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Although plant–soil feedback has been suggested as a mechanism that drives the success of invasive plants, studies that investigate differences in the intensity of plant–soil feedback among native and invasive populations of the same species are still lacking. However, such knowledge is important because it can provide an understanding of the mechanisms responsible for the spread of a species. Rorippa austriaca is a potentially invasive species - a successful range expander in Europe. We compared the plant–soil feedback of R. austriaca in populations from its native and invasive range. We explored both intraspecific feedback as well as feedback on a co-occurring grass species. Our results revealed a strong negative feedback effect as a consequence of soil conditioning by R. austriaca from the native range. On the contrary, a negative feedback effect was not observed for invasive R. austriaca. Interestingly, R. austriaca from the invasive range had a higher biomass than native R. austriaca. Our results might be explained by pathogen accumulation and soil modification by native R. austriaca, which had strong intra- and interspecific effects that seemed to be lost in the invasive R. austriaca. The loss of negative intraspecific plant–soil feedback and the increased growth of the invasive population may contribute to its successful range expansion. In spite of its increased growth, the co-occurring grass species is expected to successfully coexist with the invasive R. austriaca.

This paper provides a list of 40 vascular plant species recorded in 2015–2017 in the Polish part of the Lithuanian Lakeland (north-eastern Poland), using the ATPOL cartogram method. Two native taxa Erigeron acris subsp. droebachiensis and Rorippa austriaca, one established alien Atriplex tatarica and one casual alien Aronia × prunifolia are reported as new to the flora of the region.

To understand the biological effects of climate change, it is essential to take into account species’ evolutionary responses to their changing environments. Ongoing climate change is resulting in species shifting their geographical distribution ranges poleward. We tested whether a successful range expanding plant has rapidly adapted to the regional conditions in its novel range, and whether adaptation could be driven by herbivores. Furthermore, we investigated if enemy release occurred in the newly colonized areas and whether plant origins differed in herbivore resistance. Plants were cloned and reciprocally transplanted between three experimental sites across the range. Effects of herbivores on plant performance were tested by individually caging plants with either open or closed cages. There was no indication of (regional) adaptation to abiotic conditions. Plants originating from the novel range were always larger than plants from the core distribution at all experimental sites, with or without herbivory. Herbivore damage was highest and not lowest at the experimental sites in the novel range, suggesting no release from enemy impact. Genotypes from the core were more damaged compared to genotypes from newly colonized areas at the most northern site in the novel range, which was dominated by generalist slug herbivory. We also detected subtle shifts in chemical defenses between the plant origins. Genotypes from the novel range had more inducible defenses. Our results suggest that plants that are expanding their range with climate change may evolve increased vigor and altered herbivore resistance in their new range, analogous to invasive plants. Electronic supplementary material The online version of this article (doi:10.1007/s00442-017-3864-x) contains supplementary material, which is available to authorized users.

Due to global warming, species are expanding their range to higher latitudes. Some range expanding plants have become invasive in their new range. The Evolution of Increased Competitive Ability (EICA) hypothesis and the Shifting Defense Hypothesis (SDH) predict altered selection on plant defenses in the introduced range of invasive plants due to changes in herbivore pressures and communities. Here, we investigated chemical defenses (glucosinolates) of five native and seven invasive populations of the Eurasian invasive range expanding plant, Rorippa austriaca. Further, we studied feeding preferences of a generalist and a specialist herbivore among the populations. We detected eight glucosinolates in the leaves of R. austriaca. 8-Methylsulfinyloctyl glucosinolate was the most abundant glucosinolate in all plants. There were no overall differences between native and invasive plants in concentrations of glucosinolates. However, concentrations among populations within each range differed significantly. Feeding preference between the populations by a generalist herbivore was negatively correlated with glucosinolate concentrations. Feeding by a specialist did not differ between the populations and was not correlated with glucosinolates. Possibly, local differences in herbivore communities within each range may explain the differences in concentrations of glucosinolates among populations. Little support for the predictions of the EICA hypothesis or the SDH was found for the glucosinolate defenses of the studied native and invasive R. austriaca populations. © 2014 Springer Science+Business Media New York.

Bu calismada rorippa saplari (Rorippa austriaca) odun lifleriyle farkli oranlarda karistirilarak orta yogunluklu lif levha uretiminde degerlendirilme olanaklari arastirilmistir. Calisma kapsaminda ayrica rorippa saplarinin holoseluloz, α-seluloz, lignin ve kul icerikleri ile alkol-benzen, % 1 NaOH ve sicak-soguk su cozunurlukleri de tespit edilmistir. Bu calismada uretilen tum levhalar egilme dayanimi ve egilmede elastikiyet modulu bakimindan TS 64-5 EN 622 (1999) standartlarina gore incelendiginde yalnizca % 50 oranindaki sap ilavesinin bu standartlari karsilamadigi diger oranlardaki sap ilavesinin ise bu standartlar icerisinde kaldigi gozlemlenmistir. Uretilen tum levhalar levha yuzeyine dik cekme dayanimi bakimindan TS 64-5 EN 622 (1999) standartlarina gore incelendiginde ise yalnizca %5 oranindaki sap ilavesinin bu standartlari karsiladigi tespit edilmistir.

Plant-soil feedback is an important mechanism in plant communities affecting their species composition. Understanding plant-soil feedback is crucial for describing the interactions between plant communities and their soil communities. The effects of plant-soil feedback can be positive, negative or neutral and because of these changes plants are either coexisting or competing. Plant-soil feedback is often studied within plant succession, plant invasion and plant dominance in a plant community. In these cases, the nature and strength of influence of each species is studied. Despite the large number of previous studies on plant-soil feedback, very little is known about the temporal and spatial changes of the intensity of plant-soil feedback and the intraspecific variability in plant-soil feedback. The aim of my work was to observe the temporal changes in the plant-soil feedback of a species growing in soil which was conditioned by the same or other plant species. Another goal was to explore spatial changes in plant-soil feedback. The last objective was to test differences in the intensity of plant-soil feedback among different genotypes of one species. The results of my work demonstrated that the intensity of intraspecific plant-soil feedback of Rorippa austriaca is negative and increases with...

Summary 1 The EICA (evolution of increased competitive ability) hypothesis suggests that release from natural enemies and pathogens results in higher vigour of invasive plants as a result of the selection of less defended but rapidly growing genotypes. Slug diversity and abundance appear to be low in North America compared with Europe, and we therefore hypothesized that release from slug herbivory contributes to the invasiveness of European Brassicaceae species in North America. 2 In common garden and glasshouse experiments we compared life history and fitness parameters in native (NP) and introduced (IP) provenances of four invasive Brassicaceae species (Barbarea vulgaris, Bunias orientalis, Cardaria draba, Rorippa austriaca) that were subjected to herbivory by Arion lusitanicus. In climate chamber bioassays we investigated slug damage to seedlings and leaf discs using the same sources of plant material. 3 In all species except B. orientalis we found significant but not always consistent differences in growth and reproductive characteristics between IP and NP plants. Plants of B. vulgaris and R. austriaca from the introduced range had a considerably higher growth rate than those from the native range. While IP plants of the non-clonal B. vulgaris allocated more resources to seed production than NP plants, the IP plants of the clonal R. austriaca showed a decreased number of seeds. 4 Contrary to expectation, there were no differences between NP plants and IP plants in the number of damaged leaves and leaf area consumed by slugs, or in the proportion of seedlings damaged and killed. Nor were there interaction effects between slug treatments and provenance. 5 The results suggest that there are genetically based differences in growth and reproductive parameters between NP and IP plants. As there were no differences in herbivore damage between the provenances, this genetic differentiation is probably due to factors such as competition rather than herbivore effects. 6 In order to make progress in understanding why some species become invasive, more comparative experimental studies are needed that investigate how different kinds of antagonists (generalist and specialist herbivores and pathogens) influence the performance of plants at different life stages.

Introgressive hybridization between the invasive Rorippa austriaca and the native R. sylvestris in Germany has been studied using chloroplast DNA (trnL intron) and amplified fragment length polymorphism. Three hybrid zones between the invasive and native species were located in the Ruhr Valley (Mülheim) and at the River Main near Würzburg (Randersacker, Winterhausen). In each hybrid zone hybridization was indicated by additivity of region-specific amplified fragment length polymorphism markers proving independent hybridization events. The hybrids were either morphologically intermediate (R. x armoracioides) or were close to R. sylvestris. The trnL intron of R. austriaca is characterized by a species-specific deletion. This diagnostic chloroplast marker of R. austriaca was detected in three individuals of R. sylvestris providing evidence for introgression of the invasive chloroplast into the native species. Bidirectional introgression of R. austriaca markers into R. sylvestris and of R. sylvestris markers into R. austriaca was detected in the amplified fragment length polymorphism analysis. Some of the invasive R. austriaca populations showed high within-population variation. A possible association among introgression, within-population variation and invasion success is discussed. The morphologically intermediate hybrid R. x armoracioides is currently spreading in northern Germany. It forms large populations without its parent species R. austriaca and R. sylvestris. It is concluded that hybridization between invasive R. austriaca and native R. sylvestris may lead to the evolution of a new invasive species R. x armoracioides.

This review highlights evolutionary processes in the Brassicaceae which cause, accompany or are a consequence of biological invasions. Case studies in Capsella and Diplotaxis address the genetics of colonising species. The greatest colonising ability in Capsella bursa-pastoris is associated with polyploidy, predominant selfing, and high genetic diversity. Success of colonial populations seems to be due to the introduction of preadapted genotypes. Colonising species in Diplotaxis reveal contrasting evolutionary patterns. Genetic attributes in D. muralis include annuality, polyploidy, and predominant selfing. Very different from Capsella, D. muralis is nearly devoid of genetic diversity as revealed by molecular markers. In contrast to D. muralis, the colonising D. tenuifolia is perennial, diploid, self-incompatible, and displays high genetic diversity. Hybrid speciation, establishment of the hybrids in man-made habitats, stabilisation of their reproductive system, and reproductive isolation from the parent populations were analysed in Cardamine. The Nasturtium example highlights the importance of hybridisation for the evolution of invasiveness. The last case study concentrates on the evolutionary consequences of hybridisation between native and invading Rorippa species. Introgressive hybridisation between the invasive Rorippa austriaca and native Rorippa species is common and widespread in central Europe, and interspecific gene transfer has led to the formation of a new invasive genotype. Each successful invasion presents new aspects and sound case studies are needed in order to understand the ecology and evolution of the colonisation process and to enable us to assess the evolutionary consequences of biological invasions.

While it is widely accepted that disturbance often promotes the process of plant invasion, few data are available on specific relationships between different types of disturbance and success of plant invaders. Nor is much known about variation in invader behaviour in response to changing composition of the dominant native species in the recipient habitats. In the middle Main valley near Wurzburg (Germany), two invasive Brassicaceae forbs, Bunias orientalis and Rorippa austriaca , are frequently associated with a small number of dominant native species in the herbaceous vegetation of productive, disturbed sites. Variation in the relative dominance of these species suggests high variability between sites in the factors influencing the local invasion process. In our study, we examined variation in regeneration mode, type and frequency of disturbance, and native species composition, and considered life history differences between the two invasive species as factors contributing to the distinct dominance patterns. These factors were tested in a controlled field experiment in which individuals of the two invasive species and four native species were grown in mixed stands for almost 3 years. The development of the plants was monitored by cover values and all plants were harvested at the end of the study. All factors investigated contributed considerably to the development of distinct dominance patterns in the species mixtures. Relative to the natives, both invasive species were promoted by regeneration from vegetative fragments as compared to development from sexual offspring. While both invasive species were generally promoted by disturbance relative to the natives, they differed in their response to distinct types of disturbance, and these differences were strongly affected by species composition. Our results indicate that invasion success of R. austriaca may depend more on soil disturbance, soil transport and deposition, while B. orientalis is expected to particularly expand at mown sites that do not have dense cover by meadow grasses. Whether the native resident vegetation is mainly composed of successional competitors that suffer from disturbance or of ruderal competitors that compete early and strongly with the invasive species may be of critical importance for invasion by the two species.

A special type of clonal growth, spread by lateral roots, ishypothesized to be a favourable trait of invasive, opportunistic plant speciesof disturbed habitats. We tested this hypothesis for the invasive forbRorippa austriaca (Brassicaceae). Regenerationfrom root fragments, subsequent vegetative spread and allocation patterns inrelation to varied nutrient supply and intensity and pattern of interspecificcompetition were analyzed in container experiments. Regeneration success fromroot fragments was 100% and clonal spread was rapid but vegetativeperformance was strongly reduced under unfertilized conditions and,particularly, when interspecific competition was present. While the ratio ofabove- to belowground bio-mass did not differ considerably betweentreatments, R. austriaca allocated a high amount ofresources to belowground growth resulting in low aboveground but highbelowground biomass at harvest time relative to the matrix vegetation.Differences in shoot number or biomass between simulated gaps and denselyvegetated quadrants in the containers were (relatively) weak.Reproductive effort was less reduced under low resource levels, and the clonesdid not set seed at all, irrespective of the treatment. Our results show thatclonal growth by lateral roots and plasticity in clonal growth patterns inR. austriaca promote both exploitation of gaps andnutrient-rich microsites and resistance to competitors. Such plasticity,combined with its ability to regenerate from widely-dispersed rootfragments, contribute to the ability of the species to invade and persistwithindisturbed and spatially heterogeneous habitats.

Hybrid zones may serve as natural laboratories for evolutionary studies. One common viewpoint is that hybrids may always be less fit than their parents due to genetic discontinuities. An alternative idea is that genotype-environment interactions influence the outcome of natural hybridization. Our comparative study of two different natural hybrid zones between the invasive diploid Rorippa austriaca and the native polyploid R. sylvestris in Germany identified the ploidy level as a major determinant of hybrid fitness. Different ploidy levels and patterns of fitness were detected in different hybrid zones. In one hybrid zone (Mulheim, Ruhr valley) hybrids were pentaploid and showed a relatively high seed set, whereas in the second hybrid zone (Randersacker, Main valley) hybrids were triploid and displayed extremely low fitness values. Analyses of fitness values in different natural hybrid zones between the same two species may lead to very different conclusions about the evolutionary significance of natural hybridization.