Canadian Arctic Archipelago Conspecifics Flower Earlier in the High Arctic than the Mid-Arctic

Premise of research. The Canadian Arctic Archipelago is experiencing unprecedented climate change with temperatures rising at a rate that is twice the global average. The rapidly rising temperatures will likely impact plant phenology dramatically. The Canadian Arctic Archipelago is remote and difficult to reach, and there are few insights into the phenology of its plants. Data on current Arctic plant flowering times and how they vary across the Canadian Arctic Archipelago are needed to form a baseline to facilitate studies on the impact of climate change on Arctic plant phenology.Methodology. We recorded the flowering times of 26 species from 12 families that are common to high-Arctic (lat. 81°N) and mid-Artic (lat. 63°N) locations in Nunavut, Canada, in 2013 and 2014. We compared differences in flowering times and flower abundance between the two locations and identified factors that might explain the differences.Pivotal results. Species flowered at the same time or earlier and for a shorter duration at the high-Arctic location than at the mid-Arctic location. Different sublocales at a location explained more of the variation in flowering time than did mid- versus high-Arctic location or elevation. Peak flowering occurred one-third of the way through flowering. Plants at the mid-Arctic location produced more flowers per plant than did plants at the high-Arctic location. Relative order of species’ flowering is consistent between the mid- and high-Arctic locations and between years.Conclusions. Earlier flowering times of more northerly conspecifics are contrary to what might be expected given that temperatures are colder at the high-Arctic location than at the mid-Arctic location and that flowering time for a species is influenced by cumulative temperatures above a threshold. Our results suggest that plants at the northern location might be evolutionarily adapted to the shorter growing season and that plants have phenotypic plasticity across sublocales.