Populations that are adaptively divergent but maintain high gene flow may have greater resilience to environmental change because gene flow increases standing genetic variation and allows the spread of alleles that have already been tested elsewhere. We examined this possibility using golden perch (Macquaria ambigua) - a high dispersal, native freshwater fish of recreational importance - in the environmentally heterogeneous environment of the Murray-Darling Basin (MDB), Australia.
We developed a genome-wide SNP dataset using ddRAD for 171 golden perch in 13 sites across the MDB. We examined population structure, identified markers potentially under directional selection using genotype-environment association analyses for riverine flow, rainfall and temperature, and annotated identified candidates.
We found high gene flow across the basin and three populations with low neutral differentiation. Genotype-environment association analyses detected adaptive divergence at, conservatively, 31 of the 3,139 filtered SNPs. These were predominately linked to an arid, environmentally extreme region with unstable rainfall, and candidate loci had functions involving fat storage, stress and molecular or tissue repair.
The high connectivity of golden perch in the MDB will likely allow adaptive traits in more extreme, hydroclimatically variable environments to spread and be selected in localities that are predicted to become environmentally unstable in future climates. Our study adds to growing evidence of adaptation in the face of gene flow, and highlights the importance of considering environmental disturbance and adaptive divergence in biodiversity management.
ARC Future Fellowship (FT130101068) to L.B.B. and the associated Flinders University salary to C.R.M.A..