Fine-scale local adaptation in an invasive freshwater fish has evolved in contemporary time

Abstract

Adaptive evolutionary change in only a few generations can increase the ability of non-native invasive species to spread, and yet adaptive divergence is rarely assessed in recently established populations. In this study, we experimentally test for evidence of fine-scale local adaptation in juvenile survival and growth among three populations of an invasive freshwater fish with reciprocal transplants and common-garden experiments. Despite intrinsic differences in habitat quality, in two of three populations we detected evidence of increased survival in ‘home’ versus ‘away’ environments with a Bayesian occupancy model fitted to mark–recapture data. We found support for the ‘local’ versus ‘foreign’ criterion of local adaptation as 14 of 15 pairwise comparisons of performance were consistent with local adaptation ( p < 0.001). Patterns in growth were less clear, though we detected evidence of location- and population-level effects. Although the agents of divergent ecological selection are not known in this system, our results combine to indicate that adaptive divergence—reflected by higher relative survival of local individuals—can occur in a small number of generations and only a few kilometres apart on the landscape.