Temporal development in the impacts of plant invasions: search for the underlying mechanisms.

Many invasive plants have negative impacts on native populations and communities, but there remains much uncertainty about how these impacts develop over time. In this review, I describe the mechanisms that promote the initial dominance of invaders, the characteristics associated with large negative impacts, and present the processes that contribute to changes in invader abundance and impacts over time. Together with ecological processes such as ecosystem engineering or enemy accumulation, I show that temporal variation in impacts can be linked to evolution in both native and invasive species. I also show that multiple processes operating in the same invasion system can jointly shape long-term impacts. Finally, I present the framework of modern coexistence theory as a tool for predicting the effects of invaders on native populations, and how these effects change with processes ongoing within invaded communities.

The Reliability of Auto-Injectors in Clinical Use: A Systematic Review.

Auto-injectors are medical devices designed for the self-administration of injections by patients and for easy administration by healthcare professionals in emergency situations. Although they vary in design and application, auto-injectors are typically built around a spring-loaded syringe. Despite their widespread use in a variety of clinical settings, there have been limited attempts to assess their reliability. This systematic review investigates the reliability of auto-injectors, identifies common causes of failure, and summarizes the overall rate of malfunction. A systematic review of research published on the PubMed and Cochrane Library databases was performed in July 2022. The relevant studies were assessed for their methodological quality and risk of bias prior to extracting key study outcomes on auto-injector reliability. Finally, a summary rate covering all eligible studies was calculated.  The search identified a total of 110 articles, of which ten were found to be suitable for inclusion. The risk of bias was low, and the methodological quality was high across the ten studies. Out of a total of 2,964 injections administered from an auto-injector, there were 12 device malfunctions, giving a summary rate of 0.40% (±0.23) auto-injector failures. The causes of malfunction varied in nature, with the majority of cases (58.3%) not being specified or not identified. This review has demonstrated that auto-injectors are reliable devices. Although further research on the nature of malfunctions is needed, the low rate of malfunctions supports training programs for healthcare professionals and patients on the optimum use and maintenance of auto-injectors. It provides a rationale for their continued development.

Fitness and niche differences are both important in explaining responses of plant diversity to nutrient addition.

Plant species loss due to eutrophication is a common phenomenon in temperate perennial grasslands. It occurs in a nonrandom fashion and is usually explained by increased competitive size asymmetry between the co-occurring winner (tall species with optima in productive habitats) and loser species (small-statured plants typical for unproductive habitats). It remains unclear why nutrient addition decreases diversity in communities consisting of losers only, whereas it has little effect on winner-only communities. Here, I used the framework of modern coexistence theory to explore fertilization-driven changes in fitness and niche differences between different combinations of field-identified winner (W) and loser (L) species. I experimentally estimated competition parameters for plant species pairs constructed from a pool of eight species, including pairs of species from the same (WW, LL) and different species categories (LW) grown for approximately 2 years in control and fertilized conditions. Concurrently, I also followed plant species diversity in mesocosm communities constructed from the same species pool (four-species communities including winners, losers, or both) exposed to control and nutrient addition. I found that nutrient addition can reduce but, unexpectedly, also promote species coexistence depending on the type of species pairs. Whereas nutrient addition eroded the coexistence of losers with winners, but also with other losers, treatment had the opposite effect on the persistence of winner species. Fertilization induced large fitness differences between species in loser-winner and loser-loser combinations, but had little effect on the fitness differences of species within the winner-winner combination. In addition, the persistence of winner pairs was promoted by larger niche differences compared to loser species, irrespective of soil nutrients. The differences in how nutrient addition modified coexistence at the pairwise level were reflected by differences in the evenness of multispecies communities assembled from the corresponding species categories. These results suggest that the effect of eutrophication on plant species richness cannot simply be explained by an increased competitive asymmetry. To fully understand the effect of fertilization on the diversity of temperate grasslands, interspecific and intraspecific interactions should be explored while considering differences in species' ecological optima.

Evolution of plasticity prevents postinvasion extinction of a native forb.

Exotic plant invaders pose a serious threat to native plants. However, despite showing inferior competitive ability and decreased performance, native species often subsist in invaded communities. The decline of native populations is hypothesized to be halted and eventually reversed if adaptive evolutionary changes can keep up with the environmental stress induced by invaders, that is, when population extinction is prevented by evolutionary rescue (ER). Nevertheless, evidence for the role of ER in postinvasion persistence of native flora remains scarce. Here, I explored the population density of a native forb, Veronica chamaedrys, and evaluated the changes in the shade-responsive traits of its populations distributed along the invasion chronosequence of an exotic transformer, Heracleum mantegazzianum, which was replicated in five areas. I found a U-shaped population trajectory that paralleled the evolution of plasticity to shade. Whereas V. chamaedrys genotypes from intact, more open sites exhibited a shade-tolerance strategy (pronounced leaf area/mass ratio), reduced light availability at the invaded sites selected for a shade-avoidance strategy (greater internode elongation). Field experiments subsequently confirmed that the shifts in shade-response strategies were adaptive and secured postinvasion population persistence, as indicated by further modeling. Alternative ecological mechanisms (habitat improvement or arrival of immigrants) were less likely explanations than ER for the observed population rebound, although the contribution of maternal effects cannot be dismissed. These results suggest that V. chamaedrys survived because of adaptive evolutionary changes operating on the same timescale as the invasion-induced stress, but the generality of ER for postinvasion persistence of native plants remains unknown.

The temporal development of plant-soil feedback is contingent on competition and nutrient availability contexts.

Strength and direction of plant-soil feedback (PSF), the reciprocal interactions between plants and soil, can change over time and have distinct effects on different life stages. PSF and its temporal development can also be modified by external biotic and abiotic factors such as competition and resource availability, yet most PSF research is conducted in simple experimental settings without considering temporal changes. Here I have studied the effect of different competitive settings (intraspecific, interspecific, and no competition) and nutrient addition on the magnitude and direction of biomass-based PSF (performance in conspecific relative to heterospecific inoculum) across 46 grassland species, estimated at the 4th, 10th, and 13th month of the response phase. I also examined whether conspecific inoculum had a long-term effect on plant survival at the 36th month, and whether biomass-based PSF may predict survival-based PSF effects. PSF pooled across all treatments and time points was negative, but a significant overall temporal trend or differences among competitive settings were missing. PSF developed unimodally for interspecific competition across the three time points, whereas it declined gradually in case of intraspecific and no competition. Nutrient addition attenuated negative biomass-based PSF and eliminated negative effects of conspecific inoculum on survival. Interspecific differences in biomass-based PSF were related to survival-based PSF, but only after nutrient addition. This study demonstrates that PSF is dynamic and modulated by external abiotic and biotic factors. PSF research should consider the temporal dynamics of focal communities to properly estimate how PSF contributes to community changes, preferably directly in the field.

Nutrient-demanding species face less negative competition and plant-soil feedback effects in a nutrient-rich environment.

Plant-soil feedbacks (PSFs) and plant-plant competition influence performance and abundance of plants. To what extent the two biotic interactions are interrelated and thus affect plant performance in combination rather than in isolation remains poorly explored. It is also unclear how the abiotic context, such as resource availability, modifies individual and joint effects of PSFs and of plant-plant competition. Using a garden experiment, we assessed the strengths of PSFs, competition, and their combined effects explored under low and high nutrient levels, and related them to abundance of 46 plant species and their ecological optima with respect to soil nutrients. We found that PSFs reduced but did not eliminate differences in competitive ability of plant species. Isolated and combined effects of the biotic interactions poorly predicted local or regional abundance of species. They were rather related to species' ecological optima, as nutrient-demanding plants experienced less negative biotic effects but only in a nutrient-rich environment. Our study demonstrates that soil biota can mitigate differences in competitive ability among species. It remains to be tested whether such an equalizing effect can maintain coexistence under high nutrient availability, in which nutrient-demanding species may disproportionately benefit from less negative competition and PSF effects.

Nonlinear versus Ordinary Adaptive Control of Continuous Stirred-Tank Reactor.

Unfortunately, the major group of the systems in industry has nonlinear behavior and control of such processes with conventional control approaches with fixed parameters causes problems and suboptimal or unstable control results. An adaptive control is one way to how we can cope with nonlinearity of the system. This contribution compares classic adaptive control and its modification with Wiener system. This configuration divides nonlinear controller into the dynamic linear part and the static nonlinear part. The dynamic linear part is constructed with the use of polynomial synthesis together with the pole-placement method and the spectral factorization. The static nonlinear part uses static analysis of the controlled plant for introducing the mathematical nonlinear description of the relation between the controlled output and the change of the control input. Proposed controller is tested by the simulations on the mathematical model of the continuous stirred-tank reactor with cooling in the jacket as a typical nonlinear system.

Intraspecific variability in allelopathy of Heracleum mantegazzianum is linked to the metabolic profile of root exudates.

BACKGROUND AND AIMS: Allelopathy may drive invasions of some exotic plants, although empirical evidence for this theory remains largely inconclusive. This could be related to the large intraspecific variability of chemically mediated plant-plant interactions, which is poorly studied. This study addressed intraspecific variability in allelopathy of Heracleum mantegazzianum (giant hogweed), an invasive species with a considerable negative impact on native communities and ecosystems. METHODS: Bioassays were carried out to test the alleopathic effects of H. mantegazzianum root exudates on germination of Arabidopsis thaliana and Plantago lanceolata. Populations of H. mantegazzianum from the Czech Republic were sampled and variation in the phytotoxic effects of the exudates was partitioned between areas, populations within areas, and maternal lines. The composition of the root exudates was determined by metabolic profiling using ultra-high-performance liquid chromatography with time-of-flight mass spectrometry, and the relationships between the metabolic profiles and the effects observed in the bioassays were tested using orthogonal partial least-squares analysis. KEY RESULTS: Variance partitioning indicated that the highest variance in phytotoxic effects was within populations. The inhibition of germination observed in the bioassay for the co-occurring native species P. lanceolata could be predicted by the metabolic profiles of the root exudates of particular maternal lines. Fifteen compounds associated with this inhibition were tentatively identified. CONCLUSIONS: The results present strong evidence that intraspecific variability needs to be considered in research on allelopathy, and suggest that metabolic profiling provides an efficient tool for studying chemically mediated plant-plant interactions whenever unknown metabolites are involved.

The impact of an invasive plant changes over time.

Many exotic plant invaders pose a serious threat to native communities, but little is known about the dynamics of their impacts over time. In this study, we explored the impact of an invasive plant Heracleum mantegazzianum (giant hogweed) at 24 grassland sites invaded for different periods of time (from 11 to 48 years). Native species' richness and productivity were initially reduced by hogweed invasion but tended to recover after ~30 years of hogweed residence at the sites. Hogweed cover declined over the whole period assessed. A complementary common garden experiment suggested that the dynamics observed in the field were due to a negative plant-soil feedback; hogweed survival and biomass, and its competitive ability were lower when growing in soil inocula collected from earlier-invaded grasslands. Our results provide evidence that the initial dominance of an invasive plant species and its negative impact can later be reversed by stabilising processes.

Plant competitive interactions and invasiveness: searching for the effects of phylogenetic relatedness and origin on competition intensity.

The invasion success of introduced plants is frequently explained as a result of competitive interactions with native flora. Although previous theory and experiments have shown that plants are largely equivalent in their competitive effects on each other, competitive nonequivalence is hypothesized to occur in interactions between native and invasive species. Small overlap in resource use with unrelated native species, improved competitiveness, and production of novel allelochemicals are all believed to contribute to the invasiveness of introduced species. I tested all three assumptions in a common-garden experiment by examining the effect of plant origin and relatedness on competition intensity. Competitive interactions were explored within 12 triplets, each consisting of an invasive species, a native congeneric (or confamilial) species, and a native heterogeneric species that are likely to interact in the field. Plants were grown in pots alone or in pairs and in the absence or the presence of activated carbon to control for allelopathy. I found that competition intensity was not influenced by the relatedness or origin of competing neighbors. Although some exotic species may benefit from size advantages and species-specific effects in competitive interactions, none of the three mechanisms investigated is likely to be a principal driver of their invasiveness.

Local adaptation in the monocarpic perennial Carlina vulgaris at different spatial scales across Europe.

Spatial variation in environmental conditions can lead to local adaptation of plant populations, particularly if gene flow among populations is low. Many studies have investigated adaptation to contrasting environmental conditions, but little is known about the spatial scale of adaptive evolution. We studied population differentiation and local adaptation at two spatial scales in the monocarpic grassland perennial Carlina vulgaris. We reciprocally transplanted seedlings among five European regions (northwestern Czech Republic, central Germany, Luxembourg, southern Sweden and northwestern Switzerland) and among populations of different sizes within three of the regions. We recorded survival, growth and reproduction over three growing periods. At the regional scale, several performance traits and the individual fitness of C. vulgaris were highest if the plants were grown in their home region and they decreased with increasing transplant distance. The effects are likely due to climatic differences that increased with the geographical distance between regions. At the local scale, there were significant interactions between the effects of the population of origin and the transplant site, but these were not due to an enhanced performance of plants at their home site and they were not related to the geographical or environmental distance between the site of origin and the transplant site. The size of the population of origin did not influence the strength of local adaptation. The results of our study suggest that C. vulgaris consists of regionally adapted genotypes, and that distance is a good predictor of the extent of adaptive differentiation at large scales ( > 200 km) but not at small scales. We conclude that patterns of local adaptation should be taken into account for the efficient preservation of genetic resources, when assessing the status of a plant species and during conservation planning.