title: Contrasting patterns of genetic and phenotypic differentiation in two invasive salmonids in the southern hemisphere.
abstract: Invasion success may be expected to increase with residence time (i.e., time since first introduction) and secondary releases (i.e., those that follow the original introduction), but this has rarely been tested in natural fish populations. We compared genetic and phenotypic divergence in rainbow trout and brown trout in Chile and the Falkland Islands to test the prediction that adaptive divergence, measured as P ST/F ST, would increase with residence time and secondary releases. We also explored whether interspecific competition between invaders could drive phenotypic divergence. Residence time had no significant effect on genetic diversity, phenotypic divergence, effective population size, or signatures of expansion of invasive trout. In contrast, secondary releases had a major effect on trout invasions, and rainbow trout populations mostly affected by aquaculture escapees showed significant divergence from less affected populations. Coexistence with brown trout had a positive effect on phenotypic divergence of rainbow trout. Our results highlight an important role of secondary releases in shaping fish invasions, but do not support the contention that older invaders are more differentiated than younger ones. They also suggest that exotic trout may not have yet developed local adaptations in these recently invaded habitats, at least with respect to growth-related traits.
authors.affiliation: Department of Biosciences, Swansea University Swansea, UK.
authors.forename: Catalina
authors.initials: C
authors.lastname: Monzón-Argüello
authors.affiliation: Department of Biosciences, Swansea University Swansea, UK.
authors.forename: Sofia
authors.initials: S
authors.lastname: Consuegra
authors.affiliation: Laboratorio de Genética, Acuicultura y Biodiversidad, Universidad de Los Lagos Osorno, Chile.
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Gajardo
authors.affiliation: Department of Biosciences, Swansea University Swansea, UK.
authors.forename: Francisco
authors.initials: F
authors.lastname: Marco-Rius
authors.affiliation: Department of Biosciences, Swansea University Swansea, UK.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Fowler
authors.affiliation: Ecological Genetics Research Unit, Department of Biosciences, University of Helsinki Helsinki, Finland.
authors.forename: Jacquelin
authors.initials: J
authors.lastname: DeFaveri
authors.affiliation: Department of Biosciences, Swansea University Swansea, UK.
authors.forename: Carlos
authors.initials: C
authors.lastname: Garcia de Leaniz
keywords: Oncorhynchus mykiss; PST/FST; Salmo trutta; microsatellites; naturalization; phenotypic divergence; rapid evolution; selection