Vamosi, Steven M.Kienzle, Hannah Marie2018-04-172018-04-172018-04-16Kienzle, H. A. (2018). Impacts of non-native species on the morphology of threespine stickleback (Gasterosteus aculeatus) (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/31792http://hdl.handle.net/1880/106504Invasive species have demonstrated their capability to greatly modify ecosystems and communities. Introducing multiple species can potentially alter how a native population adapts relative to when species are introduced individually. I assessed whether native threespine stickleback (Gasterosteus aculeatus) exhibit distinct morphological characteristics corresponding to a varying combination of the presence of introduced smallmouth bass (Micropterus dolomieu) and signal crayfish (Pacifastacus leniusculus) on Vancouver Island. I also examined morphological changes over 18 - 43 years to determine whether contemporary characteristics become magnified in the presence of non-native species. There are clear distinctions in stickleback traits and body shape among non-native species combinations. Bass and crayfish lake stickleback are highly armoured, whereas bass-only lakes contain stickleback with reduced armour. Klein and Dougan Lake stickleback, which coexist with signal crayfish, showed significant increases in size over time. These patterns suggest that smallmouth bass and signal crayfish may have differential impacts on stickleback morphology.engUniversity of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.Threespine Sticklebackevolutionary ecologyInvasive speciesmorphological adaptationsmallmouth basssignal crayfishEcologymaster thesis10.11575/PRISM/31792