Invasive earthworm effects on plant functional traits and diversity

• Applicant: Professor Dr. Nico Eisenhauer
• Subject Area: Ecology and Biodiversity of Plants and Ecosystems
• Term: from 2019 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 421786068

Invasions of natural communities by nonindigenous species are a threat to native biodiversity and are currently rated as one of the most important global-scale environmental problems. Invasive species can radically transform native ecosystems when they introduce novel traits that are dissimilar from those of the native community. Among belowground invaders, invasive earthworms are receiving increasing attention because of their role as ecosystem engineers in terrestrial ecosystems and their functional dissimilarity to the native soil fauna at various locations around the world. The invasion of exotic earthworms often causes non-random changes in diversity above- and belowground, suggesting that earthworm invasion may alter how trait-mediated mechanisms impact ecosystem functioning.This project aims to elucidate how invasive exotic earthworms affect intraspecific plant functional trait variation and plant community composition using earthworm-free regions of northern North America as a model system. In order to derive a comprehensive framework regarding the mechanisms by which earthworm invasions could modify plant community composition, we will assess the plant functional traits and the taxonomic and functional composition of plant communities in different forests with active earthworm invasion fronts. We will also disentangle the underlying mechanisms to these modifications with laboratory experiments. Empirical work will be complemented by a meta-analysis of published literature on invasive earthworm effects on plant communities. Thus, the proposed work integrates different ecological scales (plant species-specific physiological and morphological traits to populations to plant communities) by using a novel, synthetic combination of field observations, laboratory experiments, and meta-analyses. First, a comprehensive field study will explore the effects of invasive earthworm communities on the functional diversity of plant communities based on realized plant traits in invaded and non-invaded areas of deciduous forests (WP1). Second, a laboratory study will allow us to differentiate the effects of different ecological groups of earthworms on plant community composition, and to disentangle the underlying mechanisms via the study of their effects on plant-plant and plant-herbivore interactions (WP2). Third, a meta-analysis will integrate the information from existing literature and WPs 1 and 2 to investigate the role of earthworms as environmental filters selecting for specific plant traits based on observed changes in plant community composition (WP3). This meta-analysis will compare the effects of different ecological groups and communities of (invasive) earthworms on plant traits, plant community diversity, and plant community composition/homogenization. The functional trait-based approach will allow us to develop a general conceptual framework of plant responses to exotic earthworms.

• DFG Programme: Research Grants