Abstract. One commonly accepted mechanism for biological invasions is that species, after introduction to a new region, leave behind their natural enemies and therefore increase in distribution and abundance. However, which enemies are escaped remains unclear. Escape from specialist invertebrate herbivores has been examined in detail, but despite the profound effects of generalist herbivores in natural communities their potential to control invasive species is poorly understood. We carried out parallel laboratory feeding bioassays with generalist invertebrate herbivores from the native (Europe) and from the introduced (North America) range using native and nonnative tetraploid populations of the invasive spotted knapweed, Centaurea stoebe. We found that the growth of North American generalist herbivores was far lower when feeding on C. stoebe than the growth of European generalists. In contrast, North American and European generalists grew equally well on European and North American tetraploid C. stoebe plants, lending no support for an evolutionary change in resistance of North American tetraploid C. stoebe populations against generalist herbivores. These results suggest that biogeographical differences in the response of generalist herbivores to novel plant species have the potential to affect plant invasions.

Background: Cardiac surgery often represents the only treatment option in patients with infective endocarditis (IE). However, IE surgery may lead to a sudden release of inflammatory mediators, which is associated with the severity of postoperative organ dysfunction. We investigated the impact of hemoadsorption during IE surgery on postoperative organ dysfunction. Methods: This multi-center, randomized, non-blinded, controlled trial assigned patients undergoing cardiac surgery for IE to hemoadsorption [integration of CytoSorb® to cardiopulmonary bypass (CPB)] or control. The Primary outcome (ΔSOFA) was defined as the difference between the mean total postoperative sequential organ failure assessment score (SOFA), calculated maximally to the 9th postoperative day, and the basal SOFA score. The analysis was by modified intention-to-treat. A predefined inter-group comparison was done using a linear mixed model for ΔSOFA including surgeon and baseline SOFA as fixed effect covariates and with the surgical center as random effect. The SOFA score assesses dysfunction in six organ systems, each scored from zero to four. Higher scores indicate worsening dysfunction. Secondary outcomes were 30-day mortality, durations of mechanical ventilation, vasopressor and renal replacement therapy. Cytokines were measured in the first 50 patients. Results: Between January 17, 2018 and January 31, 2020, A total of 288 patients were randomly assigned to hemoadsorption (n=142) or control (n=146). Four patients in the hemoadsorption and two in the control group were excluded as they did not undergo surgery. The primary outcome ΔSOFA did not differ between the hemoadsorption and the control group (1.79 ± 3.75 and 1.93 ± 3.53, respectively, 95% CI: −1.30 to 0.83, p=0.6766). Mortality at 30 days (21% hemoadsorption vs 22% control, p=0.782), the durations of mechanical ventilation, vasopressor and renal replacement therapy did not differ between groups. Levels of IL-1β and IL-18 at the end of CPB were significantly lower in the hemoadsorption than in the control group. Conclusions: This randomized trial failed to demonstrate a reduction in postoperative organ dysfunction through intraoperative hemoadsorption in patients undergoing cardiac surgery for IE. Although hemoadsorption reduced plasma cytokines at the end of CPB, there was no difference in any of the clinically relevant outcome points.

Mechanisms contributing to the invasive success of plants are still only partly understood. A main assumption is that an escape from specialized enemies in introduced ranges allows a reduction of chemical defences resulting in an increase in growth and reproduction and thus increased competitive ability of introduced plants. Not only variation in concentration but also variation in composition of chemical compounds between individuals may be a key advantage for plants introduced to novel areas impeding adaptation of different plant antagonists. To investigate quantitative and qualitative variation of putative defence compounds and investment of resources in growth, we conducted a common garden experiment in the native range with seeds of 13 native and 9 introduced populations of Tanacetum vulgare, an aromatic plant forming different chemotypes. After 3.5 months, plants of introduced populations had similar biomass but more stems and higher concentrations of volatile secondary compounds (mainly terpenes) than plants of native populations. Both native and invasive T. vulgare populations exhibited high chemotypic variation with nine chemotypes occurring on both continents, whereas several were found exclusively either in plants originating from the native (n = 10) or invasive (n = 2) range. Due to the known negative effects of many mono-and sesquiterpenes on various organisms, we propose that high concentrations of these secondary compounds accompanied by high chemotypic diversity may facilitate the invasion success of a plant species.

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