Data from: Genetic signals of artificial and natural dispersal linked to colonization of South America by non-native Chinook salmon (Oncorhynchus tshawytscha)

Genetics data have provided unprecedented insights into evolutionary
aspects of colonization by non-native populations. Yet, our understanding
of how artificial (human-mediated) and natural dispersal pathways of
non-native individuals influence genetic metrics, evolution of genetic
structure, and admixture remains elusive. We capitalize on the widespread
colonization of Chinook salmon Oncorhynchus tshawytscha in South America,
mediated by both dispersal pathways, to address these issues using data
from a panel of polymorphic SNPs. First, genetic diversity and the number
of effective breeders (Nb) were higher among artificial than natural
populations. Contemporary gene flow was common between adjacent artificial
and natural as well as adjacent natural populations but uncommon between
geographically distant populations. Second, genetic structure revealed
four distinct clusters throughout the Chinook salmon distributional range
with varying levels of genetic connectivity. Isolation-by-distance
resulted from weak differentiation between adjacent artificial and natural
as well as natural populations and with strong differentiation between
distant populations experiencing strong genetic drift. Third, genetic
mixture analyses revealed the presence of at least six donor geographic
regions from North America, some of which likely hybridized as a result of
multiple introductions. Relative propagule pressure or the proportion of
Chinook salmon propagules introduced from various geographic regions
according to government records significantly influenced genetic mixtures
for two of three artificial populations. Our findings support a model of
colonization in which high-diversity artificial populations established
first; some of these populations exhibited significant admixture resulting
from propagule pressure. Low-diversity natural populations were likely
subsequently founded from a reduced number of individuals.