The importance of antagonistic interactions for plant species coexistence and ecosystem functioning

H. Auge (UFZ), H. B. Deising (MLU), I. Hensen (MLU), M. Schädler (UFZ)

Theory predicts that species coexistence is mediated either by minimizing fitness differences among species (equalizing mechanisms), or by negative frequency-dependence increasing intraspecific relative to inter-specific interactions (stabilizing mechanisms). Within this framework, we will experimentally investigate the relative importance of equalizing vs. stabilizing processes for the maintenance of plant diversity, thereby focussing on the role of vertical food-web interactions (plant-pathogen and plant-herbivore) in grasslands as a study system. These interactions are supposed to be of particular importance for ecosystem responses to global environmental changes, as biological invasions and climate-driven shifts in species ranges will lead to novel communities and to mismatches between trophically interacting species. Therefore, we will explicitly consider the effect of exotic plant species on coexistence mechanisms, and provide basic information for future research how climate change impacts the functioning of ecological communities.

Community dynamics and ecosystem functioning during subtropical forest succession: the role of phylogeny and functional traits

H. Bruelheide (MLU), O. Purschke (UFZ), W. Durka (UFZ), S. Michalski (UFZ), C. Wirth (UL), J. Kattge (MPI-BGC)

We will study the causes and consequences of the temporal changes in multiple facets of biodiversity during post-disturbance ecosystem development. Using the Comparative Study Plots of BEF-China, we will focus on the relationships between phylogeny with functional traits, community composition, environment and ecosystem functions, to (i) test whether phylogenetic relatedness/diversity can be used as proxy for trait similarity/diversity, particularly for traits that are difficult to measure ('detection'), (ii) gain insight into the temporal dynamics of the processes generating biodiversity after disturbance ('emergence'), (iii) quantify temporal turnover in phylogenetic/functional diversity and test whether there are successional shifts in evolutionary deep lineages or functionally unique groups ('conservation'), and (iv) quantify the linkages between successional changes in environmental conditions, biodiversity and ecosystem functioning/services. Our approach of linking ecological and evolutionary processes will allow to test competing hypotheses about community assembly processes and to examine whether findings from biodiversity-ecosystem functioning experiments apply to natural communities.

Cross comparing molecular and physiological regulation in ectomycorrhizal interactions of different fungi with oak trees: a way to understand biodiversity emergence in symbioses

F. Buscot (UFZ), I. Große (MLU), S. Herrmann (UFZ), M. Tarkka (UFZ)

Ectomycorrhizas (EM) evolved parallel in different saprotroph fungal taxa. They are a model to understand biodiversity emergence in symbioses. An international team is just achieving full genome sequencing of 25 EM fungi, providing unique tools to tackle this question. We will synthesize EM between 6 EMF spread over the fungi classification and the pedunculate oak clone DF159 for which genomic resources are available as well. Cultivation systems will include organic litter patches for assessing fungal saprotrophism. Using RNASeq, we will cross compare genome regulation in plant and fungi in EM and in saprotroph colony parts. We hypothesize that (1) EM are unstable, evolutionarily dynamic associations; (2) part of the symbiosis related genes were re-invented several times; (3) genetic control of the symbiosis by the plant varies according to the EMF partners; (4) regulation patterns in both partners is related to the saprotrophic potential of the fungus; (5) there are universal EM functions that are ancient and common to other symbioses.

Trinity in biodiversity: a synthesis of metabolic scaling, niche, and neutral theory

V. Grimm (UFZ), U. Berger (TU Dresden), J. Rosindell (Imperial College London), H. Bruelheide (MLU), J. Kattge (MPI-BGC)

A particular aspect of ecological neutral theory that has not yet been sufficiently acknowledged is that differences in functional traits do not necessarily lead to differences in fitness. Ecological equivalence regarding birth-death trade-offs between different species is consistent with the assumptions of neutral theory but allows for differences in functional traits as suggested by niche theory. In the proposed project we will develop a unifying theory of metabolic scaling, demographic tradeoffs and community assembly involving both niche and neutral theory. We will base our work on systematic exploration of existing trait databases and on simulation models. We have already made preliminary progress by deriving a scaling rule for plant functional traits, which explains observed demographic trade-offs that we were able to confirm with plant data. In the proposed work, we will derive key predictions that can be tested in experimental facilities such as GCEF and iDiv’s ecotrons. Our project aims at theory-driven synthesis of three major biodiversity theories and thus at unifying biodiversity theory.

Importance of mutualistic interactions for current and future patterns of plant and bird diversity in the tropical Andes

I. Hensen (MLU), M. Schleuning (BiK-F), W. D. Kissling (Aarhus University), I. Kühn (UFZ), T. Wiegand (UFZ)

Global environmental change reshuffles ecological communities and is likely to alter biotic interactions among species. The relevance of biotic interactions for determining current and future distributions of species at large spatial scales is still debated. We study the effects of mutualistic plant-bird interactions on current and future patterns of functional plant and bird diversity in a biodiversity hotspot in the tropical Andes. We will compile a database of functional fruit and bird traits and will record current vertical distributions of plant and bird species. To estimate functional diversity in current and future communities, we will develop species distribution models that incorporate climate envelopes of species and mutualistic dependences between species, derived from quantifications of interaction strengths in mutualistic networks and spatial autocorrelations in species ranges. By developing a new analytical framework, we aim at testing the urgent question to what extent biotic interactions shape current and future patterns of biodiversity.

Identifying key community traits shaping pelagic iron-rich aggregates

K. Küsel (FSU), G. Pohnert (FSU), C. Wilhelm (UL)

This proposal will address the key question: How are interactions organized in complex communities? We will choose an aquatic model system which also offers a complex architectural structure encompassing a spatial microscale relevant for studying microbial activities. Pelagic aggregates formed in oceans or lakes are inhabited by a rich and diverse community of phytoplankton, bacteria and protozoa and are enriched in organic matter. We will focus on iron-rich aggregates formed in different lakes which will be studied both in situ and simplified in aquatic microcosms using used model organisms with (ideally) fully sequenced and annotated genomes. With this approach we aim to (i) identify major trade-offs among partners of interaction networks and (ii) use metagenomic combined with the identification of infochemicals to tackle functional biodiversity shaping the structure of these aggregates. From a strategic point of view, this project will foster aquatic biodiversity research by starting new networks of collaboration both within and outside of iDiv.

Frequency of jasmonate deficiency in plant populations: consequences for plant productivity and insect diversity

S. Meldau (MPI CE, iDiv), V. Grimm (UFZ), I. T. Baldwin (MPI CE), M. Kallenbach (MPI CE)

Intraspecific genetic diversity can directly and indirectly affect a wide range of population, community and ecosystem processes. Whether the frequency of genetic traits that mediate ecological interactions structure arthropod and plant biodiversity remains an unexplored question.   The ability to produce Jasmonic acid (JA) is tightly associated with insect resistance in all plant species tested so far; plants with reduced JA levels are more susceptible to herbivores. Under insect-free conditions, plants benefit from JA-deficiency with higher growth rates and higher fitness due to reduced investments in costly defenses. JA production after elicitation by herbivory varies in natural populations of Nicotiana attenuata plants; JA deficient genotypes have been found to occur in natural populations at a frequency below five percent. Whether this frequency is optimal for plant community productivity or whether native insect herbivore communities are evolutionary adapted to this frequency remains unknown. We will use in silico analysis informed by micro and mesocosm experiments to analyze whether the occurrence of JA-deficient genotypes is under frequency-dependent selection. Model predictions will be tested by performing experiments with isogenic populations of N. attenuata, harboring different frequencies of transgenic plants altered in their ability to produce JA. Our project thus contributes to the understanding of the function of the genetic diversity in plant populations, which, ultimately, improves theory development in evolution and ecology and can help to develop applications in conservation, restoration and agriculture.

Apiculture and the pollinator decline: A model for pathogen driven biodiversity risks

R. F.A. Moritz (MLU), V. Grimm (UFZ), J. Settele (UFZ), M. Schlegel (UL)

Global change can drive plant–pollinator systems into an extinction vortex: plants disappear, specialist pollinators go extinct accelerating floral loss. One factor to accelerate the decline of bee pollinators is the increased number of lethal pathogens. From this perspective apiculture may be a major threat to wild pollinators, because it spreads pests and pathogens that spill over into the wild. Natural honeybee populations are at risk, because wild and managed populations readily interbreed. Current theories of host-pathogen interactions ignore male haploidy and colonial life history. Yet both are essential to understand the epidemiology in social and solitary bees. We will develop this theory and test it by comparing pest and pathogen loads in wild and managed bee populations as a model system. This will form the scientific basis for establishing wild honeybees as a natural resource for rural development in developmental countries supporting both biodiversity and economy

Mapping genetic and species diversity of pollinators to the ecosystem service of pollination across changing landscapes

R. Paxton (MLU), C. Bleidorn (UL), I. Große (MLU), J. Settele (UFZ), O. Schweiger (UFZ)

Pollination is a major ecosystem service primarily undertaken by insects. The relationship between flower visitor species diversity, abundance and pollination service provision shows little consensus across studies. We test the hypothesis that genetic diversity of pollinators provides a more refined and accurate measure of pollination service provision than species diversity of flower visitors. Using the TERENO network of field sites of the UFZ and the poppy Papaver rhoeas as our model system, we will explore the relationship between pollinator diversity and abundance, genetic diversity of pollinators and ecosystem service provision. As genetic markers, we shall employ a population genomic approach using Illumina-based RAD-sequencing. Additional field sites will test the relationship between land use (urban, rural), genetic diversity and service provision, giving a strong conservation focus to the research. Urban-rural comparisons also allow us to identify potential evolutionary responses of pollinators to climate change.

Accelerated Evolution in Chromosomal Rearrangements and Speciation in Lacertid Lizards

M. Schlegel (UL), K. Nowick (UL), P. F. Stadler (UL), K. Henle (UFZ), R. Faria (CIBIO-University of Porto)

During the process of speciation, individuals of two populations acquire genetic differences leading to reproductive isolation. According to Suppressed Recombination Models (SRMs) of chromosomal speciation, genetic divergence can quickly accumulate within regions of low recombination, such as in chromosomal rearrangements (CRs). To test the hypothesis that CRs are associated with accelerated evolution driving speciation we will study two species of lizards (Lacerta viridis and L. bilineata) which recently separated during Pleistocene. To this end, we will sequence, assemble, and compare their genomes, to search for accumulated divergence near breakpoints and within rearranged regions. We will also sequence the transcriptomes of four individuals of each species as well as four hybrids for gene annotation and identification of differential gene expression patterns. We will develop a new gene assembly method to detect CRs. In the spirit of iDiv we want to contribute to better understand speciation mechanisms and emergence of biodiversity.

Carbon allocation pattern by IR spectroscopy

C. Wilhelm (UL), H. Bruelheide (MLU), C. Zörb (UL), L. Wessjohann (IPB)

Different methods of IR spectroscopy will be tested to be applicable to measure target components of the carbon allocation pattern in different functional groups of herbal plants. The hypothesis will be tested that C-allocation into proteins reflects growth investment, whereas accumulation of starch and secondary products (phenolic compounds) represents investment in resistance. It will be analysed if IR spectroscopy can easily quantify the ratio of protein, starch, cellulose and total phenols per total carbon in different plants species. If the IR method works properly, the hypothesis will be tested in a controlled competition experiment between different species under stressed and non-stressed conditions. It will be analysed if the C-allocation pattern obtained from IF spectroscopy matches with the relative biomass formation of the different species in the experiment.

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In the first general member assembly, the following people have been elected to form the centre's directorate (underlined from left to right): Prof. Dr. Beate A. Schücking, Prof. Dr. Georg Teutsch, Prof. Dr. Birgit Dräger, Prof. Dr. Francois Buscot, Prof. Dr. Helge Bruelheide, Prof. Dr. Kirsten Küsel, Prof. Dr. Klaus Dicke, Prof. Dr. Christian Wirth.