Showing papers in "Nature Ecology and Evolution in 2021"

A meta-analysis of biological impacts of artificial light at night

Abstract: Natural light cycles are being eroded over large areas of the globe by the direct emissions and sky brightening that result from sources of artificial night-time light. This is predicted to affect wild organisms, particularly because of the central role that light regimes play in determining the timing of biological activity. Although many empirical studies have reported such effects, these have focused on particular species or local communities and have thus been unable to provide a general evaluation of the overall frequency and strength of these impacts. Using a new database of published studies, we show that exposure to artificial light at night induces strong responses for physiological measures, daily activity patterns and life history traits. We found particularly strong responses with regards to hormone levels, the onset of daily activity in diurnal species and life history traits, such as the number of offspring, predation, cognition and seafinding (in turtles). So far, few studies have focused on the impact of artificial light at night on ecosystem functions. The breadth and often strength of biological impacts we reveal highlight the need for outdoor artificial night-time lighting to be limited to the places and forms-such as timing, intensity and spectrum-where it is genuinely required by the people using it to minimize ecological impacts.

Decoloniality and anti-oppressive practices for a more ethical ecology.

Abstract: Ecological research and practice are crucial to understanding and guiding more positive relationships between people and ecosystems. However, ecology as a discipline and the diversity of those who call themselves ecologists have also been shaped and held back by often exclusionary Western approaches to knowing and doing ecology. To overcome these historical constraints and to make ecology inclusive of the diverse peoples inhabiting Earth’s varied ecosystems, ecologists must expand their knowledge, both in theory and practice, to incorporate varied perspectives, approaches and interpretations from, with and within the natural environment and across global systems. We outline five shifts that could help to transform academic ecological practice: decolonize your mind; know your histories; decolonize access; decolonize expertise; and practise ethical ecology in inclusive teams. We challenge the discipline to become more inclusive, creative and ethical at a moment when the perils of entrenched thinking have never been clearer. The authors outline five decolonizing shifts that could help to transform academic ecological practice, challenging the discipline to become more inclusive, creative and ethical.

Polarization of microbial communities between competitive and cooperative metabolism.

Abstract: Resource competition and metabolic cross-feeding are among the main drivers of microbial community assembly. Yet the degree to which these two conflicting forces are reflected in the composition of natural communities has not been systematically investigated. Here, we use genome-scale metabolic modelling to assess the potential for resource competition and metabolic cooperation in large co-occurring groups (up to 40 members) across thousands of habitats. Our analysis reveals two distinct community types, which are clustered at opposite ends of a spectrum in a trade-off between competition and cooperation. At one end are highly cooperative communities, characterized by smaller genomes and multiple auxotrophies. At the other end are highly competitive communities, which feature larger genomes and overlapping nutritional requirements, and harbour more genes related to antimicrobial activity. The latter are mainly present in soils, whereas the former are found in both free-living and host-associated habitats. Community-scale flux simulations show that, whereas competitive communities can better resist species invasion but not nutrient shift, cooperative communities are susceptible to species invasion but resilient to nutrient change. We also show, by analysing an additional data set, that colonization by probiotic species is positively associated with the presence of cooperative species in the recipient microbiome. Together, our results highlight the bifurcation between competitive and cooperative metabolism in the assembly of natural communities and its implications for community modulation.

Mapping the deforestation footprint of nations reveals growing threat to tropical forests.

Abstract: Deforestation, a significant threat to biodiversity, is accelerated by global demand for commodities. Although prior literature has linked deforestation to global supply chains, here we provide a fine-scale representation of spatial patterns of deforestation associated with international trade. Using remote sensing data and a multi-region input-output model, we quantify and map the spatiotemporal changes in global deforestation footprints over 15 years (2001-2015) at a 30-m resolution. We find that, while many developed countries, China and India have obtained net forest gains domestically, they have also increased the deforestation embodied in their imports, of which tropical forests are the most threatened biome. Consumption patterns of G7 countries drive an average loss of 3.9 trees per person per year. Some of the hotspots of deforestation embodied in international trade are also biodiversity hotspots, such as in Southeast Asia, Madagascar, Liberia, Central America and the Amazonian rainforest. Our results emphasize the need to reform zero-deforestation policies through strong transnational efforts and by improving supply chain transparency, public-private engagement and financial support for the tropics.

A global-scale expert assessment of drivers and risks associated with pollinator decline.

Abstract: Pollinator decline has attracted global attention and substantial efforts are underway to respond through national pollinator strategies and action plans. These policy responses require clarity on what is driving pollinator decline and what risks it generates for society in different parts of the world. Using a formal expert elicitation process, we evaluated the relative regional and global importance of eight drivers of pollinator decline and ten consequent risks to human well-being. Our results indicate that global policy responses should focus on reducing pressure from changes in land cover and configuration, land management and pesticides, as these were considered very important drivers in most regions. We quantify how the importance of drivers and risks from pollinator decline, differ among regions. For example, losing access to managed pollinators was considered a serious risk only for people in North America, whereas yield instability in pollinator-dependent crops was classed as a serious or high risk in four regions but only a moderate risk in Europe and North America. Overall, perceived risks were substantially higher in the Global South. Despite extensive research on pollinator decline, our analysis reveals considerable scientific uncertainty about what this means for human society.

Areas of global importance for conserving terrestrial biodiversity, carbon and water

Abstract: To meet the ambitious objectives of biodiversity and climate conventions, the international community requires clarity on how these objectives can be operationalized spatially and how multiple targets can be pursued concurrently. To support goal setting and the implementation of international strategies and action plans, spatial guidance is needed to identify which land areas have the potential to generate the greatest synergies between conserving biodiversity and nature's contributions to people. Here we present results from a joint optimization that minimizes the number of threatened species, maximizes carbon retention and water quality regulation, and ranks terrestrial conservation priorities globally. We found that selecting the top-ranked 30% and 50% of terrestrial land area would conserve respectively 60.7% and 85.3% of the estimated total carbon stock and 66% and 89.8% of all clean water, in addition to meeting conservation targets for 57.9% and 79% of all species considered. Our data and prioritization further suggest that adequately conserving all species considered (vertebrates and plants) would require giving conservation attention to ~70% of the terrestrial land surface. If priority was given to biodiversity only, managing 30% of optimally located land area for conservation may be sufficient to meet conservation targets for 81.3% of the terrestrial plant and vertebrate species considered. Our results provide a global assessment of where land could be optimally managed for conservation. We discuss how such a spatial prioritization framework can support the implementation of the biodiversity and climate conventions.

Ensuring effective implementation of the post-2020 global biodiversity targets

Abstract: Biodiversity underpins the fundamental elements for human well-being including food security, human health and access to clean water. In 2010, the Aichi Targets were adopted by world leaders to address the crisis of biodiversity loss. Despite conservation efforts, none of the Aichi Targets have been fully met. However, comprehensive analysis of the reasons for failure in terms of implementation mechanisms is, to date, rare and limited in scope. Here, we demonstrate that most parties did not set effective national targets in accordance with the Aichi Targets, and investments, knowledge and accountability for biodiversity conservation have been inadequate to enable effective implementation. We recommend that the new global targets under the post-2020 Global Biodiversity Framework should be adopted by parties as the minimum national targets to achieve the 2050 Vision. We propose that financial resources for biodiversity conservation are substantially increased through a variety of sources, including the deployment of new economic instruments such as payments for ecosystem services. In addition, science-policy interfaces at all levels need to be strengthened to integrate scientific, Indigenous and local knowledge to support decision-making. We suggest that a compliance and accountability mechanism, based on monitoring systems, is created to provide transparent and credible review of parties' implementation of the new global targets.

Impacts of hypoxic events surpass those of future ocean warming and acidification.

Abstract: Over the past decades, three major challenges to marine life have emerged as a consequence of anthropogenic emissions: ocean warming, acidification and oxygen loss. While most experimental research has targeted the first two stressors, the last remains comparatively neglected. Here, we implemented sequential hierarchical mixed-model meta-analyses (721 control–treatment comparisons) to compare the impacts of oxygen conditions associated with the current and continuously intensifying hypoxic events (1–3.5 O2 mg l−1) with those experimentally yielded by ocean warming (+4 °C) and acidification (−0.4 units) conditions on the basis of IPCC projections (RCP 8.5) for 2100. In contrast to warming and acidification, hypoxic events elicited consistent negative effects relative to control biological performance—survival (–33%), abundance (–65%), development (–51%), metabolism (–33%), growth (–24%) and reproduction (–39%)—across the taxonomic groups (mollusks, crustaceans and fish), ontogenetic stages and climate regions studied. Our findings call for a refocus of global change experimental studies, integrating oxygen concentration drivers as a key factor of ocean change. Given potential combined effects, multistressor designs including gradual and extreme changes are further warranted to fully disclose the future impacts of ocean oxygen loss, warming and acidification. A meta-analysis of experimental effects of stressors on marine organisms shows that hypoxia could harm crustaceans, mollusks and fish to a larger extent than warming and acidification.

Priority list of biodiversity metrics to observe from space.

Abstract: Monitoring global biodiversity from space through remotely sensing geospatial patterns has high potential to add to our knowledge acquired by field observation. Although a framework of essential biodiversity variables (EBVs) is emerging for monitoring biodiversity, its poor alignment with remote sensing products hinders interpolation between field observations. This study compiles a comprehensive, prioritized list of remote sensing biodiversity products that can further improve the monitoring of geospatial biodiversity patterns, enhancing the EBV framework and its applicability. The ecosystem structure and ecosystem function EBV classes, which capture the biological effects of disturbance as well as habitat structure, are shown by an expert review process to be the most relevant, feasible, accurate and mature for direct monitoring of biodiversity from satellites. Biodiversity products that require satellite remote sensing of a finer resolution that is still under development are given lower priority (for example, for the EBV class species traits). Some EBVs are not directly measurable by remote sensing from space, specifically the EBV class genetic composition. Linking remote sensing products to EBVs will accelerate product generation, improving reporting on the state of biodiversity from local to global scales.

Human disturbance causes widespread disruption of animal movement.

Abstract: Disturbance and habitat modification by humans can alter animal movement, leading to negative impacts on fitness, survival and population viability However, the ubiquity and nature of these impacts across diverse taxa has not been quantified We compiled 208 studies on 167 species from terrestrial and aquatic ecosystems across the globe to assess how human disturbance influences animal movement We show that disturbance by humans has widespread impacts on the movements of birds, mammals, reptiles, amphibians, fish and arthropods More than two-thirds of 719 cases represented a change in movement of 20% or more, with increases in movement averaging 70% and decreases -37% Disturbance from human activities, such as recreation and hunting, had stronger impacts on animal movement than habitat modification, such as logging and agriculture Our results point to a global restructuring of animal movement and emphasize the need to reduce the negative impacts of humans on animal movement

ACE2 receptor usage reveals variation in susceptibility to SARS-CoV and SARS-CoV-2 infection among bat species.

Abstract: Bats are the suggested natural hosts for severe acute respiratory syndrome coronavirus (SARS-CoV) and the causal agent of the coronavirus disease 2019 (COVID-19) pandemic, SARS-CoV-2. The interaction of viral spike proteins with their host receptor angiotensin-converting enzyme 2 (ACE2) is a critical determinant of potential hosts and cross-species transmission. Here we use virus-host receptor binding and infection assays to examine 46 ACE2 orthologues from phylogenetically diverse bat species, including those in close and distant contact with humans. We found that 24, 21 and 16 of them failed to support infection by SARS-CoV, SARS-CoV-2 or both viruses, respectively. Furthermore, we confirmed that infection assays in human cells were consistent with those in two bat cell lines. Additionally, we used genetic and functional analyses to identify critical residues in bat ACE2 receptors associated with viral entry restrictions. Our results suggest that many bat species may not be the potential hosts of one or both viruses and that no correlation was identified between proximity to humans and probability of being natural hosts of SARS-CoV or SARS-CoV-2. This study demonstrates dramatic variation in susceptibility to SARS-CoV and SARS-CoV-2 infection among bat species and adds knowledge towards a better understanding of coronavirus-bat interaction.

Conserving intraspecific variation for nature’s contributions to people

Abstract: The rapid loss of intraspecific variation is a hidden biodiversity crisis. Intraspecific variation, which includes the genomic and phenotypic diversity found within and among populations, is threatened by local extinctions, abundance declines, and anthropogenic selection. However, biodiversity assessments often fail to highlight this loss of diversity within species. We review the literature on how intraspecific variation supports critical ecological functions and nature's contributions to people (NCP). Results show that the main categories of NCP (material, non-material, and regulating) are supported by intraspecific variation. We highlight new strategies that are needed to further explore these connections and to make explicit the value of intraspecific variation for NCP. These strategies will require collaboration with local and Indigenous groups who possess critical knowledge on the relationships between intraspecific variation and ecosystem function. New genomic methods provide a promising set of tools to uncover hidden variation. Urgent action is needed to document, conserve, and restore the intraspecific variation that supports nature and people. Thus, we propose that the maintenance and restoration of intraspecific variation should be raised to a major global conservation objective.

Balancing selection maintains hyper-divergent haplotypes in Caenorhabditis elegans.

Abstract: Across diverse taxa, selfing species have evolved independently from outcrossing species thousands of times. The transition from outcrossing to selfing decreases the effective population size, effective recombination rate and heterozygosity within a species. These changes lead to a reduction in genetic diversity, and therefore adaptive potential, by intensifying the effects of random genetic drift and linked selection. Within the nematode genus Caenorhabditis, selfing has evolved at least three times, and all three species, including the model organism Caenorhabditis elegans, show substantially reduced genetic diversity relative to outcrossing species. Selfing and outcrossing Caenorhabditis species are often found in the same niches, but we still do not know how selfing species with limited genetic diversity can adapt to these environments. Here, we examine the whole-genome sequences from 609 wild C. elegans strains isolated worldwide and show that genetic variation is concentrated in punctuated hyper-divergent regions that cover 20% of the C. elegans reference genome. These regions are enriched in environmental response genes that mediate sensory perception, pathogen response and xenobiotic stress response. Population genomic evidence suggests that genetic diversity in these regions has been maintained by long-term balancing selection. Using long-read genome assemblies for 15 wild strains, we show that hyper-divergent haplotypes contain unique sets of genes and show levels of divergence comparable to levels found between Caenorhabditis species that diverged millions of years ago. These results provide an example of how species can avoid the evolutionary dead end associated with selfing.

Safe fieldwork strategies for at-risk individuals, their supervisors and institutions

Abstract: As a result of identity prejudice, certain individuals are more vulnerable to conflict and violence when they are in the field. It is paramount that all fieldworkers be informed of the risks some colleagues may face, so that they can define best practice together: here we recommend strategies to minimize risk for all individuals conducting fieldwork.

Using the IUCN Red List to map threats to terrestrial vertebrates at global scale

Abstract: The Anthropocene is characterized by unparalleled human impact on other species, potentially ushering in the sixth mass extinction. Yet mitigation efforts remain hampered by limited information on the spatial patterns and intensity of the threats driving global biodiversity loss. Here we use expert-derived information from the International Union for Conservation of Nature Red List on threats to 23,271 species, representing all terrestrial amphibians, birds and mammals, to generate global maps of the six major threats to these groups: agriculture, hunting and trapping, logging, pollution, invasive species, and climate change. Our results show that agriculture and logging are pervasive in the tropics and that hunting and trapping is the most geographically widespread threat to mammals and birds. Additionally, current representations of human pressure underestimate the overall pressure on biodiversity, due to the exclusion of threats such as hunting and climate change. Alarmingly, this is particularly the case in areas of the highest biodiversity importance.

The evolution of oxygen-utilizing enzymes suggests early biosphere oxygenation.

Abstract: Production of molecular oxygen was a turning point in the Earth’s history. The geological record indicates the Great Oxidation Event, which marked a permanent transition to an oxidizing atmosphere around 2.4 Ga. However, the degree to which oxygen was available to life before oxygenation of the atmosphere remains unknown. Here, phylogenetic analysis of all known oxygen-utilizing and -producing enzymes (O2-enzymes) indicates that oxygen became widely available to living organisms well before the Great Oxidation Event. About 60% of the O2-enzyme families whose birth can be dated appear to have emerged at the separation of terrestrial and marine bacteria (22 families, compared to two families assigned to the last universal common ancestor). This node, dubbed the last universal oxygen ancestor, coincides with a burst of emergence of both oxygenases and other oxidoreductases, thus suggesting a wider availability of oxygen around 3.1 Ga. Phylogenetic dating of O2-utilizing enzymes indicates a burst of emergence several hundred million years before the Great Oxidation Event.

Conservation needs to break free from global priority mapping.

Abstract: Global priority maps have been transformative for conservation, but now have questionable utility and may crowd out other forms of research. Conservation must re-engage with contextually rich knowledge that builds global understanding from the ground up.

The island rule explains consistent patterns of body size evolution in terrestrial vertebrates.

Abstract: Island faunas can be characterized by gigantism in small animals and dwarfism in large animals, but the extent to which this so-called 'island rule' provides a general explanation for evolutionary trajectories on islands remains contentious. Here we use a phylogenetic meta-analysis to assess patterns and drivers of body size evolution across a global sample of paired island-mainland populations of terrestrial vertebrates. We show that 'island rule' effects are widespread in mammals, birds and reptiles, but less evident in amphibians, which mostly tend towards gigantism. We also found that the magnitude of insular dwarfism and gigantism is mediated by climate as well as island size and isolation, with more pronounced effects in smaller, more remote islands for mammals and reptiles. We conclude that the island rule is pervasive across vertebrates, but that the implications for body size evolution are nuanced and depend on an array of context-dependent ecological pressures and environmental conditions.

Mobilizing the past to shape a better Anthropocene.

Abstract: As our planet emerges into a new epoch in which humans dominate the Earth system, it is imperative that societies initiate a new phase of responsible environmental stewardship. Here we argue that information from the past has a valuable role to play in enhancing the sustainability and resilience of our societies. We highlight the ways that past data can be mobilized for a variety of efforts, from supporting conservation to increasing agricultural sustainability and food security. At a practical level, solutions from the past often do not require fossil fuels, can be locally run and managed, and have been tested over the long term. Past failures reveal non-viable solutions and expose vulnerabilities. To more effectively leverage increasing knowledge about the past, we advocate greater cross-disciplinary collaboration, systematic engagement with stakeholders and policymakers, and approaches that bring together the best of the past with the cutting-edge technologies and solutions of tomorrow.

Improve forest restoration initiatives to meet Sustainable Development Goal 15.

Abstract: Monoculture plantations have been promoted for the restoration of the world’s forested area, but these have not contained or reversed the loss of biodiversity. More innovative incentive policies should be implemented to shift the planet’s forest restoration policies from increasing the area of forests per se to improving their biodiversity.

Timing the origin of eukaryotic cellular complexity with ancient duplications

Abstract: Eukaryogenesis is one of the most enigmatic evolutionary transitions, during which simple prokaryotic cells gave rise to complex eukaryotic cells. While evolutionary intermediates are lacking, gene duplications provide information on the order of events by which eukaryotes originated. Here we use a phylogenomics approach to reconstruct successive steps during eukaryogenesis. We find that gene duplications roughly doubled the proto-eukaryotic gene repertoire, with families inherited from the Asgard archaea-related host being duplicated most. By relatively timing events using phylogenetic distances, we inferred that duplications in cytoskeletal and membrane-trafficking families were among the earliest events, whereas most other families expanded predominantly after mitochondrial endosymbiosis. Altogether, we infer that the host that engulfed the proto-mitochondrion had some eukaryote-like complexity, which drastically increased upon mitochondrial acquisition. This scenario bridges the signs of complexity observed in Asgard archaeal genomes to the proposed role of mitochondria in triggering eukaryogenesis.

Exacerbated drought impacts on global ecosystems due to structural overshoot

Abstract: Vegetation dynamics are affected not only by the concurrent climate but also by memory-induced lagged responses. For example, favourable climate in the past could stimulate vegetation growth to surpass the ecosystem carrying capacity, leaving an ecosystem vulnerable to climate stresses. This phenomenon, known as structural overshoot, could potentially contribute to worldwide drought stress and forest mortality but the magnitude of the impact is poorly known due to the dynamic nature of overshoot and complex influencing timescales. Here, we use a dynamic statistical learning approach to identify and characterize ecosystem structural overshoot globally and quantify the associated drought impacts. We find that structural overshoot contributed to around 11% of drought events during 1981–2015 and is often associated with compound extreme drought and heat, causing faster vegetation declines and greater drought impacts compared to non-overshoot related droughts. The fraction of droughts related to overshoot is strongly related to mean annual temperature, with biodiversity, aridity and land cover as secondary factors. These results highlight the large role vegetation dynamics play in drought development and suggest that soil water depletion due to warming-induced future increases in vegetation could cause more frequent and stronger overshoot droughts. Structural overshoot can occur when phases of excess plant growth deplete soil moisture too rapidly. The authors quantify structural overshoots using remote sensing datasets from 1981 to 2015, finding that 11% of droughts during this period could be attributed to structural overshoot.

Fossil data support a pre-Cretaceous origin of flowering plants.

Abstract: Flowering plants (angiosperms) are the most diverse of all land plants, becoming abundant in the Cretaceous and achieving dominance in the Cenozoic. However, the exact timing of their origin remains a controversial topic, with molecular clocks generally placing their origin much further back in time than the oldest unequivocal fossils. To resolve this discrepancy, we developed a Bayesian method to estimate the ages of angiosperm families on the basis of the fossil record (a newly compiled dataset of ~15,000 occurrences in 198 families) and their living diversity. Our results indicate that several families originated in the Jurassic, strongly rejecting a Cretaceous origin for the group. We report a marked increase in lineage accumulation from 125 to 72 million years ago, supporting Darwin’s hypothesis of a rapid Cretaceous angiosperm diversification. Our results demonstrate that a pre-Cretaceous origin of angiosperms is supported not only by molecular clock approaches but also by analyses of the fossil record that explicitly correct for incomplete sampling. Using a novel Bayesian method, the authors infer a pre-Cretaceous origin for multiple angiosperm families on the basis of their fossil record and present-day diversity.

The evolutionary genomics of species' responses to climate change.

Abstract: Climate change is a threat to biodiversity. One way that this threat manifests is through pronounced shifts in the geographical range of species over time. To predict these shifts, researchers have primarily used species distribution models. However, these models are based on assumptions of niche conservatism and do not consider evolutionary processes, potentially limiting their accuracy and value. To incorporate evolution into the prediction of species' responses to climate change, researchers have turned to landscape genomic data and examined information about local genetic adaptation using climate models. Although this is an important advancement, this approach currently does not include other evolutionary processes-such as gene flow, population dispersal and genomic load-that are critical for predicting the fate of species across the landscape. Here, we briefly review the current practices for the use of species distribution models and for incorporating local adaptation. We next discuss the rationale and theory for considering additional processes, reviewing how they can be incorporated into studies of species' responses to climate change. We summarize with a conceptual framework of how manifold layers of information can be combined to predict the potential response of specific populations to climate change. We illustrate all of the topics using an exemplar dataset and provide the source code as potential tutorials. This Perspective is intended to be a step towards a more comprehensive integration of population genomics with climate change science.

Metabolomic signatures of coral bleaching history

Abstract: Coral bleaching has a profound impact on the health and function of reef ecosystems, but the metabolomic effects of coral bleaching are largely uncharacterized. Here, untargeted metabolomics was used to analyse pairs of adjacent Montipora capitata corals that had contrasting bleaching phenotypes during a severe bleaching event in 2015. When these same corals were sampled four years later while visually healthy, there was a strong metabolomic signature of bleaching history. This was primarily driven by betaine lipids from the symbiont, where corals that did not bleach were enriched in saturated lyso-betaine lipids. Immune modulator molecules were also altered by bleaching history in both the coral host and the algal symbiont, suggesting a shared role in partner choice and bleaching response. Metabolomics from a separate set of validation corals was able to predict the bleaching phenotype with 100% accuracy. Experimental temperature stress induced phenotype-specific responses, which magnified differences between historical bleaching phenotypes. These findings indicate that natural bleaching susceptibility is manifested in the biochemistry of both the coral animal and its algal symbiont. This metabolome difference is stable through time and results in different physiological responses to temperature stress. This work provides insight into the biochemical mechanisms of coral bleaching and presents a valuable new tool for resilience-based reef restoration.

The emergence of the brain non-CpG methylation system in vertebrates.

Abstract: Mammalian brains feature exceptionally high levels of non-CpG DNA methylation alongside the canonical form of CpG methylation. Non-CpG methylation plays a critical regulatory role in cognitive function, which is mediated by the binding of MeCP2, the transcriptional regulator that when mutated causes Rett syndrome. However, it is unclear whether the non-CpG neural methylation system is restricted to mammalian species with complex cognitive abilities or has deeper evolutionary origins. To test this, we investigated brain DNA methylation across 12 distantly related animal lineages, revealing that non-CpG methylation is restricted to vertebrates. We discovered that in vertebrates, non-CpG methylation is enriched within a highly conserved set of developmental genes transcriptionally repressed in adult brains, indicating that it demarcates a deeply conserved regulatory program. We also found that the writer of non-CpG methylation, DNMT3A, and the reader, MeCP2, originated at the onset of vertebrates as a result of the ancestral vertebrate whole-genome duplication. Together, we demonstrate how this novel layer of epigenetic information assembled at the root of vertebrates and gained new regulatory roles independent of the ancestral form of the canonical CpG methylation. This suggests that the emergence of non-CpG methylation may have fostered the evolution of sophisticated cognitive abilities found in the vertebrate lineage.

The global distribution and environmental drivers of aboveground versus belowground plant biomass.

Abstract: A poor understanding of the fraction of global plant biomass occurring belowground as roots limits our understanding of present and future ecosystem function and carbon pools. Here we create a database of root-mass fractions (RMFs), an index of plant below- versus aboveground biomass distributions, and generate quantitative, spatially explicit global maps of RMFs in trees, shrubs and grasses. Our analyses reveal large gradients in RMFs both across and within vegetation types that can be attributed to resource availability. High RMFs occur in cold and dry ecosystems, while low RMFs dominate in warm and wet regions. Across all vegetation types, the directional effect of temperature on RMFs depends on water availability, suggesting feedbacks between heat, water and nutrient supply. By integrating our RMF maps with existing aboveground plant biomass information, we estimate that in forests, shrublands and grasslands, respectively, 22%, 47% and 67% of plant biomass exists belowground, with a total global belowground fraction of 24% (20-28%), that is, 113 (90-135) Gt carbon. By documenting the environmental correlates of root biomass allocation, our results can inform model projections of global vegetation dynamics under current and future climate scenarios.

Functional diversity effects on productivity increase with age in a forest biodiversity experiment.

Abstract: Forest restoration increases global forest area and ecosystem services such as primary productivity and carbon storage. How tree species functional composition impacts the provisioning of these services as forests develop is sparsely studied. We used 10-year data from 478 plots with 191,200 trees in a forest biodiversity experiment in subtropical China to assess the relationship between community productivity and community-weighted mean (CWM) or functional diversity (FD) values of 38 functional traits. We found that effects of FD values on productivity became larger than effects of CWM values after 7 years of forest development and that the FD values also became more reliable predictors of productivity than the CWM values. In contrast to CWM, FD values consistently increased productivity across ten different species-pool subsets. Our results imply that to promote productivity in the long term it is imperative for forest restoration projects to plant multispecies communities with large functional diversity.