Tracing the spread of European earthworms into North America using molecular markers and field experiments

• Applicants: Professor Dr. Nico Eisenhauer; Dr. Marina Schaefer
• Subject Area: Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 255872480

Large parts of North America are devoid of native earthworm species, presumably due to extirpation of the indigenous earthworm fauna during the Wisconsinan Glaciation. European earthworms have been invading North American ecosystems since the arrival of European settlers, and their presence has profound effects on the native flora and fauna by altering soil structure, nutrient cycling, plant growth, and the composition and functions of soil microorganisms and animals. Despite their ecological relevance and their functioning as ecosystem engineers, the importance of human-related dispersal, genetic variability and adaptation of European earthworms in North America is hardly investigated.The proposed project intends to investigate the invasion of European earthworms into North American ecosystems by analyzing intraspecific genetic variability at the continental scale and population genetics at local and regional scales. We focus on two of the most common invasive European earthworm species, Lumbricus terrestris and Lumbricus rubellus, representing ideal organisms to investigate invasion processes as they possess different life-histories, dispersal abilities and feeding strategies. This allows differentiation between genetic patterns caused by anthropogenic use, mobility and tolerance to abiotic factors.The project aims at answering if non-native earthworm populations in North America are genetically diverse due to introduction from many sources or genetically homogenous due to the dominance of few genetic lineages, and intends to identify colonization routes. Further, the importance of ecological factors, such as drought in summer and freezing in winter, as drivers of the genetic constitution of earthworm populations is investigated. The project is separated into three main work packages (WPs). WP1 investigates the genetic diversity and expansion routes of L. terrestris and L. rubellus at the continental scale. WP2 explores the role of recent human mediated dispersal at regional and local scales as well as differences in migration and gene flow between these two ecologically different earthworm species. WP3 investigates the adaptability of L. terrestris to environmental factors using field mesocosms and molecular markers. Earthworms represent a heretofore underappreciated model for answering general questions in invasion biology by combining molecular methods and complementary field experiments.

• DFG Programme: Research Grants
• International Connection: Canada, USA
• Participating Persons: Erin Cameron; Dr. Lee Frelich; Professor Dr. Edward Johnson; Professor Peter B. Reich