Testing local adaptation in five populations of Hyalella azteca in northern Alberta’s oil sands region

Abstract

Canada’s oil sands hold the third largest petroleum reserves worldwide. Rapid economic growth has led to increased exploitation of the surrounding boreal forest despite limited understanding of the environmental effects caused by development. Previous studies have typically focused on laboratory animals exposed to commercially available chemicals or extracts of oil sands process-affected material (OSPM; including process-affected water, tailings, and coke). The oil sands region provides an ideal location for studying local adaptations through reciprocal transplant (RT). Local adaptations require certain ecological factors to prevail, such as low gene flow, spatial variability in exposure to environmental effects, and genetic variation in traits associated with tolerance of these effects. The objectives of this research were: (1) to determine if H. azteca from habitats with naturally occurring bitumen exhibited increased tolerance to contaminants associated with industrial bitumen extraction compared to H. azteca from habitats with no naturally occurring bitumen and (2) to determine if any observed tolerance was attributable to local adaptation or plasticity. The RT occurred in reference wetlands located off oil sands leases and away from oil sands development and reclaimed sites located on oil sands leases and adjacent to mining and upgrading activities. Five populations of Hyalella azteca were tested in the RT, four from local wetlands plus one naïve laboratory population. Survival, sensitivity, and behaviour were measured before and after the RT period. Behaviour was tested in a phototaxis assay while sensitivity was assessed using 48 h acute LC50 tests. Survival varied by population and site. Pre-RT sensitivity increased along a gradient of increasing exposure to contaminants. After the RT, sensitivity decreased in every population. There were no significant differences in pre- or post-RT behaviour results for all populations. hese results show that the differences in responses among populations are likely attributable to developmental differences driven by environmental variables and not local adaptation.