Ocean warming and evolutionary responses: Life history adaptations in two genetic distinct colour morphs of Common Guillemots.

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The use of colour polymorphism as a phenotypic genetic marker in relation to life-history strategies and climatic factors is a promising way to study the effects of global warming on micro-evolutionary processes within populations and identifying which ecological processes are underpinning the occurring changes. The North Atlantic common guillemot Uria aalge possesses two genetically different colour morphs; the bridled and the unbridled morph. The frequency of the two morphs follows a north south gradient, with the frequency of bridled birds increasing with latitude. We show how fluctuations in sea surface temperature affects life-history traits of these morphs differently in two colonies with different frequency; the Isle of May in Scotland and Hornøya in Northeastern Norway. We combined non-breeding distribution data from geolocators, with Sea Surface Temperature and long-term time series data on adult survival (29 and 22 years). Additionally, we analyzed the breeding success over 22 years for different family morph combinations in relation to SST around the colony. We discuss how climate change will alter the bridling frequency and how it is possible to visualize how evolutionary adaptations to global warming will be manifest.