Digitised herbarium specimen data reveal a climate change‐related trend to an earlier, shorter Canadian Arctic flowering season, and phylogenetic signal in Arctic flowering times

The Arctic is experiencing some of the world's most rapid changes in climate. Arctic plant flowering time responses to climate change are understudied. Globally, conflicting evidence exists on whether flowering time responses to temperature are evolutionarily conserved. We scored the reproductive phenology of 17 000 digitised herbarium specimens of 97 plant species collected across the Canadian Arctic since the 1900s to determine whether and how flowering times in the Canadian Arctic have shifted over the past century; how responsive flowering times are to temperature; and whether flowering times and flowering time responses to temperature are evolutionarily conserved. We found that flowering times in the Canadian Arctic are converging, with later-flowering species shifting their flowering times to a greater degree than earlier-flowering species, resulting in a shorter flowering season. We detected a significant phylogenetic signal associated with Arctic flowering times but no phylogenetic signal in flowering time responses to temperature. A shorter flowering season in the Arctic has implications for tundra food webs and species interactions, with fitness consequences across tundra trophic levels. Digitised records allowed citizen scientists to become virtual collaborators in this project, and the research provided opportunities to improve digitised record quality for future research.