Reassessment of the risks of climate change for terrestrial ecosystems

Forecasting the risks of climate change for species and ecosystems is necessary for developing targeted conservation strategies. Previous risk assessments mapped the exposure of the global land surface to changes in climate. However, this procedure is unlikely to robustly identify priority areas for conservation actions because nonlinear physiological responses and colimitation processes ensure that ecological changes will not map perfectly to the forecast climatic changes. Here, we combine ecophysiological growth models of 135,153 vascular plant species and plant growth-form information to transform ambient and future climatologies into phytoclimates, which describe the ability of climates to support the plant growth forms that characterize terrestrial ecosystems. We forecast that 33% to 68% of the global land surface will experience a significant change in phytoclimate by 2070 under representative concentration pathways RCP 2.6 and RCP 8.5, respectively. Phytoclimates without present-day analogue are forecast to emerge on 0.3-2.2% of the land surface and 0.1-1.3% of currently realized phytoclimates are forecast to disappear. Notably, the geographic pattern of change, disappearance and novelty of phytoclimates differs markedly from the pattern of analogous trends in climates detected by previous studies, thereby defining new priorities for conservation actions and highlighting the limits of using untransformed climate change exposure indices in ecological risk assessments. Our findings suggest that a profound transformation of the biosphere is underway and emphasize the need for a timely adaptation of biodiversity management practices.

Balancing economic and ecological functions in smallholder and industrial oil palm plantations

The expansion of the oil palm industry in Indonesia has improved livelihoods in rural communities, but comes at the cost of biodiversity and ecosystem degradation. Here, we investigated ways to balance ecological and economic outcomes of oil palm cultivation. We compared a wide range of production systems, including smallholder plantations, industrialized company estates, estates with improved agronomic management, and estates with native tree enrichment. Across all management types, we assessed multiple indicators of biodiversity, ecosystem functions, management, and landscape structure to identify factors that facilitate economic-ecological win-wins, using palm yields as measure of economic performance. Although, we found that yields in industrialized estates were, on average, twice as high as those in smallholder plantations, ecological indicators displayed substantial variability across systems, regardless of yield variations, highlighting potential for economic-ecological win-wins. Reducing management intensity (e.g., mechanical weeding instead of herbicide application) did not lower yields but improved ecological outcomes at moderate costs, making it a potential measure for balancing economic and ecological demands. Additionally, maintaining forest cover in the landscape generally enhanced local biodiversity and ecosystem functioning within plantations. Enriching plantations with native trees is also a promising strategy to increase ecological value without reducing productivity. Overall, we recommend closing yield gaps in smallholder cultivation through careful intensification, whereas conventional plantations could reduce management intensity without sacrificing yield. Our study highlights various pathways to reconcile the economics and ecology of palm oil production and identifies management practices for a more sustainable future of oil palm cultivation.

Joint environmental and social benefits from diversified agriculture

Agricultural simplification continues to expand at the expense of more diverse forms of agriculture. This simplification, for example, in the form of intensively managed monocultures, poses a risk to keeping the world within safe and just Earth system boundaries. Here, we estimated how agricultural diversification simultaneously affects social and environmental outcomes. Drawing from 24 studies in 11 countries across 2655 farms, we show how five diversification strategies focusing on livestock, crops, soils, noncrop plantings, and water conservation benefit social (e.g., human well-being, yields, and food security) and environmental (e.g., biodiversity, ecosystem services, and reduced environmental externalities) outcomes. We found that applying multiple diversification strategies creates more positive outcomes than individual management strategies alone. To realize these benefits, well-designed policies are needed to incentivize the adoption of multiple diversification strategies in unison.

Effects of plant diversity on productivity strengthen over time due to trait-dependent shifts in species overyielding

Plant diversity effects on community productivity often increase over time. Whether the strengthening of diversity effects is caused by temporal shifts in species-level overyielding (i.e., higher species-level productivity in diverse communities compared with monocultures) remains unclear. Here, using data from 65 grassland and forest biodiversity experiments, we show that the temporal strength of diversity effects at the community scale is underpinned by temporal changes in the species that yield. These temporal trends of species-level overyielding are shaped by plant ecological strategies, which can be quantitatively delimited by functional traits. In grasslands, the temporal strengthening of biodiversity effects on community productivity was associated with increasing biomass overyielding of resource-conservative species increasing over time, and with overyielding of species characterized by fast resource acquisition either decreasing or increasing. In forests, temporal trends in species overyielding differ when considering above- versus belowground resource acquisition strategies. Overyielding in stem growth decreased for species with high light capture capacity but increased for those with high soil resource acquisition capacity. Our results imply that a diversity of species with different, and potentially complementary, ecological strategies is beneficial for maintaining community productivity over time in both grassland and forest ecosystems.

Plant invasion and naturalization are influenced by genome size, ecology and economic use globally

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 analysis at the global scale is lacking. Here, we employ a multi-level framework to investigate the interplay between plant characteristics (genome size, Grime's adaptive CSR-strategies and native range size) and economic use and how these factors collectively affect plant naturalization and invasion success worldwide. While our findings derived from structural equation models highlight the substantial contribution of human assistance in both the naturalization and spread of invasive plants, we also uncovered the pivotal role of species' adaptive strategies among the factors studied, and the significantly varying influence of these factors across invasion stages. We further revealed that the effects of genome size on plant invasions were partially mediated by species adaptive strategies and native range size. Our study provides insights into the complex and dynamic process of plant invasions and identifies its key drivers worldwide.

Diurnal temperature range as a key predictor of plants' elevation ranges globally

A prominent hypothesis in ecology is that larger species ranges are found in more variable climates because species develop broader environmental tolerances, predicting a positive range size-temperature variability relationship. However, this overlooks the extreme temperatures that variable climates impose on species, with upper or lower thermal limits more likely to be exceeded. Accordingly, we propose the 'temperature range squeeze' hypothesis, predicting a negative range size-temperature variability relationship. We test these contrasting predictions by relating 88,000 elevation range sizes of vascular plants in 44 mountains to short- and long-term temperature variation. Consistent with our hypothesis, we find that species' range size is negatively correlated with diurnal temperature range. Accurate predictions of short-term temperature variation will become increasingly important for extinction risk assessment in the future.

The contribution of plant life and growth forms to global gradients of vascular plant diversity

Plant life and growth forms (shortened to 'plant forms') represent key functional strategies of plants in relation to their environment and provide important insights into the ecological constraints acting on the distribution of biodiversity. Despite their functional importance, how the spectra of plant forms contribute to global gradients of plant diversity is unresolved. Using a novel dataset comprising > 295 000 species, we quantify the contribution of different plant forms to global gradients of vascular plant diversity. Furthermore, we establish how plant form distributions in different biogeographical regions are associated with contemporary and paleoclimate conditions, environmental heterogeneity and phylogeny. We find a major shift in representation of woody perennials in tropical latitudes to herb-dominated floras in temperate and boreal regions, following a sharp latitudinal gradient in plant form diversity from the tropics to the poles. We also find significant functional differences between regions, mirroring life and growth form responses to environmental conditions, which is mostly explained by contemporary climate (18-87%), and phylogeny (6-62%), with paleoclimate and heterogeneity playing a lesser role (< 23%). This research highlights variation in the importance of different plant forms to diversity gradients world-wide, shedding light on the ecological and evolutionary pressures constraining plant-trait distributions.

A latitudinal gradient in Darwin's naturalization conundrum at the global scale for flowering plants

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 is unclear. Here, using 219,520 native and 9,531 naturalized alien plant species across 487 globally distributed regions, we found a latitudinal gradient in Darwin's naturalization conundrum. Naturalized alien plant species are more closely related to native species at higher latitudes than they are at lower latitudes, indicating a greater influence of preadaptation in harsher climates. Human landscape modification resulted in even steeper latitudinal clines by selecting aliens distantly related to natives in warmer and drier regions. Our results demonstrate that joint consideration of climatic and anthropogenic conditions is critical to reconciling Darwin's naturalization conundrum.

The poleward naturalization of intracontinental alien plants

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 aliens using native and alien floras of 243 mainland regions in North America, South America, Europe, and Australia. We revealed that 4510 plant species had intracontinental origins, accounting for 3.9% of all plant species and 56.7% of all naturalized species in these continents. In North America and Europe, the numbers of intracontinental aliens peaked at mid-latitudes, while the proportion peaked at high latitudes in Europe. Notably, we found predominant poleward naturalization, primarily due to larger native species pools in low-latitudes. Geographic and climatic distances constrained the naturalization of intracontinental aliens in Australia, Europe, and North America, but not in South America. These findings suggest that poleward naturalizations will accelerate, as high latitudes become suitable for more plant species due to climate change.

Complementary ecosystem services from multiple land uses highlight the importance of tropical mosaic landscapes

Tropical agricultural landscapes often consist of a mosaic of different land uses, yet little is known about the spectrum of ecosystem service bundles and materials they provide to rural households. We interviewed 320 households on the different benefits received from prevalent land-use types in north-eastern Madagascar (old-growth forests, forest fragments, vanilla agroforests, woody fallows, herbaceous fallows, and rice paddies) in terms of ecosystem services and plant uses. Old-growth forests and forest fragments were reported as important for regulating services (e.g. water regulation), whilst fallow lands and vanilla agroforests as important for provisioning services (food, medicine, fodder). Households reported the usage of 285 plant species (56% non-endemics) and collected plants from woody fallows for varying purposes, whilst plants from forest fragments, predominantly endemics, were used for construction and weaving. Multiple land-use types are thus complementary for providing ecosystem services, with fallow lands being particularly important. Hence, balancing societal needs and conservation goals should be based on diversified and comprehensive land management.

Evolutionary imbalance, climate and human history jointly shape the global biogeography of alien plants

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.

Small genome size and variation in ploidy levels support the naturalization of vascular plants but constrain their invasive spread

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 environmental impact). The probability that a species naturalized anywhere in the world decreased with increasing monoploid genome size (DNA content of a single chromosome set). Naturalized or invasive species with intermediate monoploid genomes were reported from many regions, but those with either small or large genomes occurred in fewer regions. By contrast, large holoploid genome sizes (DNA content of the unreplicated gametic nucleus) constrained naturalization but favoured invasion. We suggest that a small genome is an advantage during naturalization, being linked to traits favouring adaptation to local conditions, but for invasive spread, traits associated with a large holoploid genome, where the impact of polyploidy may act, facilitate long-distance dispersal and competition with other species.

Climatic stability and geological history shape global centers of neo- and paleoendemism in seed plants

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.

Assembly of functional diversity in an oceanic island flora

Oceanic island floras are well known for their morphological peculiarities and exhibit striking examples of trait evolution1-3. These morphological shifts are commonly attributed to insularity and are thought to be shaped by the biogeographical processes and evolutionary histories of oceanic islands2,4. However, the mechanisms through which biogeography and evolution have shaped the distribution and diversity of plant functional traits remain unclear5. Here we describe the functional trait space of the native flora of an oceanic island (Tenerife, Canary Islands, Spain) using extensive field and laboratory measurements, and relate it to global trade-offs in ecological strategies. We find that the island trait space exhibits a remarkable functional richness but that most plants are concentrated around a functional hotspot dominated by shrubs with a conservative life-history strategy. By dividing the island flora into species groups associated with distinct biogeographical distributions and diversification histories, our results also suggest that colonization via long-distance dispersal and the interplay between inter-island dispersal and archipelago-level speciation processes drive functional divergence and trait space expansion. Contrary to our expectations, speciation via cladogenesis has led to functional convergence, and therefore only contributes marginally to functional diversity by densely packing trait space around shrubs. By combining biogeography, ecology and evolution, our approach opens new avenues for trait-based insights into how dispersal, speciation and persistence shape the assembly of entire native island floras.

Phylogenetic diversity and the structure of host-epiphyte interactions across the Neotropics

Understanding the mechanisms driving community assembly has been a major focus of ecological research for nearly a century, yet little is known about these mechanisms in commensal communities, particularly with respect to their historical/evolutionary components. Here, we use a large-scale dataset of 4,440 vascular plant species to explore the relationship between the evolutionary distinctiveness (ED) (as measured by the 'species evolutionary history' (SEH)) of host species and the phylogenetic diversity (PD) of their associated epiphyte species. Although there was considerable variation across hosts and their associated epiphyte species, they were largely unrelated to host SEH. Our results mostly support the idea that the determinants of epiphyte colonization success might involve host characteristics that are unrelated to host SEH (e.g., architectural differences between hosts). While determinants of PD of epiphyte assemblages are poorly known, they do not appear to be related to the evolutionary history of host species. Instead, they might be better explained by neutral processes of colonization and extinction. However, the high level of phylogenetic signal in epiphyte PD (independent of SEH) suggests it might still be influenced by yet unrecognized evolutionary determinants. This study highlights how little is still known about the phylogenetic determinants of epiphyte communities.

Tree islands enhance biodiversity and functioning in oil palm landscapes

In the United Nations Decade on Ecosystem Restoration1, large knowledge gaps persist on how to increase biodiversity and ecosystem functioning in cash crop-dominated tropical landscapes2. Here, we present findings from a large-scale, 5-year ecosystem restoration experiment in an oil palm landscape enriched with 52 tree islands, encompassing assessments of ten indicators of biodiversity and 19 indicators of ecosystem functioning. Overall, indicators of biodiversity and ecosystem functioning, as well as multidiversity and ecosystem multifunctionality, were higher in tree islands compared to conventionally managed oil palm. Larger tree islands led to larger gains in multidiversity through changes in vegetation structure. Furthermore, tree enrichment did not decrease landscape-scale oil palm yield. Our results demonstrate that enriching oil palm-dominated landscapes with tree islands is a promising ecological restoration strategy, yet should not replace the protection of remaining forests.

Changes of vegetation in coniferous monocultures in the context of conversion to mixed forests in 30 years - Implications for biodiversity restoration

The understorey vegetation of temperate forests harbours a major proportion of terrestrial biodiversity and fulfills an important role in ecosystem functioning. Over the past decades, temperate forest understoreys were found to change in species diversity and composition due to several anthropogenic and natural drivers. Currently, the conversion and restoration of even-aged coniferous monocultures into more diverse and mixed broad-leaved forests are major objectives of sustainable forest management in Central Europe. This forest conversion alters understorey communities and abiotic site conditions but the underlying patterns and processes are not yet fully understood. Therefore, we investigated changes in the Bavarian Spessart mountains in southwest Germany, where we re-sampled 108 semi-permanent plots from four different coniferous stand types (i.e., Norway spruce, Scots pine, Douglas fir, European larch) about 30 years after the initial assessment. On these plots, we recorded understorey vegetation and forest structure, and derived abiotic site conditions based on ecological indicator values of understorey vegetation, followed by multivariate analysis. We found changes in plant communities that point towards a decrease of soil acidity and a "thermophilization" of forest understoreys. Understorey species richness remained constant, while understorey's Shannon and Simpson diversity increased. The observed changes in forest structure explained the temporal shifts in understorey species composition. The understorey species composition did not experience a significant floristic homogenization since the 1990s. However, plant communities exhibited a reduction in species characteristic of coniferous forests and a simultaneous increase in species associated with broad-leaved forests. The increase of specialist species (closed forests and open sites) may have compensated for the detected decrease in generalist species. We conclude that the forest conversion towards mixed broad-leaved forest in the Spessart mountains of the past decades might have masked homogenization trends that are increasingly reported from Central European forest understoreys.

Global conservation prioritization for the Orchidaceae

Quantitative assessments of endemism, evolutionary distinctiveness and extinction threat underpin global conservation prioritization for well-studied taxa, such as birds, mammals, and amphibians. However, such information is unavailable for most of the world's taxa. This is the case for the Orchidaceae, a hyperdiverse and cosmopolitan family with incomplete phylogenetic and threat information. To define conservation priorities, we present a framework based on phylogenetic and taxonomic measures of distinctiveness and rarity based on the number of regions and the area of occupancy. For 25,434 orchid species with distribution data (89.3% of the Orchidaceae), we identify the Neotropics as hotspots for richness, New Guinea as a hotspot for evolutionary distinctiveness, and several islands that contain many rare and distinct species. Orchids have a similar proportion of monotypic genera as other Angiosperms, however, more taxonomically distinct orchid species are found in a single region. We identify 278 species in need of immediate conservation actions and find that more than 70% of these do not currently have an IUCN conservation assessment and are not protected in ex-situ collections at Botanical Gardens. Our study highlights locations and orchid species in urgent need of conservation and demonstrates a framework that can be applied to other data-deficient taxa.

Tree identity and canopy openness mediate oil palm biodiversity enrichment effects on insect herbivory and pollination

As the extent of oil palm (Elaeis guineensis) cultivation has expanded at the expense of tropical rainforests, enriching conventional large-scale oil palm plantations with native trees has been proposed as a strategy for restoring biodiversity and ecosystem function. However, how tree enrichment affects insect-mediated ecosystem functions is unknown. We investigated impacts on insect herbivory and pollination in the fourth year of a plantation-scale, long-term oil palm biodiversity enrichment experiment in Jambi, Sumatra, Indonesia. Within 48 plots systematically varying in size (25-1600 m² ) and planted tree species richness (1-6 species), we collected response data on vegetation structure, understory insect abundances, and pollinator and herbivore activity on chili plants (Capsicum annuum), which served as indicators of insect-mediated ecosystem functions. We examined the independent effects of plot size, tree species richness, and tree identity on these response variables, using the linear model for random partitions design. The experimental treatments were most associated with vegetation structure: tree identity mattered, as the species Peronema canescens strongly decreased (by approximately one standard deviation) both canopy openness and understory vegetation cover; whereas tree richness only decreased understory flower density. Further, the smallest plots had the lowest understory flower density and richness, presumably because of lower light availability and colonization rates, respectively. Enrichment influenced herbivorous insects and natural enemies in the understory to a lesser extent: both groups had higher abundances in plots with two enrichment species planted, possibly because higher associated tree mortality created more habitat, while herbivores decreased with increasing tree species richness, in line with the resource concentration hypothesis. Linking relationships in structural equation models showed that the negative association between P. canescens and understory vegetation cover was mediated through canopy openness. Likewise, canopy openness mediated increases in herbivore and pollinator insect abundances. Higher pollinator visitation increased phytometer yield, while impacts of insect herbivores on yield were not apparent. Our results demonstrate that even at an early stage, different levels of ecological restoration influence insect-mediated ecosystem functions, mainly through canopy openness. These findings suggest that maintaining some canopy gaps while enrichment plots develop may be beneficial for increasing habitat heterogeneity and insect-mediated ecosystem functions.

The impact of land use on non-native species incidence and number in local assemblages worldwide

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 proportions of naturalised non-native species depend on type and intensity of land use. In plants, assemblages of primary vegetation are least invaded. In the other taxa, primary vegetation is among the least invaded land-use types, but one or several other types have equally low levels of occurrence, frequency and proportions of non-native species. High land use intensity is associated with higher non-native incidence and frequency in primary vegetation, while intensity effects are inconsistent for other land-use types. These findings highlight the potential dual role of unused primary vegetation in preserving native biodiversity and in conferring resistance against biological invasions.

Links to rare climates do not translate into distinct traits for island endemics

Current models of island biogeography treat endemic and non-endemic species as if they were functionally equivalent, focussing primarily on species richness. Thus, the functional composition of island biotas in relation to island biogeographical variables remains largely unknown. Using plant trait data (plant height, leaf area and flower length) for 895 native species in the Canary Islands, we related functional trait distinctiveness and climate rarity for endemic and non-endemic species and island ages. Endemics showed a link to climatically rare conditions that is consistent with island geological change through time. However, functional trait distinctiveness did not differ between endemics and non-endemics and remained constant with island age. Thus, there is no obvious link between trait distinctiveness and occupancy of rare climates, at least for the traits measured here, suggesting that treating endemic and non-endemic species as functionally equivalent in island biogeography is not fundamentally wrong.

Global models and predictions of plant diversity based on advanced machine learning techniques

Despite the paramount role of plant diversity for ecosystem functioning, biogeochemical cycles, and human welfare, knowledge of its global distribution is still incomplete, hampering basic research and biodiversity conservation. Here, we used machine learning (random forests, extreme gradient boosting, and neural networks) and conventional statistical methods (generalized linear models and generalized additive models) to test environment-related hypotheses of broad-scale vascular plant diversity gradients and to model and predict species richness and phylogenetic richness worldwide. To this end, we used 830 regional plant inventories including c. 300 000 species and predictors of past and present environmental conditions. Machine learning showed a superior performance, explaining up to 80.9% of species richness and 83.3% of phylogenetic richness, illustrating the great potential of such techniques for disentangling complex and interacting associations between the environment and plant diversity. Current climate and environmental heterogeneity emerged as the primary drivers, while past environmental conditions left only small but detectable imprints on plant diversity. Finally, we combined predictions from multiple modeling techniques (ensemble predictions) to reveal global patterns and centers of plant diversity at multiple resolutions down to 7774 km² . Our predictive maps provide accurate estimates of global plant diversity available at grain sizes relevant for conservation and macroecology.

Humboldt's legacy: explaining the influence of environmental factors on the taxonomic and phylogenetic diversity of angiosperms along a Neotropical elevational gradient

The scientific work of Alexander von Humboldt was influenced by his interaction with the diversity and natural wealth of the Neotropics. He proposed that climate determines plant diversity along elevational gradients based on his observations. Here, we evaluated the most prominent climate-based hypotheses in explaining plant diversity along an elevational gradient that Humboldt himself visited during his journey across Mexico. Specifically, we examined how climatic variables and forest-use intensity affected species richness and phylogenetic structure of major angiosperm life forms (trees, shrubs, epiphytes, herbs and lianas) along the Cofre de Perote mountain, Veracruz, Mexico. We analysed species richness and phylogenetic structure of angiosperms at eight sites between 30 to 3500 m a.s.l. We estimated the phylogenetic structure using a mega-phylogeny of angiosperms and the abundance-weighted net relatedness index. We considered multiple environmental factors' direct and indirect effects by applying a piecewise structural equation modelling approach. Each life form responds differently to the environmental variables included in our model; however, it is observed that temperature is the main predictor of the taxonomic and phylogenetic diversity of the angiosperms studied, both when the different life forms are grouped and separated. Potential evapotranspiration and precipitation are variables that also influence some life forms' diversity, especially taxonomic diversity. The forest-use intensity negatively affected only the taxonomic diversity of trees. These results highlight the influence of studying the different life forms of angiosperms in diversity gradient models and show the great influence that temperature has in conjunction with other environmental variables to promote the taxonomic and phylogenetic diversity of plant communities. Given the current global environmental crisis, an integrative biogeographically oriented vision based on Humboldt's method is necessary. Honouring the work of Humboldt and continuing his legacy demands more research to understand the causes behind elevational diversity gradients.

The relationship between chlorophyllous spores and mycorrhizal associations in ferns: evidence from an evolutionary approach

PREMISE

Approximately 14% of all fern species have physiologically active chlorophyllous spores that are much more short-lived than the more common and dormant achlorophyllous spores. Most chlorophyllous-spored species (70%) are epiphytes and account for almost 37% of all epiphytic ferns. Chlorophyllous-spored ferns are also overrepresented among fern species in habitats with waterlogged soils, of which nearly 60% have chlorophyllous spores. Ferns in these disparate habitat types also have a low incidence of mycorrhizal associations. We therefore hypothesized that autotrophic chlorophyllous spores represent an adaptation of ferns to habitats with scarce mycorrhizal associations.

METHODS

We evaluated the coevolution of chlorophyllous spores and mycorrhizal associations in ferns and their relation to habitat type using phylogenetic comparative methods.

RESULTS

Although we did not find support for the coevolution of spore type and mycorrhizal associations, we did find that chlorophyllous spores and the absence of mycorrhizal associations have coevolved with epiphytic and waterlogged habitats. Transition rates to epiphytic and waterlogged habitats were significantly higher in species with chlorophyllous spores compared to achlorophyllous lineages.

CONCLUSIONS

Spore type and mycorrhizal associations appear to play important roles in the radiation of ferns into different habitat types. Future work should focus on clarifying the functional significance of these associations.

Naturalized alien floras still carry the legacy of European colonialism

The redistribution of alien species across the globe accelerated with the start of European colonialism. European powers were responsible for the deliberate and accidental transportation, introduction and establishment of alien species throughout their occupied territories and the metropolitan state. Here, we show that these activities left a lasting imprint on the global distribution of alien plants. Specifically, we investigated how four European empires (British, Spanish, Portuguese and Dutch) structured current alien floras worldwide. We found that compositional similarity is higher than expected among regions that once were occupied by the same empire. Further, we provide strong evidence that floristic similarity between regions occupied by the same empire increases with the time a region was occupied. Network analysis suggests that historically more economically or strategically important regions have more similar alien floras across regions occupied by an empire. Overall, we find that European colonial history is still detectable in alien floras worldwide.

Influence of different data cleaning solutions of point‐occurrence records on downstream macroecological diversity models

Digital point‐occurrence records from the Global Biodiversity Information Facility (GBIF) and other data providers enable a wide range of research in macroecology and biogeography. However, data errors may hamper immediate use. Manual data cleaning is time‐consuming and often unfeasible, given that the databases may contain thousands or millions of records. Automated data cleaning pipelines are therefore of high importance. Taking North American Ephedra as a model, we examined how different data cleaning pipelines (using, e.g., the GBIF web application, and four different R packages) affect downstream species distribution models (SDMs). We also assessed how data differed from expert data. From 13,889 North American Ephedra observations in GBIF, the pipelines removed 31.7% to 62.7% false positives, invalid coordinates, and duplicates, leading to datasets between 9484 (GBIF application) and 5196 records (manual‐guided filtering). The expert data consisted of 704 records, comparable to data from field studies. Although differences in the absolute numbers of records were relatively large, species richness models based on stacked SDMs (S‐SDM) from pipeline and expert data were strongly correlated (mean Pearson's r across the pipelines: .9986, vs. the expert data: .9173). Our results suggest that all R package‐based pipelines reliably identified invalid coordinates. In contrast, the GBIF‐filtered data still contained both spatial and taxonomic errors. Major drawbacks emerge from the fact that no pipeline fully discovered misidentified specimens without the assistance of taxonomic expert knowledge. We conclude that application‐filtered GBIF data will still need additional review to achieve higher spatial data quality. Achieving high‐quality taxonomic data will require extra effort, probably by thoroughly analyzing the data for misidentified taxa, supported by experts.

The role of phylogenetic relatedness on alien plant success depends on the stage of invasion

Darwin's naturalization hypothesis predicts successful alien invaders to be distantly related to native species, whereas his pre-adaptation hypothesis predicts the opposite. It has been suggested that depending on the invasion stage (that is, introduction, naturalization and invasiveness), both hypotheses, now known as Darwin's naturalization conundrum, could hold true. We tested this by analysing whether the likelihood of introduction for cultivation, as well as the subsequent stages of naturalization and spread (that is, becoming invasive) of species alien to Southern Africa are correlated with their phylogenetic distance to the native flora of this region. Although species are more likely to be introduced for cultivation if they are distantly related to the native flora, the probability of subsequent naturalization was higher for species closely related to the native flora. Furthermore, the probability of becoming invasive was higher for naturalized species distantly related to the native flora. These results were consistent across three different metrics of phylogenetic distance. Our study reveals that the relationship between phylogenetic distance to the native flora and the success of an alien species changes from one invasion stage to the other.

Win-win opportunities combining high yields with high multi-taxa biodiversity in tropical agroforestry

Resolving ecological-economic trade-offs between biodiversity and yields is a key challenge when addressing the biodiversity crisis in tropical agricultural landscapes. Here, we focused on the relation between seven different taxa (trees, herbaceous plants, birds, amphibians, reptiles, butterflies, and ants) and yields in vanilla agroforests in Madagascar. Agroforests established in forests supported overall 23% fewer species and 47% fewer endemic species than old-growth forests, and 14% fewer endemic species than forest fragments. In contrast, agroforests established on fallows had overall 12% more species and 38% more endemic species than fallows. While yields increased with vanilla vine density and length, non-yield related variables largely determined biodiversity. Nonetheless, trade-offs existed between yields and butterflies as well as  reptiles. Vanilla yields were generally unrelated to richness of trees, herbaceous plants, birds, amphibians, reptiles, and ants, opening up possibilities for conservation outside of protected areas and restoring degraded land to benefit farmers and biodiversity alike.

Resolving ecological-economic trade-offs is a challenge in agriculture. Here, Wurz et al. find that in Malagasy vanilla agroforests, vanilla yield is generally not related to tree, herbaceous plant, bird, amphibian, reptile and ant biodiversity, creating opportunities for conservation outside protected areas.

Introducing the Combined Atlas Framework for large‐scale web‐based data visualization – The GloNAF Atlas of Plant Invasion

Large‐scale biodiversity data, for example, on species distribution and richness information, are being mobilized and becoming available at an increasing rate. Interactive web applications like atlases have been developed to visualize available datasets and make them accessible to a wider audience. Web mapping tools are changing rapidly, and different underlying concepts have been developed to visualize datasets at a high cartographic standard.

Here, we introduce the Combined Atlas Framework for the development of interactive web atlases for ecological data visualization. We combine two existing approaches: the five stages of the user‐centred design approach for web mapping applications and the three U approach for interface success.

Subsequently, we illustrate the use of this framework by developing the Atlas of Plant Invasions based on the Global Naturalized Alien Flora (GloNAF) database. This case study illustrates how the newly developed Combined Atlas Framework with a user‐centred design philosophy can generate measurable success through communication with the target user group, iterative prototyping and competitive analysis of other existing web mapping approaches.

The framework is useful in creating an atlas that employs user feedback to determine usability and utility features within an interactive atlas system. Finally, this framework will enable a better‐informed development process of future visualization and dissemination of biodiversity data through web mapping applications and interactive atlases.

The global loss of floristic uniqueness

Regional species assemblages have been shaped by colonization, speciation and extinction over millions of years. Humans have altered biogeography by introducing species to new ranges. However, an analysis of how strongly naturalized plant species (i.e. alien plants that have established self-sustaining populations) affect the taxonomic and phylogenetic uniqueness of regional floras globally is still missing. Here, we present such an analysis with data from native and naturalized alien floras in 658 regions around the world. We find strong taxonomic and phylogenetic floristic homogenization overall, and that the natural decline in floristic similarity with increasing geographic distance is weakened by naturalized species. Floristic homogenization increases with climatic similarity, which emphasizes the importance of climate matching in plant naturalization. Moreover, floristic homogenization is greater between regions with current or past administrative relationships, indicating that being part of the same country as well as historical colonial ties facilitate floristic exchange, most likely due to more intensive trade and transport between such regions. Our findings show that naturalization of alien plants threatens taxonomic and phylogenetic uniqueness of regional floras globally. Unless more effective biosecurity measures are implemented, it is likely that with ongoing globalization, even the most distant regions will lose their floristic uniqueness.

Scientists' warning - The outstanding biodiversity of islands is in peril

Despite islands contributing only 6.7% of land surface area, they harbor ~20% of the Earth’s biodiversity, but unfortunately also ~50% of the threatened species and 75% of the known extinctions since the European expansion around the globe. Due to their geological and geographic history and characteristics, islands act simultaneously as cradles of evolutionary diversity and museums of formerly widespread lineages—elements that permit islands to achieve an outstanding endemicity. Nevertheless, the majority of these endemic species are inherently vulnerable due to genetic and demographic factors linked with the way islands are colonized. Here, we stress the great variation of islands in their physical geography (area, isolation, altitude, latitude) and history (age, human colonization, human density). We provide examples of some of the most species rich and iconic insular radiations. Next, we analyze the natural vulnerability of the insular biota, linked to genetic and demographic factors as a result of founder events as well as the typically small population sizes of many island species. We note that, whereas evolution toward island syndromes (including size shifts, derived insular woodiness, altered dispersal ability, loss of defense traits, reduction in clutch size) might have improved the ability of species to thrive under natural conditions on islands, it has simultaneously made island biota disproportionately vulnerable to anthropogenic pressures such as habitat loss, overexploitation, invasive species, and climate change. This has led to the documented extinction of at least 800 insular species in the past 500 years, in addition to the many that had already gone extinct following the arrival of first human colonists on islands in prehistoric times. Finally, we summarize current scientific knowledge on the ongoing biodiversity loss on islands worldwide and express our serious concern that the current trajectory will continue to decimate the unique and irreplaceable natural heritage of the world’s islands. We conclude that drastic actions are urgently needed to bend the curve of the alarming rates of island biodiversity loss.

Biovera-Epi: A new database on species diversity, community composition and leaf functional traits of vascular epiphytes along gradients of elevation and forest-use intensity in Mexico

Background

This data paper describes a new, comprehensive database (BIOVERA-Epi) on species distributions and leaf functional traits of vascular epiphytes, a poorly studied plant group, along gradients of elevation and forest-use intensity in the central part of Veracruz State, Mexico. The distribution data include frequencies of 271 vascular epiphyte species belonging to 92 genera and 23 families across 120 20 m × 20 m forest plots at eight study sites along an elevational gradient from sea level to 3500 m a.s.l. In addition, BIOVERA-Epi provides information on 1595 measurements of nine morphological and chemical leaf traits from 474 individuals and 102 species. For morphological leaf traits, we provide data on each sampled leaf. For chemical leaf traits, we provide data at the species level per site and land-use type. We also provide complementary information for each of the sampled plots and host trees. BIOVERA-Epi contributes to an emerging body of synthetic epiphytes studies combining functional traits and community composition.

New information

BIOVERA-Epi includes data on species frequency and leaf traits from 120 forest plots distributed along an elevational gradient, including six different forest types and three levels of forest-use intensity. It will expand the breadth of studies on epiphyte diversity, conservation and functional plant ecology in the Neotropics and will contribute to future synthetic studies on the ecology and diversity of tropical epiphyte assemblages.

BIOVERA-Tree: tree diversity, community composition, forest structure and functional traits along gradients of forest-use intensity and elevation in Veracruz, Mexico

Background

Here, we describe BIOVERA-Tree, a database on tree diversity, community composition, forest structure and functional traits collected in 120 forest plots, distributed along an extensive elevational gradient in Veracruz State, Mexico. BIOVERA-Tree includes information on forest structure from three levels of forest-use intensity, namely old-growth, degraded and secondary forest, replicated across eight elevations from sea-level to near the tree line at 3500 m and on size and location of 4549 tree individuals with a diameter at breast height ≥ 5 cm belonging to 216 species, 154 genera and 80 families. We also report measurements of eight functional traits, namely wood density for 143 species, maximum height for 216 species and leaf traits including: specific leaf area, lamina density, leaf thickness, chlorophyll content and leaf area for 148 species and leaf dry matter content for 145 species.

New information

BIOVERA-Tree is a new database comprising data collected in a rigorous sampling design along forest-use intensity and elevational gradients, contributing to our understanding of how interactive effects of forest-use intensity and elevation affect tree diversity, community composition and functional traits in tropical forests.

Mycorrhizal types influence island biogeography of plants

Plant colonization of islands may be limited by the availability of symbionts, particularly arbuscular mycorrhizal (AM) fungi, which have limited dispersal ability compared to ectomycorrhizal and ericoid (EEM) as well as orchid mycorrhizal (ORC) fungi. We tested for such differential island colonization within contemporary angiosperm floras worldwide. We found evidence that AM plants experience a stronger mycorrhizal filter than other mycorrhizal or non-mycorrhizal (NM) plant species, with decreased proportions of native AM plant species on islands relative to mainlands. This effect intensified with island isolation, particularly for non-endemic plant species. The proportion of endemic AM plant species increased with island isolation, consistent with diversification filling niches left open by the mycorrhizal filter. We further found evidence of humans overcoming the initial mycorrhizal filter. Naturalized floras showed higher proportions of AM plant species than native floras, a pattern that increased with increasing isolation and land-use intensity. This work provides evidence that mycorrhizal fungal symbionts shape plant colonization of islands and subsequent diversification.

A roadmap to plant functional island biogeography

Island biogeography is the study of the spatio-temporal distribution of species, communities, assemblages or ecosystems on islands and other isolated habitats. Island diversity is structured by five classes of process: dispersal, establishment, biotic interactions, extinction and evolution. Classical approaches in island biogeography focused on species richness as the deterministic outcome of these processes. This has proved fruitful, but species traits can potentially offer new biological insights into the processes by which island life assembles and why some species perform better at colonising and persisting on islands. Functional traits refer to morphological and phenological characteristics of an organism or species that can be linked to its ecological strategy and that scale up from individual plants to properties of communities and ecosystems. A baseline hypothesis is for traits and ecological strategies of island species to show similar patterns as a matched mainland environment. However, strong dispersal, environmental and biotic-interaction filters as well as stochasticity associated with insularity modify this baseline. Clades that do colonise often embark on distinct ecological and evolutionary pathways, some because of distinctive evolutionary forces on islands, and some because of the opportunities offered by freedom from competitors or herbivores or the absence of mutualists. Functional traits are expected to be shaped by these processes. Here, we review and discuss the potential for integrating functional traits into island biogeography. While we focus on plants, the general considerations and concepts may be extended to other groups of organisms. We evaluate how functional traits on islands relate to core principles of species dispersal, establishment, extinction, reproduction, biotic interactions, evolution and conservation. We formulate existing knowledge as 33 working hypotheses. Some of these are grounded on firm empirical evidence, others provide opportunities for future research. We organise our hypotheses under five overarching sections. Section A focuses on plant functional traits enabling species dispersal to islands. Section B discusses how traits help to predict species establishment, successional trajectories and natural extinctions on islands. Section C reviews how traits indicate species biotic interactions and reproduction strategies and which traits promote intra-island dispersal. Section D discusses how evolution on islands leads to predictable changes in trait values and which traits are most susceptible to change. Section E debates how functional ecology can be used to study multiple drivers of global change on islands and to formulate effective conservation measures. Islands have a justified reputation as research models. They illuminate the forces operating within mainland communities by showing what happens when those forces are released or changed. We believe that the lens of functional ecology can shed more light on these forces than research approaches that do not consider functional differences among species.

Persistent soil seed banks promote naturalisation and invasiveness in flowering plants

With globalisation facilitating the movement of plants and seeds beyond the native range, preventing potentially harmful introductions requires knowledge of what drives the successful establishment and spread of alien plants. Here, we examined global-scale relationships between naturalisation success (incidence and extent) and invasiveness, soil seed bank properties (type and densities) and key species traits (seed mass, seed dormancy and life form) for 2350 species of angiosperms. Naturalisation and invasiveness were strongly associated with the ability to form persistent (vs. transient) seed banks but relatively weakly with seed bank densities and other traits. Our findings suggest that seed bank persistence is a trait that better captures the ability to become naturalised and invasive compared to seed traits more widely available in trait databases. Knowledge of seed persistence can contribute to our ability to predict global naturalisation and invasiveness and to identify potentially invasive flowering plants before they are introduced.

Data Descriptor: Pacific Introduced Flora (PaciFLora)

Background

The Pacific Region has the highest density of naturalised plant species worldwide, which makes it an important area for research on the ecology, evolution and biogeography of biological invasions. While different data sources on naturalised plant species exist for the Pacific, there is no taxonomically and spatially harmonised database available for different subsets of species and islands. A comprehensive, accessible database containing the distribution of naturalised vascular plant species in the Pacific will enable new basic and applied research for researchers and will be an important information source for practitioners working in the Region.

New information

Here, we present PacIFlora, an updated and taxonomically standardised list of naturalised species, their unified nativeness, cultivation and invasive status and their distribution across the Pacific Ocean, including harmonised location denoination. This list is based on the two largest databases on naturalised plants for the Region, specifically the Pacific Island Ecosystems at Risk (PIER) and the Global Naturalised Alien Flora (GloNAF) databases. We provide an outlook for how this database can contribute to numerous research questions and conservation efforts.

Dimensions of invasiveness: Links between local abundance, geographic range size, and habitat breadth in Europe's alien and native floras

Understanding drivers of success for alien species can inform on potential future invasions. Recent conceptual advances highlight that species may achieve invasiveness via performance along at least three distinct dimensions: 1) local abundance, 2) geographic range size, and 3) habitat breadth in naturalized distributions. Associations among these dimensions and the factors that determine success in each have yet to be assessed at large geographic scales. Here, we combine data from over one million vegetation plots covering the extent of Europe and its habitat diversity with databases on species' distributions, traits, and historical origins to provide a comprehensive assessment of invasiveness dimensions for the European alien seed plant flora. Invasiveness dimensions are linked in alien distributions, leading to a continuum from overall poor invaders to super invaders-abundant, widespread aliens that invade diverse habitats. This pattern echoes relationships among analogous dimensions measured for native European species. Success along invasiveness dimensions was associated with details of alien species' introduction histories: earlier introduction dates were positively associated with all three dimensions, and consistent with theory-based expectations, species originating from other continents, particularly acquisitive growth strategists, were among the most successful invaders in Europe. Despite general correlations among invasiveness dimensions, we identified habitats and traits associated with atypical patterns of success in only one or two dimensions-for example, the role of disturbed habitats in facilitating widespread specialists. We conclude that considering invasiveness within a multidimensional framework can provide insights into invasion processes while also informing general understanding of the dynamics of species distributions.

EpiList 1.0: a global checklist of vascular epiphytes

Epiphytes make up roughly 10% of all vascular plant species globally and play important functional roles, especially in tropical forests. However, to date, there is no comprehensive list of vascular epiphyte species. Here, we present EpiList 1.0, the first global list of vascular epiphytes based on standardized definitions and taxonomy. We include obligate epiphytes, facultative epiphytes, and hemiepiphytes, as the latter share the vulnerable epiphytic stage as juveniles. Based on 978 references, the checklist includes >31,000 species of 79 plant families. Species names were standardized against World Flora Online for seed plants and against the World Ferns database for lycophytes and ferns. In cases of species missing from these databases, we used other databases (mostly World Checklist of Selected Plant Families). For all species, author names and IDs for World Flora Online entries are provided to facilitate the alignment with other plant databases, and to avoid ambiguities. EpiList 1.0 will be a rich source for synthetic studies in ecology, biogeography, and evolutionary biology as it offers, for the first time, a species-level overview over all currently known vascular epiphytes. At the same time, the list represents work in progress: species descriptions of epiphytic taxa are ongoing and published life form information in floristic inventories and trait and distribution databases is often incomplete and sometimes even wrong. Since the epiphytic growth blends into soil-rooted growth and vice versa, the inclusion or exclusion of particular species in the current list will sometimes be contentious. Thus, initiating a well-founded discussion was one of the motivations for compiling this database; our list represents 31,311 hypotheses on the life form of plant species, and we welcome feedback on possible omission or erroneous inclusions. We release these data into the public domain under a Creative Commons Zero license waiver. When you use the data in your publication, we request that you cite this data paper. If EpiList 1.0 is a major part of the data analyzed in your study, you may consider inviting the EpiList 1.0 core team as collaborators.

Agent-based modeling of the effects of forest dynamics, selective logging, and fragment size on epiphyte communities

Forest canopies play a crucial role in structuring communities of vascular epiphytes by providing substrate for colonization, by locally varying microclimate, and by causing epiphyte mortality due to branch or tree fall. However, as field studies in the three-dimensional habitat of epiphytes are generally challenging, our understanding of how forest structure and dynamics influence the structure and dynamics of epiphyte communities is scarce.Mechanistic models can improve our understanding of epiphyte community dynamics. We present such a model that couples dispersal, growth, and mortality of individual epiphytes with substrate dynamics, obtained from a three-dimensional functional-structural forest model, allowing the study of forest-epiphyte interactions. After validating the epiphyte model with independent field data, we performed several theoretical simulation experiments to assess how (a) differences in natural forest dynamics, (b) selective logging, and (c) forest fragmentation could influence the long-term dynamics of epiphyte communities.The proportion of arboreal substrate occupied by epiphytes (i.e., saturation level) was tightly linked with forest dynamics and increased with decreasing forest turnover rates. While species richness was, in general, negatively correlated with forest turnover rates, low species numbers in forests with very-low-turnover rates were due to competitive exclusion when epiphyte communities became saturated. Logging had a negative impact on epiphyte communities, potentially leading to a near-complete extirpation of epiphytes when the simulated target diameters fell below a threshold. Fragment size had no effect on epiphyte abundance and saturation level but correlated positively with species numbers.Synthesis: The presented model is a first step toward studying the dynamic forest-epiphyte interactions in an agent-based modeling framework. Our study suggests forest dynamics as key factor in controlling epiphyte communities. Thus, both natural and human-induced changes in forest dynamics, for example, increased mortality rates or the loss of large trees, pose challenges for epiphyte conservation.

Role of diversification rates and evolutionary history as a driver of plant naturalization success

Human introductions of species beyond their natural ranges and their subsequent establishment are defining features of global environmental change. However, naturalized plants are not uniformly distributed across phylogenetic lineages, with some families contributing disproportionately more to the global alien species pool than others. Additionally, lineages differ in diversification rates, and high diversification rates have been associated with characteristics that increase species naturalization success. Here, we investigate the role of diversification rates in explaining the naturalization success of angiosperm plant families. We use five global data sets that include native and alien plant species distribution, horticultural use of plants, and a time-calibrated angiosperm phylogeny. Using phylogenetic generalized linear mixed models, we analysed the effect of diversification rate, different geographical range measures, and horticultural use on the naturalization success of plant families. We show that a family's naturalization success is positively associated with its evolutionary history, native range size, and economic use. Investigating interactive effects of these predictors shows that native range size and geographic distribution additionally affect naturalization success. High diversification rates and large ranges increase naturalization success, especially of temperate families. We suggest this may result from lower ecological specialization in temperate families with large ranges, compared with tropical families with smaller ranges.