[Show abstract][Hide abstract] ABSTRACT: It is often assumed that exotic plants can become invasive when they possess novel secondary chemistry compared with native plants in the introduced range. Using untargeted metabolomic fingerprinting, we compared a broad range of metabolites of six successful exotic plant species and their native congeners of the family Asteraceae. Our results showed that plant chemistry is highly species-specific and diverse among both exotic and native species. Nonetheless, the exotic species had on average a higher total number of metabolites and more species-unique metabolites compared with their native congeners. Herbivory led to an overall increase in metabolites in all plant species. Generalist herbivore performance was lower on most of the exotic species compared with the native species. We conclude that high chemical diversity and large phytochemical uniqueness of the exotic species could be indicative of biological invasion potential.
Ecology and Evolution 07/2014; 4(13):2777-86. · 1.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Due to global warming, species are expanding their range to higher latitudes. Some range expanding plants have become invasive in their new range. The Evolution of Increased Competitive Ability (EICA) hypothesis and the Shifting Defense Hypothesis (SDH) predict altered selection on plant defenses in the introduced range of invasive plants due to changes in herbivore pressures and communities. Here, we investigated chemical defenses (glucosinolates) of five native and seven invasive populations of the Eurasian invasive range expanding plant, Rorippa austriaca. Further, we studied feeding preferences of a generalist and a specialist herbivore among the populations. We detected eight glucosinolates in the leaves of R. austriaca. 8-Methylsulfinyloctyl glucosinolate was the most abundant glucosinolate in all plants. There were no overall differences between native and invasive plants in concentrations of glucosinolates. However, concentrations among populations within each range differed significantly. Feeding preference between the populations by a generalist herbivore was negatively correlated with glucosinolate concentrations. Feeding by a specialist did not differ between the populations and was not correlated with glucosinolates. Possibly, local differences in herbivore communities within each range may explain the differences in concentrations of glucosinolates among populations. Little support for the predictions of the EICA hypothesis or the SDH was found for the glucosinolate defenses of the studied native and invasive R. austriaca populations.
Journal of Chemical Ecology 04/2014; · 2.46 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Knowledge on spatio-temporal dynamics of plant primary and secondary chemistry under natural conditions is important to assess how plant defence varies in real field conditions. Plant primary and secondary chemistry is known to vary with both season and vegetation successional stage, however, in few studies these two sources of variation have been examined in combination. Here we examine variations in primary and secondary chemistry of Jacobaea vulgaris (Asteraceae) throughout the growing season in early, mid, and late stages of secondary succession following land abandonment using a well-established chronosequence in The Netherlands. We investigated primary and secondary chemistry of both leaves and flowers, in order to determine if patterns during seasonal (phenological) development may differ among successional stages. The chemical concentration of primary and secondary chemistry compounds in J. vulgaris varied throughout the season and was affected by vegetation succession stage. Concentrations of pyrrolizidine alkaloid (PA) tertiary-amines were highest in flowers during early Summer and in fields that had been abandoned ten to twenty years ago. PA N-oxide concentrations of both leaves and flowers, on the other hand increased with the progression of both season and succession. In Spring and early Summer chlorophyll concentrations were highest, especially in the oldest fields of the chronosequence. During phenological development, nitrogen concentration increased in flowers and decreased in leaves revealing allocation of nutrients from vegetative to reproductive plant parts throughout the growing season. The highest concentrations of N-oxides and chlorophylls were detected in older fields. Thus, our results suggest that variations in plant patterns of nutritional and defence compounds throughout the growing season are depending on successional context.
[Show abstract][Hide abstract] ABSTRACT: Plant toxic biochemicals play an important role in defense against natural enemies and often are toxic to humans and livestock. Hyperspectral reflectance is an established method for primary chemical detection and could be further used to determine plant toxicity in the field. In order to make a first step for pyrrolizidine alkaloids detection (toxic defense compound against mammals and many insects) we studied how such spectral data can estimate plant defense chemistry under controlled conditions. In a greenhouse, we grew three related plant species that defend against generalist herbivores through pyrrolizidine alkaloids: Jacobaea vulgaris, Jacobaea erucifolia and Senecio inaequidens, and analyzed the relation between spectral measurements and chemical concentrations using multivariate statistics. Nutrient addition enhanced tertiary-amine pyrrolizidine alkaloids contents off. vulgaris and J. erucifolia and decreased N-oxide contents in S. inaequidens and J. vulgaris. Pyrrolizidine alkaloids could be predicted with a moderate accuracy. Pyrrolizidine alkaloid forms tertiary-amines and epoxides were predicted with 63% and 56% of the variation explained, respectively. The most relevant spectral regions selected for prediction were associated with electron transitions and C-H, O-H, and N-H bonds in the 1530 and 2100 nm regions. Given the relatively low concentration in pyrrolizidine alkaloids concentration (in the order of mg g(-1)) and resultant predictions, it is promising that pyrrolizidine alkaloids interact with incident light. Further studies should be considered to determine if such a non-destructive method may predict changes in PA concentration in relation to plant natural enemies. Spectroscopy may be used to study plant defenses in intact plant tissues, and may provide managers of toxic plants, food industry and multitrophic-interaction researchers with faster and larger monitoring possibilities. (C) 2013 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS) Published by Elsevier B.V. All rights reserved.
ISPRS Journal of Photogrammetry and Remote Sensing 01/2013; 80:51-60. · 3.31 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Recent studies revealed that plant-soil biotic interactions may cause changes in above-ground plant chemistry. It would be a new step in below-ground-above-ground interaction research if such above-ground chemistry changes could be efficiently detected. Here we test how hyperspectral reflectance may be used to study such plant-soil biotic interactions in a nondestructive and rapid way. The native plant species Jacobaea vulgaris and Jacobaea erucifolius, and the exotic invader Senecio inaequidens were grown in different soil biotic conditions. Biomass, chemical content and shoot reflectance between 400 and 2500 nm wavelengths were determined. The data were analysed with multivariate statistics. Exposing the plants to soil biota enhanced the content of defence compounds. The highest increase (400%) was observed for the exotic invader S. inaequidens. Chemical and spectral data enabled plant species to be classified with an accuracy > 85%. Plants grown in different soil conditions were classified with 50-60% correctness. Our data suggest that soil microorganisms can affect plant chemistry and spectral reflectance. Further studies should test the potential to study plant-soil biotic interactions in the field. Such techniques could help to monitor, among other things, where invasive exotic plant species develop biotic resistance or the development of hotspots of crop soil diseases.
[Show abstract][Hide abstract] ABSTRACT: Pyrrolizidine alkaloids (PAs) are the major defense compounds of plants in the Senecio genus. Here I will review the effects of PAs in Senecio on the preference and performance of specialist and generalist insect herbivores. Specialist herbivores have evolved adaptation to PAs in their host plant. They can use the alkaloids as cue to find their host plant and often they sequester PAs for their own defense against predators. Generalists, on the other hand, can be deterred by PAs. PAs can also affect survival of generalist herbivores. Usually generalist insects avoid feeding on young Senecio leaves, which contain a high concentration of alkaloids. Structurally related PAs can differ in their effects on insect herbivores, some are more toxic than others. The differences in effects of PAs on specialist and generalists could lead to opposing selection on PAs, which may maintain the genetic diversity in PA concentration and composition in Senecio species.
[Show abstract][Hide abstract] ABSTRACT: When previously isolated populations meet and mix, the resulting admixed population can benefit from several genetic advantages, including increased genetic variation, the creation of novel genotypes and the masking of deleterious mutations. These admixture benefits are thought to play an important role in biological invasions. In contrast, populations in their native range often remain differentiated and frequently suffer from inbreeding depression owing to isolation. While the advantages of admixture are evident for introduced populations that experienced recent bottlenecks or that face novel selection pressures, it is less obvious why native range populations do not similarly benefit from admixture. Here we argue that a temporary loss of local adaptation in recent invaders fundamentally alters the fitness consequences of admixture. In native populations, selection against dilution of the locally adapted gene pool inhibits unconstrained admixture and reinforces population isolation, with some level of inbreeding depression as an expected consequence. We show that admixture is selected against despite significant inbreeding depression because the benefits of local adaptation are greater than the cost of inbreeding. In contrast, introduced populations that have not yet established a pattern of local adaptation can freely reap the benefits of admixture. There can be strong selection for admixture because it instantly lifts the inbreeding depression that had built up in isolated parental populations. Recent work in Silene suggests that reduced inbreeding depression associated with post-introduction admixture may contribute to enhanced fitness of invasive populations. We hypothesize that in locally adapted populations, the benefits of local adaptation are balanced against an inbreeding cost that could develop in part owing to the isolating effect of local adaptation itself. The inbreeding cost can be revealed in admixing populations during recent invasions.
Proceedings of the Royal Society B: Biological Sciences 01/2011; 278(1702):2-8. · 5.68 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Current predictions on species responses to climate change strongly rely on projecting altered environmental conditions on species distributions. However, it is increasingly acknowledged that climate change also influences species interactions. We review and synthesize literature information on biotic interactions and use it to argue that the abundance of species and the direction of selection during climate change vary depending on how their trophic interactions become disrupted. Plant abundance can be controlled by aboveground and belowground multitrophic level interactions with herbivores, pathogens, symbionts and their enemies. We discuss how these interactions may alter during climate change and the resulting species range shifts. We suggest conceptual analogies between species responses to climate warming and exotic species introduced in new ranges. There are also important differences: the herbivores, pathogens and mutualistic symbionts of range-expanding species and their enemies may co-migrate, and the continuous gene flow under climate warming can make adaptation in the expansion zone of range expanders different from that of cross-continental exotic species. We conclude that under climate change, results of altered species interactions may vary, ranging from species becoming rare to disproportionately abundant. Taking these possibilities into account will provide a new perspective on predicting species distribution under climate change.
Philosophical Transactions of The Royal Society B Biological Sciences 07/2010; 365(1549):2025-34. · 6.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Metabolomics is a fast developing field of comprehensive untargeted chemical analyses. It has many applications and can in principle be used on any organism without prior knowledge of the metabolome or genome. The amount of functional information that is acquired with metabolomics largely depends on whether a metabolome database has been developed for the focal species. Metabolomics is a level downstream from transcriptomics and proteomics and has been widely advertised as a functional genomics and systems biology tool. Indeed, it has been successfully applied to link phenotypes to genotypes in the model plant Arabidopsis thaliana. Metabolomics is also increasingly being used in ecology (ecological metabolomics) and environmental sciences (environmental metabolomics). In ecology, the technique has led to novel insights into the mechanisms of plant resistance to herbivores. Some of the most commonly used analytical metabolomic platforms are briefly discussed in this review, as well as their limitations. We will mainly focus on the application of metabolomics in plant ecology and genetics.
[Show abstract][Hide abstract] ABSTRACT: In this Botanical Briefing we describe how the interactions between plants and their biotic environment can change during range-expansion within a continent and how this may influence plant invasiveness.
We address how mechanisms explaining intercontinental plant invasions by exotics (such as release from enemies) may also apply to climate-warming-induced range-expanding exotics within the same continent. We focus on above-ground and below-ground interactions of plants, enemies and symbionts, on plant defences, and on nutrient cycling.
Range-expansion by plants may result in above-ground and below-ground enemy release. This enemy release can be due to the higher dispersal capacity of plants than of natural enemies. Moreover, lower-latitudinal plants can have higher defence levels than plants from temperate regions, making them better defended against herbivory. In a world that contains fewer enemies, exotic plants will experience less selection pressure to maintain high levels of defensive secondary metabolites. Range-expanders potentially affect ecosystem processes, such as nutrient cycling. These features are quite comparable with what is known of intercontinental invasive exotic plants. However, intracontinental range-expanding plants will have ongoing gene-flow between the newly established populations and the populations in the native range. This is a major difference from intercontinental invasive exotic plants, which become more severely disconnected from their source populations.
Annals of Botany 03/2010; 105(6):843-8. · 3.45 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Exotic plants bring with them traits that evolved elsewhere into their new ranges. These traits may make them unattractive
or even toxic to native herbivores, or vice versa. Here, interactions between two species of specialist (Pieris rapae and P. brassicae) and two species of generalist (Spodoptera exigua and Mamestra brassicae) insect herbivores were examined on two native crucifer species in the Netherlands, Brassica nigra and Sinapis arvensis, and an exotic, Bunias orientalis. Bu. orientalis originates in eastern Europe and western Asia but is now an invasive pest in many countries in central Europe. P. rapae, P. brassicae and S. exigua performed very poorly on Bu. orientalis, with close to 100% of larvae failing to pupate, whereas survival was much higher on the native plants. In choice experiments,
the pierid butterflies preferred to oviposit on the native plants. Alternatively, M. brassicae developed very poorly on the native plants but thrived on Bu. orientalis. Further assays with a German Bu. orientalis population also showed that several specialist and generalist herbivores performed very poorly on this plant, with the exception
of Spodoptera littoralis and M. brassicae. Bu. orientalis produced higher levels of secondary plant compounds (glucosinolates) than B. nigra but not S. arvensis but these do not appear to be important factors for herbivore development. Our results suggest that Bu. orientalis is a potential demographic ‘trap’ for some herbivores, such as pierid butterflies. However, through the effects of an evolutionary
‘lottery’, M. brassicae has found its way through the plant’s chemical ‘minefield’.
-Demographic trap-Glucosinolates-Herbivore-Invasive plant-
[Show abstract][Hide abstract] ABSTRACT: Genetic differentiation among plant populations and adaptation to local environmental conditions are well documented. However, few studies have examined the potential contribution of plant antagonists, such as insect herbivores and pathogens, to the pattern of local adaptation. Here, a reciprocal transplant experiment was set up at three sites across Europe using two common plant species, Holcus lanatus and Plantago lanceolata. The amount of damage by the main above-ground plant antagonists was measured: a rust fungus infecting Holcus and a specialist beetle feeding on Plantago, both in low-density monoculture plots and in competition with interspecific neighbours. Strong genetic differentiation among provenances in the amount of damage by antagonists in both species was found. Local provenances of Holcus had significantly higher amounts of rust infection than foreign provenances, whereas local provenances of Plantago were significantly less damaged by the specialist beetle than the foreign provenances. The presence of surrounding vegetation affected the amount of damage but had little influence on the ranking of plant provenances. The opposite pattern of population differentiation in resistance to local antagonists in the two species suggests that it will be difficult to predict the consequences of plant translocations for interactions with organisms of higher trophic levels.
New Phytologist 01/2008; 180(2):524-33. · 6.74 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Evolutionary theory suggests that divergent natural selection in heterogeneous environments can result in locally adapted plant genotypes. To understand local adaptation it is important to study the ecological factors responsible for divergent selection. At a continental scale, variation in climate can be important while at a local scale soil properties could also play a role. We designed an experiment aimed to disentangle the role of climate and (abiotic and biotic) soil properties in local adaptation of two common plant species. A grass (Holcus lanatus) and a legume (Lotus corniculatus), as well as their local soils, were reciprocally transplanted between three sites across an Atlantic-Continental gradient in Europe and grown in common gardens in either their home soil or foreign soils. Growth and reproductive traits were measured over two growing seasons. In both species, we found significant environmental and genetic effects on most of the growth and reproductive traits and a significant interaction between the two environmental effects of soil and climate. The grass species showed significant home site advantage in most of the fitness components, which indicated adaptation to climate. We found no indication that the grass was adapted to local soil conditions. The legume showed a significant home soil advantage for number of fruits only and thus a weak indication of adaptation to soil and no adaptation to climate. Our results show that the importance of climate and soil factors as drivers of local adaptation is species-dependent. This could be related to differences in interactions between plant species and soil biota.
[Show abstract][Hide abstract] ABSTRACT: 1 Adaptation of plant populations to local environments has been shown in many species but local adaptation is not always apparent and spatial scales of differentiation are not well known. In a reciprocal transplant experiment we tested whether: (i) three widespread grassland species are locally adapted at a European scale; (ii) detection of local adaptation depends on competition with the local plant community; and (iii) local differentiation between neighbouring populations from contrasting habitats can be stronger than differentiation at a European scale. 2 Seeds of Holcus lanatus , Lotus corniculatus and Plantago lanceolata from a Swiss, Czech and UK population were sown in a reciprocal transplant experiment at fields that exhibit environmental conditions similar to the source sites. Seedling emergence, survival, growth and reproduction were recorded for two consecutive years. 3 The effect of competition was tested by comparing individuals in weeded monocultures with plants sown together with species from the local grassland community. To compare large-scale vs. small-scale differentiation, a neighbouring population from a contrasting habitat (wet-dry contrast) was compared with the 'home' and 'foreign' populations. 4 In P. lanceolata and H. lanatus , a significant home-site advantage was detected in fitness-related traits, thus indicating local adaptation. In L. corniculatus , an overall superiority of one provenance was found. 5 The detection of local adaptation depended on competition with the local plant community. In the absence of competition the home-site advantage was underestimated in P. lanceolata and overestimated in H. lanatus . 6 A significant population differentiation between contrasting local habitats was found. In some traits, this small-scale was greater than large-scale differentiation between countries. 7 Our results indicate that local adaptation in real plant communities cannot necessarily be predicted from plants grown in weeded monocultures and that tests on the relationship between fitness and geographical distance have to account for habitat-dependent small-scale differentiation. Considering the strong small-scale differentiation, a local provenance from a different habitat may not be the best choice in ecological restoration if distant populations from a more similar habitat are available.
Clinical and Experimental Allergy 01/2006; · 5.43 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The evolution of the diversity in plant secondary compounds is often thought to be driven by insect herbivores, although there is little empirical evidence for this assumption. To investigate whether generalist insect herbivores could play a role in the evolution of the diversity of related compounds, we examined if (1) related compounds differ in their effects on generalists, (2) there is a synergistic effect among compounds, and (3) effects of related compounds differed among insect species. The effects of pyrrolizidine alkaloids (PAs) were tested on five generalist insect herbivore species of several genera using artificial diets or neutral substrates to which PAs were added. We found evidence that structurally related PAs differed in their effects to the thrips Frankliniella occidentalis, the aphid Myzus persicae, and the locust Locusta migratoria. The individual PAs had no effect on Spodoptera exigua and Mamestra brassicae caterpillars. For S. exigua, we found indications for synergistic deterrent effects of PAs in PA mixtures. The relative effects of PAs differed between insect species. The PA senkirkine had the strongest effect on the thrips, but had no effect at all on the aphids. Our results show that generalist herbivores could potentially play a role in the evolution and maintenance of the diversity of PAs.
Journal of Chemical Ecology 08/2005; 31(7):1493-508. · 2.46 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Hybridization is known to be involved in a number of evolutionary processes, including species formation, and the generation of novel defence characteristics in plants. The genus Senecio of the Asteraceae family is highly speciose and has historically demonstrated significant levels of interspecific hybridization. The evolution of novel chemical defence characteristics may have contributed to the success of Senecio hybrids. Chemical defence against pathogens and herbivores has been studied extensively in the model species Senecio jacobaea, which is thought to hybridize in nature with Senecio aquaticus. Here, we use amplified fragment length polymorphisms (AFLPs) and pyrrolizidine alkaloid (PA) composition to confirm that natural hybridization occurs between S. jacobaea and the closely related species S. aquaticus. AFLPs are also used to estimate the ancestry of hybrids. We also demonstrate that even highly back-crossed hybrids can possess a unique mixture of defence chemicals specific to each of the parental species. This hybrid system may therefore prove to be useful in further studies of the role of hybridization in the evolution of plant defence and resistance.
[Show abstract][Hide abstract] ABSTRACT: Thus far not many studies focussed on how herbivory in one plant part affects plant defence in the other. The effects of root damage and a leaf-feeding herbivore (Mamestra brassicae) on pyrrolizidine alkaloid (PA) levels of Senecio jacobaea were investigated in a controlled environment. Three cloned S. jacobaea genotypes, which differed in PA concentrations, received four treatments: (1) no damage, (2) root damage (removing half of the root system), (3) shoot herbivory by M. brassicae larvae, (4) root damage and shoot herbivory.Shoot herbivory did not significantly affect shoot biomass, while root damage decreased both root and shoot biomass. Shoot herbivory decreased PA concentrations in the roots. Conversely, root damage increased PA concentrations in the roots. Alkaloid concentrations in the shoot showed a weak response to root damage, shoot herbivory had no effect on PA levels in the shoot. The effect of damage on the allocation of PAs to shoot and roots depended on genotype. One genotype allocated more PAs to the damaged site, another genotype did not change allocation and the third genotype allocated more PAs to the shoot if the roots were damaged. Changes in PA composition were observed in one genotype. Shoot herbivory increased erucifoline concentrations in the shoot and decreased concentrations of senecionine in the roots. In conclusion, we have shown that even in an alleged constitutively defended plant, damage of one compartment affects secondary metabolite level in the other.ZusammenfassungBis jetzt konzentrierten sich nicht viele Studien darauf, wie Herbivorie an einem Teil der Pflanze die Pflanzenabwehr in anderen Teilen beeinflusst. Die Auswirkungen von Wurzelbeschädigung und einem blattfressenden Herbivoren (Mamestra brassicae) auf den Gehalt von Pyrrolizidin-Alkaloide in Senecio jacobaea wurden in einer kontrollierten Umwelt untersucht. Drei geklonte S. jacobaea-Genotypen, die sich in den Pyrrolizidin-Alkaloid-Konzentrationen unterschieden, erhielten vier Behandlungen: (1) keine Beschädigung, (2) Wurzelbeschädigung (entfernen des halben Wurzelsystems), (3) Triebfraß durch M. brassicae-Larven und (4) Wurzelbeschädigung und Triebfraß.Der Triebfraß beeinflusste die Triebbiomasse nicht signifikant, während die Wurzelbeschädigung sowohl die Wurzel- als auch die Triebbiomasse verringerte. Der Triebfraß verringerte die Pyrrolizidin-Alkaloid-Konzentration in den Wurzeln. Umgekehrt erhöhte die Wurzelbeschädigung die Pyrrolizidin-Alkaloid-Konzentration in den Wurzeln. Die Alkaloid-Konzentrationen in den Trieben zeigten eine schwache Reaktion auf die Wurzelbeschädigung. Die Triebherbivorie hatte keine Auswirkungen auf die Pyrrolizidin-Alkaloid-Gehalte in den Trieben. Die Auswirkung der Beschädigung auf die Allokation der PAs in Trieben und Wurzeln hing vom Genotyp ab. Ein Genotyp konzentrierte die PAs mehr in den beschädigten Bereichen, ein anderer Genotyp veränderte die Allokation nicht und der dritte Genotyp konzentrierte die PAs mehr in den Trieben, wenn die Wurzeln beschädigt wurden. Veränderungen der PA-Zusammensetzung wurden bei einem Genotypen beobachtet. Der Triebfraß erhöhte die Erucifolin-Konzentrationen im Trieb und die Senecionin-Konzentrationen in den Wurzeln. Zusammenfassend haben wir gezeigt, dass auch in einer vermeintlich grundsätzlich geschützten Pflanze die Herbivorie in einem Bereich die Gehalte sekundärer Metabolite in den anderen beeinflusst.
[Show abstract][Hide abstract] ABSTRACT: We studied the variation in pyrrolizidine alkaloid (PA) patterns of lab-grown vegetative plants of 11 European Senecio jacobaea populations. Plants were classified as jacobine, erucifoline, mixed or senecionine chemotypes based on presence and absence of the PAs jacobine or erucifoline. Due to the presence of jacobine, total PA concentration in jacobine chemotypes was higher than in erucifoline chemotypes. Both relative and absolute concentrations of individual PAs differed between half-sib and clonal families, which showed that variation in PA patterns had a genetic basis. Within most populations relative abundance of PAs varied considerably between individual plants. Most populations consisted either of the jacobine chemotype or of the erucifoline chemotype, sometimes in combination with mixed or senecionine chemotypes.
[Show abstract][Hide abstract] ABSTRACT: In choice experiments with artificial leaves, we tested related pyrrolizidine alkaloids (PAs) for their stimulatory effects on the oviposition of the cinnabar moth, a specialist on the PA-containing plant Senecio jacobaea. The PAs from S. jacobaea that we tested stimulated oviposition. Monocrotaline also stimulated oviposition although this PA is not found in plants of the genus Senecio. The moths preferred ovipositing on filter paper with a PA mixture extracted from S. jacobaea to ovipositing on filter paper with single PAs. Senkirkine, heliotrine, and retrorsine did not stimulate oviposition. The nonactive retrorsine differs only in one OH group to the active senecionine, indicating that small structural differences alter the stimulatory activity of PAs. However, a PA mixture extracted from a nonhost plant, Senecio inaequidens, that consisted of 81% of the nonactive retrorsine did stimulate oviposition. Oviposition preferences between Senecio species seem to be determined by chemical compounds other than PAs.
Journal of Chemical Ecology 07/2003; 29(6):1435-46. · 2.46 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The evolution of the diversity of related secondary metabolites in plants is still poorly understood. It is often thought that the evolution of plant secondary metabolites is driven by specialist insect herbivores and under this coevolutionary model it is expected that related compounds differ in their effects on specialist herbivores. Here we focus on the diversity of pyrrolizidine alkaloids (PAs) in Senecio species and their effects on Tyria jacobaeae, a specialist moth on Senecio jacobaea. As a first step to determine the effects of related PAs on T. jacobaeae, we studied larval performance on plants from 11 S. jacobaea populations and eight Senecio species with different PA compositions. Although the populations of S. jacobaea differed in their PA compositions, there was no difference in larval performance among the populations. Larval performance differed among the eight species but we could not show a correlation with PA composition. Oviposition choice experiments showed a strong correlation between oviposition preference and larval performance on the eight species but oviposition preference did not seem to be correlated with PAs. We found no indications that related PAs differ in effects on the specialist T. jacobaeae; therefore it seems unlikely that T. jacobaeae is a driving force behind the evolution of the diversity of PAs. Alternatively, we propose that the evolution of the diversity of PAs is driven by selection pressure from generalist herbivores or that the diversity of PAs may even be selectively neutral.