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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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Factors affecting the response of Longitarsus Jacobaeae (Coleoptera: Chrysomelidae) to upwind plant odours
Bulletin of Entomological Research, 1996Co-Authors: Zhi-qiang Zhang, Peter B. McevoyAbstract:Factors (developmental state, starvation time, host local density and host distance from insects) affecting the response of the ragwort flea beetle, Longitarsus Jacobaeae (Waterhouse), to upwind plants of tansy ragwort, Senecio Jacobaeae (Compositae), were examined in a wind tunnel. There was seasonal variation in beetle response to host odours. Individuals collected during spring and early summer (6 May to 14 July 1993) showed directed movement toward the upwind plants. However, individuals collected in mid-summer (23 July 1993) showed no significant response to upwind host plants and walked randomly in the wind tunnel. Individuals collected during late summer to autumn (4 August to 23 October 1994) once again showed response to upwind plants, whereas those collected in winter (January 1994) walked randomly in the wind tunnel. The absence of beetle response to plant odours coincided with potential summer aestivation and winter ‘hibernation’. For spring and early summer beetles that responded to plant odours, the strength of the response did not change significantly with the number of plants (1, 2, 4 or 6) presented upwind in the tunnel nor with the starvation time (2, 6, 10, 12, 24 or 36 h) of the tested beetles, and these patterns were consistent for male and female beetles. Individuals responded to plants from a distance of 60 and 300 cm. The speed of movement, similar for males and females, increased slightly as L. Jacobaeae oriented more directly toward host plants.
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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.
Urs Schaffner - One of the best experts on this subject based on the ideXlab platform.
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The effects of agent hybridization on the efficacy of biological control of tansy ragwort at high elevations.
Evolutionary Applications, 2018Co-Authors: Marianna Szűcs, Urs Schaffner, Patricia E. Salerno, Brittany J. Teller, Jeffrey L. Littlefield, Ruth A. HufbauerAbstract:The success rate of weed biological control programs is difficult to evaluate and the factors affecting it remain poorly understood. One aspect which is still unclear is whether releases of multiple, genetically distinct populations of a biological control agent increase the likelihood of success, either by independent colonization of different environmental niches or by hybridization that may increase the agent's fitness and adaptive ability. Since hybridization is often invoked to explain the success of unintentionally introduced exotic species, hybridization among biocontrol agents may be similarly important in shaping the effectiveness of biological control programs. In this study, we first evaluated intraspecific hybridization among populations of a weed biological control agent, the ragwort flea beetle, Longitarsus Jacobaeae. These insects were introduced as part of a classical biological control program from Italy and Switzerland. We genotyped 204 individuals from 15 field sites collected in northwest Montana, and an additional 52 individuals that served as references for Italian and Swiss populations. Bayesian analysis of population structure assigned seven populations as pure Swiss and one population as pure Italian, while intraspecific hybrid individuals were detected in seven populations at frequencies of 5%-69%. Subsequently, we conducted a 2-year exclusion experiment using six sites with Swiss beetles and three with hybrid beetles to evaluate the impact of biological control. We found that biological control by Swiss beetles and by hybrid beetles is effective, increasing mortality of the target plant, Jacobaea vulgaris, by 42% and 45%, and reducing fecundity of surviving plants by 44% and 72%, respectively. Beetle densities were higher and mortality of larger plants was higher at sites with hybrids present. These results suggest that hybridization of ragwort flea beetles at high-elevation sites may improve biological control of tansy ragwort and that intraspecific hybridization of agents could benefit biological control programs.
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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.
Klaas Vrieling - One of the best experts on this subject based on the ideXlab platform.
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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, Klaas Vrieling, Patrick P.j. Mulder, 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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Testing the Generalist-Specialist Dilemma: The Role of Pyrrolizidine Alkaloids in Resistance to Invertebrate Herbivores in Jacobaea Species
Journal of Chemical Ecology, 2015Co-Authors: Xianqin Wei, Klaas Vrieling, Patrick P.j. Mulder, Peter G. L. KlinkhamerAbstract: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 evolutionary dilemma stemming from the contrasting effects of generalist and specialist herbivores on SMs. To test this hypothesis, 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 demonstrated that while slug feeding damage was negatively correlated with the concentration of total PAs and that of senecionine-like PAs, flea beetle feeding damage was not affected 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 correlated 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 herbivores were deterred by different structural groups of PAs while the specialist herbivores were attracted or adapted to PAs in its host plants.
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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.
Peter G. L. Klinkhamer - One of the best experts on this subject based on the ideXlab platform.
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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, Klaas Vrieling, Patrick P.j. Mulder, 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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Testing the Generalist-Specialist Dilemma: The Role of Pyrrolizidine Alkaloids in Resistance to Invertebrate Herbivores in Jacobaea Species
Journal of Chemical Ecology, 2015Co-Authors: Xianqin Wei, Klaas Vrieling, Patrick P.j. Mulder, Peter G. L. KlinkhamerAbstract: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 evolutionary dilemma stemming from the contrasting effects of generalist and specialist herbivores on SMs. To test this hypothesis, 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 demonstrated that while slug feeding damage was negatively correlated with the concentration of total PAs and that of senecionine-like PAs, flea beetle feeding damage was not affected 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 correlated 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 herbivores were deterred by different structural groups of PAs while the specialist herbivores were attracted or adapted to PAs in its host plants.
Carole Rapo - One of the best experts on this subject based on the ideXlab platform.
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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.
