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Ruth A. Hufbauer - One of the best experts on this subject based on the ideXlab platform.
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Rapid evolution of an invasive weed
The New phytologist, 2013Co-Authors: Kathryn G. Turner, Ruth A. Hufbauer, Loren H. RiesebergAbstract:Summary Trade-offs between performance and the ability to tolerate abiotic and biotic stress have been suggested to explain both the success of invasive species and phenotypic differentiation between native and invasive populations. It is critical to sample broadly across both ranges and to account for latitudinal clines and maternal effects when testing this premise. Wild-collected Centaurea diffusa seeds were grown in benign and stressful conditions (drought, flooding, nutrient stress and simulated herbivory), to evaluate whether native and introduced individuals differ in performance or life history phenotypes. A second experiment used glasshouse-grown seeds to evaluate whether patterns remain comparable when maternal environment is consistent. Many traits differed between ranges, and in all cases but one, invasive individuals grew larger, performed better, or matured later. No trade-off in performance with herbivore defense was evident. Invasive populations may have been released from a trade-off between growth and drought tolerance apparent in the native range. Larger individuals with delayed maturity and greater reproductive potential have evolved in invasive populations, a pattern evident across broad population sampling, and after latitude and maternal environment were considered. Release from abiotic stress tolerance trade-offs may be important for the invasion success of Centaurea diffusa.
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Hybridization and invasion: an experimental test with diffuse knapweed (Centaurea diffusa Lam.).
Evolutionary applications, 2011Co-Authors: Amy C. Blair, Dana M. Blumenthal, Ruth A. HufbauerAbstract:A number of studies have suggested a link between hybridization and invasion. In this study, we experimentally test the potential for hybridization to influence invasion through a greenhouse common garden study. Diffuse knapweed (DK) (Centaurea diffusa Lam.) was introduced to North America with admixture from spotted knapweed (SK) (Centaurea stoebe subsp. stoebe L.). Comparisons between North American DK (including hybrid phenotypes) and native (European) DK in a common garden did not reveal enhanced performance or increased phenotypic variance, suggesting that pre-introduction hybridization or, more generally, post-introduction evolutionary change has not significantly contributed to the invasion of DK. In contrast, early generation hybrids [artificially created Backcross 1 (BC1) plants] exhibited increased variance for eight of the examined traits, and greater leaf and reproductive shoot production when compared to North American DK. Individual BC1 lines differed for several traits, suggesting the importance of the cross for drawing conclusions from such comparisons. When compared to the parental species (DK and SK), the BC1 plants were not transgressive for any of the measured traits. Overall, these findings suggest that if diploid SK is introduced to North America, interspecific hybridization has the potential to result in even more aggressive invaders.
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Multiple introductions of two invasive Centaurea taxa inferred from cpDNA haplotypes
Diversity and Distributions, 2007Co-Authors: Ruth A. Hufbauer, René SforzaAbstract:Knowing the origin of invasive taxa, whether multiple introductions have occurred, and levels of genetic variation relative to the native range, is vital to conducting rigorous tests of hypotheses to explain biological invasions. We explore phylogeographical relationships of two Eurasian knapweed taxa that are invasive in North America, Centaurea diffusa and C. stoebe micranthos (Asteraceae), using chloroplast DNA intron sequences. We also gathered data from C. stoebe stoebe, hybrids between C. diffusa and C. stoebe stoebe (C. xpsammogena), and three other species in the genus. We sequenced 213 individuals from Eurasia and North America, and found 22 haplotypes. Centaurea diffusa has lower haplotype diversity and allelic richness in the introduced range relative to the native range. Even with reduced variation, the data suggest at least two introductions of C. diffusa. There is a trend towards reduced variation in C. stoebe micranthos, but it is not significant. One of the haplotypes found in North American C. stoebe micranthos matches a haplotype from a taxon other than C. stoebe micranthos in Europe. This suggests introgression of the chloroplast between taxa, or possibly the invasion of another Centaurea taxon into North America. Additionally, C. diffusa, C. stoebe micranthos, and C. stoebe stoebe share several haplotypes, including their most common haplotype. This suggests ongoing hybridization between the species or incomplete segregation. These data can guide further exploration for the origins of these species, and point out locations within the introduced range with unique and diverse genetic makeup.
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When invasion increases population genetic structure: a study with Centaurea diffusa.
Biological Invasions, 2007Co-Authors: Robin A. Marrs, René Sforza, Ruth A. HufbauerAbstract:Biological invasions offer excellent systems to study the evolutionary processes involved in introductions of species to new ranges. Molecular markers can reveal invasion histories and the effects of introductions on amounts and structuring of genetic variation. We used five polymorphic microsatellite loci to elucidate genetic diversity and population structure between native range and introduced range populations of a prominent North American rangeland weed, Centaurea diffusa (Asteraceae). We found that the total number of alleles and the number of private alleles was slightly higher in the native Eurasian range, and that allelic richness did not differ between the ranges, indicating overall levels of diversity were similar in Eurasia and North America. It therefore seems unlikely that this invasion has been affected by genetic bottlenecks or founder effects. Indeed, results of assignment tests suggest that multiple introductions have contributed to North America’s C. diffusa invasion. Additionally, assignment tests show that both Eurasian and North American sites had a strong pattern of mixed genetic ancestry. This mixed assignment corresponded to a lack of geographic population structure among Eurasian samples. The lack of population structure in the native range conflicts with general expectations and findings to date for invasion genetics, and cautions that even species’ native ranges may show signs of recent ecological upheaval. Despite the mixed assignments, North American samples showed strong population structure, suggesting that the invasion has been characterized by long-range dispersal of genetically distinct propagules across the introduced range.
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Nine polymorphic microsatellite markers in Centaurea stoebe L. [subspecies C. s. stoebe and C. s. micranthos (S. G. Gmelin ex Gugler) Hayek] and C. diffusa Lam. (Asteraceae)
Molecular Ecology Notes, 2006Co-Authors: Robin A. Marrs, Ruth A. Hufbauer, Steven M. Bogdanowicz, René SforzaAbstract:Centaurea stoebe (subspecies C. s. stoebe and C. s. micranthos[S. G. Gmelin ex Gugler) Hayek] and Centaurea diffusa are Eurasian plant species that have invaded much of North America. We isolated seven microsatellite loci from C. stoebe and two loci from C. diffusa. All loci described here amplify in both species and have between six and 25 alleles each. These markers will be useful in examining population structure and addressing questions regarding these invasions.
Jorge M Vivanco - One of the best experts on this subject based on the ideXlab platform.
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Phytotoxic compounds from roots of Centaurea diffusa Lam.
Plant signaling & behavior, 2009Co-Authors: Naira Quintana, Frank R Stermitz, Elie G El Kassis, Jorge M VivancoAbstract:An extract of roots of Centaurea diffusa (diffuse knapweed) yielded caryophyllene oxide and linoleic acid which were shown to be phytotoxic. Also isolated were germacrene B, a previously-known phytotoxin as well as the inactive polyene aplotaxene. A combination of these compounds, if transferred to the soil, could be one factor in the invasive behavior of this weed. Contrary to a literature report, 8-hydroxyquinoline was not detected in root exudates of in vitro grown C. diffusa nor could it be identified in the root extract. However, a recent report from a different group maintains that 8-hydroxyquinoline can be released from roots of C. diffusa following a diurnal rhythm.
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Can plant biochemistry contribute to understanding of invasion ecology
Trends in plant science, 2006Co-Authors: Inderjit, Ragan M. Callaway, Jorge M VivancoAbstract: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 naive plant species in the introduced range than against co-evolved species in the native range. In this Opinion article, we revise and expand this biochemical hypothesis and discuss experimental and conceptual advances and limitations.
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biogeographical variation in community response to root allelochemistry novel weapons and exotic invasion
Ecology Letters, 2004Co-Authors: Jorge M Vivanco, Giles C Thelen, Harsh P Bais, Frank R Stermitz, Ragan M. CallawayAbstract:Centaurea diffusa is one of the most destructive invasive weeds in the western USA and allelopathy appears to contribute to its invasiveness (Callaway & Aschehoug 2000). Here we identify a chemical from the root exudates of C. diffusa, 8-hydroxyquinoline, not previously reported as a natural product, and find that it varies biogeographically in its natural concentration and its effect as an allelochemical. 8-Hydroxyquinoline is at least three times more concentrated in C. diffusa-invaded North American soils than in this weed’s native Eurasian soils and has stronger phytotoxic effects on grass species from North America than on grass species from Eurasia. Furthermore, experimental communities built from North American plant species are far more susceptible to invasion by C. diffusa than communities built from Eurasian species, regardless of the biogeographical origin of the soil biota. Sterilization of North American soils suppressed C. diffusa more than sterilization of Eurasian soils, indicating that North American soil biota may also promote invasion by C. diffusa. Eurasian plants and soil microbes may have evolved natural resistance to 8-hydroxyquinoline while North American plants have not, suggesting a remarkable potential for evolutionary compatibility and homeostasis among plants within natural communities and a mechanism by which exotic weeds destroy these communities.
René Sforza - One of the best experts on this subject based on the ideXlab platform.
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Multiple introductions of two invasive Centaurea taxa inferred from cpDNA haplotypes
Diversity and Distributions, 2007Co-Authors: Ruth A. Hufbauer, René SforzaAbstract:Knowing the origin of invasive taxa, whether multiple introductions have occurred, and levels of genetic variation relative to the native range, is vital to conducting rigorous tests of hypotheses to explain biological invasions. We explore phylogeographical relationships of two Eurasian knapweed taxa that are invasive in North America, Centaurea diffusa and C. stoebe micranthos (Asteraceae), using chloroplast DNA intron sequences. We also gathered data from C. stoebe stoebe, hybrids between C. diffusa and C. stoebe stoebe (C. xpsammogena), and three other species in the genus. We sequenced 213 individuals from Eurasia and North America, and found 22 haplotypes. Centaurea diffusa has lower haplotype diversity and allelic richness in the introduced range relative to the native range. Even with reduced variation, the data suggest at least two introductions of C. diffusa. There is a trend towards reduced variation in C. stoebe micranthos, but it is not significant. One of the haplotypes found in North American C. stoebe micranthos matches a haplotype from a taxon other than C. stoebe micranthos in Europe. This suggests introgression of the chloroplast between taxa, or possibly the invasion of another Centaurea taxon into North America. Additionally, C. diffusa, C. stoebe micranthos, and C. stoebe stoebe share several haplotypes, including their most common haplotype. This suggests ongoing hybridization between the species or incomplete segregation. These data can guide further exploration for the origins of these species, and point out locations within the introduced range with unique and diverse genetic makeup.
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When invasion increases population genetic structure: a study with Centaurea diffusa.
Biological Invasions, 2007Co-Authors: Robin A. Marrs, René Sforza, Ruth A. HufbauerAbstract:Biological invasions offer excellent systems to study the evolutionary processes involved in introductions of species to new ranges. Molecular markers can reveal invasion histories and the effects of introductions on amounts and structuring of genetic variation. We used five polymorphic microsatellite loci to elucidate genetic diversity and population structure between native range and introduced range populations of a prominent North American rangeland weed, Centaurea diffusa (Asteraceae). We found that the total number of alleles and the number of private alleles was slightly higher in the native Eurasian range, and that allelic richness did not differ between the ranges, indicating overall levels of diversity were similar in Eurasia and North America. It therefore seems unlikely that this invasion has been affected by genetic bottlenecks or founder effects. Indeed, results of assignment tests suggest that multiple introductions have contributed to North America’s C. diffusa invasion. Additionally, assignment tests show that both Eurasian and North American sites had a strong pattern of mixed genetic ancestry. This mixed assignment corresponded to a lack of geographic population structure among Eurasian samples. The lack of population structure in the native range conflicts with general expectations and findings to date for invasion genetics, and cautions that even species’ native ranges may show signs of recent ecological upheaval. Despite the mixed assignments, North American samples showed strong population structure, suggesting that the invasion has been characterized by long-range dispersal of genetically distinct propagules across the introduced range.
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Nine polymorphic microsatellite markers in Centaurea stoebe L. [subspecies C. s. stoebe and C. s. micranthos (S. G. Gmelin ex Gugler) Hayek] and C. diffusa Lam. (Asteraceae)
Molecular Ecology Notes, 2006Co-Authors: Robin A. Marrs, Ruth A. Hufbauer, Steven M. Bogdanowicz, René SforzaAbstract:Centaurea stoebe (subspecies C. s. stoebe and C. s. micranthos[S. G. Gmelin ex Gugler) Hayek] and Centaurea diffusa are Eurasian plant species that have invaded much of North America. We isolated seven microsatellite loci from C. stoebe and two loci from C. diffusa. All loci described here amplify in both species and have between six and 25 alleles each. These markers will be useful in examining population structure and addressing questions regarding these invasions.
Loren H. Rieseberg - One of the best experts on this subject based on the ideXlab platform.
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Genomic Analyses of Phenotypic Differences Between Native and Invasive Populations of Diffuse Knapweed (Centaurea diffusa)
Frontiers in Ecology and Evolution, 2021Co-Authors: Kathryn G. Turner, Christopher J. Grassa, Katherine L. Ostevik, Loren H. RiesebergAbstract:Invasive species represent excellent opportunities to study the evolutionary potential of traits important to success in novel environments. Although some ecologically-important traits have been identified in invasive species, little is typically known about the genetic mechanisms that underlie invasion success in non-model species. Here, we use a genome-wide association (GWAS) approach to identify the genetic basis of trait variation in the non-model, invasive, diffuse knapweed (Centaurea diffusa Lam. [Asteraceae]). To assist with this analysis, we have assembled the first draft genome reference and fully annotated plastome assembly for this species, and the one of the first from this large, weedy, genus, which is of major ecological and economic importance. We collected phenotype data from 372 individuals from four native and four invasive populations of C. diffusa grown in a common environment. Using these individuals, we produced reduced-representation genotype-by-sequencing (GBS) libraries and identified 7058 SNPs. We identify two SNPs associated with leaf width in these populations, a trait which significantly varies between native and invasive populations. In this rosette forming species, increased leaf width is a major component of increased biomass, a common trait in invasive plants correlated with increased fitness. Finally, we use annotations from Arabidopsis thaliana to identify 98 candidate genes that are near the associated SNPs and highlight several good candidates for leaf width variation.
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Adjusted location information for collected C. diffusa populations
2016Co-Authors: Kathryn G. Turner, Hélène Fréville, Loren H. RiesebergAbstract:Adjusted location and collection information for populations of native and invasive Centaurea diffusa (diffuse knapweed) used in the experimental PCA and occurrence PCA
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Bioclimatic data C. diffusa experimental populations
2016Co-Authors: Kathryn G. Turner, Hélène Fréville, Loren H. RiesebergAbstract:Geographic and climatic information for 14 sampled populations of native and invasive Centaurea diffusa (diffuse knapweed). Also, first three principal components from an analysis of this data
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DK_TR001-1L
2016Co-Authors: Zhao Lai, Kathryn G. Turner, Nolan C. Kane, Chris Grassa, Loren H. RiesebergAbstract:Collection ID: DK_TR001-1L | Taxon: Centaurea diffusa Lam. | Common name: Diffuse knapweed | Collection locality: Kirklarelì, Turkey (latitude 41.45, longitude 27.14) | Plant tissues employed for EST library development: Leaves | Library type: Normalized, double-stranded | Sequence type: 45
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Phenological trait data, from C. diffusa common garden
2016Co-Authors: Kathryn G. Turner, Hélène Fréville, Loren H. RiesebergAbstract:Phenological trait data for experimental populations of Centaurea diffusa, measured throughout experiment Trait values measured in common field experiment in Montpellier, France, 2011. File also include the first three principal components from the experimental PCA of the bioclimatic data for these populations
Judith H. Myers - One of the best experts on this subject based on the ideXlab platform.
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Influences of two life-history stages of the weevil, Larinus minutus, on its host plant Centaurea diffusa
Ecological Entomology, 2013Co-Authors: Andrea E. A. Stephens, Judith H. MyersAbstract:1. We hypothesised that, for weed biological control, using species that feed as both adults and larvae would be advantageous. Here, we test the impacts of adult and larval feeding of Larinus minutus (Col.: Curculionidae), a successful biological control agent of diffuse knapweed, Centaurea diffusa (Asteraceae), in British Columbia, Canada. 2. At one site, the observations of the present study showed that the intensity of adult weevil feeding did not predict the level of larval attack. Experiments found no evidence for plant-mediated competition between the life-history stages. 3. At two sites and in two years, experimental manipulations of adult and/or larval feeding damage were conducted and plant performance measured. Neither antagonistic nor synergistic interactions occurred, but at each of the two sites a different life-history stage was responsible for reduction in the number of seeds produced by the plants. 4. Although one of the two different feeding modes was redundant at each site, the ability of adults and larvae to reduce plant performance in different areas makes the species effective in a wider range of environments.
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Successful biological control of diffuse knapweed, Centaurea diffusa, in British Columbia, Canada
Biological Control, 2009Co-Authors: Judith H. Myers, Caroline Jackson, Hillary Quinn, Shannon R. White, Jenny S. CoryAbstract:The biological control program for diffuse knapweed, Centaurea diffusa Lamarck, a Eurasian plant that has invaded large areas of grasslands in western North America, has gone on for over 35 years. This program involved the release of 12 biological control agents of which four are numerous and widely distributed; two species of Tephritid flies, Urophora affinis and Urophora quadrifasciata, the root boring beetle, Sphenoptera jugoslavica, and the most recently established weevil Larinus minutus. Field observations show that diffuse knapweed densities declined at sites in British Columbia Canada where the weevil L. minutus became established. Decline in diffuse knapweed density did not occur where densities of L. minutus were low. Field cage experiments showed that feeding by L. minutus damaged rosette leaves and bolting stems, and reduced seed production, seedling density and the density of rosette and flowering diffuse knapweed plants.
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Plant community changes after the reduction of an invasive rangeland weed, diffuse knapweed, Centaurea diffusa
Biological Control, 2009Co-Authors: Andrea E. A. Stephens, Pam G. Krannitz, Judith H. MyersAbstract:Abstract The expected outcome of weed control in natural systems is that the decline of a dominant weed will result in an increase in diversity of the plant community but this has seldom been tested. Here we evaluate the response of the plant community following the decline of diffuse knapweed (Centaurea diffusa) in six different pastures at White Lake, BC, Canada over five years. This period followed the establishment, spread and high levels of attack by the introduced European weevil, Larinus minutus, as part of a biological control program. Knapweed declined immediately before and during the study period, but, contrary to expectations, the species richness and diversity of the rangeland plant community did not increase. The absolute cover of native and introduced forbs and grasses increased following knapweed decline, but only the introduced grasses showed a consistent increase in cover relative to the other life-forms. However, unlike in other studies, the native plants dominated the study site. We conclude that the changes in plant communities following successful biological control are variable among programs and that the impact of replacement species must be evaluated in assessing the success of ecological restoration programs that use biological control to manage an undesirable weed.
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Why reduced seed production is not necessarily translated into successful biological weed control.
2000Co-Authors: Judith H. Myers, C. Risley, N. R. SpencerAbstract:Insects introduced as biological control agents of diffuse knapweed, Centaurea diffusa, primarily reduce seed production. Knapweed densities appear to be resilient to greatly reduced seed production. We have used measurements of seedling density and survival, and production of seeds by flowering diffuse knapweed plants to develop functions for a model of knapweed populations. These simulations show that improved seedling survival can compensate for reduced seed production. The model indicates that the introduction of seed predators may even increase plant density under some relationships between seedling density and survival, and flowering plant density and seed production. We suggest that it is important to demonstrate that weeds are seed limited before introducing exotic herbivores whose impact is to reduce seed numbers. Successful biological control of knapweed may be achieved by insect herbivores that increase the mortality of later growth stages of plants such as the rosette stage for which survival is not as strongly related to density. Knapweed is likely to be typical of invasive weeds with high seed production and this study suggests that seed feeders are not likely to be successful control agents for most weeds.