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Rapid evolution of weed biological control agents (BCAs) to new biotic and abiotic conditions is poorly understood and so far only little considered both in pre-release and post-release studies, despite potential major negative or positive implications for risks of nontargeted attacks or for colonizing yet unsuitable habitats, respectively. Provision of genetic resources, such as assembled and annotated genomes, is essential to assess potential adaptive processes by identifying underlying genetic mechanisms. Here, we provide the first sequenced genome of a phytophagous insect used as a BCA, that is, the leaf beetle Ophraella communa , a promising BCA of common ragweed, recently and accidentally introduced into Europe. A total 33.98 Gb of raw DNA sequences, representing ∼43-fold coverage, were obtained using the PacBio SMRT-Cell sequencing approach. Among the five different assemblers tested, the SMARTdenovo assembly displaying the best scores was then corrected with Illumina short reads. A final genome of 774 Mb containing 7,003 scaffolds was obtained. The reliability of the final assembly was then assessed by benchmarking universal single-copy orthologous genes (>96.0% of the 1,658 expected insect genes) and by remapping tests of Illumina short reads (average of 98.6 ± 0.7% without filtering). The number of protein-coding genes of 75,642, representing 82% of the published antennal transcriptome, and the phylogenetic analyses based on 825 orthologous genes placing O. communa in the monophyletic group of Chrysomelidae, confirm the relevance of our genome assembly. Overall, the genome provides a valuable resource for studying potential risks and benefits of this BCA facing environmental novelties. [ABSTRACT FROM AUTHOR]

A correction is presented for the article "Can enemy release explain the invasion success of the diploid Leucanthemum vulgare in North America?" that was published in the previous issue of the periodical.

Plant invasion is the outcome of complicated interactions of both biotic and abiotic environments (i.e. eutrophication and human-induced propagules) under global anthropogenic change. Here, we want to know why some alien clonal plant species become invasive and others do not in the introduced range with variations of both abiotic and biotic environments under global anthropogenic change. We selected three invasive alien and three co-occurring, non-invasive alien clonal plant species in China, and grew them under the constant or variable soil nutrient environments in a native community with low or high vegetative propagule pressure (i.e. simulating pressure of anthropogenic alien propagules). Invasive alien species produced more biomass than non-invasives. Interestingly, invasive species benefited significantly greater from high propagule pressure than non-invasives. Biomass and evenness of native communities were greater with non-invasive than with invasive target species. Invasive plants showed a greater increase of leaf N and decrease of leaf C: N ratio when subject to variable nutrients in comparison to constant nutrients than non-invasives. The negative effects of variable nutrients on evenness of native communities were significantly greater under invasive than non-invasive target species. Moreover, biomass of native communities was significantly negatively related to biomass of invasive species. Variable nutrients significantly promoted the negative biomass relationship between non-invasive species and native communities under high propagule pressure and the negative biomass-evenness relationship between invasive species and native communities. Our study suggests that soil nutrient variability and vegetative propagule pressure influence the growth and leaf C and N uptake of alien clonal plant species in native experimental communities, especially under the high propagule pressure and nutrient variability. Invasive alien clonal species have higher performance and advantages over non-invasives. Future studies should also test the mechanisms that invasive and non-invasive or native plants differ in native communities of native or introduced ranges in the field. Unlabelled Image • Plant invasion is the outcome of interactions of biotic and abiotic environmental factors under global anthropogenic change. • We tested the responses of invasive and non-invasive clonal plants to variations of soil nutrient and propagule pressure. • Invasive alien clonal species had greater increase of leaf N than non-invasives in the variable nutrient treatment. • Invasive alien clonal species have higher performance and advantages over non-invasives in variable environments. [ABSTRACT FROM AUTHOR]

Outcomes of weed biological control projects are highly variable, but a mechanistic understanding of how top-down and bottom-up factors influence the success of weed biological control is often lacking. We grew Rumex obtusifolius, the most prominent native weed in European grasslands, in the presence and absence of competition from the grass Lolium perenne and subjected it to herbivory through targeted inoculation with root-boring Pyropteron spp. To explore whether the interactive effects of competition and inundative biological control were size-dependent, R. obtusifolius was planted covering a large range of plant sizes found in managed grasslands. Overall, competition from the grass sward reduced aboveground biomass and final root mass of R. obtusifolius about 62- and 7.5-fold, respectively, and increased root decay of R. obtusifolius from 14 to 58%. Herbivory alone increased only root decay. However, grass competition significantly enhanced infestation by Pyropteron spp. and, as a consequence, enhanced the impact of herbivory on aboveground biomass and final root mass. The synergistic effect was so strong that R. obtusifolius plants grown from initially smaller roots did no longer develop. Inoculating R. obtusifolius with Pyropteron species in grasslands should be further pursued as a promising inundative biological control strategy in the weed's native range. [ABSTRACT FROM AUTHOR]

Parthenium weed (Parthenium hysterophorus L.) is a noxious weed and a flagship invasive that has been spreading throughout Israel and the Palestinian Authority since 1980. In other regions affected by this invader, parthenium weed has been managed through classical biological control releases of Epiblema strenuana, a stem-galling tortricid moth native to North America. More recently, a congeneric moth, Epiblema minutana has been identified from Israel. To better understand the implications of E. minutana for controlling parthenium weed, we investigated the spread of E. minutana within Israel and the Palestinian Authority from 2012 to 2019 and explored its host range. We used a series of no-choice experiments in field cages to evaluate damage on naturalized Ambrosia spp., Xanthium italicum and parthenium weed as well as potential non-target, commercial cultivars of sunflower (Helianthus annuus L.) and niger (Guizotia abysinnica (L. f.) Cassini). We also evaluated damage in the field, where we found substantial gall formation on Ambrosia spp., but none on P. hysterophorus or other genera. The geographical distribution increased from an estimated 424 km² in 2017 to 1671 km² in 2019. While E. minutana shows promise as a biological control agent of Ambrosia spp. and does not attack the oil crops sunflower and niger, it is not a suitable biological control agent of parthenium weed. [ABSTRACT FROM AUTHOR]

Climate change may affect plant–herbivore interactions and their associated ecosystem functions. In an experimental evolution approach, we subjected replicated populations of the invasive Ambrosia artemisiifolia to a combination of simulated warming and herbivory by a potential biocontrol beetle. We tracked genomic and metabolomic changes across generations in field populations and assessed plant offspring phenotypes in a common environment. Using an integrated Bayesian model, we show that increased offspring biomass in response to warming arose through changes in the genetic composition of populations. In contrast, increased resistance to herbivory arose through a shift in plant metabolomic profiles without genetic changes, most likely by transgenerational induction of defences. Importantly, while increased resistance was costly at ambient temperatures, warming removed this constraint and favoured both vigorous and better defended plants under biocontrol. Climate warming may thus decrease biocontrol efficiency and promote Ambrosia invasion, with potentially serious economic and health consequences. [ABSTRACT FROM AUTHOR]

Weeds can originate from adjacent habitats, dispersing naturally from non‐crop habitats as well as brought in from other crop fields by machinery or as contaminants of crop seeds. This constant dispersal may homogenise populations and transmit resistance genes. In this study, we examined (a) the genetic variation in quantitative traits and (b) the level of resistance to two widely used herbicides, amidosulfuron + iodosulfuron‐methyl‐sodium and florasulam + 2,4‐D, in eight population pairs of Sinapis arvensis from crop and adjacent non‐crop habitats across eight regions in Northern Algeria. Our quantitative genetic approach on phenotypic and phenological data of plants grown under controlled conditions from seeds of these populations showed similar levels of within‐population genetic variation and no genetic differentiation in quantitative traits between the two habitat types. This points to an important exchange of S. arvensis seeds and/or pollen between the two habitat types, but not among crop fields at the regional scale, as we found a strong regional effect for most of the plant traits for both habitat types that correlated with longitudinal temperature and precipitation gradients. We also found an absence of resistance against the two herbicides at a detection level of 10%. Florasulam + 2,4‐D showed a higher level and speed of phytotoxicity compared to amidosulfuron + iodosulfuron‐methyl‐sodium. Given our findings, we propose measures for more efficient management of S. arvensis, including minimisation of seed dispersal during transport of straw balls, crop rotation to avoid the build‐up of herbicide resistance, and management of populations in the close vicinity of crop fields. [ABSTRACT FROM AUTHOR]

Endozoochory is known as an important mechanism for the spread of weeds. We carried out experiments to assess the fate of seeds of several weed species (Convolvulus arvensis, Cuscuta campestris, Rumex crispus, Hordeum spontaneum and Sorghum halepense) after passing through the gut of sheep and goat. Eighteen animals of both sheep and goat received diet mixed with seeds of the weed species or control with only wheat bran (five weed species + control × three replications). Results showed that a higher proportion of seeds were missing after passage through the sheep gut than in goats. In goats, a greater proportion of seeds were dead after passage, but the number of seeds collected from dung was also greater. Weed species differed, with the highest seed recovery and viability in Cuscuta campestris. Based on time of seed passages through the animal gut estimated for the different weed species, we recommend that sheep should be kept in a corral for 96 hr to minimise seed transportation via their faeces. For goats, if R. crispus and C. arvensis seeds could be excluded from the diet, then maintaining them for 96 hr in an animal stall would ensure little seed transportation via dung, but we found R. crispus and C. arvensis seeds to be present and viable in goat dung even 120 hr after feeding. Very large numbers of viable seeds can be found in goat and sheep dung, so the use of rotted manure is highly recommended to avoid transportation of viable seeds via manure fertilisers. [ABSTRACT FROM AUTHOR]

Predicting plant distributions under climate change is constrained by our limited understanding of potential rapid adaptive evolution. In an experimental evolution study with the invasive common ragweed (Ambrosia artemisiifolia L.) we subjected replicated populations of the same initial genetic composition to simulated climate warming. Pooled DNA sequencing of parental and offspring populations showed that warming populations experienced greater genetic divergence from their parents, than control populations. In a common environment, offspring from warming populations showed more convergent phenotypes in seven out of nine plant traits, with later flowering and larger biomass, than plants from control populations. For both traits, we also found a significantly higher ratio of phenotypic to genetic differentiation across generations for warming than for control populations, indicating stronger response to selection under warming conditions. As a measure for evolutionary rate, the phenotypic and sequence divergence between generations were assessed using the Haldane metric. Our approach combining comparisons between generations (allochronic) and between treatments (synchronic) in an experimental evolutionary field study, and linking population genomic data with phenotyping analyses provided a powerful test to detect rapid responses to selection. Our findings demonstrate that ragweed populations can rapidly evolve in response to climate change within a single generation. Short‐term evolutionary responses to climate change may aggravate the impact of some plant invaders in the future and should be considered when making predictions about future distributions and impacts of plant invaders. [ABSTRACT FROM AUTHOR]

One of the biggest challenges in classical biological control of invasive weeds is predicting the likelihood of success. Ambrosia artemisiifolia, a North American plant species that has become invasive in Europe, causes economic losses due to health problems resulting from its huge amount of highly allergenic pollen and as a weed to agricultural crops resulting from high seed densities. Here we assessed whether the pollen and seed output of the annual A. artemisiifolia (at the end of the season) is related to in-season abundance of, or damage by, the accidentally introduced biological control agent Ophraella communa. We monitored the growth and leaf damage of individually labelled A. artemisiifolia plants at four locations in Northern Italy and recorded abundance of different O. communa life stages at regular intervals. We found that the in-season level of leaf damage by O. communa consistently helped to explain seed production in combination with plant volume and site throughout the season. Feeding damage, plant volume and site also explained pollen production by A. artemisiifolia six weeks before male flower formation. At three out of four sites, plants with more than 10% leaf damage in mid-June or early July had a very low likelihood of seed formation. Leaf damage proved to be a better explanatory variable than O. communa abundance. Our results suggest that the monitoring of the in-season leaf damage can help to project the local impact of O. communa on A. artemisiifolia at the end of the season and thus inform management regarding the needs for additional measures to control this prominent invader. [ABSTRACT FROM AUTHOR]

Common ragweed (Ambrosia artemisiifolia L.) is a widely distributed and harmful invasive plant that is an important source of highly allergenic pollen grains and a prominent crop weed. As a result, ragweed causes huge costs to both human health and agriculture in affected areas. Efficient mitigation requires accurate mapping of ragweed densities that, until now, has not been achieved accurately for the whole of Europe. Here we provide two inventories of common ragweed abundances with grid resolutions of 1 km and 10 km. These "top-down" inventories integrate pollen data from 349 stations in Europe with habitat and landscape management information, derived from land cover data and expert knowledge. This allows us to cover areas where surface observations are missing. Model results were validated using "bottom–up" data of common ragweed in Austria and Serbia. Results show high agreement between the two analytical methods. The inventory shows that areas with the lowest ragweed abundances are found in Northern and Southern European countries and the highest abundances are in parts of Russia, parts of Ukraine and the Pannonian Plain. Smaller hotspots are found in Northern Italy, the Rhône Valley in France and in Turkey. The top-down approach is based on a new approach that allows for cross-continental studies and is applicable to other anemophilous species. Due to its simplicity, it can be used to investigate such species that are difficult and costly to identify at larger scales using traditional vegetation surveys or remote sensing. The final inventory is open source and available as a georeferenced tif file, allowing for multiple usages, reducing costs for health services and agriculture through well-targeted management interventions. Unlabelled Image • An approach for distribution modelling of anemophilous species using pollen data • Validated against plant observations of ragweed and cross validation • European-wide coverage revealing many new invaded regions. • 1 km & 10 km inventories covering all of Europe. [ABSTRACT FROM AUTHOR]

Premise of the Study: Genome duplication is associated with multiple changes at different levels, including interactions with pollinators and herbivores. Yet little is known whether polyploidy may also shape belowground interactions. Methods: To elucidate potential ploidy‐specific interactions with arbuscular mycorrhizal fungi (AMF), we compared mycorrhizal colonization and assembly of AMF communities in roots of diploid and tetraploid Centaurea stoebe s.l. (Asteraceae) co‐occurring in a Central European population. In a follow‐up greenhouse experiment, we tested inter‐cytotype differences in mycorrhizal growth response by combining ploidy, substrate, and inoculation with native AMF in a full‐factorial design. Key Results: All sampled plants were highly colonized by AMF, with the Glomeraceae predominating. AMF‐community composition revealed by 454‐pyrosequencing reflected the spatial distribution of the hosts, but not their ploidy level or soil characteristics. In the greenhouse experiment, the tetraploids produced more shoot biomass than the diploids did when grown in a more fertile substrate, while no inter‐cytotype differences were found in a less fertile substrate. AMF inoculation significantly reduced plant growth and improved P uptake, but its effects did not differ between the cytotypes. Conclusions: The results do not support our hypotheses that the cytotype structure in a mixed‐ploidy population of C. stoebe is mirrored in AMF‐community composition and that ploidy‐specific fungal communities contribute to cytotype co‐existence. Causes and implications of the observed negative growth response to AMF are discussed. [ABSTRACT FROM AUTHOR]

Classical biological control is an important means of managing the increasing threat of invasive plants. It constitutes the introduction of natural enemies from the native range of the target plant into the invaded area. This method may be the only cost-effective solution to control the rapidly expanding common ragweed, Ambrosia artemisiifolia, in non-crop habitats in Europe. Therefore, candidate biocontrol agents urgently need to be assessed for their suitability for ragweed control in Europe. A previous literature review prioritized the host-specific leaf beetle Ophraella slobodkini as a candidate agent for ragweed control in Europe, whereas it rejected its oligophagous congener O. communa. Meanwhile, O. communa was accidentally introduced and became established south of the European Alps, and we show here that it is expanding its European range. We then present a short version of the traditional pre-release risk-benefit assessment for these two candidate agents to facilitate fast decision-making about further research efforts. We selected two complementary tests that can be conducted relatively rapidly and inform about essential risks and benefits. We conducted a comparative no-choice juvenile performance assay using leaves of ragweed and sunflower, the most important non-target plant, in Petri dishes in climatic conditions similar to that in the current European range of O. communa. This informs on the fundamental host range and potential for increasing abundance on these host plants. The results confirm that O. slobodkini does not survive on, and is hence unlikely to cause severe damage to sunflower, while O. communa can survive but develops more slowly on sunflower than on ragweed. In parallel, our species distribution models predict no suitable area for the establishment of O. slobodkini in Europe, while O. communa is likely to expand its current range to include a maximum of 18% of the European ragweed distribution. Based on this early assessment, the prioritization and further assessment of O. slobodkini seem unwarranted whereas the results urgently advocate further risk-benefit analysis of O. communa. Having revealed that most of the European area colonized by ragweed is unlikely to be suitable for these species of Ophraella we suggest the use of such relatively short and cheap preliminary assessment to prioritise other candidate agents or strains for these areas. [ABSTRACT FROM AUTHOR]

Climate change effects on crop production are of high concern in arid regions that are suffering from increased drought. We parameterized the APSIM-Wheat (The Agricultural Production Systems sIMulator) model using data of two field experiments conducted in 2017 at two locations (Karaj and Khomein) in Iran differing in temperature and precipitation. The experiment was a split plot with four replications. Main plots measured 17 m by 5 m with four irrigation regimes of full irrigation (I 1), deficit irrigation from grain filling (I 2,), from beginning of flowering (I 2), and during the whole growth period (I 4). Sub-plots measured 3 m by 5 m with nitrogen (N) levels of 200 (N 1), 100 (N 2) and 50 (N 3) kg/ha of urea (46 % N). N 1 resulted in highest wheat biomass, grain yield, harvesting index and leaf area index (LAI), with the differences between the N levels decreasing with increasing water deficit period. The model was parameterized for both localities with data of treatment I 1 +N 1 , then evaluated over 11 combinations of irrigation and nitrogen rates. Root mean square of errors (RMSE) were 0.3 and 0.15 t/ha for wheat biomass and grain yield, and 3.54 days for wheat phenology and 0.28 for LAI simulations. After model calibration, we ran the model with 20 general circulation models (GCMs) under two representative concentration pathways (RCP 4.5 and RCP 8.5), and crop production was projected for three future time periods. For 2010–2039, models simulate a marginal increase in wheat yield, however, with 2040–2069 and 2070–2099, most models simulate a decreased growing season length and grain yield. Nitrogen application was found to decrease the drought impact. Additionally, model simulation suggests that earlier sowing time and excessive irrigation are of benefit in adapting to climate change impact. Thus, in arid environments where additional irrigation is not an option, increased nitrogen application in combination with an earlier sowing time could be an effective adaptation strategy for future wheat production. • Cropping systems in arid regions are highly suffering from climate change impacts. • Data of field experiments were used to parameterize the APSIM-Wheat model • Climate change scenarios simulate significant decrease in wheat yield after 2040. • Early sowing with nitrogen fertilization could alleviate climate change impact. • Over-irrigation is not an option as water shortage is severely increasing. [ABSTRACT FROM AUTHOR]

• A temperature-dependent numerical model for a weed biocontrol agent is presented. • Temperatures used to drive the model were satellite-derived or measured locally. • Model predictions were compared to observations in a caged field experiment. • Phenology predictions, driven by both temperature sources were similar. • This model can be used to predict weed biocontrol impact. Herbivorous insects play important roles in agriculture as pests or as weed biological control agents. Predicting the timing of herbivore insect population development can thus be of paramount importance for agricultural planning and sustainable land management. Numerical simulation models driven by temperature are often used to predict insect pest population build-up in agriculture. Such simulation models intend to use station-derived temperatures to drive the development of the target insect, although this temperature may differ substantially from that experienced by the insect on the plant. To improve the estimations, it has been suggested to replace air temperature in the model by land surface temperature (LST) data. Here, we use a numerical simulation model of insect population dynamics driven by either air temperature (combined with atmospheric temperature soundings) or land surface temperature derived from satellites to predict the population trends of the leaf beetle Ophraella communa, a potential biological control agent of Ambrosia artemisiifolia in Europe. For this, we conducted an extensive field experiment that included caged O. communa populations at five sites along an altitudinal gradient (125–1250 m a.s.l.) in Northern Italy during 2015 and 2016. We compared our model predictions using air or land surface temperature with observed beetle population build-up. Model predictions with both air and land surface temperatures predicted a similar phenology to observed populations but overestimated the abundance of the observed populations. When taking into consideration the error of the two measurement methods, the predictions of the model were in overlapping timeframes. Therefore, the current model driven by LST can be used as a proxy for herbivore impact, which is a novel tool for weed biocontrol. [ABSTRACT FROM AUTHOR]

• Performance and survival of Ophraella communa populations differ in their response to temperature. • Variation in thermal reaction norms for survival indicate the potential of O. communa populations to cope with variation in environmental conditions. • We found no risk of increasing non-target effects on sunflower under different temperature regimes. • There was no significant correlation between genetic diversity and phenotypic trait means. Although biological control agents (BCAs) are an effective tool for limiting the impact of invasive alien plants (IAPs), mismatch between the BCA and IAP, exacerbated by future climate change, may affect biocontrol efficacy and the likelihood of there being non-target effects. In a common-environment experiment, we measured leaf consumption, performance (i.e. development time and adult weight), and survival in 11 populations of the leaf beetle Ophraella communa from its native (North America) and introduced (China, Europe) ranges under three temperatures treatments (20 °C, 27 °C, 31 °C) and on two plant species, the target IAP Ambrosia artemisiifolia (common ragweed) and the closely-related crop Helianthus annuus (sunflower) , a potential subsidiary non-target host. Leaf consumption, development time, adult weight and survival differed significantly in the different populations without any significant geographical pattern. Specifically, there was variation in levels of survival at different temperatures between populations, with highest levels of leaf consumption and survival in the Fogang (China) population at all temperatures, while survival was highest in other populations under colder and warmer conditions. In general, we observed faster development and a marginal increase in adult weight, but decreasing survival, with increasing temperatures in all populations. The beetles consumed much more common ragweed than sunflower leaves, with no difference evident in the consumption levels on sunflower under cooler or warmer temperature conditions. Moreover, cold temperatures negatively affected the survival of beetles feeding on sunflower, potentially leading to a reduction of fitness on the non-target host. Genetic composition and diversity, assessed using microsatellite markers, showed higher allelic richness and expected heterozygosity in native US populations compared to introduced Chinese populations and lower allelic richness and expected heterozygosity in US and Italian populations at the edge of the distribution compared to core populations. Overall, Chinese populations showed low genetic diversity, likely due to releases after mass rearing. Although there were differences in genetic diversity among populations, we did not find correlations between genetic diversity and phenotypic trait means. Our results indicate that some of the populations examined might be able to cover areas that are heavily infested by common ragweed or are expected be so under climate warming but are predicted to be presently unsuitable for the beetle. [ABSTRACT FROM AUTHOR]

• Cultivar mixture can enhance bean competitiveness and by this decrease weed cover. • Cultivar mixture can allow highest yield with herbicide application at half rate. • Dose optimization with a cultivar mixture prevents herbicide over usage. • Cultivar mixture with reduced herbicide dose is a more ecofriendly weed management. Integrated weed control methods are increasingly demanded to maintain high yield while alleviating negative environmental side effects of control measures. Five field experiments were conducted during 2015–2017 at three locations in Iran to determine the advantage of exploiting enhanced competitive ability of bean (Phaseolus vulgaris L.) via cultivar mixture to reduce herbicide dose. For all experiments, the experimental design was split-plot in randomized complete block with four replications. Main plots were assigned to the factor "herbicide dose" with 5 levels between 0 and 100 % of recommended dose and subplots comprised monoculture of a stand growth type cultivar (STAND), monoculture of a climbing growth type cultivar (CLIMB) and the substitutive (50 % STAND/50 % CLIMB) cultivar mixture (MIXCR). Without herbicide application, the yield of STAND, CLIMB and MIXCR was estimated at 588, 1026, and 1637 kg ha−1, and the corresponding weed biomass (W 0) at 388, 215, and 239 g m-2, respectively. The herbicide dose to decrease W 0 by 50 % (ed 50) was estimated as 69 % of the recommended dose for STAND, while it was 53 and 45 % for CLIMB and MIXCR, respectively. Herbicide application at full rate increased the average yield of STAND by 2610 kg ha−1, but 1115 and 1532 kg ha-1 for CLIMB and MIXCR, respectively. Potential yield of CLIMB at full herbicide rate application was 2141 kg ha−1, while STAND and MIXCR showed statistically the same potential of producing 3198 and 3169 kg h−1 bean yield. However, MIXCR could achieve its potential yield at half of the recommended dose. Relative yield total (RYT) was lower than or equal to one at 75 % and 100 % of the recommended dose, but with decreasing herbicide dose to 50 or 25 % RYT raised to 1.2. Careful selection of cultivars for growing in mixture that combines strong competitor with high yield cultivars is crucial to achieve potential yield with less dependence on herbicides. As we could show for bean, this will help to overcome conflicting management objectives to reach both environmental and economic goals in weed control and crop production. [ABSTRACT FROM AUTHOR]

• Ophraella communa, a biocontrol agent of ragweed, was recently found in Europe. • Risk assessments of non-target effects of this beetle were lacking for Europe. • It is known to be Heliantheae-specific; no European native members of this tribe. • We found spill-over but no sustained attack on members of Inuleae and Coreopsideae. • Risks of non-target attack of European plant species by O. communa appear to be low. In 2013, the North American oligophagous leaf beetle, Ophraella communa LeSage (Coleoptera: Chrysomelidae), was found in Europe for the first time. Recent studies in Northern Italy and Southern Switzerland record extensive defoliation by O. communa on its preferred host, common ragweed, Ambrosia artemisiifolia L. (Asteraceae, Tribe Heliantheae), and reductions in its flowering and seeding. In some regions in Northern Italy, this has reportedly led to a > 80% depletion in airborne A. artemisiifolia pollen concentrations. The potential for non-target damage by O. communa to closely related native European plant species was previously unknown. During extensive field surveys covering 18 populations of nine potential non-target species, we found adult O. communa on a single plant individual. In a common garden field experiment in Northern Italy in an area with high O. communa densities, leaf damage was highest on two other Asteraceae species, Dittrichia graveolens (L.) Greuter and Pentanema helveticum (Weber) D.Gut.Larr. (both in the Tribe Inuleae). While adult feeding was observed on most of the test plant species, only D. graveolens , which has recently extended its range and is now an invasive species in Western Europe , sustained all life stages of O. communa in the common garden and in laboratory experiments. We found no evidence of substantial non-target effects by O. communa that could potentially threaten populations of European native plant species that are taxonomically closely related to ragweed. [ABSTRACT FROM AUTHOR]

Exotic plant invaders can promote others via direct or indirect facilitation, known as "invasional meltdown." Increased soil nutrients can also promote invaders by increasing their competitive impacts, but how this might affect meltdown is unknown. In a mesocosm experiment, we evaluated how eight exotic plant species and eight Eurasian native species responded individually to increasing densities of the invasive plant Conyza canadensis, while varying the supply and fluctuations of nutrients. We found that increasing density of C. canadensis intensified competitive suppression of natives but intensified facilitation of other exotics. Higher and fluctuating nutrients exacerbated the competitive effects on natives and facilitative effects on exotics. Overall, these results show a pronounced advantage of exotics over native target species with increased relative density of C. canadensis under high nutrient availability and fluctuation. We integrate these results with the observation that exotic species commonly drive increases in soil resources to suggest the Resource-driven Invasional Meltdown and Inhibition of Natives hypothesis in which biotic acceleration of resource availability promotes other exotic species over native species, leading to invasional meltdown., (© 2024 The Author(s). Ecology published by Wiley Periodicals LLC on behalf of The Ecological Society of America.)

Water availability strongly influences the survival, growth, and reproduction of most terrestrial plant species. Experimental evidence has well documented the effect of changes in total amount of water availability on non-native vs. native plants. However, little is known about how fluctuations in water availability affect these two groups, although more extreme fluctuations in water availability increasingly occur with prolonged drought and extreme precipitation events. Here, we grew seven non-native and seven native plant species individually in the greenhouse. Then, we exposed them to four watering treatments, each treatment with the same total amount of water, but with different divisions: W1 (added water 16 times with 125 mL per time), W2 (8 times, 250 mL per time), W3 (4 times, 500 mL per time), and W4 (2 times, 1000 mL per time). We found that both non-native and native plants produced the most biomass under medium frequency/magnitude watering treatments (W2 and W3). Interestingly, non-native plants produced 34% more biomass with the infrequent, substantial watering treatment (W4) than with frequent, minor watering treatment (W1), whereas native plants showed opposite patterns, producing 26% more biomass with W1 than with W4. Differences in the ratio of root to shoot under few/large and many/small watering treatments of non-native vs. native species probably contributed to their different responses in biomass production. Our results advance the current understanding of the effect of water availability on non-native plants, which are affected not only by changes in amount of water availability but also by fluctuations in water availability. Furthermore, our results indicate that an increased few/large precipitation pattern expected under climate change conditions might further promote non-native plant invasions. Future field experiments with multiple phylogenetically controlled pairs of non-native and native species will be required to enhance our understanding of how water availability fluctuations impact on non-native invasions., (© 2024 The Author(s). Ecology and Evolution published by John Wiley & Sons Ltd.)

Accidental introductions of biological weed control (BWC) agents (i) offer opportunities to assess host use of agents with a potentially broader fundamental host-range than those approved for field release directly in target areas; (ii) urge national authorities to rapidly respond as they may threaten native species or crops, and by this (iii) help advancing post-release studies, a neglected aspect of BWC. Through detailed insights gained from studying the recent accidental introduction of the ragweed leaf beetle Ophraella communa into Europe, we derive suggestions for overcoming barriers to adoption of BWC by re-evaluating the predictive power of pre-release studies and, thus, the presently strict criteria for deciding upon their release that might exclude safe and efficient agents. By using the allergenic weed Ambrosia artemisiifolia and the accidentally introduced BWC agent O. communa as study system, we also hope to raise the awareness of authorities to consider biological control more prominently as a key approach for pest management in the 'One Health' concept, which aims to sustainably balance and optimize the health of people, animals, plants and ecosystems. © 2023 Society of Chemical Industry., (© 2023 Society of Chemical Industry.)

Functional traits are frequently proposed to determine the invasiveness of alien species. However, few empirical studies have directly manipulated functional traits and tested their importance in the invasion success of alien species into native plant communities, particularly under global change. We manipulated clonal integration (a key clonal functional trait) of four alien clonal plants by severing inter-ramet connections or keeping them intact and simulated their invasion into native plant communities with two levels of species diversity, population density and nutrient availability. High community diversity and density impeded the invasion success of the alien clonal plants. Clonal integration of the alien plants promoted their invasion success, particularly in the low-density communities associated with low species diversity or nutrient addition, which resulted in a negative correlation between the performance of alien plants and native communities, as expected under global change. Thus, clonal integration can favor the invasion success of alien clonal plants into degraded resident communities with a high degree of disturbance and eutrophication. Our findings confirm the role of clonal functional traits in facilitating alien plant invasions into native plant communities and suggest that clonal functional traits should be considered to efficiently restore degraded communities heavily invaded by alien clonal plants., (© 2022 The Ecological Society of America.)

Invasive alien species (IAS) can substantially affect ecosystem services and human well-being. However, quantitative assessments of their impact on human health are rare and the benefits of implementing IAS management likely to be underestimated. Here we report the effects of the allergenic plant Ambrosia artemisiifolia on public health in Europe and the potential impact of the accidentally introduced leaf beetle Ophraella communa on the number of patients and healthcare costs. We find that, prior to the establishment of O. communa, some 13.5 million persons suffered from Ambrosia-induced allergies in Europe, causing costs of Euro 7.4 billion annually. Our projections reveal that biological control of A. artemisiifolia will reduce the number of patients by approximately 2.3 million and the health costs by Euro 1.1 billion per year. Our conservative calculations indicate that the currently discussed economic costs of IAS underestimate the real costs and thus also the benefits from biological control.

Classical biological control (also called importation biological control) of weeds has a remarkable track record for efficiency and safety, but further improvement is still needed, particularly to account for potential evolutionary changes after release. Here, we discuss the increasing yet limited evidence of post-introduction evolution and describe approaches to predict evolutionary change. Recent advances include using experimental evolution studies over several generations that combine -omics tools with behavioral bioassays. This novel approach in weed biocontrol is well suited to explore the potential for rapid evolutionary change in real-time and thus can be used to estimate more accurately potential benefits and risks of agents before their importation. We outline this approach with a chrysomelid beetle used to control invasive common ragweed., (Copyright © 2020 Elsevier Inc. All rights reserved.)

A little known, unculturable ascomycete, referred to as Phyllachora ambrosiae, can destroy the inflorescences of Ambrosia artemisiifolia, an invasive agricultural weed and producer of highly allergenic pollen. The fungus often remains undetectable in ragweed populations. This work was conducted to understand its origin and pathogenesis, a prerequisite to consider its potential as a biocontrol agent. The methods used included light and transmission electron microscopy, nrDNA sequencing, phylogenetic analyses, artificial inoculations, and the examination of old herbarium and recent field specimens from Hungary, Korea, Ukraine and USA. The Eurasian and the North American specimens of this fungus were to represent two distinct, although closely related lineages that were only distantly related to other lineages within the Ascomycota. Consequently, we describe a new genus that includes Cryptophyllachora eurasiatica gen. et sp. nov. and C. ambrosiae comb. nov., respectively. The pathogenesis of C. eurasiatica was shown in A. artemisiifolia. No evidence was found for either seed-borne transmission or systemic infection. Two hypotheses were developed to explain the interaction between C. eurasiatica and A. artemisiifolia: (i) as yet undetected seed-borne transmissions and latent, systemic infections; or (ii) alternative hosts.