Data from: Hybridization alters growth and migratory life history expression of native trout

Human-mediated hybridization threatens many native species, but the
effects of introgressive hybridization on life history expression are
rarely quantified, especially in vertebrates. We quantified the effects of
non-native rainbow trout admixture on important life history traits
including growth and partial migration behavior in three populations of
westslope cutthroat trout over five years. Rainbow trout admixture was
associated with increased summer growth rates in all populations, and
decreased spring growth rates in two populations with cooler spring
temperatures. These results indicate that non-native admixture may
increase growth under warmer conditions, but cutthroat trout have higher
growth rates during cooler periods. Non-native admixture consistently
increased expression of migratory behavior, suggesting that there is a
genomic basis for life history differences between these species. Our
results show that effects of interspecific hybridization on fitness traits
can be the product of genotype-by-environment interactions even when there
are minor differences in environmental optima between hybridizing species.
These results also indicate that while environmentally mediated traits
like growth may play a role in population-level consequences of admixture,
strong genetic influences on migratory life history differences between
these species likely explains the continued spread of non-native
hybridization at the landscape-level, despite selection against hybrids at
the population-level.