Mark van Kleunen

• University of Konstanz

Information on the determinants of taxonomic and phylogenetic diversity of invasive plant species is crucial for managing invasive plants. With globalization, most countries have experienced substantial economic losses and environmental damage due to biological invasions. We analysed the determinants of variation in the diversity and phylogenetic s...

Global tree species mapping using remote sensing data is vital for biodiversity monitoring, forest management, and ecological research. However, progress in this field has been constrained by the scarcity of large-scale, labeled datasets. To address this, we introduce GlobalGeoTree, a comprehensive global dataset for tree species classification. Gl...

Costs of reproduction arise when investments into current reproduction reduce future reproductive fitness. Studies on reproductive costs use diverse approaches, including the analysis of gene expression, physiology, trade‐offs between reproduction and growth/survival, and the impact of reproductive investments on population growth. These studies de...

With the number of naturalized alien plant species continuously increasing, it has become of major interest to understand how they can coexist with or even outcompete native species. Plant–soil interactions and soil spatial heterogeneity are thought to play major roles in the coexistence of plant species. Depending on the strengths of conspecific a...

In this contribution of the Hypothesis Description series, we provide an overview of one of the longest-standing hypotheses in invasion science: Darwin's naturalisation hypothesis. We present a brief summary of past definitions and propose the revised definition “high phylogenetic distance between non-native species and the recipient community incr...

Soil heterogeneity (i.e. the heterogeneous distribution of nutrients, soil types or other soil characteristics) has been found to promote the invasion success of naturalized alien plants (i.e. plants that have been introduced by humans to new ranges, where they have established persistent populations) when competing with native plants. However, nat...

Biodiversity entails species diversity both within a trophic level (horizontal diversity) and across levels (vertical diversity). While invasion resistance studies usually focus on horizontal diversity, vertical diversity could provide additional biotic resistance to invasion. Quantifying the role of such 2D diversity will provide a more comprehens...

Urban areas are foci for the introduction of non‐native plant species, and they often act as launching sites for invasions into the wider environment. Although interest in biological invasions in urban areas is growing rapidly, and the extent and complexity of problems associated with invasions in these systems have increased, data on the compositi...

Background and aims Microplastics affect plant growth and change abiotic and biotic soil properties, such as soil structure and soil-community composition. However, how microplastics affect plant-soil interactions, such as plant-soil feedbacks (PSFs), is still poorly understood. Here, we tested how artificial particles affect heterospecific PSFs, d...

Quantifying how co‐acting global change factors (GCFs) influence plant invasion is crucial for predicting future invasion dynamics. We did a meta‐analysis to assess pairwise effects of five GCFs (elevated CO2, drought, eutrophication, increased rainfall and warming) on native and alien plants. We found that alien plants, compared to native plants,...

Plant invasions pose significant threats to native ecosystems, human health, and global economies. However, the complex and multidimensional nature of factors influencing plant invasions makes it challenging to predict and interpret their invasion success accurately. Using a robust machine learning algorithm, random forest, and an extensive suite o...

1. Urban areas are foci for the introduction of non-native plant species, and they often act as launching sites for invasions into the wider environment. Although interest in biological invasions in urban areas is growing rapidly, and the extent and complexity of problems associated with invasions in these systems have increased, data on the compos...

Global environmental change and plant invasion are both recognized as key indicators of the Anthropocene, with the former potentially accelerating the latter. Still, whether multiple co-acting global change factors (GCFs) influence plant invasions even stronger remains untested despite the fact that in nature GCFs usually act together rather than a...

Grasslands are highly diverse ecosystems providing important ecosystem services, but they currently face a variety of anthropogenic stressors simultaneously. Quantifying grassland responses to global change factors (GCFs) is crucial for developing effective strategies to mitigate the negative impacts of global change on grassland communities and to...

Solidago canadensis, native to North America, is an invasive species in many areas of the world, where it causes serious damage to natural ecosystems and economic losses. However, a dearth of genetic resources and molecular markers has hampered our understanding of its invasion history. Here, we de novo assembled 40 complete chloroplast genomes of...

Environmental filtering and dispersal history limit plant distributions and affect biogeographical patterns, but how their relative importance varies across evolutionary timescales is unresolved. Phylogenetic beta diversity quantifies dissimilarity in evolutionary relatedness among assemblages and might help resolve the ecological and biogeographic...

Although herbivory and allelopathy play important roles in plant invasions, their roles in mediating the effect of plant diversity on invasion resistance remain unknown. In a 2‐year field experiment, we constructed native plant communities with four levels of species richness (one, two, four, and eight species) and used a factorial combination of i...

Elton's biotic resistance hypothesis predicts that biodiversity can resist the establishment of invasive plants. However, whether and how within‐species diversity mediates the impacts of successfully established invaders is poorly understood, particularly in the face of climate change. We used an experimental system to test the effect of intraspeci...

Aim The enemy release hypothesis states that the invasion success of non‐native species is partly due to their escape from natural enemies, e.g., herbivores. Large‐scale studies of herbivory using multiple species across multiple sites are needed to test the generality of herbivory release in non‐native plants. Location Europe. Methods We carried...

In this contribution of the Hypothesis Description series, we provide an overview of one of the longest-standing hypotheses in invasion science: Darwin's naturalization hypothesis. We present a brief summary of past definitions and propose the revised definition “low phylogenetic similarity between non-native species and the recipient community inc...

Aim Functional traits help to understand the ecological processes underlying biological invasions. The extent to which trait data are available for alien plants at the global scale is unknown. In this study, we assess the availability of trait data and identify global gaps and biases Location Global Time Period Present Major taxa studied Vascul...

Background and aims Microplastics affect plant growth and change abiotic and biotic soil properties, such as soil structure or soil-community composition. However, how microplastics affect plant-soil interactions, such as plant-soil feedbacks (PSFs), is still poorly understood. Here, we tested how artificial particles affect heterospecific PSFs, de...

Plants infected by parasitic species might be further stressed by climate warming as both factors can influence the host plant's nutrient acquisition and growth. The root economics space, defined by root functional traits, reflects a plant's nutrient acquisition strategy. However, the combined effects of warming and parasitism on root functional tr...

Background and aims Plant investment in secondary metabolites can be driven by abiotic factors such as nitrogen (N) availability and variation in biotic factors such as root-associated microbes. However, few studies have tested their combined effect on allelopathy. Here, we test whether and how N addition (i.e. eutrophication) and soil microbes mod...

Elton’s biotic resistance hypothesis posits that species-rich communities are more resistant to invasion. However, it remains unknown how species, phylogenetic and functional richness, along with environmental and human-impact factors, collectively affect plant invasion as alien species progress along the introduction–naturalization–invasion contin...

Terrestrial plant communities often become invaded by alien species, which may benefit from high growth rates, strong phenotypic plasticity and reduced negative impacts from local soil communities. At the same time, terrestrial communities are increasingly more often exposed to periods of drought. However, how drought affects the competition betwee...

Biological invasions, identified as one of the primary drivers of ecosystem change, present significant threats to biodiversity, economies, and human health. Globally, with 37,000 naturalized species and an annual cost of approximately 423 billion USD, addressing the issue of invasive species is increasingly urgent. This paper underscores the neces...

The ecological impact of non‐native species arises from their establishment in local assemblages. However, the rates of non‐native spread in new regions and their determinants have not been comprehensively studied. Here, we combined global databases documenting the occurrence of non‐native species and residence of non‐native birds, mammals, and vas...

Exotic plant invaders can promote others via direct or indirect facilitation, known as “invasional meltdown.” Increased soil nutrients can also promote invaders by increasing their competitive impacts, but how this might affect meltdown is unknown. In a mesocosm experiment, we evaluated how eight exotic plant species and eight Eurasian native speci...

Background and aims Soil heterogeneity has been found to promote plant invasion, as many naturalized alien species benefit more from nutrient-rich patches than native species do. However, it remains unclear whether naturalized alien species also benefit more from growing on patch boundaries than from growing in the patch centres of heterogeneous so...

To maximize their fitness, plants have to adjust their allocation strategy according to their abiotic and biotic environments. Plants can use the ratio of red to far‐red light (R:FR) to sense neighbours, allowing them to modify their growth in response to aboveground competition. In this study, we used supplemental FR light to artificially lower th...

Biodiversity often helps communities resist invasion. However, it is unclear whether this diversity–invasion relationship holds true under environmental changes. Here, we conduct a meta-analysis of 1010 observations from 25 grassland studies in which plant species richness is manipulated together with one or more environmental change factors to tes...

Species traits may determine plant interactions along with soil microbiome, further shaping plant–soil feedbacks (PSFs). However, how plant traits modulate PSFs and, consequently, the dominance of plant functional groups remains unclear. We used a combination of field surveys and a two‐phase PSF experiment to investigate whether forbs and graminoid...

Biodiversity commonly contributes to ecosystem functioning and provides ecosystem services. Biochar application is frequently used to remediate soils contaminated with heavy metals. As many invasive plant species can quickly form huge amounts of biomass, they are potentially useful for producing biochar for remediating contaminated soils. However,...

Background and aims Naturalized alien and native plants can impact each other directly when they grow next to each other, but also indirectly through their soil legacies. These alien-native interactions can also be modified by the presence of a third alien or native species. However, it is unknown how the performance of co-growing alien and native...

The ecological consequences of microplastic pollution for plants remain largely unknown, and the few studies that tested the effects usually focused on a single type of microplastic and a single plant species. However, most plants will be exposed to multiple microplastic types simultaneously, and the effects may vary among species. To test the effe...

Elton’s biotic resistance hypothesis posits that species-rich communities are more resistant to invasion. Yet, there is evidence that species richness alone may not fully explain community resistance, as phylogenetic and functional richness, along with environmental factors and human-induced disturbances, also play pivotal roles. Additionally, it r...

Changes in species' native range size and occupancy have been dramatically accelerated by anthropogenic pressures in the last centuries. At the same time humans have introduced thousands of species beyond their historic range limits, and some of these have established self-sustaining populations (i.e. become naturalized). It is known that particula...

Alien species can have massive impacts on native biodiversity, ecosystem functioning, and human livelihoods. Assessing which species from currently cultivated alien floras may escape into the wild and naturalize is essential for efficient and proactive ecosystem management and biodiversity conservation. Climate change has already promoted the natur...

Although native species diversity is frequently reported to enhance invasion resistance, within‐species diversity of native plants can also moderate invasions. While the positive diversity–invasion resistance relationship is often attributed to competition, indirect effects mediated through plant–soil feedbacks can also influence the relationship....

Human factors and plant characteristics are important drivers of plant invasions, which threaten ecosystem integrity, biodiversity and human well-being. However, while previous studies often examined a limited number of factors or focused on a specific invasion stage (e.g., naturalization) for specific regions, a multi-factor and multi-stage analys...

Organismal functional strategies form a continuum from slow- to fast-growing organisms, in response to common drivers such as resource availability and disturbance. However, whether there is synchronisation of these strategies at the entire community level is unclear. Here, we combine trait data for >2800 above- and belowground taxa from 14 trophic...

Successful alien species may experience a period of quiescence, known as the lag phase, before becoming invasive and widespread. The existence of lags introduces severe uncertainty in risk analyses of aliens as the present state of species is a poor predictor of future distributions, invasion success and impact. Predicting a species’ ability to inv...

Changes in precipitation patterns are one of the most pervasive components of climate change. It has been suggested that the increased frequency of extreme drought and flooding events could affect the outcome of competition between native and invasive plants. However, empirical evidence for this prediction remains scarce. We combined controlled exp...

Parasitic plants have been shown to affect soil-organic-matter (SOM) decomposition, but the mechanism is unknown. As arbuscular mycorrhizal fungi (AMF) can affect decomposition and compete with parasitic plants for carbon, we hypothesized that parasitic plants can indirectly regulate decomposition by suppressing AMF. We conducted two experiments in...

Background and Aims Naturalized alien and native plants can impact each other directly when they grow next to each other, but also indirectly through their soil legacies. These alien-native interactions can also be modified by the presence of a third alien or native species. However, it is unknown how the performance of co-growing alien and native...

Aim Spreading infectious diseases associated with introduced pathogens can have devastating effects on native biota and human livelihoods. We analyse the global distribution of 100 major alien fungal and oomycete pathogens with substantial socio‐economic and environmental impacts and examine their taxonomy, ecological characteristics, temporal accu...

Aim Worldwide, floras are becoming homogenized at global scales, but regional patterns vary. Here, we present the first assessment for the Malesian phytogeographical region in terms of the timing of introductions, direction, magnitude and drivers of floristic change due to alien plant naturalizations. Location Malesian phytogeographic region, incl...

Aims Most naturalized plants are escapees from cultivation. Inventories of cultivated introduced species thus offer unique, still underutilized, opportunities to assess naturalization drivers of introduced plants. We used a comprehensive inventory of 13,718 introduced species cultivated in China's botanical gardens to test which species characteris...

Microplastics can affect their surroundings physically and chemically, resulting in diverse effects on plant-soil systems. Similar to other substances (e.g. nutrients and water), microplastics in the environment occur in patches. Such heterogeneous distributions could affect plant responses to plastic pollution. Yet, this has remained untested. We...

Darwin’s naturalization conundrum describes two seemingly contradictory hypotheses regarding whether alien species closely or distantly related to native species should be more likely to naturalize in regional floras. Both expectations have accumulated empirical support, and whether such apparent inconsistency can be reconciled at the global scale...

Plant introductions outside their native ranges by humans have led to substantial ecological consequences. While we have gained considerable knowledge about intercontinental introductions, the distribution and determinants of intracontinental aliens remain poorly understood. Here, we studied naturalized (i.e., self-sustaining) intracontinental alie...

Nitrogen (N) has been considered a crucial factor influencing plant invasions. Many studies have assessed responses of alien plants to different N availabilities. However, in natural soils, N comes in different inorganic and organic forms. Few studies have explored yet whether responses of alien species to different N forms are related to their nat...

Background and Aims Soil heterogeneity can be caused by plant-soil feedback (PSF), but little is known about how this affects plant growth and the distribution of roots. Moreover, as invasive and native plant species frequently differ in PSF and root-foraging ability, they may differ in their responses to PSF-mediated soil heterogeneity. Methods W...

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...

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 differenc...

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...

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 iden...

Karyological characteristics are among the traits underpinning the invasion success of vascular plants. Using 11 049 species, we tested the effects of genome size and ploidy levels on plant naturalization (species forming self‐sustaining populations where they are not native) and invasion (naturalized species spreading rapidly and having environmen...

Across the tree of life, organismal functional strategies form a continuum from slow-to fast-growing organisms, in response to common drivers such as resource availability and disturbance. However, the synchronization of these strategies at the entire community level is untested. We combine trait data for >2800 above-and belowground taxa from 14 tr...

Alien species can have massive impacts on native biodiversity and ecosystem functioning. Assessing which species from currently cultivated alien floras may escape into the wild and naturalize is hence essential for ecosystem management and biodiversity conservation. Climate change has promoted the naturalization of many alien plants in temperate re...

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 stud...

Human assistance and species’ characteristics are among the key drivers of plant invasions, which profoundly threaten ecosystem integrity, biodiversity and human well-being. However, previous studies have typically focused on one or a few factors or a particular invasion stage (e.g., naturalization) at regional scales. Here, we employed a multileve...

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 factori...

Breakdown of self-incompatibility has frequently been attributed to loss-of-function mutations of alleles at the locus responsible for recognition of self-pollen (i.e. the S-locus). However, other potential causes have rarely been tested. Here, we show that self-compatibility of S1S1-homozygotes in selfing populations of the otherwise self-incompat...

Plant–soil feedbacks (PSFs), soil-mediated plant effects on conspecific or heterospecific successors, are a major driver of vegetation development. It has been proposed that specialist plant antagonists drive differences in PSF responses between conspecific and heterospecific plants, whereas contributions of generalist plant antagonists to PSFs rem...

Aim Investigating major freshwater fish flows (translocations) between biogeographic 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 Studie...

Although herbivory and allelopathy play important roles in plant invasions, their roles in mediating the effect of plant diversity on invasion resistance remain unknown. We performed a two-year field experiment in which we manipulated plant-species richness, herbivory and allelopathy, and then experimentally invaded the plots with the invasive Soli...

Background and Aims Soil heterogeneity can be caused by plant-soil feedback (PSF), but little is known about how such PSF-mediated soil heterogeneity affects plant growth and the distribution of roots. Moreover, as invasive and native plant species frequently differ in PSF and in root-foraging ability, they may also differ in their responses to PSF...

While the regional distribution of non-native species is increasingly well documented for some taxa, global analyses of non-native species in local assemblages are still missing. Here, we use a worldwide collection of assemblages from five taxa - ants, birds, mammals, spiders and vascular plants - to assess whether the incidence, frequency and prop...

Biological invasions have become a worldwide problem, and measures to efficiently prevent and control invasions are still in development. Like many other parts of the world, China is undergoing a dramatic increase in plant invasions. Most of the currently 933 established (i.e., naturalized) plant species, of which 214 are categorized as invasive, h...

Major regional gaps exist in the reporting and accessibility of naturalized plant species distribution data, especially within Southeast Asia. Here, we present the Malesian Naturalized Alien Flora database (MalNAF), the first standardized island-group level checklist of naturalized vascular plant species for the Malesian phytogeographical region. W...

Assessing phylogenetic endemism, i.e., the distribution of geographically restricted and evolutionarily unique species, is key to understanding biogeographic patterns and processes and critical for global conservation planning. Here, we quantified the geographic distribution and drivers of phylogenetic endemism for ~320,000 seed plants worldwide an...

Plant communities experience impacts of increasing numbers of global change factors (e.g., warming, eutrophication, pollution). Consequently, unpredictable global change effects could arise. However, information about multi-factor effects on plant communities is scarce. To test plant-community responses to multiple global change factors (GCFs), we...

Although most studies on the ecological effects of microplastic pollution focus on a single type of synthetic polymer and a single species, most organisms will be exposed to multiple polymer types simultaneously and the effects may vary among species. To test the effects of polymer diversity on plants, we grew single plants of eight invasive and ei...

Elton’s diversity-invasibility hypothesis predicts that high-diversity native communities should be less easily invaded than low-diversity communities. Although various mechanisms have been proposed to explain it, it remains unclear which of those mechanisms is more important and whether they operate simultaneously. Using one pool of native plant s...