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Klaas Vrieling - One of the best experts on this subject based on the ideXlab platform.
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Local adaptation in oviposition choice of a specialist herbivore: The cinnabar moth
Acta Oecologica, 2017Co-Authors: Xianqin Wei, Patrick P.j. Mulder, Klaas Vrieling, Peter G. L. KlinkhamerAbstract:Abstract Specialist herbivores feed on a restricted number of related plant species and may suffer food shortage if overexploitation leads to periodic defoliation of their food plants. The density, size and quality of food plants are important factors that determine the host plant choice of specialist herbivores. To explore how all these factors influence their oviposition behaviour, we used the cinnabar moth Tyria Jacobaeae and the hybrids of a cross between Jacobaea vulgaris and J. aquatica as a study system. While defoliation by the cinnabar moth is common in the coastal area of The Netherlands, it is relatively rare in inland ragwort population. Ragworts contain pyrrolizidine alkaloids (PAs) and those that are found in coastal areas are rich in jacobine-like PAs while those that occur inland are rich in erucifoline-like PAs. We tested how the oviposition preference was influenced by plant size, nitrogen and water content and PA composition. We used cinnabar moth populations from a regularly defoliated area, Meijendel, and Bertogne, a rarely defoliated area. Our results revealed no effects of nitrogen or water content on oviposition preference. Moths from both populations laid larger egg batches on the plants rich in jacobine-like PAs. Moths from Meijendel preferred larger plants and spread their eggs over more egg batches that were, on average, smaller than those of Bertogne moths. These results suggest that Meijendel moths adopted a oviposition strategy to cope with potential defoliation.
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Testing the Generalist-Specialist Dilemma: The Role of Pyrrolizidine Alkaloids in Resistance to Invertebrate Herbivores in Jacobaea Species
2016Co-Authors: Xianqin Wei, Patrick P.j. Mulder, Klaas Vrieling, Peter G. L. KlinkhamerAbstract:Abstract Plants produce a diversity of secondary metabolites (SMs) to protect them from generalist herbivores. On the other hand, specialist herbivores use SMs for host plant recognition, feeding and oviposition cues, and even sequester SMs for their own defense. Therefore, plants are assumed to face an evolu-tionary dilemma stemming from the contrasting effects of generalist and specialist herbivores on SMs. To test this hy-pothesis, bioassays were performed with F2 hybrids from Jacobaea species segregating for their pyrrolizidine alkaloids (PAs), using a specialist flea beetle (Longitarsus Jacobaeae) and a generalist slug (Deroceras invadens). Our study dem-onstrated that while slug feeding damage was negatively cor-related with the concentration of total PAs and that of senecionine-like PAs, flea beetle feeding damage was not af-fected by PAs. It was positively correlated though, with leaf fresh weight. The generalist slug was deterred by senecionine-like PAs but the specialist flea beetle was adapted to PAs in its host plant. Testing other herbivores in the same plant system, it was observed that the egg number of the specialist cinnabar moth was positively correlated with jacobine-like PAs, while the silver damage of generalist thrips was negatively correlat-ed with senecionine- and jacobine-like PAs, and the pupae number of generalist leaf miner was negatively correlated with otosenine-like PAs. Therefore, while the specialist herbivores showed no correlation whatsoever with PA concentration, the generalist herbivores all showed a negative correlation with at least one type of PA. We concluded that the generalist herbi-vores were deterred by different structural groups of PAs while the specialist herbivores were attracted or adapted to PAs in its host plants. Keywords Secondary metabolites diversity. F2 hybrids. Deroceras invadens. Longitarsus Jacobaeae. Jacobaea vulgaris. Feeding damag
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Are effects of common ragwort in the Ames test caused by pyrrolizidine alkaloids
Mutation Research, 2015Co-Authors: Toine F.h. Bovee, Peter G. L. Klinkhamer, Richard J.r. Helsdingen, Ron Laurentius Hoogenboom, Monique De Nijs, Xiaojie Liu, Klaas Vrieling, Ad A. C. M. Peijnenburg, Patrick P.j. MulderAbstract:It has previously been demonstrated by others that acetone extracts of Senecio Jacobaea (syn. Jacobaea vulgaris, common or tansy ragwort) test positive in the Salmonella/microsome mutagenicity test (Ames test). Pyrrolizidine alkaloids (PAs) are thought to be responsible for these mutagenic effects. However, it was also observed that the major PA present in common ragwort, jacobine, produced a negative response (with and without the addition of rat liver S9) in Salmonella test strains TA98, TA100, TA1535 and TA1537. To investigate which compounds in the plant extracts were responsible for the positive outcome, the present study investigated the contents and mutagenic effects of methanol and acetone extracts prepared from dried ground S. Jacobaea and Senecio inaequidens (narrow-leafed ragwort). Subsequently, a fractionation approach was set up in combination with LC-MS/MS analysis of the fractions. It was shown that the positive Ames test outcomes of S. Jacobaea extracts are unlikely to be caused by PAs, but rather by the flavonoid quercetin. This study also demonstrates the importance of identifying compounds responsible for positive test results in bioassays.
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Parallel evolution in an invasive plant: effect of herbivores on competitive ability and regrowth of Jacobaea vulgaris.
Ecology letters, 2015Co-Authors: Tiantian Lin, Peter G. L. Klinkhamer, Klaas VrielingAbstract:A shift in the composition of the herbivore guild in the invasive range is expected to select for plants with a higher competitive ability, a lower regrowth capacity and a lower investment in defence. We show here that parallel evolution took place in three geographically distinct invasive regions that differed significantly in climatic conditions. This makes it most likely that indeed the shifts in herbivore guilds were causal to the evolutionary changes. We studied competitive ability and regrowth of invasive and native Jacobaea vulgaris using an intraspecific competition set-up with and without herbivory. Without herbivores invasive genotypes have a higher competitive ability than native genotypes. The invasive genotypes were less preferred by the generalist Mamestra brassicae but more preferred by the specialist Tyria Jacobaeae, consequently their competitive ability was significantly increased by the first and reduced by the latter. Invasive genotypes showed a lower regrowth ability in both herbivore treatments.
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Pyrrolizidine alkaloid composition influences cinnabar moth oviposition preferences in Jacobaea hybrids.
Journal of Chemical Ecology, 2013Co-Authors: Dandan Cheng, Ed Van Der Meijden, Klaas Vrieling, Patrick P.j. Mulder, Peter G. L. KlinkhamerAbstract:Plants produce a variety of secondary metabolites (PSMs) that may be selective against herbivores. Yet, specialist herbivores may use PSMs as cues for host recognition, oviposition, and feeding stimulation, or for their own defense against parasites and predators. This summarizes a dual role of PSMs: deter generalists but attract specialists. It is not clear yet whether specialist herbivores are a selective force in the evolution of PSM diversity. A prerequisite for such a selective force would be that the preference and/or performance of specialists is influenced by PSMs. To investigate these questions, we conducted an oviposition experiment with cinnabar moths (Tyria Jacobaeae) and plants from an artificial hybrid family of Jacobaea vulgaris and Jacobaea aquatica. The cinnabar moth is a specialist herbivore of J. vulgaris and is adapted to pyrrolizidine alkaloids (PAs), defensive PSMs of these plants. The number of eggs and egg batches oviposited by the moths were dependent on plant genotype and positively correlated to concentrations of tertiary amines of jacobine-like PAs and some otosenine-like PAs. The other PAs did not correlate with oviposition preference. Results suggest that host plant PAs influence cinnabar moth oviposition preference, and that this insect is a potential selective factor against a high concentration of some individual PAs, especially those that are also involved in resistance against generalist herbivores.
Peter B. Mcevoy - One of the best experts on this subject based on the ideXlab platform.
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Controlling a plant invader by targeted disruption of its life cycle
Journal of Applied Ecology, 2012Co-Authors: Joseph T. Dauer, Peter B. Mcevoy, John Van SickleAbstract:Summary 1. Pest management strategies should be informed by research on a broad suite of biotic and abiotic interactions. We used a life table response experiment (LTRE) to assess the reliability of ragwort Jacobaea vulgaris management recommendations based on interactions of (i) time of disturbance to initiate experimental units, (ii) herbivory from two biological control organisms, the cinnabar moth Tyria Jacobaeae and ragwort flea beetle Longitarsus Jacobaeae and (iii) interspecific competition by perennial grasses. 2. Our LTRE combines a factorial experiment with a linear, deterministic matrix model for ragwort populations representing transitions among three stages: 1st year juveniles, ≥2nd year juveniles and adults. Elasticity analysis identified potentially vulnerable ragwort transitions, and a contributions analysis confirmed which treatments influenced these transitions. Ultimate treatment effects were quantified as the reduction in population growth rates and time to local extinction. 3. Elasticity analyses found the ragwort’s biennial pathway, juvenile to adult transition and fertility transition were most influential and most amenable to manipulation across all community configurations. The flea beetle and perennial grass competition had negative effects on survival and fertility, whereas the cinnabar moth only reduced fertility and induced the perennial pathway. 4. All combinations of insects or increased plant competition reduced the growth rate of ragwort. Full interspecific competition and the flea beetle resulted in a significantly greater and faster decline in the ragwort populations than the cinnabar moth. Moreover, this pattern was consistent between two times of initial disturbance. 5.Synthesis and applications. Maximizing plant competition provides the fastest way to control ragwort. If this option is unavailable, for example, grazed or disturbed land, the ragwort flea beetle provides excellent management to lower ragwort densities without the potential nontarget effects of the cinnabar moth. Factorial experiments and matrix models help to evaluate interacting factors that influence invasive species’ vulnerabilities, inform how to intervene in a weed life cycle to reduce weed abundance and confirm recommendations that are robust to community variation.
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Responses of ragwort flea beetle Longitarsus Jacobaeae (Coleoptera: Chrysomelidae) to signals from host plants
Bulletin of Entomological Research, 1995Co-Authors: Zhi-qiang Zhang, Peter B. McevoyAbstract:Responses of adult flea beetles Longitarsus Jacobaeae (Waterhouse), to signals from ragwort plants ( Senecio Jacobaea Linnaeus) were studied by recording their directions of movement in a wind tunnel and their colonization of host-plants in the field. Starved beetle individuals, irrespective of gender, orientated toward upwind host-plants over a distance of 60 cm in the wind tunnel, whereas satiated beetles did not. In the absence of upwind host-plants, all beetles moved randomly in all directions, regardless of whether they were starved or satiated. Starved beetle individuals did not show directed movement towards hosts when plants were downwind in the wind tunnel, nor when in the presence of host-plants when the wind was absent. Groups of starved beetles orientated to upwind host-plants in the wind tunnel, as did individual beetles. In the field, plants over 60 cm upwind of the released beetles were found and colonized by more beetles than downwind plants, in spite of the presence of background vegetation. This confirms the result of laboratory experiments that L. Jacobaeae can orient to upwind host-plants.
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Attraction of Longitarsus Jacobaeae Males to Cues Associated with Conspecific Females (Coleoptera: Chrysomelidae)
Environmental Entomology, 1994Co-Authors: Zhi-qiang Zhang, Peter B. McevoyAbstract:Responses of the ragwort Ilea beetle, Longitarsus Jacobaeae (Waterhouse), to cues associated with conspecific beetles were examined using two-choice tests in the laboratory and in the field. In the laboratory test, a male or female flea beetle was allowed to choose between two tansy ragwort ( Senecio Jacobaea L.) leaves, one that had been previously exposed to five male or female beetles for 1 d, and the other without any previous exposure to conspecific beetles. Male beetles were found more often on leaves that had been previously exposed to female beetles than on the clean leaves without female-associated cues, but were randomly distributed when the treated leaves were previously exposed to male beetles. Female beetles were randomly distributed between the two leaves, regardless of whether one leaf was previously exposed to male beetles or female beetles. Similar tests using filter paper as substrate instead of leaves showed similar results, suggesting that male beetles responded to cues associated with female beetles rather than to plants. In a field experiment, ragwort leaves that had been previously exposed to female beetles attracted more male beetles than leaves without female-associated cues. The evidence suggests that L. Jacobaeae females emit a sex pheromone that is attractive to male beetles. Attraction of male beetles to leaves exposed to females may be one of the mechanisms underlying the clumped distribution of flea beetles within plants.
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effects of vegetation disturbances on insect biological control of tansy ragwort senecio Jacobaea
Ecological Applications, 1993Co-Authors: Peter B. Mcevoy, Nathan T. RuddAbstract:Our study had two major objectives: (1) to clarify the roles of buried seed and different types of localized disturbance in activating outbreaks of a pasture weed (tansy ragwort, Senecio Jacobaea), and (2) to measure the effectiveness of two natural enemies (the cinnabar moth Tyria Jacobaeae and a ragwort flea beetle, Longitarsus Jacobaeae) in inhibiting weed population increase and spread. We conducted a 5-yr field experiment on the coast of Oregon using a randomized-block design with four blocks x three levels of disturbance (background vegetation was Tilled, Clipped, Unaltered) x two levels of cin- nabar moth (Exposed, Protected) x two levels of flea beetle (Exposed, Protected) = 48 plots (each plot was 0.25 m2). Disturbance consistently increased ragwort abundance (measured as density of juve- niles, adults, and their offspring; cover; and biomass); the effect was generally greater in Tilled compared to Clipped disturbance treatments. We also found striking differences in the contribution of each natural enemy to ragwort control. The flea beetle quickly reduced ragwort survival, and this led to a strong and rapid reduction in ragwort abundance. The cinnabar moth reduced ragwort fecundity, but this did not translate into reductions in ragwort cover (measured in 1986 and 1987) or biomass (measured annually from 1986 through 1990). These results establish that (1) ragwort populations were limited more by availability of microsites for germination and establishment than by availability of seed, (2) the ragwort flea beetle was the key factor regulating ragwort abundance, and (3) reduction in ragwort fecundity by the cinnabar moth had little effect on the dynamics of ragwort populations on local scales of space and time. These findings underscore the value of field experiments for investigating the dynamics of biological control systems, the manner in which they are regulated, and their response to perturbation. They further establish how colonization and invasion by ragwort depend on attributes of the disturbance and of natural enemy regimes.
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Combining the cinnabar moth (Tyria Jacobaeae) and the ragwort flea beetle (Longitarsus Jacobaeae) for control of ragwort (Senecio Jacobaea): an experimental analysis.
The Journal of Applied Ecology, 1992Co-Authors: R. R. James, Peter B. Mcevoy, Caroline CoxAbstract:1. A field experiment tested the independent and combined effects of the cinnabar moth (Tyria Jacobaeae) and the ragwort flea beetle (Longitarsus Jacobaeae) on ragwort (Senecio Jacobaea). These insect herbivores feed on different stages of the host-plant and at different times of the year and were introduced to North America as biological control agents. 2. Flea beetles alone were found to reduce vegetative ragwort densities by 95%, and flower production by 39%, as compared to plants in control plots. Damage by cinnabar moths was simulated by removing all leaves and capitula from generative plants, but plants were able to regenerate some of the foliage and flowers
Peter G. L. Klinkhamer - One of the best experts on this subject based on the ideXlab platform.
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Local adaptation in oviposition choice of a specialist herbivore: The cinnabar moth
Acta Oecologica, 2017Co-Authors: Xianqin Wei, Patrick P.j. Mulder, Klaas Vrieling, Peter G. L. KlinkhamerAbstract:Abstract Specialist herbivores feed on a restricted number of related plant species and may suffer food shortage if overexploitation leads to periodic defoliation of their food plants. The density, size and quality of food plants are important factors that determine the host plant choice of specialist herbivores. To explore how all these factors influence their oviposition behaviour, we used the cinnabar moth Tyria Jacobaeae and the hybrids of a cross between Jacobaea vulgaris and J. aquatica as a study system. While defoliation by the cinnabar moth is common in the coastal area of The Netherlands, it is relatively rare in inland ragwort population. Ragworts contain pyrrolizidine alkaloids (PAs) and those that are found in coastal areas are rich in jacobine-like PAs while those that occur inland are rich in erucifoline-like PAs. We tested how the oviposition preference was influenced by plant size, nitrogen and water content and PA composition. We used cinnabar moth populations from a regularly defoliated area, Meijendel, and Bertogne, a rarely defoliated area. Our results revealed no effects of nitrogen or water content on oviposition preference. Moths from both populations laid larger egg batches on the plants rich in jacobine-like PAs. Moths from Meijendel preferred larger plants and spread their eggs over more egg batches that were, on average, smaller than those of Bertogne moths. These results suggest that Meijendel moths adopted a oviposition strategy to cope with potential defoliation.
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Testing the Generalist-Specialist Dilemma: The Role of Pyrrolizidine Alkaloids in Resistance to Invertebrate Herbivores in Jacobaea Species
2016Co-Authors: Xianqin Wei, Patrick P.j. Mulder, Klaas Vrieling, Peter G. L. KlinkhamerAbstract:Abstract Plants produce a diversity of secondary metabolites (SMs) to protect them from generalist herbivores. On the other hand, specialist herbivores use SMs for host plant recognition, feeding and oviposition cues, and even sequester SMs for their own defense. Therefore, plants are assumed to face an evolu-tionary dilemma stemming from the contrasting effects of generalist and specialist herbivores on SMs. To test this hy-pothesis, bioassays were performed with F2 hybrids from Jacobaea species segregating for their pyrrolizidine alkaloids (PAs), using a specialist flea beetle (Longitarsus Jacobaeae) and a generalist slug (Deroceras invadens). Our study dem-onstrated that while slug feeding damage was negatively cor-related with the concentration of total PAs and that of senecionine-like PAs, flea beetle feeding damage was not af-fected by PAs. It was positively correlated though, with leaf fresh weight. The generalist slug was deterred by senecionine-like PAs but the specialist flea beetle was adapted to PAs in its host plant. Testing other herbivores in the same plant system, it was observed that the egg number of the specialist cinnabar moth was positively correlated with jacobine-like PAs, while the silver damage of generalist thrips was negatively correlat-ed with senecionine- and jacobine-like PAs, and the pupae number of generalist leaf miner was negatively correlated with otosenine-like PAs. Therefore, while the specialist herbivores showed no correlation whatsoever with PA concentration, the generalist herbivores all showed a negative correlation with at least one type of PA. We concluded that the generalist herbi-vores were deterred by different structural groups of PAs while the specialist herbivores were attracted or adapted to PAs in its host plants. Keywords Secondary metabolites diversity. F2 hybrids. Deroceras invadens. Longitarsus Jacobaeae. Jacobaea vulgaris. Feeding damag
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Are effects of common ragwort in the Ames test caused by pyrrolizidine alkaloids
Mutation Research, 2015Co-Authors: Toine F.h. Bovee, Peter G. L. Klinkhamer, Richard J.r. Helsdingen, Ron Laurentius Hoogenboom, Monique De Nijs, Xiaojie Liu, Klaas Vrieling, Ad A. C. M. Peijnenburg, Patrick P.j. MulderAbstract:It has previously been demonstrated by others that acetone extracts of Senecio Jacobaea (syn. Jacobaea vulgaris, common or tansy ragwort) test positive in the Salmonella/microsome mutagenicity test (Ames test). Pyrrolizidine alkaloids (PAs) are thought to be responsible for these mutagenic effects. However, it was also observed that the major PA present in common ragwort, jacobine, produced a negative response (with and without the addition of rat liver S9) in Salmonella test strains TA98, TA100, TA1535 and TA1537. To investigate which compounds in the plant extracts were responsible for the positive outcome, the present study investigated the contents and mutagenic effects of methanol and acetone extracts prepared from dried ground S. Jacobaea and Senecio inaequidens (narrow-leafed ragwort). Subsequently, a fractionation approach was set up in combination with LC-MS/MS analysis of the fractions. It was shown that the positive Ames test outcomes of S. Jacobaea extracts are unlikely to be caused by PAs, but rather by the flavonoid quercetin. This study also demonstrates the importance of identifying compounds responsible for positive test results in bioassays.
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Parallel evolution in an invasive plant: effect of herbivores on competitive ability and regrowth of Jacobaea vulgaris.
Ecology letters, 2015Co-Authors: Tiantian Lin, Peter G. L. Klinkhamer, Klaas VrielingAbstract:A shift in the composition of the herbivore guild in the invasive range is expected to select for plants with a higher competitive ability, a lower regrowth capacity and a lower investment in defence. We show here that parallel evolution took place in three geographically distinct invasive regions that differed significantly in climatic conditions. This makes it most likely that indeed the shifts in herbivore guilds were causal to the evolutionary changes. We studied competitive ability and regrowth of invasive and native Jacobaea vulgaris using an intraspecific competition set-up with and without herbivory. Without herbivores invasive genotypes have a higher competitive ability than native genotypes. The invasive genotypes were less preferred by the generalist Mamestra brassicae but more preferred by the specialist Tyria Jacobaeae, consequently their competitive ability was significantly increased by the first and reduced by the latter. Invasive genotypes showed a lower regrowth ability in both herbivore treatments.
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Pyrrolizidine alkaloid composition influences cinnabar moth oviposition preferences in Jacobaea hybrids.
Journal of Chemical Ecology, 2013Co-Authors: Dandan Cheng, Ed Van Der Meijden, Klaas Vrieling, Patrick P.j. Mulder, Peter G. L. KlinkhamerAbstract:Plants produce a variety of secondary metabolites (PSMs) that may be selective against herbivores. Yet, specialist herbivores may use PSMs as cues for host recognition, oviposition, and feeding stimulation, or for their own defense against parasites and predators. This summarizes a dual role of PSMs: deter generalists but attract specialists. It is not clear yet whether specialist herbivores are a selective force in the evolution of PSM diversity. A prerequisite for such a selective force would be that the preference and/or performance of specialists is influenced by PSMs. To investigate these questions, we conducted an oviposition experiment with cinnabar moths (Tyria Jacobaeae) and plants from an artificial hybrid family of Jacobaea vulgaris and Jacobaea aquatica. The cinnabar moth is a specialist herbivore of J. vulgaris and is adapted to pyrrolizidine alkaloids (PAs), defensive PSMs of these plants. The number of eggs and egg batches oviposited by the moths were dependent on plant genotype and positively correlated to concentrations of tertiary amines of jacobine-like PAs and some otosenine-like PAs. The other PAs did not correlate with oviposition preference. Results suggest that host plant PAs influence cinnabar moth oviposition preference, and that this insect is a potential selective factor against a high concentration of some individual PAs, especially those that are also involved in resistance against generalist herbivores.
Urs Schaffner - One of the best experts on this subject based on the ideXlab platform.
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Hybrid vigor in the biological control agent, Longitarsus Jacobaeae
Evolutionary Applications, 2012Co-Authors: Marianna Szűcs, Sanford D. Eigenbrode, Mark Schwarzländer, Urs SchaffnerAbstract:Hybridization is an important evolutionary mechanism that can increase the fitness and adaptive potential of populations. A growing body of evidence supports its importance as a key factor contributing to rapid evolution in invasive species, but the effects of hybridization have rarely been assessed in intentionally introduced biological control agents. We investigated hybrids between a Swiss and an Italian population of the beetle, Longitarsus Jacobaeae, a biological control agent of Jacobaea vulgaris, by reciprocally crossing individuals in the laboratory. Phenological traits of F1 and F2 hybrid lineages showed intermediate values relative to their parental populations, with some maternal influence. Fitness of the F2 generation, measured as lifetime fecundity, was higher than that of the Italian parent in one of the lineages and higher than that of either parent in the other hybrid lineage. The increased fecundity of hybrids may benefit tansy ragwort biological control by increasing the establishment success and facilitating a more rapid population buildup in the early generations. Even though the long-term consequences of hybridization in this and other systems are hard to predict, intentional hybridization may be a useful tool in biological control strategies as it would promote similar microevolutionary processes operating in numerous targeted invasive species.
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Post-introduction evolution in the biological control agent Longitarsus Jacobaeae (Coleoptera: Chrysomelidae).
Evolutionary applications, 2012Co-Authors: Marianna Szűcs, Urs Schaffner, William J. Price, Mark SchwarzländerAbstract:Rapid evolution has rarely been assessed in biological control systems despite the similarity with biological invasions, which are widely used as model systems. We assessed post-introduction climatic adaptation in a population of Longitarsus Jacobaeae, a biological control agent of Jacobaea vulgaris, which originated from a low-elevation site in Italy and was introduced in the USA to a high-elevation site (Mt. Hood, Oregon) in the early 1980s. Life-history characteristics of beetle populations from Mt. Hood, from two low-elevation sites in Oregon (Italian origin) and from a high-elevation site from Switzerland were compared in common gardens. The performance of low- and high-elevation populations at a low- and a high-elevation site was evaluated using reciprocal transplants. The results revealed significant changes in aestival diapause and shifts in phenology in the Mt. Hood population, compared with the low-elevation populations. We found increased performance of the Mt. Hood population in its home environment compared with the low-elevation populations that it originated from. The results indicate that the beetles at Mt. Hood have adapted to the cooler conditions by life-history changes that conform to predictions based on theory and the phenology of the cold-adapted Swiss beetles.
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is there rapid evolutionary response in introduced populations of tansy ragwort Jacobaea vulgaris when exposed to biological control
Evolutionary Ecology, 2010Co-Authors: Klaas Vrieling, Carole Rapo, Heinz Mullerscharer, Urs SchaffnerAbstract:Differences in the herbivore community between a plant’s native (specialists and generalists) and introduced range (almost exclusively generalists) may lead to the evolution of reduced allocation to defences against specialist herbivores in the introduced range, allowing for increased allocation to competitive ability and to defences against generalist herbivores. Following this logic, the introduction of biological control agents should reverse this evolutionary shift and select for plants with life-history traits that are more similar to those of plants in the native range than those of plants in the introduced range that have not been exposed to biological control. In a common garden experiment, we compared performance and resistance traits of tansy ragwort, Jacobaea vulgaris, among populations from the introduced range (New Zealand and North America) that have either been exposed to or grown free from the biological control agent Longitarsus Jacobaeae. For comparison, we included populations from the native European range. We found lower levels of generalist-deterrent pyrrolizidine alkaloids (PAs) and of soluble phenolics in New Zealand populations with than in populations without exposure to L. Jacobaeae, while the opposite pattern was detected among North American populations. Contrary to expectation, populations with exposure to L. Jacobaeae revealed more feeding damage by L. Jacobaeae than populations without exposure. Introduced populations had higher levels of PAs and reproductive output than native J. vulgaris populations. Jacobaea vulgaris was introduced in different parts of the world some 100–130 years ago, while L. Jacobaeae was introduced only some 20–40 years ago. Hence, the larger differences observed between native and introduced populations, as compared to introduced populations with and without biological control history, may result from different time scales available for selection to act.
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Do vigour of introduced populations and escape from specialist herbivores contribute to invasiveness
Journal of Ecology, 2005Co-Authors: Michael Stastny, Urs Schaffner, Elizabeth ElleAbstract:Summary 1 Plant species may become invasive due to a lack of natural enemies (e.g. herbivores) in their introduced range. Absence of herbivores may result in selection for the loss of costly herbivore-resistance traits, which are expected to show a trade-off with vigour or competitive ability (the evolution of increased competitive ability, or EICA, hypothesis). 2 We conducted a common garden experiment in Switzerland, in which we compared herbivore resistance and vigour of Senecio Jacobaea plants exposed to the specialist flea beetle Longitarsus Jacobaeae, for four populations originating within the native range (Europe), and four from regions where it had been introduced (New Zealand, USA) and was unaffected by L. Jacobaeae. Our predictions were that, compared with plants from the native populations, plants from introduced populations would experience greater herbivory (due to loss of resistance traits), and exhibit more vigorous growth. 3 As expected, we found that introduced S. Jacobaea grew larger, and had greater reproductive output, than plants from the native range. Larger plants experienced more feeding damage, and introduced plants were consumed more even when size differences were controlled. Introduced plants also exhibited a greater relative ability to reproduce after damage was sustained, i.e. higher tolerance to herbivory. 4 Contrary to predictions, however, plants from introduced populations had higher total pyrrolizidine alkaloid production (chemical defence against herbivores). 5 Although plants from introduced ranges exhibited life-history traits consistent with EICA predictions, similar phenotypes were common in one of the populations from the native range, suggesting that EICA may not fully explain the invasion success of S. Jacobaea. 6 Our results imply that increased competitive ability (vigour) of invasive plants may be associated with changes in resistance as well as tolerance to herbivory, and both types of anti-herbivore defence may need to be examined simultaneously to advance our understanding of invasiveness.
Chris D. Thomas - One of the best experts on this subject based on the ideXlab platform.
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Patchiness and spatial pattern in the insect community on ragwort Senecio Jacobaea
Oikos, 1991Co-Authors: Susan Harrison, Chris D. ThomasAbstract:Cinnabar moth (Tyria Jacobaeae) frequently defoliates ragwort (Senecio Jacobaea), with potentially severe impacts upon other insects sharing this host plant. However, defoliation tends to be spatially localized because the plant is patchy and the moth (apparently) a poor disperser. Here we examine the hypothesis that isolated patches of ragwort form spatial refuges for ragwort-feeding insects, helping them to coexist with the cinnabar moth
