Predicting the habitat suitability for populations of Pacific cod under different climate change scenarios considering intraspecific genetic variation

Abstract

Several studies have demonstrated the importance of integrating intraspecific genetic variation in forecasting the habitat suitability of species under climate change scenarios. The Pacific cod (Gadus macrocephalus) is an economically important fish species in the North Pacific that can be classified into western and eastern populations based on molecular phylogeographic data. Herein, we first quantified the realized niche of the two Pacific cod populations using n-dimensional hypervolumes and estimated the niche differentiation between the populations. We then projected the habitat suitability based on the georeferenced occurrence records and environmental predictors using species distribution models (SDMs) at the population and species levels. The low niche overlap demonstrated the marked niche differentiation between the two populations. The distinct responses of the populations to climate predictors implied that the population-level SDM produced more reliable projections than the corresponding species-level SDM. The model indicated that the eastern population expanded its suitable area northward, while maintaining most of its current habitat and exhibited resilience to climate impacts. However, the western population lost much of its current suitable area, while colonizing a new habitat in a small section of the offshore waters of the Japanese Sea, implying the vulnerability of this population to climate change. This study highlights the necessity of incorporating intraspecific genetic variation into SDMs to predict the habitat suitability of Pacific cod on the global scale. The spatiotemporal predictive maps of habitat suitability provide crucial information for designing climate-adaptive conservation and management strategies based on more precise taxonomic units for the sustainability of Pacific cod.