Threespine stickleback (Gasterosteus aculeatus) are a model organism for studies of coevolutionary genetics and immune response. Stickleback populations are broadly distributed throughout the Northern Hemisphere where they’re capable of colonizing both freshwater and marine habitats. Despite being a model organism, little is known about the most recent population expansion in the Laurentian Great Lakes. This ongoing study aims to address current and historical population structure and identify their means of introduction using a combination of samples from natural history collections and those that are newly collected. A capture-sequencing probe set will be used to standardize SNP enrichment across sample types and identify evidence of founder’s effects patterns. Future work will explore morphologic diversity and the genetic diversity of an obligate tapeworm parasite (Schistocephalus solidus).