Seed dormancy and longevity in subarctic and alpine populations of Silene suecica

Despite the strong environmental control of seed dormancy and longevity, their changes along latitudes are poorly understood. The aim of this study was to assess seed dormancy and longevity in different populations across the distribution of the arctic–alpine plant Silene suecica. Seeds of seven populations collected from alpine (Spain, Italy, Scotland) and subarctic (Sweden, Norway) populations were incubated at four temperature regimes and five cold stratification intervals for germination and dormancy testing. Seed longevity was studied by exposing seeds to controlled ageing (45 °C, 60% RH) and regularly sampled for germination. Fresh seeds of S. suecica germinated at warm temperature (20/15 °C) and more in subarctic (80–100%) compared to alpine (20–50%) populations showed a negative correlation with autumn temperature (i.e., post-dispersal period). Seed germination increased after cold stratification in all populations, with different percentages (30–100%). Similarly, there was a large variation of seed longevity (p50 = 12–32 days), with seeds from the wettest locations showing faster deterioration rate. Subarctic populations of S. suecica were less dormant, showing a warmer suitable temperature range for germination, and a higher germinability than alpine populations. Germination and dormancy were driven by an interplay of geographical and climatic factors, with alpine and warm versus subarctic and cool autumn conditions, eliciting a decrease and an increase of emergence, respectively. Germination and dormancy patterns typically found in alpine habitats may not be found in the arctic.