Epsilon Open Archive

Abstract

When plant species compete for pollinators, climate warming may cause directional change in flowering overlap, thereby shifting the strength of pollinator-mediated plant-plant interactions. Such shifts are likely accentuated in the rapidly warming Arctic. Targeting a plant community in Northeast Greenland, we asked (a) whether the relative phenology of plants is shifting with spatial variation in temperature, (b) whether local plants compete for pollination, and (c) whether shifts in climatic conditions are likely to affect this competition. We first searched for climatic imprints on relative species phenology along an elevational gradient. We then tested for signs of competition with increasing flower densities: reduced pollinator visits, reduced representation of plant species in pollen loads, and reduced seed production. Finally, we evaluated how climate change may affect this competition. Compared to a dominant species,Dryas integrifolia x octopetala, the relative timing of other species shifted along the environmental gradient, withSilene acaulisandPapaver radicatumflowering earlier toward higher elevation. This shift resulted in larger niche overlap, allowing for an increased potential for competition for pollination. Meanwhile,Dryasemerged as a superior competitor by attracting 97.2% of flower visits. HigherDryasdensity resulted in reduced insect visits and less pollen ofS. acaulisbeing carried by pollinators, causing reduced seed set byS. acaulis. Our results show that current variation in climate shifts the timing and flowering overlap between dominant and less-competitive plant species. With climate warming, such shifts in phenology within trophic levels may ultimately affect interactions between them, changing the strength of competition among plants.