Climate-linked evolution and genetics in a warming Arctic

Ruth Rivkin, Kiersten King, Jon Aars, Kristin Laidre, Alexandra Langwieder, David McGeachy, Levi Newediuk , Stephen D Petersen, Nicholas Pilfold, Aryn P Wilder, Geoff York, Evan S Richardson, Colin Garroway

Knowledge of evolutionary patterns and genetic variation across a species’ range is important for determining conservation and management strategies. The Arctic is the fastest-warming ecosystem on Earth and has already reached temperature increases not expected in the rest of the world until the end of the century. Consequently, synthesizing patterns of evolutionary and genetic change in Arctic species will be instructive for understanding future change in other systems. Here, we present a literature review of peer-reviewed published research exploring evolutionary processes in polar bears, a sentinel species for climate action. The wealth of knowledge generated from the long-term monitoring of polar bears has provided data for exploring patterns of evolutionary change associated with climate change. Warming temperatures have led to significant reductions in sea ice coverage and availability, contributing to declines in genetic variation in some, but not all, polar bear subpopulations. Natural selection driven by warming and selective subsistence harvests may be contributing to the evolution of smaller body sizes in polar bears. However, evidence of adaptive change in polar bears remains limited, despite clear behavioural and phenological plasticity in the species in response to changing sea ice conditions. Following our review, we suggest pathways for identifying the effects of climate warming on the evolution and genetic variation in polar bears, which may improve strategies for locally supported conservation and management decisions. Our results highlight the general complexity of predicting the consequences of warming for wide-ranging, genetically structured, and adaptively specialized species such as polar bears, and underscore the importance of developing evolutionarily informed management and conservation priorities for species threatened by climate change.