota and exotic plant invasion. | invasive plants are an economic problem and a threat to the conservation of natural systems. escape from natural enemies might contribute to successful invasion, with most work emphasizing the role of insect herbivores; however, microbial pathogens are attracting increased attention. soil biota in some invaded ecosystems may promote 'exotic' invasion, and plant-soil feedback processes are also important. thus, relatively rare species native to north america consistently demonstrate negative feed ... | 2004 | 14973484 |
| intraspecific and interspecific interactions mediated by a phytotoxin, (-)-catechin, secreted by the roots of centaurea maculosa (spotted knapweed). | centarea maculosa lam. (spotted knapweed) is one of the most destructive invasive weeds in the western united states, particularly in pastures and rangelands. one of the components that may contribute to its invasiveness is the naturally produced, root-secreted allelochemical (-)-catechin. this compound has been shown to have broad-spectrum phytotoxic activity, possibly assisting c. maculosa in displacing native plant communities. as a recently characterized phytochemical, little is known about ... | 2003 | 14682522 |
| finally, proof of weapons of mass destruction. | allelopathy (one species' use of chemicals to harm other species) may be a key ingredient in successful invasions of alien plants into established communities. bais et al. show that in response to elicitation by common soil fungi, spotted knapweed (centaurea maculosa) launches an ineffective defense against the fungi that results in extensive collateral damage to neighboring plants. specifically, the flavonoid (-)-catechin, released from the roots of knapweed, produces a massive reactive oxygen ... | 2003 | 14534326 |
| altered gene expression in three plant species in response to treatment with nep1, a fungal protein that causes necrosis. | nep1 is an extracellular fungal protein that causes necrosis when applied to many dicotyledonous plants, including invasive weed species. using transmission electron microscopy, it was determined that application of nep1 (1.0 micro g ml(-)(1), 0.1% [v/v] silwet-l77) to arabidopsis and two invasive weed species, spotted knapweed (centaurea maculosa) and dandelion (taraxacum officinale), caused a reduction in the thickness of the cuticle and a breakdown of chloroplasts 1 to 4 h after treatment. me ... | 2003 | 12857840 |
| structure-dependent phytotoxicity of catechins and other flavonoids: flavonoid conversions by cell-free protein extracts of centaurea maculosa (spotted knapweed) roots. | invasive plants are believed to succeed in part by secretion of allelochemicals, thus displacing competing plant species. centaurea maculosa (spotted knapweed) provides a classic example of this process. we have previously reported that spotted knapweed roots secrete (+/-)-catechin and that (-)-catechin, but not (+)-catechin, is phytotoxic and hence may be a major contributor to c. maculosa's invasive behavior in the rhizosphere. in this communication, we explore both structure/activity relation ... | 2003 | 12568546 |
| supercooling capacity of urophora affinis and u. quadrifasciata (diptera: tephritidae) on spotted knapweed: comparisons among plants, sites, time of season, and gall densities. | larval supercooling points of urophora affinis frauenfeld and u. quadrifasciata (meigen) were compared among plants, six research sites in western montana, four fall/winter time periods, and among gall densities. these two tephritid fly species are introduced biological control agents of spotted knapweed, centaurea maculosa lamarck, and diffuse knapweed, centaurea diffusa lamarck. few differences in larval supercooling points for u. affinis and u. quadrifasciata were found among plants, and wher ... | 2001 | 11163931 |
| non-target effects of an introduced biological control agent on deer mouse ecology. | release of exotic insects as biological control agents is a common approach to controlling exotic plants. though controversy has ensued regarding the deleterious direct effects of biological control agents to non-target species, few have examined the indirect effects of a "well-behaved" biological control agent on native fauna. we studied a grassland in west-central montana infested with spotted knapweed (centaurea maculosa) to examine the effects of knapweed invasion and two gall flybiological ... | 2000 | 28307949 |
| physiological and growth responses of centaurea maculosa (asteraceae) to root herbivory under varying levels of interspecific plant competition and soil nitrogen availability. | centaurea maculosa seedlings were grown in pots to study the effects of root herbivory by agapeta zoegana l. (lep.: cochylidae) and cyphocleonus achates fahr. (col.: curculionidae), grass competition and nitrogen shortage (each present or absent), using a full factorial design. the aims of the study were to analyse the impact of root herbivory on plant growth, resource allocation and physiological processes, and to test if these plant responses to herbivory were influenced by plant competition a ... | 1992 | 28313386 |
| structural analysis of the phytophagous insect guilds associated with the roots of centaurea maculosa lam. c. diffusa lam., and c. vallesiaca jordan in europe: : i. field observations. | during extensive field surveys in central and eastern europe, 21 herbivorous root insect species were found on centaurea maculosa ssp. rhenana boreau, 12 species on c. diffusa lam. and 11 species on c. vallesiaca jordan, representing 12 families in 4 orders. the large geographic distribution (species-area function), the high number of centaurea spp. present (host speciation rate), and the high apparency of the rosettes and the rich food resources offered by the roots during winter, together with ... | 1989 | 28311900 |
| an antibacterial principle from centaurea maculosa. | | 1949 | 16561665 |