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A number of invasive plant species, such as Alternanthera philoxeroides, have been documented to be able to accumulate trace metal elements in their tissues. Since metal accumulation in plants can serve as a defence against herbivores, we hypothesized that metal pollution will increase herbivore resistance of metal‐accumulating invasive plant species and such a benefit will grant them a competitive advantage over local co‐occurring plants. In this study, we compared the differences in plant growth and herbivore feeding preference between A. philoxeroides and its native congener Alternanthera sessilis in single and mixed cultures with and without soil cadmium (Cd) pollution. The results showed that A. philoxeroides plants were more tolerant to Cd stress and accumulated more Cd in the leaves than A. sessilis. Cd exposure increased the resistance of A. philoxeroides against a specialist and a generalist herbivore compared with A. sessilis. Competition experiments indicated that Cd stress largely increased the competitive advantage of A. philoxeroides over A. sessilis with or without herbivore pressures. The differences in herbivore resistance between the two plant species under soil Cd stress are most likely due to the deterring effect of Cd accumulation and Cd‐enhanced mechanical defences rather than changes in leaf specialized metabolites. Summary Statement: Soil cadmium pollution largely increased the resistance of the invasive weed A. philoxeroides against both a generalist and a specialist herbivore, giving it a competitive advantage over the local competitor A. sessilis regardless of the presence or absence of herbivore pressure. [ABSTRACT FROM AUTHOR]

Plants produce many secondary metabolites showing considerable inter‐ and intraspecific diversity of concentration and composition as a strategy to cope with environmental stresses. The evolution of plant defenses against herbivores and pathogens can be unraveled by understanding the mechanisms underlying chemical diversity. Pyrrolizidine alkaloids are a class of secondary metabolites with high diversity. We performed a qualitative and quantitative analysis of 80 pyrrolizidine alkaloids with liquid chromatography‐tandem mass spectrometry of leaves from 17 Jacobaea species including one to three populations per species with 4–10 individuals per population grown under controlled conditions in a climate chamber. We observed large inter‐ and intraspecific variation in pyrrolizidine alkaloid concentration and composition, which were both species‐specific. Furthermore, we sequenced 11 plastid and three nuclear regions to reconstruct the phylogeny of the 17 Jacobaea species. Ancestral state reconstruction at the species level showed mainly random distributions of individual pyrrolizidine alkaloids. We found little evidence for phylogenetic signals, as nine out of 80 pyrrolizidine alkaloids showed a significant phylogenetic signal for Pagel's λ statistics only, whereas no significance was detected for Blomberg's K measure. We speculate that this high pyrrolizidine alkaloid diversity is the result of the upregulation and downregulation of specific pyrrolizidine alkaloids depending on ecological needs rather than gains and losses of particular pyrrolizidine alkaloid biosynthesis genes during evolution. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Habitat fragmentation weakens the connection between populations and is accompanied with isolation by distance ( IBD) and local adaptation (isolation by adaptation, IBA), both leading to genetic divergence between populations. To understand the evolutionary potential of a population and to formulate proper conservation strategies, information on the roles of IBD and IBA in driving population divergence is critical. The putative ancestor of Asian cultivated rice ( Oryza sativa) is endangered in China due to habitat loss and fragmentation. We investigated the genetic variation in 11 Chinese Oryza rufipogon populations using 79 microsatellite loci to infer the effects of habitat fragmentation, IBD and IBA on genetic structure. Historical and current gene flows were found to be rare ( mh = 0.0002-0.0013, mc = 0.007-0.029), indicating IBD and resulting in a high level of population divergence ( FST = 0.343). High within-population genetic variation ( HE = 0.377-0.515), relatively large effective population sizes ( N e = 96-158), absence of bottlenecks and limited gene flow were found, demonstrating little impact of recent habitat fragmentation on these populations. Eleven gene-linked microsatellite loci were identified as outliers, indicating local adaptation. Hierarchical AMOVA and partial Mantel tests indicated that population divergence of Chinese O. rufipogon was significantly correlated with environmental factors, especially habitat temperature. Common garden trials detected a significant adaptive population divergence associated with latitude. Collectively, these findings imply that IBD due to historical rather than recent fragmentation, followed by local adaptation, has driven population divergence in O. rufipogon. [ABSTRACT FROM AUTHOR]

The Late Quaternary was a time of rapid climatic oscillations and drastic environmental changes. In general, species can respond to such changes by behavioral accommodation, distributional shifts, ecophenotypic modifications (nongenetic), evolution (genetic) or ultimately face local extinction. How those responses manifested in the past is essential for properly predicting future ones especially as the current warm phase is further intensified by rising levels of atmospheric carbon dioxide. Here, we use ancient DNA ( aDNA) and morphological features in combination with ecological niche modeling ( ENM) to investigate genetic and nongenetic responses of Central European Palearctic shrews to past climatic change. We show that a giant form of shrew, previously described as an extinct Pleistocene Sorex species, represents a large ecomorph of the common shrew ( Sorex araneus), which was replaced by populations from a different gene-pool and with different morphology after the Pleistocene Holocene transition. We also report the presence of the cold-adapted tundra shrew ( S. tundrensis) in Central Europe. This species is currently restricted to Siberia and was hitherto unknown as an element of the Pleistocene fauna of Europe. Finally, we show that there is no clear correlation between climatic oscillations within the last 50 000 years and body size in shrews and conclude that a special nonanalogous situation with regard to biodiversity and food supply in the Late Glacial may have caused the observed large body size. [ABSTRACT FROM AUTHOR]

According to the IPCC, the global average temperature is likely to increase by 1.4-5.8 °C over the period from 1990 to 2100. In Polar regions, the magnitude of such climatic changes is even larger than in temperate and tropical biomes. This amplified response is particularly worrisome given that the so-far moderate warming is already impacting Arctic ecosystems. Predicting species responses to rapid warming in the near future can be informed by investigating past responses, as, like the rest of the planet, the Arctic experienced recurrent cycles of temperature increase and decrease (glacial-interglacial changes) in the past. In this study, we compare the response of two important prey species of the Arctic ecosystem, the collared lemming and the narrow-skulled vole, to Late Quaternary climate change. Using ancient DNA and Ecological Niche Modeling ( ENM), we show that the two species, which occupy similar, but not identical ecological niches, show markedly different responses to climatic and environmental changes within broadly similar habitats. We empirically demonstrate, utilizing coalescent model-testing approaches, that collared lemming populations decreased substantially after the Last Glacial Maximum; a result consistent with distributional loss over the same period based on ENM results. Given this strong association, we projected the current niche onto future climate conditions based on IPCC 4.0 scenarios, and forecast accelerating loss of habitat along southern range boundaries with likely associated demographic consequences. Narrow-skulled vole distribution and demography, by contrast, was only moderately impacted by past climatic changes, but predicted future changes may begin to affect their current western range boundaries. Our work, founded on multiple lines of evidence suggests a future of rapidly geographically shifting Arctic small mammal prey communities, some of whom are on the edge of existence, and whose fate may have ramifications for the whole Arctic food web and ecosystem. [ABSTRACT FROM AUTHOR]

Summary [ABSTRACT FROM AUTHOR]

Introduction - Pyrrolizidine alkaloids (PAs) serve an important function in plant defence. Objective - To compare different extraction methods and detection techniques, namely gas chromatography with nitrogen phosphorus detection (GC-NPD) and liquid chromatography tandem mass spectrometry (LC-MS/MS) with quadrupole analysers for analysing PAs in Jacobaea vulgaris. Methodology - Both formic acid and sulfuric acid were tested for PA extraction from dry plant material. For GC-NPD, reduction is required to transform PA N-oxides into tertiary amines. Zinc and sodium metabisulfite were compared as reducing agents. Results - The lowest PA concentration measured with GC-NPD was approximately 0.03 mg/g and with LC-MS/MS 0.002 mg/g. The detection of major PAs by both techniques was comparable but a number of minor PAs were not detected by GC-NPD. With the LC-MS/MS procedure higher concentrations were found in plant extracts, indicating that losses may have occurred during the sample preparation for the GC-NPD method. Zinc proved a more effective reducing agent than sodium metabisulfite. The sample preparation for LC-MS/MS analysis using formic acid extraction without any reduction and purification steps is far less complex and less time consuming compared to GC-NPD analysis with sulfuric acid extraction and PA N-oxide reduction with zinc and purification. Conclusions - In terms of sensitivity and discrimination, formic acid extraction in combination with LC-MS/MS detection is the method of choice for analysing PAs (both free and N-oxides forms) in plant material. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Natural hybridization is increasingly recognized as an important process for the ecology and evolution of natural plant populations and species. There is a great need to initiate more studies based on natural populations in order to elucidate the possible role of hybrids in nature. The reproductive success of early generation hybrids can make or break hybrid lineages and may determine the genetic structure of hybrid swarms or the potential for gene flow through future generations, but studies of hybrid reproductive success are lacking. Here we measured components of male and female reproductive success in Senecio jacobaea and S. aquaticus (Asteraceae) species and F1 hybrids between these species under laboratory conditions, and we measured reproductive output from crosses producing F1, F2, and backcross (BC) generation hybrids. F1 hybrids were readily produced, and on average, the success of crosses producing subsequent generations (F2, BC) decreased (though remained substantial), but the success of crosses was highly dependent on the genotypes involved. Also, F1 hybrids were bigger, produced more flowers, and therefore produced more pollen than parental plants. Finally, crosses between parents were asymmetrical, such that S. aquaticus produced more and larger F1 seeds than did S. jacobaea. [ABSTRACT FROM AUTHOR]

• Here we tested two possible nonexclusive explanations for the maintenance of a hybrid swarm betweenSenecio jacobaeaandSenecio aquaticus; first, that genotype-by-environment interactions involving water and nutrient clines are involved in hybrid fitness, and second, heterosis in early hybrid generations may provide an initial hybrid advantage that contributes to hybrid persistence.• In three climate chamber studies, fitness and root growth were measured for parental species and natural and artificialF1 hybrids, in order to determine whether hybrids occur in habitats where they are more fit than parental species.• Natural hybrids, which are generally back-crossed toS. jacobaea, always equaledS. jacobaeain growth characteristics. Maternal effects played a role in the fitness ofF1 hybrids, with offspring fromS. jacobaeamothers exhibiting higher fitness than those fromS. aquaticusmothers, and compared with parental species and natural hybrids.• Natural hybrids are not distributed in zones where they are most fit with respect to nutrient and water regimes. Superior fitness of early generation hybrids may contribute to hybrid swarm stability.New Phytologist(2005)doi: 10.1111/j.1469-8137.2005.01370.x© New Phytologist(2005) [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We measured the relationship between selfing rates and flower number in an experimental population of bumblebee pollinated Cynoglossum officinale, with plants differing in flower number. Results were compared with the prediction of a model based on pollen dynamics and pollinator behaviour. The selfing rate, as measured by multilocus oligonucleotide DNA fingerprinting, increased with flower number and ranged from 0% to 70%. Flowers on large plants received an equal number of visits from bumblebees as flowers on small plants. On large plants more flowers in a row were visited, inducing geitonogamy. The overall relationship between selfing rate and number of flowers can be explained by pollen dynamics and pollinator behaviour without invoking postpollination processes such as differential pollen tube growth and abortion. [ABSTRACT FROM AUTHOR]