Counter-gradient variation in gene expression between fish populations facilitates colonization of low-dissolved oxygen environments

In this study, we investigated the role of phenotypic plasticity in gene expression during colonization. To do this, we compared gene expression between two cyprinid fishes in the same region: Enteromius apleurogramma, a species that has undergone a recent range expansion, and E. neumayeri, a long-established native species. We caught both species from low-dissolved oxygen (DO) and high-DO habitats and sampled tissue either immediately after capture from the field or after a two-week acclimation under high-DO conditions, allowing us to test for both evolved and plastic differences in low-DO vs high-DO populations of each species.