Population genetics reveal patterns of natural colonisation of an ecologically and commercially important invasive fish

Ciar O’Toole, Karl P. Phillips, Caroline Bradley, Jamie Coughlan, Eileen Dillane, Ian A. Fleming, Thomas E. Reed, Peter A.H. Westley, Tom F. Cross, Philip McGinnity, Paulo A. Prodöhl

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Although historical records of introductions that trigger successful biological invasions are common, subsequent patterns of dispersal and colonisation routes are unclear. We use microsatellites to examine genetic population structuring of established invasive brown trout (Salmo trutta) populations in Newfoundland, Canada, for evidence of “natural” dispersal, human-mediated introductions, and colonisation routes. We also explored ancestry of contemporary populations relative to presumed progenitors. Results analysed using STRUCTURE, DAPC, a NJ tree and FST comparisons support records of historical introductions; current Newfoundland populations are largely descended from Scottish stock, with St. John’s the primary introduction site. Subsequent dispersal of these trout was facilitated principally by anadromy, largely consistent with a classic stepping-stone model, with significant isolation-by-distance. With one exception, dispersal along the north and south coasts of the Avalon peninsula appears to be natural and independent, involving stochastic processes resulting in unique outcomes for population composition. This study is a good example of dispersal patterns during a contemporary invasion underscoring the potential for non-anadromous founders to re-express anadromy, facilitating colonization of distant sites.
Original languageEnglish
Pages (from-to)1497-1511
Number of pages15
JournalCanadian Journal of Fisheries and Aquatic Sciences
Issue number10
Early online date30 Sep 2021
Publication statusPublished - Oct 2021


  • Aquatic Science
  • Ecology, Evolution, Behavior and Systematics


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