Increasing frequency and intensity of droughts threaten grassland ecosystems. Semi-natural grasslands vary in age from ancient to younger sites established on former arable land. While species richness and composition are known to affect drought resilience, little is known about how grassland age shapes drought responses through eco-evolutionary processes at the plant population level. We explored how grassland age and local plant-soil adaptation shape the drought resilience of plant populations by reciprocally combining soils and genotypes of a common grass, Briza media, collected from young, intermediate, and ancient grasslands - last cultivated 28-63, 63-84, and > 84-300 years ago, respectively-and subjecting the resulting mesocosms to a drought event. Ancient grassland soils enhanced drought resistance and recovery compared with younger soils. Enhanced drought resilience was primarily explained by lower abundance of putative fungal pathogens in older soils. Plants grown in 'home' soils from their sites of origin were more productive and invested less in root production to withstand water stress, indicating the important role of local plant-soil adaptation. Our results show the long-lasting legacy of land use history in soil microbial communities and their significant role in shaping drought resilience across grassland populations.

Anthropogenic biodiversity decline threatens the functioning of ecosystems and the many benefits they provide to humanity1. As well as causing species losses in directly affected locations, human influence might also reduce biodiversity in relatively unmodified vegetation if far-reaching anthropogenic effects trigger local extinctions and hinder recolonization. Here we show that local plant diversity is globally negatively related to the level of anthropogenic activity in the surrounding region. Impoverishment of natural vegetation was evident only when we considered community completeness: the proportion of all suitable species in the region that are present at a site. To estimate community completeness, we compared the number of recorded species with the dark diversity-ecologically suitable species that are absent from a site but present in the surrounding region2. In the sampled regions with a minimal human footprint index, an average of 35% of suitable plant species were present locally, compared with less than 20% in highly affected regions. Besides having the potential to uncover overlooked threats to biodiversity, dark diversity also provides guidance for nature conservation. Species in the dark diversity remain regionally present, and their local populations might be restored through measures that improve connectivity between natural vegetation fragments and reduce threats to population persistence.

Recent divergence can obscure species boundaries among closely related taxa. Silene section Italicae (Caryophyllaceae) has been taxonomically controversial, with about 30 species described. We investigate species delimitation within this section using 500 specimens sequenced for one nuclear and two plastid markers. Despite the use of a small number of genes, the large number of sequenced samples allowed confident delimitation of 50% of the species. The delimitation of other species (e.g., Silene nemoralis, S. nodulosa and S. andryalifolia) was more challenging. We confirmed that seven of the ten chasmophyte species in the section are not related to each other but are, instead, genetically closer to geographically nearby species belonging to Italicae yet growing in open habitats. Adaptation to chasmophytic habitats therefore appears to have occurred independently, as a result of convergent evolution within the group. Species from the Western Mediterranean Basin showed more conflicting species boundaries than species from the Eastern Mediterranean Basin, where there are fewer but better-delimited species. Significant positive correlations were found between an estimation of the effective population size of the taxa and their extent of occurrence (EOO) or area of occupancy (AOO), and negative but non-significant correlations between the former and the posterior probability (PP) of the corresponding clades. These correlations might suggest a lower impact of incomplete lineage sorting in species with low effective population sizes and small distributional ranges compared with that in species inhabiting large areas. Finally, we confirmed that S. italica and S. nemoralis are distinct species, that S. nemoralis might furthermore include two different species and that S. velutina from Corsica and S. hicesiae from the Lipari Islands are sister species.

There is an increasing recognition that, although the climate change and biodiversity crises are fundamentally connected, they have been primarily addressed independently and a more integrated global approach is essential to tackle these two global challenges. Nature-based Solutions (NbS) are hailed as a pathway for promoting synergies between the climate change and biodiversity agendas. There are, however, uncertainties and difficulties associated with the implementation of NbS, while the evidence regarding their benefits for biodiversity remains limited. We identify five key research areas where incomplete or poor information hinders the development of integrated biodiversity and climate solutions. These relate to refining our understanding of how climate change mitigation and adaptation approaches benefit biodiversity conservation; enhancing our ability to track and predict ecosystems on the move and/or facing collapse; improving our capacity to predict the impacts of climate change on the effectiveness of NbS; developing solutions that match the temporal, spatial and functional scale of the challenges; and developing a comprehensive and practical framework for assessing, and mitigating against, the risks posed by the implementation of NbS. Policy implications. The Conference of the Parties (COP) for the United Nations Framework Convention on Climate Change (COP26) and the Convention on Biological Diversity (COP15) present a clear policy window for developing coherent policy frameworks that align targets across the nexus of biodiversity and climate change. This window should (a) address the substantial and chronic underfunding of global biodiversity conservation, (b) remove financial incentives that negatively impact biodiversity and/or climate change, (c) develop higher levels of integration between the biodiversity and climate change agendas, (d) agree on a monitoring framework that enables the standardised quantification and comparison of biodiversity gains associated with NbS across ecosystems and over time and (e) rethink environmental legislation to better support biodiversity conservation in times of rapid climatic change.

Aims: Understanding fine- grain diversity patterns across large spatial extents is fundamental for macroecological research and biodiversity conservation. Using the GrassPlot database, we provide benchmarks of fine- grain richness values of Palaearctic open habitats for vascular plants, bryophytes, lichens and complete vegetation (i.e., the sum of the former three groups). Location: Palaearctic biogeographic realm. Methods: We used 126,524 plots of eight standard grain sizes from the GrassPlot database: 0.0001, 0.001, 0.01, 0.1, 1, 10, 100 and 1,000 m 2 and calculated the mean richness and standard deviations, as well as maximum, minimum, median, and first and third quartiles for each combination of grain size, taxonomic group, biome, region, vegetation type and phytosociological class. Results: Patterns of plant diversity in vegetation types and biomes differ across grain sizes and taxonomic groups. Overall, secondary (mostly semi- natural) grasslands and natural grasslands are the richest vegetation type. The open- access file ”GrassPlot Diversity Benchmarks” and the web tool “GrassPlot Diversity Explorer” are now available online (https://edgg.org/datab ases/Grass landD ivers ityEx plorer) and provide more insights into species richness patterns in the Palaearctic open habitats. Conclusions: The GrassPlot Diversity Benchmarks provide high- quality data on species richness in open habitat types across the Palaearctic. These benchmark data can be used in vegetation ecology, macroecology, biodiversity conservation and data quality checking. While the amount of data in the underlying GrassPlot database and their spatial coverage are smaller than in other extensive vegetation- plot databases, species recordings in GrassPlot

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Questions To what extent does the long-term process of grassland succession reflect changes in nutrient availability or other effects of grassland history? Plant communities in ancient, semi-natural pastures include many species associated with nutrient-poor soils. However, semi-natural pasture communities can also develop on previously arable sites - as nutrient levels decline over time. In Europe, Ellenberg N-values represent species' overall nutrient preferences and are often used as a proxy for soil nutrient availability. But how well do N-values actually reflect species' relationships with measured nutrient concentrations during grassland succession? Location A successional series of grazed, previously arable to ancient, grasslands on the Baltic island of oland, Sweden. Methods We collected data on community composition and soil nutrient (phosphorus, ammonium, nitrate) concentrations. We used Bayesian joint-community modelling to parameterize species' relationships with nutrients and grassland age, and quantified the relative contributions of the variables. Species responses were then compared with Ellenberg N-values. Results Phosphorus was the best explanatory variable for most species. However, species occurrences were not simply explained by gradients in particular nutrients, but by combinations of different nutrients and grassland age. There was overall agreement between N-values and species' nutrient responses - although the occurrences of species with identical N-values may be explained by different nutrients. Species with high and low N-values represent more reliable nutrient indicators than intermediate-N species, but their occurrences also reflect other factors that, as with nutrients, depend on the grassland age. Conclusions Our results confirm that Ellenberg N provides a robust indication of the overall nutrient preferences of individual grassland species. However, in grassland sites developing on previously arable land - where nutrient availability is strongly associated with habitat age - N-values may represent an integrated response not only to nutrients but also to other historical processes that drive grassland community assembly.

Ambitionen att minska kottkonsumtionen ar lovvard men riskerar att sla hart mot den biologiska mangfalden och ekosystemtjanster. Om vara naturbetesmarker forsvinner kan vi inte leva upp till FN:s internationella hallbarhetsmal och vara egna svenska miljomal som vi forbundit oss att jobba mot, skriver ett flertal forskare.

DN DEBATT 15/3. Sedan industrialiseringens borjan har vi anvant omkring fyra femtedelar av den mangd fossilt kol som far forbrannas for att vi ska klara Parisavtalet. Vi har bara en femtedel kvar och det ar brattom att kraftigt reducera utslappen. Det har Greta Thunberg och de strejkande ungdomarna forstatt. Darfor stodjer vi deras krav, skriver 270 klimatforskare.

How the patterns of niche occupancy vary from species‐poor to species‐rich communities is a fundamental question in ecology that has a central bearing on the processes that drive patterns of biodiversity. As species richness increases, habitat filtering should constrain the expansion of total niche volume, while limiting similarity should restrict the degree of niche overlap between species. Here, by explicitly incorporating intraspecific trait variability, we investigate the relationship between functional niche occupancy and species richness at the global scale. We assembled 21 datasets worldwide, spanning tropical to temperate biomes and consisting of 313 plant communities representing different growth forms. We quantified three key niche occupancy components (the total functional volume, the functional overlap between species and the average functional volume per species) for each community, related each component to species richness, and compared each component to the null expectations. As species richness increased, communities were more functionally diverse (an increase in total functional volume), and species overlapped more within the community (an increase in functional overlap) but did not more finely divide the functional space (no decline in average functional volume). Null model analyses provided evidence for habitat filtering (smaller total functional volume than expectation), but not for limiting similarity (larger functional overlap and larger average functional volume than expectation) as a process driving the pattern of functional niche occupancy. Synthesis . Habitat filtering is a widespread process driving the pattern of functional niche occupancy across plant communities and coexisting species tend to be more functionally similar rather than more functionally specialized. Our results indicate that including intraspecific trait variability will contribute to a better understanding of the processes driving patterns of functional niche occupancy.

GrassPlot is a collaborative vegetation-plot database organised by the Eurasian Dry Grassland Group (EDGG) and listed in the Global Index of Vegetation-Plot Databases (GIVD ID EU-00-003). GrassPlot collects plot records (releves) from grasslands and other open habitats of the Palaearctic biogeographic realm. It focuses on precisely delimited plots of eight standard grain sizes (0.0001; 0.001;... 1,000 m(2)) and on nested-plot series with at least four different grain sizes. The usage of GrassPlot is regulated through Bylaws that intend to balance the interests of data contributors and data users. The current version (v. 1.00) contains data for approximately 170,000 plots of different sizes and 2,800 nested-plot series. The key components are richness data and metadata. However, most included datasets also encompass compositional data. About 14,000 plots have near-complete records of terricolous bryophytes and lichens in addition to vascular plants. At present, GrassPlot contains data from 36 countries throughout the Palaearctic, spread across elevational gradients and major grassland types. GrassPlot with its multi-scale and multi-taxon focus complements the larger international vegetationplot databases, such as the European Vegetation Archive (EVA) and the global database " sPlot". Its main aim is to facilitate studies on the scale-and taxon-dependency of biodiversity patterns and drivers along macroecological gradients. GrassPlot is a dynamic database and will expand through new data collection coordinated by the elected Governing Board. We invite researchers with suitable data to join GrassPlot. Researchers with project ideas addressable with GrassPlot data are welcome to submit proposals to the Governing Board.

The NDVI is a remotely sensed vegetation index that is frequently used in ecological studies. There is, however, a lack of studies that evaluate the ability of the NDVI to detect fine‐scale variation in grassland plant community composition and species richness. Ellenberg indicators characterize the environmental preferences of plant species—and community‐mean Ellenberg values have been used to explore the environmental drivers of community assembly. We used variation partitioning to test the ability of satellite‐based NDVI to explain community‐mean Ellenberg nutrient (mN) and moisture (mF) indices, and the richness of habitat‐specialist species in dry grasslands of different ages. The grasslands represent a gradient of decreasing soil nutrient status. If community composition is determined by the responses of individual species to the underlying environmental conditions and if, at the same time, community composition determines the optical characteristics of the vegetation canopy, then positive relationships between the NDVI and mN and mF are expected. Many grassland specialists are intolerant of nutrient‐rich soils. If specialist richness is negatively related to soil‐nutrient levels, then a negative association between the NDVI and specialist richness is expected. However, because grassland community composition is not only influenced by abiotic variables but also by other spatial and temporal drivers, we included spatial variables and grassland age in the statistical analyses. The NDVI explained the majority of the variation in mF, and also contributed to a substantial proportion of the variation in mN. However, variation in specialist richness and the lowest values of mN were explained by grassland age and spatial variables—but were poorly explained by the NDVI. Synthesis and applications. The NDVI showed a good ability to detect variation in plant community composition, and should provide a valuable tool for assessing fine‐scale environmental variation in grasslands or for monitoring changes in grassland habitat properties. However, because the concentration of grassland specialists not only depends on environmental variables but also on the age and spatial context of the grasslands, the NDVI is unlikely to allow the identification of grasslands with high numbers of specialist species.

BACKGROUND:Phosphoglucose isomerase (PGI, EC 5.3.1.9) is an essential metabolic enzyme in all eukaryotes. An earlier study of the PgiC1 gene, which encodes cytosolic PGI in the grass Festuca ovina L., revealed a marked difference in the levels of nucleotide polymorphism between the 5' and 3' portions of the gene.METHODS:In the present study, we characterized the sequence polymorphism in F. ovina PgiC1 in more detail and examined possible explanations for the non-uniform pattern of nucleotide polymorphism across the gene.RESULTS:Our study confirms that the two portions of the PgiC1 gene show substantially different levels of DNA polymorphism and also suggests that the peptide encoded by the 3' portion of PgiC1 is functionally and structurally more important than that encoded by the 5' portion. Although there was some evidence of purifying selection (dN/dS test) on the 5' portion of the gene, the signature of purifying selection was considerably stronger on the 3' portion of the gene (dN/dS and McDonald-Kreitman tests). Several tests support the action of balancing selection within the 5' portion of the gene. Wall's B and Q tests were significant only for the 5' portion of the gene. There were also marked peaks of nucleotide diversity, Tajima's D and the dN/dS ratio at or around a PgiC1 codon site (within the 5' portion of the gene) that a previous study had suggested was subject to positive diversifying selection.CONCLUSIONS:Our results suggest that the two portions of the gene have been subject to different selective regimes. Purifying selection appears to have been the main force contributing to the relatively low level of polymorphism within the 3' portion of the sequence. In contrast, it is possible that balancing selection has contributed to the maintenance of the polymorphism within the 5' portion of the gene.

DN Debatt: Sverige har atagit sig att skydda 20 procent av landets land- och sotvattensomraden till 2020. Men hittills har bara 4–5 procent av den omfattande produktiva skogen bevarats. For att na de demokratiskt beslutade malen maste Skogsstyrelsens beslut om stopp for inventering av nyckelbiotoper havas, skriver sju forskare.

Small remnants of non-arable habitat within the farmland mosaic are considered important for the conservation of farmland biodiversity, but their contribution to landscape-scale species richness is poorly understood. In the present study, we examined the relative contributions of different habitat types to the landscape-scale species richness of vascular plants within farmland of varying landscape complexity. We also analysed pollen collected by bees to examine the extent to which the different habitat types contributed towards the provisioning of floral resources for three taxa (Bombus terrrestris, Megachile sp. and Osmia bicornis). We found that plant species richness increased with landscape complexity (defined as the proportion of semi-natural habitats). The relative contribution of small fragments of non-arable habitat to total plant species richness was high within all landscape types, especially in relation to the small area they covered. The importance of small non-arable fragments for the provisioning of floral resources to bees varied over time and between taxa. Bombus terrestris used the different habitat types differently during different parts of the growing season: arable fields were important early in the season, leys late in the season, and small non-arable habitat fragments during the mid-season when no mass-flowering crops were in bloom. In contrast, Megachile sp. and O. bicornis mainly foraged on plants occurring within grasslands. We conclude that small fragments of non-arable habitat are important for plant species richness at the landscape-scale and that their importance for plants may cascade to the bees that use them as foraging resources. Consequently, it is important to consider the entire landscape mosaic when taking actions to conserve farmland species.

Many species that are typical of calcareous, semi-natural grasslands (“typical grassland species”) are declining in Europe as a result of habitat-loss and -fragmentation. Whereas populations of these species are expected to be largest in old semi-natural grasslands, these species may also occur in successional grasslands on previously arable fields. We used a space-for-time approach to analyse changes in the frequencies of typical grassland species, and changes in soil properties, over a 280-year arable-to-grassland succession within a Swedish landscape. Our study revealed that a number of typical grassland species had higher frequencies in mid-successional (50–279years) than in old (≥280years) grasslands. Mid-successional grasslands also contained many of the typical grassland species that were present in old grasslands, but at lower frequencies, and had soil conditions similar to those of old grasslands. Early-successional (5–14 and 15–49years) grasslands contained few typical grassland species. In highly fragmented landscapes, mid-successional grasslands provide additional habitat for many typical grassland species, and can function as temporary refugia (“substitute habitat”) for these species until old grasslands are “restored”. The overall population sizes of some typical grassland species and red-listed species are likely to be substantially increased by the presence of mid-successional grasslands within the landscape. Our study suggests that, rather than focussing solely on old grassland fragments, conservation strategies for typical grassland species should adopt a dynamic, landscape-based perspective that recognizes the role of successional grasslands. Ensuring a continuous development of mid-successional grasslands is expected to be beneficial for populations of many typical grassland species.

Semi-natural grasslands with grazing management are characterized by high fine-scale species richness and have a high conservation value. The fact that fine-scale surveys of grassland plant communities are time-consuming may limit the spatial extent of ground-based diversity surveys. Remote sensing tools have the potential to support field-based sampling and, if remote sensing data are able to identify grassland sites that are likely to support relatively higher or lower levels of species diversity, then field sampling efforts could be directed towards sites that are of potential conservation interest. In the present study, we examined whether aerial hyperspectral (414–2501 nm) remote sensing can be used to predict fine-scale plant species diversity (characterized as species richness and Simpson’s diversity) in dry grazed grasslands. Vascular plant species were recorded within 104 (4 m × 4 m) plots on the island of Öland (Sweden) and each plot was characterized by a 245-waveband hyperspectral data set. We used two different modeling approaches to evaluate the ability of the airborne spectral measurements to predict within-plot species diversity: (1) a spectral response approach, based on reflectance information from (i) all wavebands, and (ii) a subset of wavebands, analyzed with a partial least squares regression model, and (2) a spectral heterogeneity approach, based on the mean distance to the spectral centroid in an ordinary least squares regression model. Species diversity was successfully predicted by the spectral response approach (with an error of ca. 20%) but not by the spectral heterogeneity approach. When using the spectral response approach, iterative selection of important wavebands for the prediction of the diversity measures simplified the model but did not improve its predictive quality (prediction error). Wavebands sensitive to plant pigment content (400–700 nm) and to vegetation structural properties, such as above-ground biomass (700–1300 nm), were identified as being the most important predictors of plant species diversity. We conclude that hyperspectral remote sensing technology is able to identify fine-scale variation in grassland diversity and has a potential use as a tool in surveys of grassland plant diversity.

We used allozymes to investigate the structure of genetic variation in populations of the perennial herb Silene nutans at local (Denmark), regional (Nordic area) and wide (over a 19° latitudinal gradient) geographic scales in north-western Europe. New data from Denmark were combined with data from previously studied Fennoscandian and western populations. We related patterns of nuclear variation for 26 Fennoscandian and western populations to the phylogeographic patterns revealed by four plastid (chloroplast) DNA markers. Levels of genetic diversity were similar within Denmark and Sweden/N Finland. Compared to Sweden/N Finland, the Danish populations show lower and nonsignificant F IS values. The genetic structure reveals no grouping of the Danish populations according to their geographic origin (Jutland-Zealand). Within Nordic populations (from Denmark, Sweden and N Finland), there is a weak geographic pattern of allozyme differentiation. The high latitude populations are genetically depauperate compared with populations from Western Europe. At the whole north-western European scale, the structure of allozyme variation within S. nutans shows geographic differentiation (Nordic versus western populations), and some congruence with plastid phylogeographic patterns. A high level of allozyme genetic differentiation is found between Nordic and western populations (8.0 %), but also between populations within haplotype categories (19.4 %). The overall geographic structure of allozyme variation of S. nutans appears to be primarily a reflection of past (postglacial) migration history, whereas more recent adaptive and stochastic processes have occurred at more local scales.