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The rate of non-native species introductions continues to increase, with directionality from continents to islands. It is no longer single species but entire networks of coevolved and newly interacting continental species that are establishing on islands. The consequences of multispecies introductions on the population dynamics and interactions of native and introduced species will depend on the form of trophic limitation on island ecosystems. Freed from biotic constraints in their native range, species introduced to islands no longer experience top-down limitation, instead becoming limited by and disrupting bottom-up processes that dominate on resource-limited islands. This framing of the ecological and evolutionary relationships among introduced species with one another and their ecosystem has important consequences for conservation. Whereas on continents the focus of conservation is on restoring native apex species and top-down limitation, on islands the focus must instead be on removing introduced animal and plant species to restore bottom-up limitation.

Aims: We investigated urban grasslands to: (1) explore current patterns of plant species richness in high-maintenance vs low-maintenance grasslands, (2) investigate environmental drivers of plant species richness and composition, and (3) derive management recommendations and assess the potential for plant species introduction. Location: Cities of Cologne (50°56' N, 6°57' E) and Münster (51°57' N, 7°37' E), North Rhine-Westphalia, Germany. Methods: We performed plant inventories and measured soil and above-ground biomass characteristics in 100 urban grasslands in two cities differing in population size and environmental setting. The data set covered 35 high-maintenance grasslands, which are cut or mulched up to 14 times a year, and 65 lowmaintenance grasslands with one to two cuts per year or sheep grazing. We used ANCOVA and DCA to assess drivers of vegetation composition and species richness. The floristic potential and options to restore biodiversity were assessed taking into account maintenance intensity and key abiotic variables of the grasslands using thresholds derived from published literature and our own data. Results: High-maintenance urban grasslands harboured significantly lower plant species richness compared to low-maintenance grasslands. However, plant species richness of both grassland types turned out to be lower than that of comparable semi-natural agricultural grasslands. Floristic composition was primarily conditioned by maintenance intensity, but for plant species richness environmental factors such as soil pH, phosphorus availability and city were additionally important. Just eight of the 100 studied urban grasslands were found to be already valuable and species-rich, whereas the vast majority showed relatively low species richness but a high potential for species introduction. Conclusions: Apparently, most urban grasslands exhibited quite constrained plant species richness, suffering from high-maintenance intensity but probably also from dispersal and seed limitations. Nevertheless, as the majority of the studied grasslands showed favourable abiotic preconditions for higher plant species richness, restoration techniques using species introduction could be an easy and promising method to support grassland biodiversity in urban areas.

The search for traits associated with plant invasiveness has yielded contradictory results, in part because most previous studies have failed to recognize that different traits are important at different stages along the introduction–naturalization–invasion continuum. Here we show that across six different habitat types in temperate Central Europe, naturalized non-invasive species are functionally similar to native species occurring in the same habitat type, but invasive species are different as they occupy the edge of the plant functional trait space represented in each habitat. This pattern was driven mainly by the greater average height of invasive species. These results suggest that the primary determinant of successful establishment of alien species in resident plant communities is environmental filtering, which is expressed in similar trait distributions. However, to become invasive, established alien species need to be different enough to occupy novel niche space, i.e. the edge of trait space. Plant functional traits may help distinguish introduced species that will become invasive from those that do not. Here, Divíšek et al. show that functional profiles of naturalized plant species are similar to natives, while those of invasive plant species exist at the edge of the functional trait space.

Fil: Zuloaga, Fernando Omar. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Botánica Darwinion. Academia Nacional de Ciencias Exactas, Físicas y Naturales. Instituto de Botánica Darwinion; Argentina

We studied the effects of Bischofia javanica on species diversity and structural composition of plantation and secondary forests in Kakamaga rainforest in western Kenya. The invasive exotic tree species was introduced to the area in 1960s and planted as a pure plantation stand to assist in rehabilitating logged primary forest sites. By 1990s, the species had established in nearby secondary and plantation forest stands in which it was not planted. The study sought to determine how invasion of the exotic species had affected species diversity, species evenness and stand density in plantation and secondary forests within the rainforest. The study was carried out in nine forest types, namely: old-growth secondary forest, middle-aged secondary forest, young secondary forest, mixed indigenous plantation, Maesopsis, Cupressus, Pinus and Bischofia monoculture plantations, and disturbed primary forest. These forest types were nested as sub-blocks in three forest blocks. The results indicated that B. javanica was the only non-native woody species among several native woody species that recruited naturally in plantation and secondary forests. It did not grow in the disturbed primary forest. Its recruitment was significantly more aggressive than that of native species. It lowered species diversity but increased species evenness in all plantation and secondary forests. Its relative abundance was 30.6%, dominating the seedling, sapling and tree densities of plantation and secondary forests. It is necessary to remove the tree species from the rainforest before it takes over the whole forest ecosystem.

The factors that promote invasive behavior in introduced plant species occur across many scales of biological and ecological organization. Factors that act at relatively small scales, for example the evolution of biological traits associated with invasiveness, scale up to shape species distributions amongst different climates and habitats, as well as other characteristics linked to invasion, such as attractiveness for cultivation (and by extension propagule pressure). To identify drivers of invasion it is therefore necessary to disentangle the contribution of multiple factors that are interdependent. To this end, we formulated a conceptual model describing the process of invasion of central European species into North America based on a sequence of 'drivers'. We then used confirmatory path analysis to test whether the conceptual model is supported by a statistical model inferred from a comprehensive database containing 466 species. The path analysis revealed that invasion of central-European plants in North America, in terms of the number of North American regions invaded, most strongly depends on minimum residence time in the invaded range and the number of habitats occupied by species in their native range. In addition to the confirmatory path analysis, we identified the effects of various biological traits on several important drivers of the conceptualized invasion process. The data supported a model, which included indirect effects of biological traits on invasion via their effect on the number of native range habitats occupied and cultivation in the native range. For example, persistent seed banks and longer flowering periods are positively correlated with number of native habitats, while a stress-tolerant life strategy is negatively correlated with native-range cultivation. However, the importance of the biological traits is nearly an order of magnitude less than that of the larger-scale drivers and highly dependent on the invasion stage (traits were associated only with native-range drivers). This suggests that future research should explicitly link biological traits to the different stages of invasion, and that a failure to consider minimum residence time or characteristics of the native range may seriously overestimate the role of biological traits, which in turn may result in spurious predictions of plant invasiveness.

Aim: Introductions of exotic species have globally modified the structure and function of native assemblages and are recognized as one of the major threats to biodiversity. The current patterns, processes and consequences of invasion have been intensively studied globally, but studies reporting the long-term dynamics of invasions over large areas are rare. Here, we measured how the temporal changes in fish assemblage composition in a Chinese highland isolated-lake landscape drive taxonomic dissimilarity and its turnover component over three successive time periods spanning the last 75 years. Location: Yun-Gui Plateau, 15 isolated lakes. Methods: The Sørensen and Simpson indices were used to quantify changes in taxonomic dissimilarity and its turnover component over 1940-2015. Results: We report a decline of taxonomic dissimilarity between lakes through time, mainly due to a decrease in species turnover. Such a homogenization process was due to the combined effects of the invasion of the same non-native species in most lakes and of extirpation of narrow endemic species. The strong decline in species dissimilarity and turnover was triggered by a high historical level of dissimilarity among assemblages. At a regional scale, the combined effect of introductions and extirpations modified the distance decay of taxonomic similarity between lakes. Surprisingly, this beta-diversity gradient is currently no longer supported by biogeographic and evolutionary processes, but by the human-mediated introduction of distinct exotic species in some lakes. Moreover, an extinction debt process was evident as extirpations sometimes occurred many years after the introduction of non-native species. Main conclusions: Our study highlights that high historical differentiation of fishes in isolated lakes has turned to homogenization with dramatic loss of endemic species due to intensive introductions. This provides a striking example of human domination over an extended lake landscape and its associated irreparable biodiversity damages on isolated systems historically dominated by narrow endemic species.

We present strong evidence that pathogens play a critical role in structuring plant communities and maintaining plant diversity. Pathogens mediate plant species coexistence through trade-offs between competitive ability and resistance to pathogens and through pathogen specialization. Experimental tests of individual plant-pathogen interactions, tests of feedback through host-specific changes in soil communities, and field patterns and field experimentation consistently identify pathogens as important to plant species coexistence. These direct tests are supported by observations of the role of pathogens in generating the productivity gains from manipulations of plant diversity and by evidence that escape from native pathogens contributes to success of introduced plant species. Further work is necessary to test the role of pathogen dynamics in large-scale patterns of plant diversity and range limits, the robustness of coexistence to coevolutionary dynamics, the contribution of different pathogens, and the role of pathogens in plant succession.

Invasive alien plant species can cause considerable ecological, economic, and social impacts, and the number of impactful species will likely increase with globalisation and anthropogenic climate change. Preventing potentially invasive alien plant species from becoming introduced is the most cost‐effective way to protect Norway's ecosystems from future invasions. We developed and applied a new method for horizon scanning to identify high‐risk potentially invasive alien plant species that are not yet present in Norway but could be introduced and become naturalised and invasive in the future. Starting with 16 866 species known to be naturalised somewhere globally, we employed a simple and novel method for assessing the climate match of each species' known distribution to Norway's climate, then used economic and environmental impact data to narrow them down further. Of the species identified, we implemented species distribution models to predict the potential distribution of these high‐risk species in Norway under both current and projected future (2060–2080) climate scenarios. A total of 265 plant species were identified as posing a high invasion risk to Norway. Under the current climate, their distributions were mostly limited to the southeast and coastal regions of Norway. However, under future climate change scenarios, the species' potential distribution increased significantly, with their ranges expanding northwards and further inland. Several invasion hotspots containing large numbers of species were identified close to urban areas such as Oslo, which is of particular concern as urban areas are amongst the most highly invaded environments globally. We strongly recommend that the import into Norway of species identified in this study be closely monitored and/or restricted to reduce the risk of invasions and to safeguard Norway's native biodiversity. We have also presented a novel and widely applicable method of horizon scanning with a particular focus on climate matching between species and the area of interest for both current and future climate scenarios.

Research and publication of the planet's remaining plant and fungal species as yet unknown to science is essential if we are to address the United Nations Sustainable Development Goal (SDG) 15 “Life on Land” which includes the protection of terrestrial ecosystems and halting of biodiversity loss. If species are not known to science, they cannot be assessed on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species and so the possibility to protect them from extinction is reduced. Furthermore, until species are known to science they cannot be fully scientifically evaluated for their potential as new foods, medicines, and products which would help address SDGs 1,2,3, and 8. Societal Impact Statement Research and publication of the planet's remaining plant and fungal species as yet unknown to science is essential if we are to address the United Nations Sustainable Development Goal (SDG) 15 “Life on Land” which includes the protection of terrestrial ecosystems and halting of biodiversity loss. If species are not known to science, they cannot be assessed on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species and so the possibility to protect them from extinction is reduced. Furthermore, until species are known to science they cannot be fully scientifically evaluated for their potential as new foods, medicines, and products which would help address SDGs 1,2,3, and 8. Summary Scientific discovery, including naming new taxa, is important because without a scientific name, a species is invisible to science and the possibilities of researching its ecology, applications and threats, and conserving it, are greatly reduced. We review new scientific discoveries in the plant and fungal kingdoms, based largely on new names of taxa published in 2019 and indexed in the International Plant Names Index and Index Fungorum. Numbers of new species in both kingdoms were similar with 1942 new species of plant published and 1882 species of fungi. However, while >50% of plant species have likely been discovered, >90% of fungi remain unknown. This gulf likely explains the greater number of higher order taxa for fungi published in 2019: three classes, 18 orders, 48 families and 214 genera versus one new family and 87 new genera for plants. We compare the kingdoms in terms of rates of scientific discovery, globally and in different taxonomic groups and geographic areas, and with regard to the use of DNA in discovery. We review species new to science, especially those of interest to humanity as new products, and also by life‐form. We consider where future such discoveries can be expected. We recommend an urgent increase in investment in scientific discovery of plant and fungal species, while they still survive. Priorities include more investment in training taxonomists, in building and equipping collections‐based research centers for them, especially in species‐rich, income‐poor countries where the bulk of species as yet unknown to science are thought to occur.