2023-11, Rittelmann-Woods, Elina, Lachaise, Tom, van Kleunen, Mark

Soil microplastic pollution can have negative effects on organisms, including plants, but the underlying mechanisms are not fully understood. We tested whether structural or chemical properties of a microplastic cause its effects on plant above- and belowground growth and whether these effects can be influenced by earthworms. We conducted a factorial experiment in a greenhouse with seven common Central European grassland species. Microplastic granules of the synthetic rubber ethylene propylene diene monomer (EPDM),1 a frequently used infill material of artificial turfs, and cork granules with a comparable size and shape to the EPDM granules were used to test for structural effects of granules in general. To test for chemical effects, EPDM-infused fertilizer was used, which should have contained any leached water-soluble chemical components of EPDM. Two Lumbricus terrestris individuals were added to half of the pots, to test whether these earthworms modify effects of EPDM on plant growth. EPDM granules had a clear negative effect on plant growth, but since cork granules had a negative effect of similar magnitude, with an average decrease in biomass of 37 % in presence of granules, this is likely due to the structural properties of granules (i.e., size and shape). For some belowground plant traits, EPDM had a stronger effect than cork, which shows that there must be other factors playing into the effects of EPDM on plant growth. The EPDM-infused fertilizer did not have any significant effect on plant growth by itself, but it had in interaction with other treatments. Earthworms had an overall positive effect on plant growth and mitigated most of the negative effects of EPDM. Our study shows that EPDM microplastic can have negative effects on plant growth, and that these might be more related to its structural than to its chemical properties.

2023-08-09, Zhao, Zihua, Hui, Cang, Peng, Shuo, Yi, Shanqing, Li, Zhihong, Reddy, Gadi V. P., van Kleunen, Mark

1. While there has been great interest in species characteristics that promote invasiveness, still little is known about the characteristics that distinguish invasive from non-invasive insects. Using a database on the naturalised distributions of alien insects and expert opinions about their impacts, we identified the world's 100 worst invasive insect species. 2. By comparing species characteristics reported in the literature using a meta-analysis, between the 100 worst invasive species and related non-invasive species, we found that invasive insects overall have more pathways of introduction, occur in more habitats, have higher fecundities, higher voltinism, more genes, shorted lifespans and faster development from egg to adult. Some of the differences in species characteristics related to propagule pressures, life-histories and biotic interactions, conditional on whether the non-invasive species compared is known to be naturalised somewhere, whether the invasive species is globally distributed, and the climatic region of the species. 3. Synthesis and applications. We show for the first time, using a multi-species comparative approach, that invasive insects differ in several characteristics from related non-invasive insects. Our results show that invasive species, such as Spodoptera frugiperda, typically are habitat generalists with a high fecundity, a short lifespan and fast development, whereas the importance of female body size and number of enemies are context dependent. Our study can guide and improve existing screening tools for assessing the invasion potential of alien insects.

2023-07-17, Cai, Lirong, Kreft, Holger, Taylor, Amanda, Schrader, Julian, Dawson, Wayne, Essl, Franz, van Kleunen, Mark, Pergl, Jan, Pyšek, Petr, Winter, Marten, Weigelt, Patrick

Assessing the distribution of geographically restricted and evolutionarily unique species and their underlying drivers is key to understanding biogeographical processes and critical for global conservation prioritization. Here, we quantified the geographic distribution and drivers of phylogenetic endemism for ~320,000 seed plants worldwide and identified centers and drivers of evolutionarily young (neoendemism) and evolutionarily old endemism (paleoendemism). Tropical and subtropical islands as well as tropical mountain regions displayed the world’s highest phylogenetic endemism. Most tropical rainforest regions emerged as centers of paleoendemism, while most Mediterranean-climate regions showed high neoendemism. Centers where high neo- and paleoendemism coincide emerged on some oceanic and continental fragment islands, in Mediterranean-climate regions and parts of the Irano-Turanian floristic region. Global variation in phylogenetic endemism was well explained by a combination of past and present environmental factors (79.8 to 87.7% of variance explained) and most strongly related to environmental heterogeneity. Also, warm and wet climates, geographic isolation, and long-term climatic stability emerged as key drivers of phylogenetic endemism. Neo- and paleoendemism were jointly explained by climatic and geological history. Long-term climatic stability promoted the persistence of paleoendemics, while the isolation of oceanic islands and their unique geological histories promoted neoendemism. Mountainous regions promoted both neo- and paleoendemism, reflecting both diversification and persistence over time. Our study provides insights into the evolutionary underpinnings of biogeographical patterns in seed plants and identifies the areas on Earth with the highest evolutionary and biogeographical uniqueness—key information for setting global conservation priorities.

2023-05-31, Muñoz‐Mas, Rafael, Essl, Franz, van Kleunen, Mark, Seebens, Hanno, Dawson, Wayne, Casal, Christine Marie V., García‐Berthou, Emili

Aim: Investigating major freshwater fish flows (translocations) between biogeo-graphic regions and their temporal dynamics and also quantifying spatial patterns and temporal changes in the array of introduced species, and the emergence and distance between major donor and recipient regions.Location: Global.Time Period: 1800– 2020.Major Taxa Studied: Freshwater fishes.Methods: We analysed a global dataset on freshwater fish introductions (4241 events of 688 species). Freshwater fish flows were investigated with flow diagrams and χ2tests, while PERMANOVA (permutational multivariate analysis of variance) was used to test the association between species and regions and temporal shifts. Cluster analysis revealed major recipient areas and composition of the introduced species. Finally, changes in distances between donor and recipient sites were tested with PERMANOVA.Results: The number of introductions between biogeographic regions mirrored the European and North American dominance before World War II (WWII) and the trends in recreational fishing, biocontrol programmes and food production, especially in the Sino-Oriental region, which has a long tradition of aquaculture and fishkeeping. Over the years, the origins and composition of introduced species changed uniquely in each biogeographic region, although the most introduced species are common to every region. Salmonids and other cold-water species were frequently introduced be-fore the 1950s, whereas tropical ornamental and aquaculture species currently pre-vail. Distances between donor and recipient sites did not vary over the time. After WWII, the Sino-Oriental region consolidated its dominance and the Ethiopian and Neotropical regions emerged as new global donor and recipient regions.Main Conclusions: Global policy should focus on tropical ornamental and aquaculture species, which could benefit from global warming, especially in the Sino-Oriental re-gion, because it currently dominates freshwater fish species flows, and the Ethiopia and Neotropical regions, because they recently emerged as important global donor and recipient regions of freshwater fish introductions.

2023-09-07, Zhang, Xue, van Kleunen, Mark, Chang, Chunling, Liu, Yanjie

A fundamental question in ecology is which species will prevail over others amid changes in both environmental mean conditions and their variability. Although the widely accepted fluctuating resource hypothesis predicts that increases in mean resource availability and variability therein will promote nonnative plant invasion, it remains unclear to what extent these effects might be mediated by soil microbes. We grew eight invasive nonnative plant species as target plants in pot‐mesocosms planted with five different synthetic native communities as competitors, and assigned them to eight combinations of two nutrient‐fluctuation (constant vs. pulsed), two nutrient‐availability (low vs. high) and two soil‐microbe (living vs. sterilized) treatments. We found that when plants grew in sterilized soil, nutrient fluctuation promoted the dominance of nonnative plants under overall low nutrient availability, whereas the nutrient fluctuation had minimal effect under high nutrient availability. In contrast, when plants grew in living soil, nutrient fluctuation promoted the dominance of nonnative plants under high nutrient availability rather than under low nutrient availability. Analysis of the soil microbial community suggests that this might reflect that nutrient fluctuation strongly increased the relative abundance of the most dominant pathogenic fungal family or genus under high nutrient availability, while decreasing it under low nutrient availability. Our findings are the first to indicate that besides its direct effect, environmental variability could also indirectly affect plant invasion via changes in soil microbial communities.

2023-08, Pouteau, Robin, van Kleunen, Mark, Strasberg, Dominique

Alien species are considered a major driver of extinction risk. Preventing high-impact aliens from being introduced is more necessary than ever to mitigate the current biodiversity crisis. Invasive species risk assessments look at the characteristics of potential invaders but rarely consider how different they are from the native residents that they might threaten. Therefore, we tested whether the impacts of an alien species on a native species can be predicted using the pairwise phylogenetic distance (PPD) between them. Specifically, we analysed whether the PPD of 1407 pairs of native–invasive alien plants is related to the extinction risk of the native plants. We showed that natives threatened by close alien relatives have a significantly higher extinction risk, especially on oceanic islands. This finding argues for consideration of PPD, or at least the presence of congeneric or confamilial native species, in risk assessment of potential impacts of newly introduced alien species and priorization of management of already naturalized alien species.

2023-07-03, Freitag, Martin, Hölzel, Norbert, Neuenkamp, Lena, van der Plas, Fons, Manning, Peter, Abrahão, Anna, Bergmann, Joana, Boeddinghaus, Runa, Bolliger, Ralph, van Kleunen, Mark

1. Experimental evidence shows that grassland plant diversity enhances ecosystem functioning. Yet, the transfer of results from controlled biodiversity experiments to naturally assembled ‘real world’ ecosystems remains challenging due to environmental variation among sites, confounding biodiversity ecosystem functioning relations in observational studies. To bridge the gap between classical biodiversity-ecosystem functioning experiments and observational studies of naturally assembled and managed ecosystems, we created regionally replicated, within-site gradients of species richness by seeding across agricultural grasslands differing in land-use intensity (LUI) and abiotic site conditions. 2. Within each of 73 grassland sites, we established a full-factorial experiment with high-diversity seeding and topsoil disturbance and measured 12 ecosystem functions related to productivity, and carbon and nutrient cycling after 4 years. We then analysed the effects of plant diversity (seeded richness as well as realized richness), functional community composition, land use and abiotic conditions on the ecosystem functions within (local scale) as well as among grassland sites (landscape scale). 3. Despite the successful creation of a within-site gradient in plant diversity (average increase in species richness in seeding treatments by 10%–35%), we found that only one to two of the 12 ecosystem functions responded to realized species richness, resulting in more closed nitrogen cycles in more diverse plant communities. Similar results were found when analysing the effect of the seeding treatment instead of realized species richness. Among sites, ecosystem functioning was mostly driven by environmental conditions and LUI. Also here, the only functions related to plant species richness were those associated with a more closed nitrogen cycle under increased diversity. 4. The minor effects of species enrichment we found suggest that the functionally-relevant niche space is largely saturated in naturally assembled grasslands, and that competitive, high-functioning species are already present. 5. Synthesis: While nature conservation and cultural ecosystem services can certainly benefit from plant species enrichment, our study indicates that restoration of plant diversity in naturally assembled communities may deliver only relatively weak increases in ecosystem functioning, such as a more closed nitrogen cycle, within the extensively to moderate intensively managed agricultural grasslands of our study.

2023-08-31, Fristoe, Trevor, Bleilevens, Jonas, Kinlock, Nicole L., Yang, Qiang, Zhang, Zhijie, Dawson, Wayne, Essl, Franz, Kreft, Holger, Pergl, Jan, van Kleunen, Mark

Human activities are causing global biotic redistribution, translocating species and providing them with opportunities to establish populations beyond their native ranges. Species originating from certain global regions, however, are disproportionately represented among naturalized aliens. The evolutionary imbalance hypothesis posits that differences in absolute fitness among biogeographic divisions determine outcomes when biotas mix. Here, we compile data from native and alien distributions for nearly the entire global seed plant flora and find that biogeographic conditions predicted to drive evolutionary imbalance act alongside climate and anthropogenic factors to shape flows of successful aliens among regional biotas. Successful aliens tend to originate from large, biodiverse regions that support abundant populations and where species evolve against a diverse backdrop of competitors and enemies. We also reveal that these same native distribution characteristics are shared among the plants that humans select for cultivation and economic use. In addition to influencing species’ innate potentials as invaders, we therefore suggest that evolutionary imbalance shapes plants’ relationships with humans, impacting which species are translocated beyond their native distributions.

2023-08, Pouteau, Robin, van Kleunen, Mark, Strasberg, Dominique

Alien species are considered a major driver of extinction risk. Preventing high-impact aliens from being introduced is more necessary than ever to mitigate the current biodiversity crisis. Invasive species risk assessments look at the characteristics of potential invaders but rarely consider how different they are from the native residents that they might threaten. Therefore, we tested whether the impacts of an alien species on a native species can be predicted using the pairwise phylogenetic distance (PPD) between them. Specifically, we analysed whether the PPD of 1407 pairs of native–invasive alien plants is related to the extinction risk of the native plants. We showed that natives threatened by close alien relatives have a significantly higher extinction risk, especially on oceanic islands. This finding argues for consideration of PPD, or at least the presence of congeneric or confamilial native species, in risk assessment of potential impacts of newly introduced alien species and priorization of management of already naturalized alien species.

2023-06-09, Li, Yan, Mamonova, Ekaterina, Köhler, Nadja, van Kleunen, Mark, Stift, Marc