The Arctic is experiencingthe fastest rates of globalwarming,leadingto shiftsin the distributionof its biotaandincreasingthe potentialfor hybridization. However, genomicevidenceof recenthybridization events in theArctic remainsunexpectedlyrare. Here, we use whole-genomesequencingof contemporary and 122-year-oldhistoricalspecimensto investigate the originof an Arctic hybridpopulation of Atlanticpuffins(Fr aterculaarctica)on Bjørnøya, Norway. We show that the hybridization between the High Arctic, large-bodiedsubspeciesF. a. naumanniand the temperate, smaller-sizedsubspeciesF. a. arcticabeganas recentlyas six generationsagodue to an unexpectedsouthward rangeexpansionofF. a. naumanni.Moreover, we find a significanttemporalloss of geneticdiversityacross Arctic and temperate puffinpopulations.Our observationsprovide compellinggenomicevidenceof the impacts of recentdistributionalshiftsand loss of diversityin Arctic communitiesduringthe 20th century.publishedVersio
