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Global change encompasses many co-occurring anthropogenic drivers, which can act synergistically or antagonistically on ecological systems. Predicting how different global change drivers simultaneously contribute to observed biodiversity change is a key challenge for ecology and conservation. However, we lack the mechanistic understanding of how multiple global change drivers influence the vital rates of multiple interacting species. We propose that reaction norms, the relationships between a driver and vital rates like growth, mortality, and consumption, provide insights to the underlying mechanisms of community responses to multiple drivers. Understanding how multiple drivers interact to affect demographic rates using a reaction-norm perspective can improve our ability to make predictions of interactions at higher levels of organization-that is, community and food web. Building on the framework of consumer-resource interactions and widely studied thermal performance curves, we illustrate how joint driver impacts can be scaled up from the population to the community level. A simple proof-of-concept model demonstrates how reaction norms of vital rates predict the prevalence of driver interactions at the community level. A literature search suggests that our proposed approach is not yet used in multiple driver research. We outline how realistic response surfaces (i.e., multidimensional reaction norms) can be inferred by parametric and nonparametric approaches. Response surfaces have the potential to strengthen our understanding of how multiple drivers affect communities as well as improve our ability to predict when interactive effects emerge, two of the major challenges of ecology today.

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Plant diversity loss can alter plant–plant and plant–rhizosphere microbiome interactions. These altered interactions, in turn, may exert diversity‐driven selection pressure to which plants respond with phenotypic changes. Diverse plant communities may favour the survival and fitness of individuals with traits that avoid competition. Conversely, monocultures may accumulate species‐specific pests favouring greater investment in defence traits. Yet, it is unknown how altered plant rhizosphere interactions influence the plant diversity‐driven selection for altered plant phenotypes. We tested for plant diversity‐driven selection on plant above‐ground traits and how these traits are modified by their rhizosphere microbial communities after 11 years in experimental plant monocultures and mixtures. Plants propagated from monocultures or mixtures were grown in combination with their ‘home’ versus ‘away’ arbuscular mycorrhizal fungi (AMF) or non‐AMF microbes in two separate experiments using five and eight plant species, respectively. We hypothesized that plants in monocultures may be selected for better defence and better performance in association with rhizosphere microbial communities compared with plants in mixtures. Monoculture and mixture plants significantly differed in their above‐ground phenotypes. As predicted, plant traits related to defence (greater leaf mass per area and leaf dry matter content, reduced leaf damage) were more pronounced in monoculture plants in both experiments. Effects of the rhizosphere microbial communities, which generally enhanced plant growth, tended to be species‐specific. Significant three‐way interactions between diversity‐driven selection, AMF treatment and plant species showed that home versus away effects could be positive or negative, depending on plant species. We conclude that long‐term differences in plant diversity lead to selection for altered plant phenotypes. Such differences may be further modified in association with the AMF microbial communities derived from the different plant diversity treatments, but often outcomes are species‐specific. This suggests that plant species differ in their capacity to respond to diversity loss and associated changes in rhizosphere microbial communities, making it complicated to predict community‐level responses to such loss.

Plant and soil microbial diversities are linked through a range of interactions, including the exchange of carbon and nutrients but also herbivory and pathogenic effects. Over time, associations between plant communities and their soil microbiota may strengthen and become more specific, resulting in stronger associations between plant and soil microbial diversity. We tested this hypothesis at the end of a 4-year field experiment in 48 plots with different plant species compositions established 13 years earlier in a biodiversity experiment in Jena, Germany. We factorially crossed plant community history (old vs. new plant communities) and soil legacy (old vs. new soil) with plant diversity (species richness levels 1, 2, 4 and 8, each with 12 different species compositions). We use the term ‘plant community history’ to refer to the co-occurrence history of plants in different species compositions in the Jena Experiment. We determined soil bacterial and fungal community composition in terms of operational taxonomic units (OTUs) using 16S rRNA gene and ITS DNA sequencing. Plant community history (old plants) did not affect overall soil community composition but differentially affected bacterial richness and abundances of specific bacterial taxa in association with specific plant species compositions. Soil legacy (old soil) markedly increased soil bacterial richness and evenness and decreased fungal evenness. Soil fungal richness increased with plant species richness, regardless of plant community history or soil legacy, with the strongest difference between plant monocultures and mixtures. Specific plant species compositions and functional groups were associated with specific bacterial and fungal community compositions. Grasses increased fungal richness and evenness and legumes decreased fungal evenness, but bacterial diversity was not affected. Synthesis. Our findings indicate that as experimental ecosystems varying in plant diversity develop over time (2002–2010), plant species associate with specific soil microbial taxa. This can have long-lasting effects on below-ground community composition in re-assembled plant communities, as reflected in strong soil legacy signals still visible after 4 years (2011–2015). Effects of plant community history on soil communities are subtle and may take longer to fully develop.

Understanding factors that maintain ecosystem stability is critical in the face of environmental change. Experiments simulating species loss from grassland have shown that losing biodiversity decreases ecosystem stability. However, as the originally sown experimental communities with reduced biodiversity develop, plant evolutionary processes or the assembly of interacting soil organisms may allow ecosystems to increase stability over time. We explored such effects in a long‐term grassland biodiversity experiment with plant communities with either a history of co‐occurrence (selected communities) or no such history (naive communities) over a 4‐yr period in which a major flood disturbance occurred. Comparing communities of identical species composition, we found that selected communities had temporally more stable biomass than naive communities, especially at low species richness. Furthermore, selected communities showed greater biomass recovery after flooding, resulting in more stable post‐flood productivity. In contrast to a previous study, the positive diversity–stability relationship was maintained after the flooding. Our results were consistent across three soil treatments simulating the presence or absence of co‐selected microbial communities. We suggest that prolonged exposure of plant populations to a particular community context and abiotic site conditions can increase ecosystem temporal stability and resilience due to short‐term evolution. A history of co‐occurrence can in part compensate for species loss, as can high plant diversity in part compensate for the missing opportunity of such adaptive adjustments.

In grassland biodiversity experiments the positive biodiversity–ecosystem functioning relationship generally increases over time. However, we know little about the underlying short-term evolutionary processes. Using five plant species selected for twelve years in a biodiversity experiment in mixture or monoculture and plants without such a selection history, we assessed whether differential selection altered productivity, biodiversity effects, and functional trait differences within newly assembled monocultures and 2-species mixtures. Plants without a past community selection history in the biodiversity experiment produced the lowest assemblage biomass and showed the weakest biodiversity effects. In newly assembled mixtures, plants with a selection history in mixtures produced more biomass than plants with a monoculture selection history. Biodiversity effects were generally positive and differed significantly between selection histories. However, contrary to our expectations, biodiversity effects were not stronger for mixture-type plants. Biodiversity effects were influenced by both trait differences between plants and community-weighted means, but these relationships were mostly independent of selection history. Our findings suggest that twelve years of selection history in monocultures or species mixtures differentiated plants of each species into monoculture- and mixture-types. Such rapid evolution of different community-types within grassland species and its effect on ecosystem services and functioning are likely to be important for species conservation practice.

Although the monitoring and prediction of ecosystem dynamics under global change have been extensively assessed, large gaps remain in our knowledge, including a need for concepts in rapid evolution and phenotypic plasticity, and a lack of large-scale and long-term monitoring. Recent genomic studies using the model species Arabidopsis predict that plastic and evolutionary changes in phenology may affect plant reproduction. We propose that three genomic-scale methods would enhance global change studies. First, genome-wide RNA sequencing enables monitoring of diverse functional traits and phenology. Second, sequencing of DNA variants highlights the importance of genetic variation and evolution. Third, DNA metabarcoding provides efficient and unbiased ecosystem monitoring. Integrating these genomic-scale studies with remote sensing will promote the understanding and prediction of biodiversity change.

Soil microbes are known to be key drivers of several essential ecosystem processes such as nutrient cycling, plant productivity and the maintenance of plant species diversity. However, how plant species diversity and identity affect soil microbial diversity and community composition in the rhizosphere is largely unknown. We tested whether, over the course of 11 years, distinct soil bacterial communities developed under plant monocultures and mixtures, and if over this time frame plants with a monoculture or mixture history changed in the bacterial communities they associated with. For eight species, we grew offspring of plants that had been grown for 11 years in the same field monocultures or mixtures (plant history in monoculture vs. mixture) in pots inoculated with microbes extracted from the field monoculture and mixture soils attached to the roots of the host plants (soil legacy). After 5 months of growth in the glasshouse, we collected rhizosphere soil from each plant and used 16S rRNA gene sequencing to determine the community composition and diversity of the bacterial communities. Bacterial community structure in the plant rhizosphere was primarily determined by soil legacy and by plant species identity, but not by plant history. In seven of the eight plant species the number of individual operational taxonomic units with increased abundance was larger when inoculated with microbes from mixture soil. We conclude that plant species richness can affect below-ground community composition and diversity, feeding back to the assemblage of rhizosphere bacterial communities in newly establishing plants via the legacy in soil.

Biodiversity often increases plant productivity. In long-term grassland experiments, positive biodiversity effects on plant productivity commonly increase with time. Also, it has been shown that such positive biodiversity effects persist not only in the local environment but also when plants are transferred into a common environment. Thus, we hypothesized that community diversity had acted as a selective agent, resulting in the emergence of plant monoculture and mixture types with differing genetic composition. To test our hypothesis, we grew offspring from plants that were grown for eleven years in monoculture or mixture environments in a biodiversity experiment (Jena Experiment) under controlled glasshouse conditions in monocultures or two-species mixtures. We used epiGBS, a genotyping-by-sequencing approach combined with bisulfite conversion to provide integrative genetic and epigenetic data. We observed significant genetic and epigenetic divergence according to selection history in three out of five perennial grassland species, namelyGalium mollugo,Prunella vulgarisandVeronica chamaedrys, with epigenetic differences mostly reflecting the genetic differences. In addition, current diversity levels in the glasshouse had weak effects on epigenetic variation. However, given the limited genome coverage of the reference-free bisulfite method epiGBS, it remains unclear how much of this epigenetic divergence was independent of underlying genetic differences. Our results thus suggest that selection of genetic variants, and possibly epigenetic variants, caused the rapid emergence of monoculture and mixture types within plant species in the Jena Experiment.

Soil microbes are known to be involved in a number of essential ecosystem processes such as nutrient cycling, plant productivity and the maintenance of plant species diversity. However, how plant species diversity and identity affect soil microbial diversity and community composition is largely unknown. We tested whether, over the course of 11 years, distinct soil bacterial communities developed under plant monocultures and mixtures, and if over this timeframe plants with a monoculture or mixture history changed in the microbial communities they associated with. For eight species, we grew offspring of plants that had been grown for 11 years in the same monocultures or mixtures (monoculture- or mixture-type plants) in pots inoculated with microbes extracted from the monoculture and mixture soils. After five months of growth in the glasshouse, we collected rhizosphere soil from each plant and used 16S-rRNA gene sequencing to determine the community composition and diversity of the bacterial communities. Microbial community structure in the plant rhizosphere was primarily determined by soil legacy (monoculture vs. mixture soil) and by plant species identity, but not by plant legacy (monoculture- vs. mixture-type plants). In seven out of the eight plant species bacterial abundance was larger when inoculated with microbes from mixture soil. We conclude that plant diversity can strongly affect belowground community composition and diversity, feeding back to the assemblage of rhizosphere microbial communities in newly establishing plants. Thereby our work demonstrates that concerns for plant biodiversity loss are also concerns for soil biodiversity loss.

Understanding factors that increase ecosystem stability is critical in the face of environmental change. Experiments simulating species loss from grassland ecosystems have shown that losing biodiversity decreases the ability of ecosystems to buffer negative effects of disturbances. However, as the originally sown experimental communities with reduced biodiversity develop, plant evolutionary processes or the assembly of interacting soil organisms may allow them to develop stability and resilience over time. We explored such effects in a long-term grassland biodiversity experiment with plant communities with either a history of co-occurrence (selected communities) or no such history (naïve communities) over a four-year period in which a major flood disturbance occurred.We found selected communities had temporally more stable biomass than the same communities of naïve plants, especially at low species richness. Furthermore, selected communities showed greater short-term biomass recovery after flooding, resulting in more stable post-flood productivity. In contrast to a previous study, the positive diversity–stability relationship was maintained after the flooding. Our results were consistent across three soil treatments simulating the presence or absence of co-selected microbial communities. We suggest that prolonged exposure of plant populations to a particular community context and abiotic site conditions can increase ecosystem temporal stability and resistance to disturbance. We argue that selection during the course of a biodiversity experiment is the most parsimonious explanation for these effects. A history of co-occurrence can in part compensate for species loss, as can high plant diversity in part compensate for the missing opportunity of such adaptive adjustments.

1. Biodiversity loss not only impairs ecosystem functioning but can also alter the selection for traits in plant communities. At high diversity selection favours traits that allow for greater niche partitioning, whereas at low diversity selection may favour greater defence against pathogens. However, it is unknown whether changes in plant diversity also select for altered interactions with soil organisms. 2. We assessed whether the responses in plant growth and functional traits to their local arbuscular mycorrhizal fungal (AMF) communities have been altered by the diversity of the plant communities from which both plants and AMF communities were obtained. We grew plants with AMF communities that originated from either plant monocultures or mixtures in a fully factorial design that included both negative and positive controls, by inoculating no AMF or a foreign AMF respectively. 3. We found that AMF from plant mixtures were more beneficial than monoculture AMF for two out of five plant species. Plants from mixtures generally grew better than those from monocultures, but suffered greater damage by leaf pathogens. Although plant growth and phenotypic responses were dependent on the AMF communities with which they associated, we found little evidence for plant growth responses specific to their local AMF communities and results differed between species and traits. 4. Our results show that plants from mixtures were selected for increased growth at the expense of reduced defence and vice versa for plants from monocultures, providing evidence for plant diversity-dependent selection on competitive growth vs. defence. Furthermore, our study suggests that effects of a common history between plants and AMF do not follow a general pattern leading to increased or decreased mutualism. 5. Synthesis: Here we provide evidence that biodiversity loss can alter evolutionary trajectories of plant phenotypes and responses to their local AMF communities. However, the selection for altered plant-AMF interactions differ between plant species. To understand how plant communities respond and evolve under a changing environment requires further knowledge about life strategies of plant species and their above-belowground interactions.

Species extinctions from local communities can negatively affect ecosystem functioning 1 . Statistical and ecological mechanisms underlying these impacts are well studied 2-4 but the role of evolutionary mechanisms has rarely been addressed 5,6 . In particular, it is not known to what extent local populations are co-adapted, not only to their environment but also to each other, because such a co-adaption would suggest that species extinctions can result in a larger than expected decline in ecosystem functioning. We used a long-term field biodiversity experiment with 52 plant species to determine if natural selection at the level of entire communities intensified the effects of biodiversity on ecosystem functioning. We re-assembled communities with 8-year co-selection histories adjacent to communities with identical species composition but no history of co-selection on native soil from the experiment and on novel soil. Over four years, selected plant communities were more productive and expressed stronger biodiversity effects than naive communities. Novel soil increased productivity initially but not in the longer term. Our findings suggest that plant community selection can lead to increased community-level functioning, regardless of the soil in which they were assembled. As a consequence, it may take many years to reconstruct well-functioning communities if one reassembles them with populations lacking a common selection history.

Background: Little is known about interactions between filamentous heterotrophs and filamentous cyanobacteria. Here, interactions between the filamentous heterotrophic bacteria Fibrella aestuarina (strain BUZ 2) and Fibrisoma limi (BUZ 3) with an axenic strain of the autotrophic filamentous cyanobacterium Nostoc muscorum (SAG 25.82) were studied in mixed cultures under nutrient rich (carbon source present in medium) and poor (carbon source absent in medium) conditions. Findings: F. aestuarina BUZ 2 significantly reduced the cyanobacterial population whereas F. limi BUZ 3 did not. Physical contact between heterotrophs and autotroph was observed and the cyanobacterial cells showed some level of damage and lysis. Therefore, either contact lysis or entrapment with production of extracellular compounds in close vicinity of host cells could be considered as potential modes of action. The supernatants from pure heterotrophic cultures did not have an effect on Nostoc cultures. However, supernatant from mixed cultures of BUZ 2 and Nostoc had a negative effect on cyanobacterial growth, indicating that the lytic compounds were only produced in the presence of Nostoc. The growth and survival of tested heterotrophs was enhanced by the presence of Nostoc or its metabolites, suggesting that the heterotrophs could utilize the autotrophs and its products as a nutrient source. However, the autotroph could withstand and out-compete the heterotrophs under nutrient poor conditions. Conclusions: Our results suggest that the nutrients in cultivation media, which boost or reduce the number of heterotrophs, were the important factor influencing the outcome of the interplay between filamentous heterotrophs and autotrophs. For better understanding of these interactions, additional research is needed. In particular, it is necessary to elucidate the mode of action for lysis by heterotrophs, and the possible defense mechanisms of the autotrophs. Background Cyanobacteria are photoautotrophic bacteria obtaining their carbon and energy by photosynthesis, while heterotrophic bacteria rely on organic compounds as their carbon and energy source. Within their natural aquatic environment, autotrophic cyanobacteria and heterotrophic bacteria live in a close relationship and can interact in various ways (synergistic, neutral, antagonistic). At present, little is known about such interactions, especially between filamentous cyanobacteria and filamentous heterotrophs. Few studies touching those