The bzzzt of frirends. Interspecific competition in Arctic plants for pollination services.

Abstract: The Arctic has a harsh environment that is challenging for the flora and fauna that inhabits the region. The ruling abiotic factors of the region results is a low species richness that creates a potential challenge for the region’s plant species. Here, sexual reproduction becomes more difficult due to fewer accessible pollinators and a short period during the summer that I suitable for flowering. As a consequence of this, we can expect interspecific competition for pollination between plant species when the living conditions get more extreme. There is also the potential that plant species in the region are utilizing alternative strategies for reproduction, like autonomous selfing, to a higher degree when outcrossing is not as available. The aim of the study was to see if interspecific competition in Arctic plants changed between a southern and a northern Arctic site and to investigate if the plants had a dependency on pollinator services. Plant-pollinator networks from the High Arctic Svalbard and the subarctic eastern mountain of Tväråklumparna, Sweden, were described by catching pollinators that were interacting with flowers. By applying Müller’s index, the interspecific competition was estimated at the sites. In addition, a pollination experiment was performed for the species mountain avens (Dryas octopetala) and moss campion (Silene acaulis), that are present at both sites. Three treatments were used, an open treatment, a hand-pollination and an exclusion treatment, to estimate pollinator dependency and pollen limitation. At the network level, the degree of interspecific competition was higher at Svalbard, compared to the site at Tväråklumparna (p = 0.02). While it couldn’t be concluded that S. acaulis had a stronger impact on other plant species at any of the sites. However, D. octopetala appeared to be a strong competitor at Svalbard that attracted many of the local pollinators. Pollinator dependence seemed to be occurring in the species but while being able to reproduce by autonomous selfing, the selfing rates at Svalbard were low. This is raising the question of a relationship between a species’ reproductive assurance and the selfing rate. Further research is needed to investigate if there is a connection between the two.