Adaptation in a keystone grazer under novel predation pressure

Understanding how species adapt to environmental change is necessary to protect biodiversity and ecosystem services. Growing evidence suggests species can adapt rapidly to novel selection pressures like predation from invasive species, but the repeatability and predictability of selection remain poorly understood in wild populations. We tested how a keystone aquatic herbivore, Daphnia pulicaria, evolved in response to predation pressure by the introduced zooplanktivore Bythotrephes longimanus. Using high-resolution 210Pb-dated sediment cores from 12 lakes in Ontario (Canada), which primarily differed in invasion status by Bythotrephes, we compared Daphnia population genetic structure over time using whole-genome sequencing of individual resting embryos. We found strong genetic differentiation between populations ca. 70 years before versus 30 years after Bythotrephes invasion, with no difference over this period in uninvaded lakes. Compared with uninvaded lakes, we identified, on average..., , , # Adaptation in a keystone grazer under novel predation pressure

[https://doi.org/10.5061/dryad.0k6djhb82](https://doi.org/10.5061/dryad.0k6djhb82)

# **Data Summary**

This dataset contains data files and code to replicate and visualise the results of the population genetic structure (principal coordinate analysis; genetic admixture) and genetic diversity (pairwise genetic differentiation - FST; nucleotide diversity) analyses, based on whole genome data of 97 individual *Daphnia pulicaria* resting embryos, sequenced on an Illumina NovaSeq platform. It also contains data and code for the resting embryo size (ephippial size) and genomic sequencing coverage models. Additional data files and code used to generate supplementary figures and tables associated with the same manuscript, include lake water chemistry survey data used to select sampling sites (2006), updated water chemistry profiles from the time of sampling (2021), plankton sample counts, sediment core isotope profiles used in ...