Intraspecific plant-soil feedback and intraspecific overyielding in Arabidopsis thaliana

1\. Understanding the mechanisms of community coexistence and ecosystem functioning may help to counteract the current biodiversity loss and its potentially harmful consequences. In recent years, plant-soil feedback that can, for example, be caused by below-ground microorganisms, has been suggested to play a role in maintaining plant coexistence and to be a potential driver of the positive relationship between plant diversity and ecosystem functioning. Most of the studies addressing these topics have focused on the species level. However, in addition to interspecific interactions, intraspecific interactions might be important for the structure of natural communities. 2\. Here we examine intraspecific coexistence and intraspecific diversity effects using 10 natural accessions of the model species Arabidopsis thaliana (L.) Heynh. We assessed morphological intraspecific diversity by measuring several above- and below-ground traits. We performed a plant-soil feedback experiment that was based on these trait differences between the accessions in order to determine whether A. thaliana experiences feedback at intraspecific level as a result of trait differences. We also experimentally tested the diversity-productivity relationship at intraspecific level. 3\. We found strong differences in above- and below-ground traits between the A. thaliana accessions. Overall, plant-soil feedback occurred at intraspecific level. However, accessions differed in the direction and strength of this feedback: some accessions grew better on their own soils, some on soils from other accessions. Furthermore, we found positive diversity effects within A. thaliana: accession mixtures produced a higher total above-ground biomass than accession monocultures. 4\. Differences between accessions in their feedback response could not be explained by morphological traits. Therefore, we suggest that they might have been caused by accession-specific accumulated soil communities, root exudates or by accession-specific resource use based on genetic differences that are not expressed in morphological traits. 5\. Synthesis. Our results provide some of the first evidence for intraspecific plant-soil feedback and intraspecific overyielding. These findings may have wider implications for the maintenance of variation within species and the importance of this variation for ecosystem functioning. Our results highlight the need for an increased focus on intraspecific processes in plant diversity research to fully understand the mechanisms of coexistence and ecosystem functioning.Ecology and Evolution, 4 (12), 2533-254

Multitrophic biodiversity enhances ecosystem functions, services and ecological intensification in agriculture

One central challenge for humanity is to mitigate and adapt to an ongoing climate and biodiversity crisis while providing resources to a growing human population. Ecological intensification (EI) aims to maximize crop productivity while minimizing impacts on the environment, especially by using biodiversity to improve ecosystem functions and services. Many EI measures are based on trophic interactions between organisms (e.g. pollination, biocontrol). Here, we investigate how research on multitrophic effects of biodiversity on ecosystem functioning could advance the application of EI measures in agriculture and forestry. We review previous studies and use qualitative analyses of the literature to test how important variables such as land-use parameters or habitat complexity affect multitrophic diversity, ecosystem functions and multitrophic biodiversity–ecosystem functioning relationships. We found that positive effects of biodiversity on ecosystem functions are prevalent in production systems, largely across ecosystem function dimensions, trophic levels, study methodologies and different ecosystem functions, however, with certain context dependencies. We also found strong impacts of land use and management on multitrophic biodiversity and ecosystem functions. We detected knowledge gaps in terms of data from underrepresented geographical areas, production systems, organism groups and functional diversity measurements. Additionally, we identified several aspects that require more attention in the future, such as trade-offs between multiple functions, temporal dynamics, effects of climate change, the spatial scale of the measures and their implementation. This information will be vital to ensure that agricultural and forest landscapes produce resources for humanity sustainably within the environmental limits of the planet

in situ experiment

The increasing amount of plastic littered into the sea may provide a new substratum for benthic organisms. These marine fouling communities on plastic have not received much scientific attention. We present, to our knowledge, the first comprehensive analysis of their macroscopic community composition, their primary production and the polymer degradation comparing conventional polyethylene (PE) and a biodegradable starch-based plastic blend in coastal benthic and pelagic habitats in the Mediterranean Sea. The biomass of the fouling layer increased significantly over time and all samples became heavy enough to sink to the seafloor. The fouling communities, consisting of 21 families, were distinct between habitats, but not between polymer types. Positive primary production was measured in the pelagic, but not in the benthic habitat, suggesting that large accumulations of floating plastic could pose a source of oxygen for local ecosystems, as well as a carbon sink. Contrary to PE, the biodegradable plastic showed a significant loss of tensile strength and disintegrated over time in both habitats. These results indicate that in the marine environment, biodegradable polymers may disintegrate at higher rates than conventional polymers. This should be considered for the development of new materials, environmental risk assessment and waste management strategies

Forest management intensity affects aquatic communities in artificial tree holes

Forest management could potentially affect organisms in all forest habitats. However, aquatic communities in water-filled tree-holes may be especially sensitive because of small population sizes, the risk of drought and potential dispersal limitation. We set up artificial tree holes in forest stands subject to different management intensities in two regions in Germany and assessed the influence of local environmental properties (tree-hole opening type, tree diameter, water volume and water temperature) as well as regional drivers (forest management intensity, tree-hole density) on tree-hole insect communities (not considering other organisms such as nematodes or rotifers), detritus content, oxygen and nutrient concentrations. In addition, we compared data from artificial tree holes with data from natural tree holes in the same area to evaluate the methodological approach of using tree-hole analogues. We found that forest management had strong effects on communities in artificial tree holes in both regions and across the season. Abundance and species richness declined, community composition shifted and detritus content declined with increasing forest management intensity. Environmental variables, such as tree-hole density and tree diameter partly explained these changes. However, dispersal limitation, indicated by effects of tree-hole density, generally showed rather weak impacts on communities. Artificial tree holes had higher water temperatures (on average 2° C higher) and oxygen concentrations (on average 25% higher) than natural tree holes. The abundance of organisms was higher but species richness was lower in artificial tree holes. Community composition differed between artificial and natural tree holes. Negative management effects were detectable in both tree-hole systems, despite their abiotic and biotic differences. Our results indicate that forest management has substantial and pervasive effects on tree-hole communities and may alter their structure and functioning. We furthermore conclude that artificial tree-hole analogues represent a useful experimental alternative to test effects of changes in forest management on natural communities.Fil: Petermann, Jana S.. University of Salzburg; Austria. Berlin-Brandenburg Institute of Advanced Biodiversity Research; AlemaniaFil: Rohland, Anja. Friedrich Schiller University; AlemaniaFil: Sichardt, Nora. Friedrich Schiller University; AlemaniaFil: Lade, Peggy. Friedrich Schiller University; AlemaniaFil: Guidetti, Brenda Yamile. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Friedrich Schiller University; AlemaniaFil: Weisser, Wolfgang W.. Friedrich Schiller University; Alemania. Technische Universität München; AlemaniaFil: Gossner, Martin M.. Friedrich Schiller University; Alemania. Technische Universität München; Alemani

Fear of predation alters clone-specific performance in phloem-feeding prey

Fear of predation has been shown to affect prey fitness and behaviour, however, to date little is known about the underlying genetics of responses to predator-associated risk. In an effort to fill this gap we exposed four naïve clones of green peach aphid (Myzus persicae), maintained on the model crop Brassica oleracea, to different types of cues from aphid lion (Chrysoperla carnea). The respective predation risks, we termed Fear Factors, were either lethal (consumption by predator), or non-lethal (non-consumptive predator- associated cues: plant-tethered predator cadavers and homogenised shoot- sprayed or soil-infused blends of predator remains). Our results show that the non-lethal risk cues differentially impeded prey reproductive success that varied by clone, suggesting genotype-specific response to fear of predation. Furthermore, whether plants were perceived as being safe or risky influenced prey responses as avoidance behaviour in prey depended on clone type. Our findings highlight that intra-specific genetic variation underlies prey responses to consumptive and non-consumptive effects of predation. This allows selection to act on anti-predator responses to fear of predation that may ramify and influence higher trophic levels in model agroecosystems

Nonlinear effects of environmental drivers shape macroinvertebrate biodiversity in an agricultural pondscape

Agriculture is a leading cause of biodiversity loss and significantly impacts freshwater biodiversity through many stressors acting locally and on the landscape scale. The individual effects of these numerous stressors are often difficult to disentangle and quantify, as they might have nonlinear impacts on biodiversity. Within agroecosystems, ponds are biodiversity hotspots providing habitat for many freshwater species and resting or feeding places for terrestrial organisms. Ponds are strongly influenced by their terrestrial surroundings, and understanding the determinants of biodiversity in agricultural landscapes remains difficult but crucial for improving conservation policies and actions. We aimed to identify the main effects of environmental and spatial variables on α-, β-, and γ-diversities of macroinvertebrate communities inhabiting ponds (n = 42) in an agricultural landscape in the Northeast Germany, and to quantify the respective roles of taxonomic turnover and nestedness in the pondscape. We disentangled the nonlinear effects of a wide range of environmental and spatial variables on macroinvertebrate α- and β-biodiversity. Our results show that α-diversity is impaired by eutrophication (phosphate and nitrogen) and that overshaded ponds support impoverished macroinvertebrate biota. The share of arable land in the ponds' surroundings decreases β-diversity (i.e., dissimilarity in community), while β-diversity is higher in shallower ponds. Moreover, we found that β-diversity is mainly driven by taxonomic turnover and that ponds embedded in arable fields support local and regional diversity. Our findings highlight the importance of such ponds for supporting biodiversity, identify the main stressors related to human activities (eutrophication), and emphasize the need for a large number of ponds in the landscape to conserve biodiversity. Small freshwater systems in agricultural landscapes challenge us to compromise between human demands and nature conservation worldwide. Identifying and quantifying the effects of environmental variables on biodiversity inhabiting those ecosystems can help address threats impacting freshwater life with more effective management of pondscapes

Pathways for cross-boundary effects of biodiversity on ecosystem functioning

The biodiversity-ecosystem functioning concept asserts that processes in ecosystems are markedly influenced by species richness and other facets of biodiversity. However, biodiversity-ecosystem functioning studies have been largely restricted to single ecosystems, ignoring the importance of functional links - such as the exchange of matter, energy, and organisms - between coupled ecosystems. Here we present a basic concept and outline three pathways of cross boundary biodiversity effects on ecosystem processes and propose an agenda to assess such effects, focusing on terrestrial-aquatic linkages to illustrate the case. This cross-boundary perspective of biodiversity-ecosystem functioning relationships presents a promising frontier for biodiversity and ecosystem science with repercussions for the conservation, restoration, and management of biodiversity and ecosystems from local to landscape scales.Peer reviewe

Dominant predators mediate the impact of habitat size on trophic structure in bromeliad invertebrate communities

Local habitat size has been shown to influence colonization and extinction processes of species in patchy environments. However, species differ in body size, mobility, and trophic level, and may not respond in the same way to habitat size. Thus far, we have a limited understanding of how habitat size influences the structure of multitrophic communities and to what extent the effects may be generalizable over a broad geographic range. Here, we used water-filled bromeliads of different sizes as a natural model system to examine the effects of habitat size on the trophic structure of their inhabiting invertebrate communities. We collected composition and biomass data from 651 bromeliad communities from eight sites across Central and South America differing in environmental conditions, species pools, and the presence of large-bodied odonate predators. We found that trophic structure in the communities changed dramatically with changes in habitat (bromeliad) size. Detritivore : resource ratios showed a consistent negative relationship with habitat size across sites. In contrast, changes in predator : detritivore (prey) ratios depended on the presence of odonates as dominant predators in the regional pool. At sites without odonates, predator : detritivore biomass ratios decreased with increasing habitat size. At sites with odonates, we found odonates to be more frequently present in large than in small bromeliads, and predator : detritivore biomass ratios increased with increasing habitat size to the point where some trophic pyramids became inverted. Our results show that the distribution of biomass amongst food-web levels depends strongly on habitat size, largely irrespective of geographic differences in environmental conditions or detritivore species compositions. However, the presence of large-bodied predators in the regional species pool may fundamentally alter this relationship between habitat size and trophic structure. We conclude that taking into account the response and multitrophic effects of dominant, mobile species may be critical when predicting changes in community structure along a habitat-size gradient.Fil: Petermann, Jana S.. Freie Universitat Berlin. Institute of Biology; AlemaniaFil: Farjalla, Vinicius F.. Universidade Federal do Rio de Janeiro; BrasilFil: Jocque, Merlijn. State University Of New Jersey; Estados UnidosFil: Kratina, Pavel. Queen Mary University Of London. School of Biological and Chemical Sciences; Reino UnidoFil: Macdonald, Andrew. University Of British Columbia; CanadáFil: Marino, Nicholas. Universidade Federal do Rio de Janeiro; BrasilFil: de Omena, Paula. Universidade Estadual de Campinas; BrasilFil: Piccoli, Gustavo. Universidade de Sao Paulo; BrasilFil: Richardson, Michael. Universidad de Puerto Rico; Puerto RicoFil: Richardson, Barbara. Universidad de Puerto Rico; Puerto RicoFil: Romero, Gustavo. Universidade Estadual de Campinas; BrasilFil: Videla, Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto Multidisciplinario de Biología Vegetal (p); Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Centro de Investigaciones Entomológicas de Córdoba; ArgentinaFil: Srivastava, Diane. University Of British Columbia; Canad

Plant Species Loss Affects Life-History Traits of Aphids and Their Parasitoids

The consequences of plant species loss are rarely assessed in a multi-trophic context and especially effects on life-history traits of organisms at higher trophic levels have remained largely unstudied. We used a grassland biodiversity experiment and measured the effects of two components of plant diversity, plant species richness and the presence of nitrogen-fixing legumes, on several life-history traits of naturally colonizing aphids and their primary and secondary parasitoids in the field. We found that, irrespective of aphid species identity, the proportion of winged aphid morphs decreased with increasing plant species richness, which was correlated with decreasing host plant biomass. Similarly, emergence proportions of parasitoids decreased with increasing plant species richness. Both, emergence proportions and proportions of female parasitoids were lower in plots with legumes, where host plants had increased nitrogen concentrations. This effect of legume presence could indicate that aphids were better defended against parasitoids in high-nitrogen environments. Body mass of emerged individuals of the two most abundant primary parasitoid species was, however, higher in plots with legumes, suggesting that once parasitoids could overcome aphid defenses, they could profit from larger or more nutritious hosts. Our study demonstrates that cascading effects of plant species loss on higher trophic levels such as aphids, parasitoids and secondary parasitoids begin with changed life-history traits of these insects. Thus, life-history traits of organisms at higher trophic levels may be useful indicators of bottom-up effects of plant diversity on the biodiversity of consumers

Integrating community assembly and biodiversity to better understand ecosystem function: the Community Assembly and the Functioning of Ecosystems (CAFE) approach.

The research of a generation of ecologists was catalysed by the recognition that the number and identity of species in communities influences the functioning of ecosystems. The relationship between biodiversity and ecosystem functioning (BEF) is most often examined by controlling species richness and randomising community composition. In natural systems, biodiversity changes are often part of a bigger community assembly dynamic. Therefore, focusing on community assembly and the functioning of ecosystems (CAFE), by integrating both species richness and composition through species gains, losses and changes in abundance, will better reveal how community changes affect ecosystem function. We synthesise the BEF and CAFE perspectives using an ecological application of the Price equation, which partitions the contributions of richness and composition to function. Using empirical examples, we show how the CAFE approach reveals important contributions of composition to function. These examples show how changes in species richness and composition driven by environmental perturbations can work in concert or antagonistically to influence ecosystem function. Considering how communities change in an integrative fashion, rather than focusing on one axis of community structure at a time, will improve our ability to anticipate and predict changes in ecosystem function