The effects of defaunation on plants' capacity to track climate change

The emergence and demise of giant sloths

The emergence of multi-tonne herbivores is a recurrent aspect of the Cenozoic mammalian radiation. Several of these giants have vanished within the past 130,000 years, but the timing and macroevolutionary drivers behind this pattern of rise and collapse remain unclear for some megaherbivore lineages. Using trait modeling that combines total-evidence evolutionary trees and a comprehensive size dataset, we show that sloth body mass evolved with major lifestyle shifts and that most terrestrial lineages reached their largest sizes through slower evolutionary rates compared with extant arboreal forms. Size disparity increased during the late Cenozoic climatic cooling, but paleoclimatic changes do not explain the rapid extinction of ground sloths that started approximately 15,000 years ago. Their abrupt demise suggests human-driven factors in the decline and extinction of ground sloths.

Widespread ecological novelty across the terrestrial biosphere

Human activities have transformed many wild and semiwild ecosystems into novel states without historical precedent. Without knowing the current distribution of what drives the emergence of such novelty, predicting future ecosystem states and informing conservation and restoration policies remain difficult. Here we construct global maps of three key drivers generating novel conditions-climate change, defaunation and floristic disruption-and summarize them to a measure of total novelty exposure. We show that the terrestrial biosphere is widely exposed to novel conditions, with 58% of the total area exposed to high levels of total novelty. All climatic regions and biomes are exposed to substantial levels of novelty. Relative contributions of individual drivers vary between climatic regions, with climate changes and defaunation the largest contributors globally. Protected areas and key biodiversity areas, whether formally protected or not, have similar exposure, with high total novelty experienced in 58% of cells inside protected areas and 56% inside key biodiversity areas. Our results highlight the importance of investigating ecosystem and biodiversity responses to rising ecological novelty for informing actions towards biosphere stewardship.

The network architecture and phylogeographic drivers of interactions between rodents and seed plants at continental scales

Rodents are known to interact with seed plants in three different ways, including predation in situ, scatter hoarding and larder hoarding of seeds. These behaviours span a spectrum from mutualistic seed dispersal to predation, and they are related to species' and environmental characteristics. We used interaction networks to evaluate the structure and drivers of rodent-seed plant interactions, including geography, phylogeny and traits at continental scales. We constructed five aggregated networks, each representing a continent and containing three subnetworks defined by foraging behaviours, tested questions about their network structures and analysed the driving signals shaping rodent-seed plant interactions at network and species levels. Rodent-seed plant networks varied across continents. We found most rodents exhibited a significant propensity for one foraging behaviour and detected significant modular structures in both aggregated networks and subnetworks. We detected significant co-phylogenetic signals between rodents and seed plants. Distance matrix-based regressions on interaction and module dissimilarity of rodents suggest geographical and phylogenetic forces are important in the assembly of rodent-seed plant networks. In addition, multiple species traits correlated with the roles of rodents within aggregated networks; however, the specific traits associated with these roles varied among interaction types. Our results highlight that geography and phylogenetics are dominant in structuring the architecture of rodent-seed plant networks at continental scales and reveal challenges regarding spatial and taxa coverage in rodent-seed plant interactions.

Global Avian Frugivore-Fruit Trait Matching Decreases Toward the Tropics

Trait matching, the phenomenon where ecological interactions are mediated by compatibility, constitutes a cornerstone of frugivore-fruit interaction network dynamics. Given that biotic interactions have long been hypothesized to be more intense or specialized in the tropics, the intensity of trait matching patterns might likewise exhibit a latitudinal gradient in frugivory networks, yet this remains unverified. Here, we established a dataset encompassing 200 avian frugivorous networks to explore the relationships between the body mass and gape size of frugivore birds and fruit traits (size and color) on a global scale. Our results indicated that frugivore traits were closely associated with fruit traits regardless of the climate, demonstrating a biotic match between the two counterparts. We detected a significant decrease in frugivore-fruit trait matching toward the tropics, which challenges prevailing concepts considering the high biodiversity therein. Our structural equation modeling clarified that latitude and temperature exert an indirect influence on trait matching by affecting gape size and fruit traits. These discoveries emphasize the impact of the latitudinal gradient of temperature in driving the observed patterns of trait matching. The weaker trait matching in tropical regions may suggest more complex interactions therein and also highlights the potential for altered network structures amid global climate change.

Decoupling Responses of Phyllosphere and Rhizosphere Bacterial Communities to Spatiotemporal Environmental Changes

Understanding and predicting how plant-associated microbes respond to environmental changes is of key importance to understanding future plant performance. Yet, how aboveground and belowground plant-associated microbial communities, which may interactively affect plant performance, simultaneously respond to environmental changes, remains unknown. To fill this gap, we monitored temporal changes of phyllosphere and rhizosphere bacterial communities of three perennial species at 18 sites spanning a 1500 m elevational gradient. We showed distinct temporal trajectories of these community types, likely reflecting their differential responses to abiotic (e.g., air moisture) and biotic (e.g., plant specific leaf area) environmental factors. Further, using a transplantation experiment with the same plant species and their rhizosphere soils, we show that a portion of bacterial taxa from transplanted communities persisted in plants' rhizosphere 2 months after being transplanted to warmer sites. In contrast, phyllosphere communities were primarily harbored by taxa colonizing from local communities. Notably, the relative growth rate of transplanted plants at new versus original sites was positively correlated with the compositional dissimilarity between their phyllosphere and rhizosphere bacterial communities. Together, our results highlight the role of compartment-by-environment interactions in shaping the plant holobiome communities and emphasize the need to understand the impacts of such interactions on plant performance under global change.

The ecology of plant extinctions

Extinctions occur when enough individual plants die without replacement to extirpate a population, and all populations are extirpated. While the ultimate drivers of plant extinctions are known, the proximate mechanisms at individual and population level are not. The fossil record supports climate change as the major driver until recently, with land-use change dominating in recent millennia. Climate change may regain its leading role later this century. Documented recent extinctions have been few and concentrated among narrow-range species, but population extirpations are frequent. Predictions for future extinctions often use flawed methods, but more than half of all plants could be threatened by the end of this century. We need targeted interventions tailored to the needs of each threatened species.

Functional Traits and Phylogenetic Effects Drive Germination of Lemur-Passed Seeds

Frugivore-mediated seed dispersal drives ecological functioning across tropical forests. The biological mechanisms affecting seed dispersal outcomes, as well as the role of specific functional traits in plants and their dispersers, is still not well understood. To address this gap, we conducted germination experiments in eight species of captive and two species of wild lemurs, which disperse different plant species. We (1) quantified the effects of pulp removal, seed priming, and feces effects (nutrient/microbial fertilization) through gut passage as mechanisms, (2) determined the effect of frugivore species on germination, and (3) assessed how individual plant and animal traits affected two seed germination outcomes: success rates and time-to-germination. Accounting for phylogenetic non-independence of plants and estimating phylogenetic signal, we evaluated the effects of lemur gut passage and functional traits in a Bayesian framework. Seed priming during gut passage was the primary mechanism through which lemurs improved germination rates and decreased time-to-germination. Gut passage influenced the effect of seed length on germination probability but not time-to germination. Germination outcomes varied by disperser species and seed size. Furthermore, seeds passed by male lemurs were 40% more likely to germinate than those passed by female lemurs. Germination probability was more similar for closely related plant species compared to those that were more distantly related, while the plant phylogenetic effects on time-to-germination were weaker. Moreover, germination depended on experimental setting; for example, lemur gut passage decreased time-to-germination in captive, but not wild settings. Our results highlight the complexity of biological mechanisms determining seed dispersal outcomes; ecological and evolutionary factors were important drivers of germination. Considering a diversity of potential effects is critical for advancing a mechanistic understanding of species interactions and their outcomes.

Defaunation impacts on the carbon balance of tropical forests

The urgent need to mitigate and adapt to climate change necessitates a comprehensive understanding of carbon cycling dynamics. Traditionally, global carbon cycle models have focused on vegetation, but recent research suggests that animals can play a significant role in carbon dynamics under some circumstances, potentially enhancing the effectiveness of nature-based solutions to mitigate climate change. However, links between animals, plants, and carbon remain unclear. We explored the complex interactions between defaunation and ecosystem carbon in Earth's most biodiverse and carbon-rich biome, tropical rainforests. Defaunation can change patterns of seed dispersal, granivory, and herbivory in ways that alter tree species composition and, therefore, forest carbon above- and belowground. Most studies we reviewed show that defaunation reduces carbon storage 0-26% in the Neo- and Afrotropics, primarily via population declines in large-seeded, animal-dispersed trees. However, Asian forests are not predicted to experience changes because their high-carbon trees are wind dispersed. Extrapolating these local effects to entire ecosystems implies losses of ∼1.6 Pg CO2 equivalent across the Brazilian Atlantic Forest and 4-9.2 Pg across the Amazon over 100 years and of ∼14.7-26.3 Pg across the Congo basin over 250 years. In addition to being hard to quantify with precision, the effects of defaunation on ecosystem carbon are highly context dependent; outcomes varied based on the balance between antagonist and mutualist species interactions, abiotic conditions, human pressure, and numerous other factors. A combination of experiments, large-scale comparative studies, and mechanistic models could help disentangle the effects of defaunation from other anthropogenic forces in the face of the incredible complexity of tropical forest systems. Overall, our synthesis emphasizes the importance of-and inconsistent results when-integrating animal dynamics into carbon cycle models, which is crucial for developing climate change mitigation strategies and effective policies.

Climb forest, climb: diverse disperser communities are key to assist plants tracking climate change on altitudinal gradients

Climate change is forcing species to shift their distribution ranges. Animal seed dispersers might be particularly important in assisting plants tracking suitable climates to higher elevations. However, this role is still poorly understood due to a lack of comprehensive multi-guild datasets along elevational gradients. We compiled seed dispersal networks for the five altitudinal vegetation belts of the Tenerife Island (0-3718 m above sea level) to explore how plant and animal species might facilitate the mutual colonisation of uphill habitats under climate change. The overall network comprised 283 distinct interactions between 73 plant and 27 animal species, with seed dispersers offering viable pathways for plants to colonise upper vegetation belts. A pivotal role is played by a lizard as island-level hub, while four birds and one introduced mammal (rabbit) are also important connectors between belts. Eleven plant species were empirically found to be actively dispersed to elevations beyond their current known range, with observed vertical dispersal distances largely surpassing those required to escape climate change. Furthermore, over half of the plants arriving at higher elevations were exotic. Functionally diverse disperser communities are crucial for enabling plants tracking climate change on mountains, but exotic plants might particularly benefit from this upward lift.

Epigenetic responses of trees to environmental stress in the context of climate change

In long-lived tree populations, when environmental change outpaces rates of evolutionary adaptation, plasticity in traits related to stress tolerance, dormancy, and dispersal may be vital for preventing extinction. While a population's genetic background partly determines its ability to adapt to a changing environment, so too do the many types of epigenetic modifications that occur within and among populations, which vary on timescales orders of magnitude faster than the emergence of new beneficial alleles. Consequently, phenotypic plasticity driven by epigenetic modification may be especially critical for sessile, long-lived organisms such as trees that must rely on this plasticity to keep pace with rapid anthropogenic environmental change. While studies have reported large effects of DNA methylation, histone modification, and non-coding RNAs on the expression of stress-tolerance genes and resulting phenotypic responses, little is known about the role of these effects in non-model plants and particularly in trees. Here, we review new findings in plant epigenetics with particular relevance to the ability of trees to adapt to or escape stressors associated with rapid climate change. Such findings include specific epigenetic influences over drought, heat, and salinity tolerance, as well as dormancy and dispersal traits. We also highlight promising findings concerning transgenerational inheritance of an epigenetic 'stress memory' in plants. As epigenetic information is becoming increasingly easy to obtain, we close by outlining ways in which ecologists can use epigenetic information better to inform population management and forecasting efforts. Understanding the molecular mechanisms behind phenotypic plasticity and stress memory in tree species offers a promising path towards a mechanistic understanding of trees' responses to climate change.

Global Projection of Terrestrial Vertebrate Food Webs Under Future Climate and Land-Use Changes

Food webs represent an important nexus between biodiversity and ecosystem functioning, yet considering changes in food webs around the world has been limited by data availability. Previous studies have predicted food web collapses and coextinction, but changes in food web structure have been less investigated under climate warming and anthropogenic pressures on a global scale. We systematically amassed information about species' diets, traits, distributions, habitat use, and phylogenetics in the real world and used machine learning to predict changes in global meta-food webs of terrestrial vertebrates under climate and land-use changes. By year 2100, terrestrial vertebrate food webs are expected to decrease in web size by 32% and trophic links by 49%. Projections predict declines of over 25% in modularity, predator generality, and diversity of trophic groups. Increased species' dispersal could ameliorate these trends but indicate disproportionate vulnerability of regional food webs. Unlike many previous studies, this work combines extensive empirical data with advanced modeling techniques, providing a more detailed and spatially explicit prediction of how global food webs will respond to climate and land-use changes. Overall, our study predicts terrestrial vertebrate food webs will undergo drastic and spatially heterogeneous structural changes.

Global Trends of Trait Matching in Avian Frugivory and Its Consequences for the Complementarity and Irreplaceability of Birds

It is generally accepted that small birds cannot eat large fruits and that highly frugivorous species prefer lipid-poor ones (morphological and nutritional trait-matching). Yet, it is unclear if these rules operate globally and if their strength varies with latitude and on islands. This could have important functional implications for the degree of complementarity and irreplaceability of birds. We analyse avian frugivory in 59 communities across the globe and show that trait-matching is widespread. The strength of morphological trait-matching increased with latitude, and especially on islands, leading to high complementarity between large and small birds. However, whether this resulted in irreplaceability depended on the range of fruit sizes available in the community. Nutritional trait-matching was also common, but did not lead to complementarity or irreplaceability because birds with contrasting diets did not show opposite responses to lipid-poor fruits. We show that trait-matching is pervasive, but its functional consequences are complex.

Defaunation Increases Clustering and Fine-Scale Spatial Genetic Structure in a Small-Seeded Palm Despite Remaining Small-Bodied Frugivores

Anthropogenic pressures such as hunting are increasingly driving the localised functional extinctions of large- and medium-sized wildlife in tropical forests, a phenomenon broadly termed 'defaunation'. Concurrently in these areas, smaller-bodied species benefit from factors such as competitive release and increase in numbers. This transformation of the wildlife community can impact species interactions and ecosystem services such as seed dispersal and seed-mediated geneflow with far-reaching consequences. Evidence for negative genetic effects following defaunation is well-documented in large-seeded plants that require large frugivores for long-distance seed dispersal. However, how defaunation affects plants with small or medium-small seeds (< 1.5 cm), which tend to be consumed and dispersed by frugivorous mutualists of a range of body sizes and responses to anthropogenic threats, is not well understood. To better understand defaunation's impacts on tropical plant communities, we investigated spatial and genetic patterns in a hyperabundant medium-to-small-seeded palm, Euterpe precatoria in three sites with different defaunation levels. Results indicate that defaunation is associated with higher fine-scale spatial genetic structure among seedlings and increased spatial clustering within seedling cohorts and between seedlings and conspecific adults, as well as a reduction in nearest-neighbour distances between seedlings and conspecific adults. There were no clear effects on inbreeding or genetic diversity. However, we caution these trends may indicate that defaunation reduces seed dispersal services for species previously presumed to be robust to deleterious effects of losing large frugivores by virtue of having smaller seeds and broad suites of dispersal agents, and negative downstream effects on genetic diversity could occur.

Evidence of a European seed dispersal crisis

Seed dispersal is crucial for ecosystem persistence, especially in fragmented landscapes, such as those common in Europe. Ongoing defaunation might compromise effective seed dispersal, but the conservation status of pairwise interactions remains unknown. With a literature review, we reconstructed the first European-wide seed dispersal network and evaluated the conservation status of interactions by assessing each interacting partner's IUCN (International Union for Conservation of Nature) conservation status and population trends. We found that a third of the disperser species and interactions face potential extinction and that 30% of the plant species have most of their dispersers threatened or declining. Our study reveals a developing seed dispersal crisis in Europe and highlights large knowledge gaps regarding the dispersers and conservation status of zoochorous plants, urging further scrutiny and action to conserve the seed dispersal service.

The global loss of avian functional and phylogenetic diversity from anthropogenic extinctions

Humans have been driving a global erosion of species richness for millennia, but the consequences of past extinctions for other dimensions of biodiversity-functional and phylogenetic diversity-are poorly understood. In this work, we show that, since the Late Pleistocene, the extinction of 610 bird species has caused a disproportionate loss of the global avian functional space along with ~3 billion years of unique evolutionary history. For island endemics, proportional losses have been even greater. Projected future extinctions of more than 1000 species over the next two centuries will incur further substantial reductions in functional and phylogenetic diversity. These results highlight the severe consequences of the ongoing biodiversity crisis and the urgent need to identify the ecological functions being lost through extinction.

Global primary predictors of extinction risk in primates

Identifying the main predictors of species' extinction risk while accounting for the effects of spatial and phylogenetic structures in the data is key to preventing species loss in tropical forests through adequate conservation practices. We recorded 22 705 precise geographical locations of primate occurrence across four major geographic realms (Neotropics, mainland Africa, Madagascar and Asia) to assess predictors of threat status using a novel Bayesian spatio-phylogenetic approach. We estimated the relative contributions of fixed factors (forest amount, body mass, home range, diel activity, locomotion, evolutionary distinctiveness and climatic instability) and random factors (space and phylogeny) to primate extinction risk. Precipitation instability increased the extinction risk in the Neotropics but decreased it in mainland Africa and Madagascar. Forest amount was negatively associated with extinction risk in all realms except Madagascar. Body mass increased the extinction risk in the Neotropics and Madagascar, whereas home range increased the extinction risk in mainland Africa and decreased it in Asia. Evolutionary distinctiveness negatively influenced extinction risk only in mainland Africa. Our findings highlight the importance of climate change mitigation and forest protection strategies. Increasing the protection of large primates and reducing hunting are also essential.

Is adaptation associated with long-term persistence beyond a geographic range limit?

Adaptation to new habitats might facilitate species' range shifts in response to climate change. In 2005, we transplanted experimental populations of coastal dune plant Camissoniopsis cheiranthifolia into 4 sites within and 1 site beyond its poleward range limit. Beyond-range transplants had high fitness but often delayed reproduction. To test for adaptation associated with experimental range expansion, we transplanted descendants from beyond- and within-range populations after 10 generations in situ into 2 sites within the range, 1 at the range edge, and 2 sites beyond the range. We expected to detect adaptation to beyond-range conditions due to substantial genetic variation within experimental populations and environmental variation among sites. However, individuals from beyond-range experimental populations were not fitter than those from within the range when planted at either beyond-range site, indicating no adaptation to the beyond-range site or beyond-range environments in general. Beyond-range descendants also did not suffer lower fitness within the range. Although reproduction was again delayed beyond the range, late reproduction was not favored more strongly beyond than within the range, and beyond-range descendants did not delay reproduction more than within-range descendants. Persistence in beyond-range environments may not require adaptation, which could allow a rapid response to climate change.

Seed quality as a proxy of climate-ready orphan legumes: the need for a multidisciplinary and multi-actor vision

In developing countries, orphan legumes stand at the forefront in the struggle against climate change. Their high nutrient value is crucial in malnutrition and chronic diseases prevention. However, as the 'orphan' definition suggests, their seed systems are still underestimated and seed production is scanty. Seed priming is an effective, sustainable strategy to boost seed quality in orphan legumes for which up-to-date guidelines are required to guarantee reliable and reproducible results. How far are we along this path? What do we expect from seed priming? This brings to other relevant questions. What is the socio-economic relevance of orphan legumes in the Mediterranean Basin? How to potentiate a broader cultivation in specific regions? The case study of the BENEFIT-Med (Boosting technologies of orphan legumes towards resilient farming systems) project, developed by multidisciplinary research networks, envisions a roadmap for producing new knowledge and innovative technologies to improve seed productivity through priming, with the long-term objective of promoting sustainability and food security for/in the climate-sensitive regions. This review highlights the existing drawbacks that must be overcome before orphan legumes could reach the state of 'climate-ready crops'. Only by the integration of knowledge in seed biology, technology and agronomy, the barrier existing between research bench and local agricultural fields may be overcome, generating high-impact technical innovations for orphan legumes. We intend to provide a powerful message to encourage future research in line with the United Nations Agenda 2030 for Sustainable Development.

Coevolutionary hotspots favour dispersal and fuel biodiversity in mutualistic landscapes under environmental changes

Mutualistic interactions are key to sustaining Earth's biodiversity. Yet, we are only beginning to understand how coevolution in mutualistic assemblages can shape the distribution and persistence of species across landscapes. Here, we combine the geographic mosaic theory of coevolution with metacommunity dynamics to understand how geographically structured selection can shape patterns of richness, dispersal, extinction and persistence of mutualistic species. In this model, species may experience strong or weak reciprocal selection imposed by mutualisms within each patch (i.e. hotspots and coldspots, respectively). Using numerical simulations, we show that mutualistic coevolution leads to a concentration of species richness at hotspots. Such an effect occurs because hotspots sustain higher rates of colonization and lower rates of extinction than coldspots, whether the environment changes or not. Importantly, under environmental changes, coldspots fail to sustain a positive colonization-to-extinction balance. Rather, species persistence within coldspots relies on hotspots acting as biodiversity sources and enhancing population dispersal across the landscape. In fact, even a few hotspots in the landscape can fuel the spatial network of dispersal of populations in the metacommunity. Our study highlights that coevolutionary hotspots can act as biodiversity sources, favouring colonization and allowing species to expand their distribution across landscapes even in changing environments. This article is part of the theme issue 'Diversity-dependence of dispersal: interspecific interactions determine spatial dynamics'.

Behavioural changes in the city: The common black garden ant defends aphids more aggressively in urban environments

Urbanisation alters biodiversity patterns and threatens to disrupt mutualistic interactions. Aside from pollination, however, little is known about how mutualisms change in cities. Our study aimed to assess how urbanisation affects the protective mutualism between ants and aphids, investigating potential behavioural changes in mutualistic ants and their implications for aphids in urban environments. To do so, we studied the protective mutualism between the pink tansy aphid (Metopeurum fuscoviride) and the black garden ant (Lasius niger) along an urbanisation gradient in Berlin, Germany. In nine locations along this gradient, we measured aphid colony dynamics and proxies for parasitism, quantified the investment of ants in tending aphids and conducted behavioural assays to test the aggressiveness of ant responses to a simulated attack on the aphids. We found that aphid colonies flourished and were equally tended by ants across the urbanisation gradient, with a consistent positive density dependence between aphid and ant numbers. However, ants from more urbanised sites responded more aggressively to the simulated attack. Our findings suggest that this protective mutualism is not only maintained in the city, but that ants might even rely more on it and defend it more aggressively, as other food resources may become scarce and more unpredictable with urbanisation. We thereby provide unique insights into this type of mutualism in the city, further diversifying the growing body of work on mutualisms across urbanisation gradients.

Biodiversity loss impacts top-down regulation of insect herbivores across ecosystem boundaries

Biodiversity loss, as driven by anthropogenic global change, imperils biosphere intactness and integrity. Ecosystem services such as top-down regulation (or biological control; BC) are susceptible to loss of extinction-prone taxa at upper trophic levels and secondary 'support' species e.g., herbivores. Here, drawing upon curated open-access interaction data, we structurally analyze trophic networks centered on the fall armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae) and assess their robustness to species loss. Tri-partite networks link 80 BC organisms (invertebrate or microbial), 512 lepidopteran hosts and 1194 plants (including 147 cultivated crops) in the Neotropics. These comprise threatened herbaceous or woody plants and conservation flagships such as saturniid moths. Treating all interaction partners functionally equivalent, random herbivore loss exerts a respective 26 % or 108 % higher impact on top-down regulation in crop and non-crop settings than that of BC organisms (at 50 % loss). Equally, random loss of BC organisms affects herbivore regulation to a greater extent (13.8 % at 50 % loss) than herbivore loss mediates their preservation (11.4 %). Yet, under moderate biodiversity loss, (non-pest) herbivores prove highly susceptible to loss of BC organisms. Our topological approach spotlights how agriculturally-subsidized BC agents benefit vegetation restoration, while non-pest herbivores uphold biological control in on- and off-farm settings alike. Our work underlines how the on-farm usage of endemic biological control organisms can advance conservation, restoration, and agricultural sustainability imperatives. We discuss how integrative approaches and close interdisciplinary cooperation can spawn desirable outcomes for science, policy and practice.

Species-level correlates of land-use responses and climate-change sensitivity in terrestrial vertebrates

Land-use and climate change are major pressures on terrestrial biodiversity. Species' extinction risk and responses to human pressures relate to ecological traits and other characteristics in some clades. However, large-scale comparative assessments of the associations between traits and responses to multiple human pressures across multiple clades are needed. We investigated whether a set of ecological characteristics that are commonly measured across terrestrial vertebrates (ecological traits and geographic range area) are associated with species' responses to different land-use types and species' likely sensitivity to climate change. We aimed to test whether generalizable patterns in response to these pressures arise across both pressures and across vertebrate clades, which could inform assessments of the global signature of human pressures on vertebrate biodiversity and guide conservation efforts. At the species level, we investigated associations between land-use responses and ecological characteristics with a space-for-time substitution approach, making use of the PREDICTS database. We investigated associations between ecological characteristics and expected climate-change sensitivity, estimated from properties of species realized climatic niches. Among the characteristics we considered, 3 were consistently associated with strong land-use responses and high climate-change sensitivity across terrestrial vertebrate classes: narrow geographic range, narrow habitat breadth, and specialization on natural habitats (which described whether a species occurs in artificial habitats or not). The associations of other traits with species' land-use responses and climate-change sensitivity often depended on species' class and land-use type, highlighting an important degree of context dependency. In all classes, invertebrate eaters and fruit and nectar eaters tended to be negatively affected in disturbed land-use types, whereas invertebrate-eating and plant- and seed-eating birds were estimated to be more sensitive to climate change, raising concerns about the continuation of ecological processes sustained by these species under global changes. Our results highlight a consistently higher sensitivity of narrowly distributed species and habitat specialists to land-use and climate change, which provides support for capturing such characteristics in large-scale vulnerability assessments.

Unravelling the functional and phylogenetic dimensions of novel ecosystem assemblages

Human activities are causing taxonomic rearrangements across ecosystems that often result in the emergence of novel communities (assemblies with no historical representative). It is commonly assumed that these changes in the taxonomic makeup of ecosystems also inevitably lead to changes in other aspects of biodiversity, namely functional and phylogenetic diversity. However, this assumption is not always valid, as the changes in functional and phylogenetic composition resulting from taxonomic shifts depend on the level of redundancy in the evaluated community. Therefore, we need improved theoretical frameworks to predict when we can expect coordinated or decoupled responses among these three facets of biodiversity. To advance this understanding, we discuss the conceptual and methodological issues that complicate establishing a link between taxonomic rearrangements driven by human activities and the associated functional and phylogenetic changes. Here, we show that is crucial to consider the expected changes in functional and phylogenetic composition as communities are reshaped owing to human drivers of biodiversity loss to forecast the impacts of novel assemblages on ecosystem functions and the services they provide to humanity. This article is part of the theme issue 'Ecological novelty and planetary stewardship: biodiversity dynamics in a transforming biosphere'.

Projected future climatic forcing on the global distribution of vegetation types

Most emissions scenarios suggest temperature and precipitation regimes will change dramatically across the globe over the next 500 years. These changes will have large impacts on the biosphere, with species forced to migrate to follow their preferred environmental conditions, therefore moving and fragmenting ecosystems. However, most projections of the impacts of climate change only reach 2100, limiting our understanding of the temporal scope of climate impacts, and potentially impeding suitable adaptive action. To address this data gap, we model future climate change every 20 years from 2000 to 2500 CE, under different CO2 emissions scenarios, using a general circulation model. We then apply a biome model to these modelled climate futures, to investigate shifts in climatic forcing on vegetation worldwide, the feasibility of the migration required to enact these modelled vegetation changes, and potential overlap with human land use based on modern-day anthromes. Under a business-as-usual scenario, up to 40% of terrestrial area is expected to be suited to a different biome by 2500. Cold-adapted biomes, particularly boreal forest and dry tundra, are predicted to experience the greatest losses of suitable area. Without mitigation, these changes could have severe consequences both for global biodiversity and the provision of ecosystem services. This article is part of the theme issue 'Ecological novelty and planetary stewardship: biodiversity dynamics in a transforming biosphere'.

A nature-positive future with biological invasions: theory, decision support and research needs

In 2050, most areas of biodiversity significance will be heavily influenced by multiple drivers of environmental change. This includes overlap with the introduced ranges of many alien species that negatively impact biodiversity. With the decline in biodiversity and increase in all forms of global change, the need to envision the desired qualities of natural systems in the Anthropocene is growing, as is the need to actively maintain their natural values. Here, we draw on community ecology and invasion biology to (i) better understand trajectories of change in communities with a mix of native and alien populations, and (ii) to frame approaches to the stewardship of these mixed-species communities. We provide a set of premises and actions upon which a nature-positive future with biological invasions (NPF-BI) could be based, and a decision framework for dealing with uncertain species movements under climate change. A series of alternative management approaches become apparent when framed by scale-sensitive, spatially explicit, context relevant and risk-consequence considerations. Evidence of the properties of mixed-species communities together with predictive frameworks for the relative importance of the ecological processes at play provide actionable pathways to a NPF in which the reality of mixed-species communities are accommodated and managed. This article is part of the theme issue 'Ecological novelty and planetary stewardship: biodiversity dynamics in a transforming biosphere'.

Towards a novel biosphere in 2300: rapid and extensive global and biome-wide climatic novelty in the Anthropocene

Recent climate change has effectively rewound the climate clock by approximately 120 000 years and is expected to reverse this clock a further 50 Myr by 2100. We aimed to answer two essential questions to better understand the changes in ecosystems worldwide owing to predicted climate change. Firstly, we identify the locations and time frames where novel ecosystems could emerge owing to climate change. Secondly, we aim to determine the extent to which biomes, in their current distribution, will experience an increase in climate-driven ecological novelty. To answer these questions, we analysed three perspectives on how climate changes could result in novel ecosystems in the near term (2100), medium (2200) and long term (2300). These perspectives included identifying areas where climate change could result in new climatic combinations, climate isoclines moving faster than species migration capacity and current environmental patterns being disaggregated. Using these metrics, we determined when and where novel ecosystems could emerge. Our analysis shows that unless rapid mitigation measures are taken, the coverage of novel ecosystems could be over 50% of the land surface by 2100 under all change scenarios. By 2300, the coverage of novel ecosystems could be above 80% of the land surface. At the biome scale, these changes could mean that over 50% of locations could shift towards novel ecosystems, with the majority seeing these changes in the next few decades. Our research shows that the impact of climate change on ecosystems is complex and varied, requiring global action to mitigate and adapt to these changes. This article is part of the theme issue 'Biodiversity dynamics and stewardship in a transforming biosphere'. This article is part of the theme issue 'Ecological novelty and planetary stewardship: biodiversity dynamics in a transforming biosphere'.

Navigating ecological novelty towards planetary stewardship: challenges and opportunities in biodiversity dynamics in a transforming biosphere

Human-induced global changes, including anthropogenic climate change, biotic globalization, trophic downgrading and pervasive land-use intensification, are transforming Earth's biosphere, placing biodiversity and ecosystems at the forefront of unprecedented challenges. The Anthropocene, characterized by the importance of Homo sapiens in shaping the Earth system, necessitates a re-evaluation of our understanding and stewardship of ecosystems. This theme issue delves into the multifaceted challenges posed by the ongoing ecological planetary transformation and explores potential solutions across four key subthemes. Firstly, it investigates the functioning and stewardship of emerging novel ecosystems, emphasizing the urgent need to comprehend the dynamics of ecosystems under uncharted conditions. The second subtheme focuses on biodiversity projections under global change, recognizing the necessity of predicting ecological shifts in the Anthropocene. Importantly, the inherent uncertainties and the complexity of ecological responses to environmental stressors pose challenges for societal responses and for accurate projections of ecological change. The RAD framework (resist-accept-direct) is highlighted as a flexible yet nuanced decision-making tool that recognizes the need for adaptive approaches, providing insights for directing and adapting to Anthropocene dynamics while minimizing negative impacts. The imperative to extend our temporal perspective beyond 2100 is emphasized, given the irreversible changes already set in motion. Advancing methods to study ecosystem dynamics under rising biosphere novelty is the subject of the third subtheme. The fourth subtheme emphasizes the importance of integrating human perspectives into understanding, forecasting and managing novel ecosystems. Cultural diversity and biological diversity are intertwined, and the evolving relationship between humans and ecosystems offers lessons for future stewardship. Achieving planetary stewardship in the Anthropocene demands collaboration across scales and integration of ecological and societal perspectives, scalable approaches fit to changing, novel ecological conditions, as well as cultural innovation. This article is part of the theme issue 'Ecological novelty and planetary stewardship: biodiversity dynamics in a transforming biosphere'.

Trophic rewilding as a restoration approach under emerging novel biosphere conditions

Rewilding is a restoration approach that aims to promote self-regulating complex ecosystems by restoring non-human ecological processes while reducing human control and pressures. Rewilding is forward-looking in that it aims to enhance functionality for biodiversity, accepting and indeed promoting the dynamic nature of ecosystems, rather than fixating on static composition or structure. Rewilding is thus especially relevant in our epoch of increasingly novel biosphere conditions, driven by strong human-induced global change. Here, we explore this hypothesis in the context of trophic rewilding - the restoration of trophic complexity mediated by wild, large-bodied animals, known as 'megafauna'. This focus reflects the strong ecological impacts of large-bodied animals, their widespread loss during the last 50,000 years and their high diversity and ubiquity in the preceding 50 million years. Restoring abundant, diverse, wild-living megafauna is expected to promote vegetation heterogeneity, seed dispersal, nutrient cycling and biotic microhabitats. These are fundamental drivers of biodiversity and ecosystem function and are likely to gain importance for maintaining a biodiverse biosphere under increasingly novel ecological conditions. Non-native megafauna species may contribute to these effects as ecological surrogates of extinct species or by promoting ecological functionality within novel assemblages. Trophic rewilding has strong upscaling potential via population growth and expansion of wild fauna. It is likely to facilitate biotic adaptation to changing climatic conditions and resilience to ecosystem collapse, and to curb some negative impacts of globalization, notably the dominance of invasive alien plants. Finally, we discuss the complexities of realizing the biodiversity benefits that trophic rewilding offers under novel biosphere conditions in a heavily populated world.

Resource partitioning in a novel herbivore assemblage in South America

Human-induced species declines and extinctions have led to the downsizing of large-herbivore assemblages, with implications for many ecosystem processes. Active reintroduction of extirpated large herbivores or their functional equivalents may help to reverse this trend and restore diverse ecosystems and their processes. However, it is unclear whether resource competition between native and non-native herbivores could threaten restoration initiatives, or to what extent (re)introduced species may influence local vegetation dynamics. To answer these questions, we investigated the diets of a novel South American herbivore assemblage that includes resident native species, reintroduced native species and introduced non-native species. We examined plant composition, diet breadth and the overlap between species to describe the local herbivory profile and the potential for resource competition. Using DNA metabarcoding on faecal samples (n = 465), we analysed the diets of the herbivore assemblage in the Rincón del Socorro rewilding area of Iberá National Park, Argentina. We compared the species richness of faecal samples, the occurrence of plant families/growth forms and the compositional similarity of samples (inter- and intraspecifically). Our results indicate species-level taxonomic partitioning of plant resources by herbivores in this system. Differences in sample richness, composition and diet breadth reflected a diverse range of herbivory strategies, from grazers (capybara) to mixed feeders/browsers (brocket deer, lowland tapir). Differences in diet compositional similarity (Jaccard) revealed strong taxonomic resource partitioning. The two herbivores with the most similar diets (Pampas deer and brocket deer) still differed by more than 80%. Furthermore, all but one species (axis deer) had more similar diet composition intraspecifically than compared to the others. Overall, we found little evidence for resource competition between herbivore species. Instead, recently reintroduced native species and historically introduced non-natives are likely expanding the range of herbivory dynamics in the ecosystem. Further research will be needed to determine the full ecological impacts of these (re)introduced herbivores. In conclusion, we show clear differences in diet breadth and composition among native, reintroduced and non-native herbivore species that may be key to promoting resource partitioning, species coexistence and the restoration of ecological function.

Response of Extremely Small Populations to Climate Change-A Case of Trachycarpus nanus in Yunnan, China

Climate change affects the geographical distribution of plant species. Rare Trachycarpus nanus with a narrow distribution range, high medicinal value and extremely small population is facing increasing extinction risks under global climate change. In this study, 96 recorded occurrences and 23 environmental factors are used to predict the potential suitable area of T. nanus based on the optimized MaxEnt (3.4.4) model and ArcGIS (10.7) software. The results show that when the parameters are FC = LQ and RM = 1, the MaxEnt model is optimal and AUC = 0.946. The distribution patterns were predicted in the past, present, and four future phases, i.e., 2021-2040 (2030), 2041-2060 (2050), 2061-2080 (2070), and 2081-2100 (2090). The main factors are the annual precipitation (bio12), mean temperature of the coldest quarter (bio11), temperature seasonality (bio4), precipitation of the wettest quarter (bio16), and isothermality (bio3). The potential distribution of T. nanus is primarily concentrated in central Chuxiong, encompassing a total potential suitable area of 5.65 × 104 km2. In historical periods, the total habitat area is smaller than that in the present. In the future, the potential suitable area is generally increased. The centroid analysis shows that T. nanus will move to a high-altitude area and to the southeast. But its dispersal capacity may not keep up with the climate change rate. Therefore, additional protection sites for this species should be appropriately established and the habitat connectivity should be enhanced.

Bringing traits back into the equation: A roadmap to understand species redistribution

Ecological and evolutionary theories have proposed that species traits should be important in mediating species responses to contemporary climate change; yet, empirical evidence has so far provided mixed evidence for the role of behavioral, life history, or ecological characteristics in facilitating or hindering species range shifts. As such, the utility of trait-based approaches to predict species redistribution under climate change has been called into question. We develop the perspective, supported by evidence, that trait variation, if used carefully can have high potential utility, but that past analyses have in many cases failed to identify an explanatory value for traits by not fully embracing the complexity of species range shifts. First, we discuss the relevant theory linking species traits to range shift processes at the leading (expansion) and trailing (contraction) edges of species distributions and highlight the need to clarify the mechanistic basis of trait-based approaches. Second, we provide a brief overview of range shift-trait studies and identify new opportunities for trait integration that consider range-specific processes and intraspecific variability. Third, we explore the circumstances under which environmental and biotic context dependencies are likely to affect our ability to identify the contribution of species traits to range shift processes. Finally, we propose that revealing the role of traits in shaping species redistribution may likely require accounting for methodological variation arising from the range shift estimation process as well as addressing existing functional, geographical, and phylogenetic biases. We provide a series of considerations for more effectively integrating traits as well as extrinsic and methodological factors into species redistribution research. Together, these analytical approaches promise stronger mechanistic and predictive understanding that can help society mitigate and adapt to the effects of climate change on biodiversity.

The late-Quaternary megafauna extinctions: Patterns, causes, ecological consequences and implications for ecosystem management in the Anthropocene

Across the last ~50,000 years (the late Quaternary) terrestrial vertebrate faunas have experienced severe losses of large species (megafauna), with most extinctions occurring in the Late Pleistocene and Early to Middle Holocene. Debate on the causes has been ongoing for over 200 years, intensifying from the 1960s onward. Here, we outline criteria that any causal hypothesis needs to account for. Importantly, this extinction event is unique relative to other Cenozoic (the last 66 million years) extinctions in its strong size bias. For example, only 11 out of 57 species of megaherbivores (body mass ≥1,000 kg) survived to the present. In addition to mammalian megafauna, certain other groups also experienced substantial extinctions, mainly large non-mammalian vertebrates and smaller but megafauna-associated taxa. Further, extinction severity and dates varied among continents, but severely affected all biomes, from the Arctic to the tropics. We synthesise the evidence for and against climatic or modern human (Homo sapiens) causation, the only existing tenable hypotheses. Our review shows that there is little support for any major influence of climate, neither in global extinction patterns nor in fine-scale spatiotemporal and mechanistic evidence. Conversely, there is strong and increasing support for human pressures as the key driver of these extinctions, with emerging evidence for an initial onset linked to pre-sapiens hominins prior to the Late Pleistocene. Subsequently, we synthesize the evidence for ecosystem consequences of megafauna extinctions and discuss the implications for conservation and restoration. A broad range of evidence indicates that the megafauna extinctions have elicited profound changes to ecosystem structure and functioning. The late-Quaternary megafauna extinctions thereby represent an early, large-scale human-driven environmental transformation, constituting a progenitor of the Anthropocene, where humans are now a major player in planetary functioning. Finally, we conclude that megafauna restoration via trophic rewilding can be expected to have positive effects on biodiversity across varied Anthropocene settings.

Food webs: Where is the uniqueness?

Conservation planning relies on mapping areas of unique biological diversity and high vulnerability. A new study has found that unique trophic networks are threatened by warming climate in the Arctic and high human footprint in southern Europe.

Seed dispersal function of the brown bear Ursus arctos on Hokkaido Island in northern Japan: gut passage time, dispersal distance, germination, and effects of remaining pulp

Megafauna are important seed dispersers because they can disperse large quantities of seeds over long distances. In Hokkaido, Japan, the largest terrestrial animal is the brown bear (Ursus arctos) and other megafauna seed dispersers are lacking. Thus, brown bears are expected to have an important function as seed dispersers in Hokkaido. In this study, we, for the first time, evaluated the seed dispersal function of brown bears in Hokkaido using three fleshy-fruited trees and studied: (1) gut passage time (GPT) in feeding experiments, (2) seed dispersal distance using tracking data of wild bears, and (3) the effect of gut passage and pulp removal on germination rate. Most seeds were defecated intact, and less than 6% were broken. The average GPT without pulp was 3 h and 56 min to 6 h and 13 min, depending on the plant and trial. Each plant's average simulated seed dispersal distance was 202-512 m. The dispersal distance of Actinidia arguta seeds with pulp was significantly longer than those without pulp because of their longer GPT. The germination rate of defecated seeds without pulp was 19-51%, depending on the plant, and was significantly higher or not different comparing with that of seeds with pulp. We concluded that brown bears in Hokkaido are effective seed dispersers. In managing brown bears in Hokkaido, such ecological functions should be considered along with conserving the bear population and reducing human-bear conflicts.

Vulnerability of terrestrial vertebrate food webs to anthropogenic threats in Europe

Vertebrate species worldwide are currently facing significant declines in many populations. Although we have gained substantial knowledge about the direct threats that affect individual species, these threats only represent a fraction of the broader vertebrate threat profile, which is also shaped by species interactions. For example, threats faced by prey species can jeopardize the survival of their predators due to food resource scarcity. Yet, indirect threats arising from species interactions have received limited investigation thus far. In this study, we investigate the indirect consequences of anthropogenic threats on biodiversity in the context of European vertebrate food webs. We integrated data on trophic interactions among over 800 terrestrial vertebrates, along with their associated human-induced threats. We quantified and mapped the vulnerability of various components of the food web, including species, interactions, and trophic groups to six major threats: pollution, agricultural intensification, climate change, direct exploitation, urbanization, and invasive alien species and diseases. Direct exploitation and agricultural intensification were two major threats for terrestrial vertebrate food webs: affecting 34% and 31% of species, respectively, they threaten 85% and 69% of interactions in Europe. By integrating network ecology with threat impact assessments, our study contributes to a better understanding of the magnitude of anthropogenic impacts on biodiversity.

Long-term vegetation trajectories to inform nature recovery strategies: The Greater Côa Valley as a case study

Active and passive approaches to rewilding and ecological restoration are increasingly considered to promote nature recovery at scale. However, historical data on vegetation trajectories have rarely been used to inform decisions on whether active or passive management is most appropriate to aid recovery of a specific ecosystem, which can lead to sub-optimal approaches being deployed and reduced biodiversity benefits. To demonstrate how understanding past changes can inform future management strategies, this study used satellite remote sensing data to analyse the changes in land cover and primary productivity within the Greater Côa Valley in Portugal, which has experienced wide-scale land abandonment. Results show that some areas in the Valley regenerated well following land abandonment in the region, leading to a more heterogeneous landscape of habitats for wildlife, whereas in other areas passive recovery was slow. As Rewilding Portugal intensifies its nature recovery efforts in the region, this study calls for strategic deployment of passive and active approaches to maximise conservation benefits. More broadly, our results highlight how baseline vegetational trajectories and contextual information can help inform whether active or passive management approaches may be suitable on a site-by-site basis for both rewilding and restoration projects.

More than 17,000 tree species are at risk from rapid global change

Trees are pivotal to global biodiversity and nature's contributions to people, yet accelerating global changes threaten global tree diversity, making accurate species extinction risk assessments necessary. To identify species that require expert-based re-evaluation, we assess exposure to change in six anthropogenic threats over the last two decades for 32,090 tree species. We estimated that over half (54.2%) of the assessed species have been exposed to increasing threats. Only 8.7% of these species are considered threatened by the IUCN Red List, whereas they include more than half of the Data Deficient species (57.8%). These findings suggest a substantial underestimation of threats and associated extinction risk for tree species in current assessments. We also map hotspots of tree species exposed to rapidly changing threats around the world. Our data-driven approach can strengthen the efforts going into expert-based IUCN Red List assessments by facilitating prioritization among species for re-evaluation, allowing for more efficient conservation efforts.

Soil properties constrain predicted poleward migration of plants under climate change

Many plant species are predicted to migrate poleward in response to climate change. Species distribution models (SDMs) have been widely used to quantify future suitable habitats, but they often neglect soil properties, despite the importance of soil for plant fitness. As soil properties often change along latitudinal gradients, higher-latitude soils might be more or less suitable than average conditions within the current ranges of species, thereby accelerating or slowing potential poleward migration. In this study, we built three SDMs - one with only climate predictors, one with only soil predictors, and one with both - for each of 1870 plant species in Eastern North America, in order to investigate the relative importance of soil properties in determining plant distributions and poleward shifts under climate change. While climate variables were the most important predictors, soil properties also had a substantial influence on continental-scale plant distributions. Under future climate scenarios, models including soil predicted much smaller northward shifts in distributions than climate-only models (c. 40% reduction). Our findings strongly suggest that high-latitude soils are likely to impede ongoing plant migration, and they highlight the necessity of incorporating soil properties into models and predictions for plant distributions and migration under environmental change.

Intraspecific variation in seed size is mediated by seed dispersal modes and animal dispersers - evidence from a global-scale dataset

Seed dispersal mechanisms play a crucial role in driving evolutionary changes in seed and fruit traits. While previous studies have primarily focussed on the mean or maximum values of these traits, there is also significant intraspecific variation in them. Therefore, it is pertinent to investigate whether dispersal mechanisms can explain intraspecific variations in these traits. Taking seed size as a case study, we compiled a global dataset comprising 3424 records of intraspecific variation in seed size (IVSS), belonging to 691 plant species and 131 families. We provided the first comprehensive quantification of dispersal mechanism effects on IVSS. Biotic-dispersed species exhibited a larger IVSS than abiotic-dispersed species. Synzoochory species had a larger IVSS than endozoochory, epizoochory, and myrmecochory species. Vertebrate-dispersed species exhibited a larger IVSS than invertebrate-dispersed species, and species dispersed by birds exhibited a larger IVSS than mammal-dispersed species. Additionally, a clear negative correlation was detected between IVSS and disperser body mass. Our results prove that the IVSS is associated with the seed dispersal mechanism. This study advances our understanding of the dispersal mechanisms' crucial role in seed size evolution, encompassing not only the mean value but also the variation.

Potential sources of time lags in calibrating species distribution models

The Anthropocene is characterized by a rapid pace of environmental change and is causing a multitude of biotic responses, including those that affect the spatial distribution of species. Lagged responses are frequent and species distributions and assemblages are consequently pushed into a disequilibrium state. How the characteristics of environmental change-for example, gradual 'press' disturbances such as rising temperatures due to climate change versus infrequent 'pulse' disturbances such as extreme events-affect the magnitude of responses and the relaxation times of biota has been insufficiently explored. It is also not well understood how widely used approaches to assess or project the responses of species to changing environmental conditions can deal with time lags. It, therefore, remains unclear to what extent time lags in species distributions are accounted for in biodiversity assessments, scenarios and models; this has ramifications for policymaking and conservation science alike. This perspective piece reflects on lagged species responses to environmental change and discusses the potential consequences for species distribution models (SDMs), the tools of choice in biodiversity modelling. We suggest ways to better account for time lags in calibrating these models and to reduce their leverage effects in projections for improved biodiversity science and policy.

Predicting the Potential Distribution of the Szechwan Rat Snake (Euprepiophis perlacea) and Its Response to Climate Change in the Yingjing Area of the Giant Panda National Park

Climate change is a significant driver of changes in the distribution patterns of species and poses a threat to biodiversity, potentially resulting in species extinctions. Investigating the potential distribution of rare and endangered species is crucial for understanding their responses to climate change and for the conservation of biodiversity and ecosystem management. The Szechwan rat snake (Euprepiophis perlacea) is an endemic and endangered species co-distributed with giant pandas, and studying its potential distribution contributes to a better understanding of the distribution pattern of endangered species. In this study, we confirmed seven presence points of this species in the Yingjing Area of the Giant Panda National Park, and selected eleven key factors to predict the potential distribution of E. perlacea under current and future scenarios using MaxEnt models. Our study consistently achieved AUC values exceeding 0.79, meeting the precision requirements of the models. The results indicated that the high potential distribution area of E. perlacea is mainly located near Yunwu mountain and the giant panda rewilding and reintroduction base, accounting for approximately 12% of the protected area. Moreover, we identified the primary environmental factors influencing the distribution of E. perlacea as the distance from streams and the slope degree, with their contribution rates exceeding 41% and 31%, respectively. In comparison to the current scenario, the potential habitat range for E. perlacea did not show an overall reduction in the context of future climate scenarios. To ensure the long-term preservation of E. perlacea, it is advisable to validate its actual distribution based on the models' results. Particular attention should be given to safeguarding its core distribution areas and raising awareness among residents within the potential distribution range about the conservation of E. perlacea.

Climate change should drive mammal defaunation in tropical dry forests

Human-induced climate change has intensified negative impacts on socioeconomic factors, the environment, and biodiversity, including changes in rainfall patterns and an increase in global average temperatures. Drylands are particularly at risk, with projections suggesting they will become hotter, drier, and less suitable for a significant portion of their species, potentially leading to mammal defaunation. We use ecological niche modelling and community ecology biodiversity metrics to examine potential geographical range shifts of non-volant mammal species in the largest Neotropical dryland, the Caatinga, and evaluate impacts of climate change on mammal assemblages. According to projections, 85% of the mammal species will lose suitable habitats, with one quarter of species projected to completely lose suitable habitats by 2060. This will result in a decrease in species richness for more than 90% of assemblages and an increase in compositional similarity to nearby assemblages (i.e., reduction in spatial beta diversity) for 70% of the assemblages. Small-sized mammals will be the most impacted and lose most of their suitable habitats, especially in highlands. The scenario is even worse in the eastern half of Caatinga where habitat destruction already prevails, compounding the threats faced by species there. While species-specific responses can vary with respect to dispersal, behavior, and energy requirements, our findings indicate that climate change can drive mammal assemblages to biotic homogenization and species loss, with drastic changes in assemblage trophic structure. For successful long-term socioenvironmental policy and conservation planning, it is critical that findings from biodiversity forecasts are considered.

Resurrected seeds from herbarium specimens reveal rapid evolution of drought resistance in a selfing annual

PREMISE

Increased aridity and drought associated with climate change are exerting unprecedented selection pressures on plant populations. Whether populations can rapidly adapt, and which life history traits might confer increased fitness under drought, remain outstanding questions.

METHODS

We utilized a resurrection ecology approach, leveraging dormant seeds from herbarium collections to assess whether populations of Plantago patagonica from the semi-arid Colorado Plateau have rapidly evolved in response to approximately ten years of intense drought in the region. We quantified multiple traits associated with drought escape and drought resistance and assessed the survival of ancestors and descendants under simulated drought.

RESULTS

Descendant populations displayed a significant shift in resource allocation, in which they invested less in reproductive tissues and relatively more in both above- and below-ground vegetative tissues. Plants with greater leaf biomass survived longer under terminal drought; moreover, even after accounting for the effect of increased leaf biomass, descendant seedlings survived drought longer than their ancestors.

CONCLUSIONS

Our results document rapid adaptive evolution in response to climate change in a selfing annual and suggest that shifts in tissue allocation strategies may underlie adaptive responses to drought in arid or semi-arid environments. This work also illustrates a novel approach, documenting that under specific circumstances, seeds from herbarium specimens may provide an untapped source of dormant propagules for future resurrection experiments.

Worldwide Late Pleistocene and Early Holocene population declines in extant megafauna are associated with Homo sapiens expansion rather than climate change

The worldwide extinction of megafauna during the Late Pleistocene and Early Holocene is evident from the fossil record, with dominant theories suggesting a climate, human or combined impact cause. Consequently, two disparate scenarios are possible for the surviving megafauna during this time period - they could have declined due to similar pressures, or increased in population size due to reductions in competition or other biotic pressures. We therefore infer population histories of 139 extant megafauna species using genomic data which reveal population declines in 91% of species throughout the Quaternary period, with larger species experiencing the strongest decreases. Declines become ubiquitous 32-76 kya across all landmasses, a pattern better explained by worldwide Homo sapiens expansion than by changes in climate. We estimate that, in consequence, total megafauna abundance, biomass, and energy turnover decreased by 92-95% over the past 50,000 years, implying major human-driven ecosystem restructuring at a global scale.

Herbivory limits success of vegetation restoration globally

Restoring vegetation in degraded ecosystems is an increasingly common practice for promoting biodiversity and ecological function, but successful implementation is hampered by an incomplete understanding of the processes that limit restoration success. By synthesizing terrestrial and aquatic studies globally (2594 experimental tests from 610 articles), we reveal substantial herbivore control of vegetation under restoration. Herbivores at restoration sites reduced vegetation abundance more strongly (by 89%, on average) than those at relatively undegraded sites and suppressed, rather than fostered, plant diversity. These effects were particularly pronounced in regions with higher temperatures and lower precipitation. Excluding targeted herbivores temporarily or introducing their predators improved restoration by magnitudes similar to or greater than those achieved by managing plant competition or facilitation. Thus, managing herbivory is a promising strategy for enhancing vegetation restoration efforts.

A global assessment of the Raunkiaeran shortfall in plants: geographic biases in our knowledge of plant traits

This article is part of the Special Collection ‘Global plant diversity and distribution’. See https://www.newphytologist.org/global-plant-diversity for more details.

Megaherbivores provide biotic resistance against alien plant dominance

While human-driven biological invasions are rapidly spreading, finding scalable and effective control methods poses an unresolved challenge. Here, we assess whether megaherbivores-herbivores reaching ≥1,000 kg of body mass-offer a nature-based solution to plant invasions. Invasive plants are generally adapted to maximize vegetative growth. Megaherbivores, with broad dietary tolerances, could remove large biomass of established plants, facilitating new plant growth. We used a massive dataset obtained from 26,838 camera stations and 158,979 vegetation plots to assess the relationships between megaherbivores, native plants and alien plants across India (~121,330 km2). We found a positive relationship between megaherbivore abundance and native plant richness and abundance, and a concomitant reduction in alien plant abundance. This relationship was strongest in protected areas with midproductive ecosystem and high megaherbivore density but it was lost in areas where thicket-forming alien plants predominated (>40% cover). By incorporating the role of ecosystem productivity, plants traits and densities of megaherbivores on megaherbivore-vegetation relationships, our study highlights a function of megaherbivores in controlling alien plant proliferation and facilitating diverse native plants in invaded ecosystems. The study shows great potential for megafauna-based trophic rewilding as a nature-based solution to counteract dominance of plant invasions.

Large mammals and trees in eastern monsoonal China: anthropogenic losses since the Late Pleistocene and restoration prospects in the Anthropocene

Massive human-induced declines of large-sized animals and trees (megabiota) from the Late Pleistocene to the Anthropocene have resulted in downsized ecosystems across the globe, in which components and functions have been greatly simplified. In response, active restoration projects of extant large-sized species or functional substitutes are needed at large scales to promote ecological processes that are important for ecosystem self-regulation and biodiversity maintenance. Despite the desired global scope of such projects, they have received little attention in East Asia. Here, we synthesise the biogeographical and ecological knowledge of megabiota in ancient and modern China, with relevant data mostly located in eastern monsoonal China (EMC), aiming to assess its potential for restoring functionally intact ecosystems modulated by megabiota. We found that during the Late Pleistocene, 12 mammalian megafaunal (carnivores ≥15 kg and herbivores ≥500 kg) species disappeared from EMC: one carnivore Crocuta ultima (East Asian spotted hyena) and 11 herbivores including six megaherbivores (≥1000 kg). The relative importance of climate change and humans in driving these losses remains debated, despite accumulating evidence in favour of the latter. Later massive depletion of megafauna and large-sized (45-500 kg) herbivores has been closely associated with agricultural expansion and societal development, especially during the late Holocene. While forests rich in large timber trees (33 taxa in written records) were common in the region 2000-3000 years ago, millennial-long logging has resulted in considerable range contractions and at least 39 threatened species. The wide distribution of C. ultima, which likely favoured open or semi-open habitats (like extant spotted hyenas), suggests the existence of mosaic open and closed vegetation in the Late Pleistocene across EMC, in line with a few pollen-based vegetation reconstructions and potentially, or at least partially, reflecting herbivory by herbivorous megafauna. The widespread loss of megaherbivores may have strongly compromised seed dispersal for both megafruit (fleshy fruits with widths ≥40 mm) and non-megafruit plant species in EMC, especially in terms of extra-long-distance (>10 km) dispersal, which is critical for plant species that rely on effective biotic agents to track rapid climate change. The former occurrence of large mammals and trees have translated into rich material and non-material heritages passed down across generations. Several reintroduction projects have been implemented or are under consideration, with the case of Elaphurus davidianus a notable success in recovering wild populations in the middle reaches of the Yangtze River, although trophic interactions with native carnivorous megafauna have not yet been restored. Lessons of dealing with human-wildlife conflicts are key to public support for maintaining landscapes shared with megafauna and large herbivores in the human-dominated Anthropocene. Meanwhile, potential human-wildlife conflicts, e.g. public health risks, need to be scientifically informed and effectively reduced. The Chinese government's strong commitment to improved policies of ecological protection and restoration (e.g. ecological redlines and national parks) provides a solid foundation for a scaling-up contribution to the global scope needed for solving the crisis of biotic downsizing and ecosystem degradation.

Feedback loops between 3D vegetation structure and ecological functions of animals

Ecosystems function in a series of feedback loops that can change or maintain vegetation structure. Vegetation structure influences the ecological niche space available to animals, shaping many aspects of behaviour and reproduction. In turn, animals perform ecological functions that shape vegetation structure. However, most studies concerning three-dimensional vegetation structure and animal ecology consider only a single direction of this relationship. Here, we review these separate lines of research and integrate them into a unified concept that describes a feedback mechanism. We also show how remote sensing and animal tracking technologies are now available at the global scale to describe feedback loops and their consequences for ecosystem functioning. An improved understanding of how animals interact with vegetation structure in feedback loops is needed to conserve ecosystems that face major disruptions in response to climate and land-use change.

Tropical Trees Will Need to Acclimate to Rising Temperatures-But Can They?

For tropical forests to survive anthropogenic global warming, trees will need to avoid rising temperatures through range shifts and "species migrations" or tolerate the newly emerging conditions through adaptation and/or acclimation. In this literature review, we synthesize the available knowledge to show that although many tropical tree species are shifting their distributions to higher, cooler elevations, the rates of these migrations are too slow to offset ongoing changes in temperatures, especially in lowland tropical rainforests where thermal gradients are shallow or nonexistent. We also show that the rapidity and severity of global warming make it unlikely that tropical tree species can adapt (with some possible exceptions). We argue that the best hope for tropical tree species to avoid becoming "committed to extinction" is individual-level acclimation. Although several new methods are being used to test for acclimation, we unfortunately still do not know if tropical tree species can acclimate, how acclimation abilities vary between species, or what factors may prevent or facilitate acclimation. Until all of these questions are answered, our ability to predict the fate of tropical species and tropical forests-and the many services that they provide to humanity-remains critically impaired.