Land-use effects on trophic niche variation across taxonomic groups and trophic levels (TrophNiche)

• Applicant: Dr. Maria Alejandra Parreno
• Subject Area: Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions ; Ecology of Land Use
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 512303035

Biodiversity is shaped by organismal differences in the consumption, utilization and allocation of nutrients. The trophic niches of consumers depend on the spectrum of food resources available in the landscape, with cascading effects from lower to higher levels in food webs. In TrophNiche, I aim to calculate and compare the effect of land use and resource availability on variation, positions and overlaps in trophic niche sizes for different taxonomic and functional groups across trophic levels (e.g. consumers, pollinators, parasitoids). The project consists of (i) a synthesis of existing data in the database Bexis (ca. 170 datasets) and (ii) a field study across the three regions of the Biodiversity Exploratories, to collect under-represented organisms and complete trophic links by analyzing their stable isotope profile. As a preliminary work, I have identified and summarized existing datasets from previous projects in collaboration with its authors. These datasets include information on foraging interactions (e.g. metabarcoding of gut content and pollen, observational records of consumer-resource) and stoichiometric data (e.g. nutritional profiles, stable isotopes). Using them, I will calculate the ecological niche of species using isotopic position, richness, divergence, evenness and dispersion indexes, disparity and n-dimensional hypervolumes, depending on the source data.The field study will fill gaps in trophic links for key invertebrate species missing from the database (e.g., ants, aphids, parasitoids, grasshopers) and plants associated with them in grassland food webs. Missing species will be collected in the 150 grassland plots from the exploratories and for each of them signature profiles for C and N stable isotopes will be analyzed. Species isotopic signatures will be represented in a biplot to analytically assess shifts, overlaps and redundancies in trophic niches across trophic levels along an environmental land use gradient. I expect that under reduced resource diversity and availability in intensively managed land, the trophic niche sizes and variation will be also be lower and decreasing with land use intensity. Furthermore, I expect this variation to be functional/taxonomic group-specific, smaller at lower trophic levels and more pronounced aboveground than belowground. This novel dataset will be complementary to the existing ones and together they will allow new insights into cascading effects in food webs due to land use management. TrophNich is a system-wide integration across trophic levels in landscapes under stress due to land use, which will provide valuable insights on the underlying dynamics of organismic interactions and ecology of land use.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 1374: Biodiversity Exploratories