Utilizing genomic time series to investigate evolutionary change in an aquatic invader

• Applicant: Christine Ewers, Ph.D.
• Subject Area: Evolution, Anthropology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 571448581

Invasive species are a major driver of global change as novel predators, pathogens, competitors and pests, with significant ecological and economic impacts. At the same time, they offer the unique opportunity to study the evolutionary processes underlying the successful colonization of novel habitats as they unfold. The evolution of introduced species has long remained enigmatic: while small numbers of founding individuals should increase inbreeding and limit the adaptive potential of an introduced population, adaptation may in fact be necessary for its success. During the geographical spread of an invasive species, further so-called genetic bottlenecks should occur, while adaptations to new ecological conditions may often be equally as necessary. Empirical studies suggest that adaptation is common and that invasive potential is enhanced by repeated introductions and hybridization between closely related species, leading to increased genetic diversity. However, the role of small population size in the success of invasive species has rarely been explicitly investigated. In general, there are no studies that comprehensively elucidate the tempo and magnitude of evolution throughout the invasion process, nor the relative importance of the two evolutionary modes, selection and drift. I aim to fill this knowledge gap using genomic time series based on natural history collections and contemporary populations of the Chinese mitten crab (Eriocheir sinensis H. Milne Edwards, 1853). Considered one of the world's 100 worst invasive species, affecting freshwater, brackish and marine environments alike, it has spread across Europe and parts of North America since the early 20th century. Large natural history collections and extensive genomic resources make this species a prime study system for a temporal invasion genomics approach. I propose to first investigate contemporary population genomics across the non-native range, and then compare these contemporary with historical data for the same populations to infer the overall tempo and magnitude of evolution as well as broad evolutionary trends. For two populations, the collection of several hundred specimens throughout the last century would allow me to obtain fine-scale temporal resolution of the invasion process, which I would use to more confidently infer the magnitude of drift and selection, as well as the timing and fate of hybridization events. Finally, western natural history collections also house Chinese mitten crabs collected from their native range. As the source populations have remained unidentified even after the analysis of genome-scale population genomic data from across the native range, querying the past may reveal the sources of this notorious invasive species and allow me to reconstruct the evolution due to the introduction events themselves. In short, I propose a temporally highly resolved comprehensive reconstruction of the evolutionary processes underlying a successful aquatic invasion.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Ben Krause-Kyora