Variations in reproductive output in alpine populations of Ranunculus acris

Abstract

Abstract Plant reproduction is affected both directly by small-scale abiotic heterogeneity in the alpine topography (abiotic), and indirectly through flower density and plant-pollinator interactions (biotic). In this study we investigated how different abiotic and biotic factors influence reproductive output in alpine populations of Ranunculus acris over a two-year period. We used ten snowmelt gradients in an alpine area at Finse, southern Norway, where each gradient contained three stages representing three different times of snowmelt. Reproductive output, measured as both seed mass and number of seeds, in alpine R. acris was affected by different factors, varying between years and timing of snowmelt. Higher temperatures during seed maturation resulted in higher reproductive output in both years, with a lower output later in the growing season. We also found a negative correlation between seed mass and R. acris density in the surrounding vegetation in the second year, when flower density was substantially higher than in the first year. We found no signs of pollen limitation, suggesting that pollinators did not limit reproductive output. Our study shows that reproductive output in R. acris is affected by both abiotic and biotic factors, and since timing and length of the flowering period in alpine environments are expected to change due to climate change, this could have further implications for plants in this study system.