Impact of \u3ci\u3eMecinus Janthinus\u3c/i\u3e (Coleoptera: Curculionidae) on the Growth and Reproduction of \u3ci\u3eLinaria Dalmatica\u3c/i\u3e (Scrophulariaceae)

Dalmatian toadflax, Linaria dalmatica (L.) Mill. (Scrophulariaceae), a native to the eastern Mediterranean and Black Sea regions of Europe and Asia, has invaded over one million hectares in the western United States and Canada, in habitats similar to its native range. Once established, the aggressive vegetative growth of the plant allows it to invade undisturbed habitats where it can out-compete most other vegetation, placing native plant communities at risk. Biological control of L. dalmatica with Mecinus janthinus Thomson (Coleoptera: Curculionidae) has shown promise in the field. In both studies reported in this paper, the presence of insect attack reduced L. dalmatica plant growth and reduced plant reproductive potential. In a field sleeve cage study, insect- attacked stems were significantly shorter (18 cm) and had 50-70% fewer fruits and flowers than the control stems at the end of the study period. M. janthinus attacked stems showed little apical growth, fewer fruits and flowers, and lower stem biomass relative to control stems. Similar results were observed in the potted plant study where the influence of the extensive root system of the plant was eliminated. This negative impact by the insect is caused both by adult feeding in the apical portion of the plant and the physical destruction of the plant stem from larvae feeding. The decrease in the insect-attacked stem heights may also have an impact on seed dispersal from the mature reproductive structures. A combination of decreased seed production through M. janthinus biological control and poor seedling competition in the moisture limited sites common to north-central Washington State and other similarly dry habitats may negatively influence L. dalmatica populations more than general models predict

DEB ensis vs. data

Along the Dutch coast (North sea) large quantities of sand are mined in certain locations to supply sand for coastal defence at other locations in order to retain the existing coastline. Without these nourishments of sand the coast would erode and eventually this erosion would lead to an increased risk of flooding. This project provides the opportunity to use measured environmental data to predict growth of Ensis directus using the DEBEnsis model and compare it to measured biotic data on Ensis. Here we report on the findings of the comparison of field data and model estimates and suggest improvements, both in field measurements, experiments and (adjustments to DEB) modelling. For this study, Ensis directus was taken as a model organism, because of its high dominance in biomass in the Dutch coastal zone

Data from: Density dependence, precipitation, and biological control agent herbivory influence landscape-scale dynamics of the invasive Eurasian plant Linaria dalmatica

1. Resource availability and natural enemies are among the most commonly cited mechanisms affecting competitive ability of invasive plants, but their simultaneous effects on plant dynamics are seldom evaluated in the field. Understanding how endogenous and exogenous factors affect invasive plant abundance is essential when evaluating the impact of classical weed biological control agents because misinterpretations of the mechanisms regulating plant demography may bias inference of herbivore impact. 2. In this study we report results from a citizen-science monitoring program initiated to evaluate the effects of the stem–mining weevil Mecinus janthiniformis on the Eurasian invasive weed Dalmatian toadflax Linaria dalmatica. We used a discrete model of population dynamics to evaluate the relative importance of endogenous and exogenous processes affecting changes in ramet density of L. dalmatica at 38 spatially replicated sites in Idaho, USA. 3. Analysis of per capita population growth rates based on ramet density indicated the presence of direct density dependence, which was most likely due to intraspecific competition. Changes in ramet density were not influenced by the abundance of the resident plant community. 4. Precipitation had a strong, positive effect on ramet density of L. dalmatica while the abundance of M. janthiniformis had a weaker, but significant, negative effect after accounting for the density dependence. There was no support for an interactive effect between precipitation and herbivory. 5. Synthesis and applications. Our results indicate that biological control is an important factor affecting weed population growth at the landscape scale, but they also suggest that biological control impact may vary considerably on local infestations due to site-specific variation in rainfall and density-dependent processes. We recommend that invasive plant management strategies integrate precipitation and biological control agent monitoring into their programs to estimate expected biological control efficacy. Alternative control methods should be prioritized in areas where herbivore impact is expected to be low

Monitoring the in vivo redox state of plant mitochondria: effect of respiratory inhibitors, abiotic stress and assessment of recovery from oxidative challenge.

In animals, the impact of ROS production by mitochondria on cell physiology, death, disease and ageing is well recognised. In photosynthetic organisms such as higher plants, however, the chloroplast and peroxisomes are the major sources of ROS during normal metabolism and the importance of mitochondria in oxidative stress and redox signalling is less well established. To address this, the in vivo oxidation state of a mitochondrially-targeted redox-sensitive GFP (mt-roGFP2) was investigated in Arabidopsis leaves. Classical ROS-generating inhibitors of mitochondrial electron transport (rotenone, antimycin A and SHAM) had no effect on mt-roGFP oxidation when used singly, but combined inhibition of complex III and alternative oxidase by antimycin A and SHAM did cause significant oxidation. Inhibitors of complex IV and aconitase also caused oxidation of mt-roGFP2. This oxidation was not apparent in the cytosol whereas antimycin A+SHAM also caused oxidation of cytosolic roGFP2. Menadione had a much greater effect than the inhibitors, causing nearly complete oxidation of roGFP2 in both mitochondria and cytosol. A range of severe abiotic stress treatments (heat, salt, and heavy metal stress) led to oxidation of mt-roGFP2 while hyperosmotic stress had no effect and low temperature caused a slight but significant decrease in oxidation. Similar changes were observed for cytosolic roGFP2. Finally, the recovery of oxidation state of roGFP in mitochondria after oxidation by H(2)O(2) treatment was dramatically slower than that of either the cytosol or chloroplast. Together, the results highlight the sensitivity of the mitochondrion to redox perturbation and suggest a potential role in sensing and signalling cellular redox challenge

field sampling data

This file includes the field sampling data of Linaria dalmatica, its biological control agent Mecinus janthiniformis, and resident plant community cover and environmental data at 38 sites in Idaho USA from 2007 to 2011

Genetic diversity and structure of Crupina vulgaris (common crupina): a noxious rangeland weed of the western United States

Common crupina (Crupina vulgaris) is a federal noxious weed in the western USA that is currently the target of a classical biological control programme using the fungus Ramularia crupinae. We first identified and determined the location of populations of the two varieties of common crupina in the western United States and assessed the pattern of genetic diversity and structure of these populations. We found seven AFLP (Amplified Fragment Length Polymorphism) genotypes for 326 plants in 17 populations. AFLP genotypes correlated with two taxa, either C. vulgaris var. vulgaris or C. vulgaris var. brachypappa. This annual species is outcrossing, but relies on selfing when pollination does not occur, which may explain why less than 1% of the genetic variation is within populations. We found strong population genetic structuring and can typically predict genotype or variety for a given location. Researchers and managers will be able to predict and survey for differential efficacy of R. crupinae on the different genotypes and varieties during initial biological control field releases, thereby increasing the likelihood of successful biocontrol establishment and impact

Potential for biological control of Phragmites australis in North America

Phragmites australis is a cosmopolitan plant that is undergoing a population explosion in freshwater and tidal wetlands on the east coast of North America. The rapid spread of P. australis in recent years and the virtual absence of native herbivores feeding on P. australis have led wetland ecologists to believe that either the species or more aggressive genotypes were introduced. The historical record of the occurrence of P. australis in North America and the scarcity of indigenous herbivores provide conflicting evidence for the status of the species as native or introduced. A comparison of P. australis populations from North America and other continents using advanced genetic techniques is underway to help determine the status of current and historic North American genotypes. Literature and field surveys reveal that of the 26 herbivores currently known to feed on P. australis in North America (many accidentally introduced during the last decade), only 5 are native. In Europe, over 170 herbivore species have been reported feeding on P. australis, some causing significant damage. Of these herbivores, rhizome-feeding species with considerable negative impact on P. australis performance include the lepidopterans Rhizedra lutosa (already present in North America), Phragmataecia castaneae, Chilo phragmitella, and Schoenobius gigantella. Stemboring moths in the genera Archanara and Arenostola and the chloropid fly Platycephala planifrons can have large detrimental impacts on P. australis in Europe and should be evaluated for their potential as biological control agents. In addition, the interaction of potential control agents with accidentally introduced P. australis herbivores needs to be evaluated in North America. Regardless of the results of the genetic analyses, any decision to introduce additional host-specific herbivores in an attempt to control P. australis will require considerable dialogue. This decision needs to weigh the current negative ecological and economic impacts of P. australis and the benefits and risks of a biological control program. © 2001 Elsevier Science

Propagule Pressure, Genetic Structure, and Geographic Origins of \u3cem\u3eChondrilla juncea\u3c/em\u3e (Asteraceae): An Apomictic Invader on Three Continents

Premise of the study: Assessing propagule pressure and geographic origins of invasive species provides insight into the invasion process. Rush skeletonweed (Chondrilla juncea; Asteraceae) is an apomictic, perennial plant that is invasive in Australia, South America (Argentina), and North America (Canada and the United States). This study comprehensively compares propagule pressure and geographic structure of genotypes to improve our understanding of a clonal invasion and enhance management strategies. Methods: We analyzed 1056 native range plants from Eurasia and 1156 plants from three invaded continents using amplified fragment length polymorphism (AFLP) techniques. We used measures of diversity (Simpson’s D) and evenness (E), analysis of molecular variance, and Mantel tests to compare invasions, and genotype similarity to determine origins of invasive genotypes. Key results: We found 682 unique genotypes in the native range, but only 13 in the invaded regions. Each invaded region contained distinct AFLP genotypes, suggesting independent introduction events, probably with different geographic origins. Relatively low propagule pressure was associated with each introduction around the globe, but levels of among-population variation differed. We found exact AFLP genotype matches between the native and invaded ranges for five of the 13 invasive genotypes. Conclusions: Invasion dynamics can vary across invaded ranges within a species. Intensive sampling for molecular analyses can provide insight for understanding intraspecific invasion dynamics, which can hold significance for the management of plant species, especially by finding origins and distributions of invasive genotypes for classical biological control efforts