The magnet species effect of two-leaf squill (<i>Scilla</i> spp.) on pollinator competition with the snowdrop (<i>Galanthus nivalis</i> L.).

Abstract

<h4>Introduction</h4>Plant-pollinator interactions may have positive, negative, or neutral influences on pollination and reproductive success of co-occurring plants. Some plants are highly attractive for pollinators (magnet species) and their presence can be beneficial for neighboring plants in terms of increased pollinator availability.<h4>Methods</h4>Combining field and laboratory data, we examined pollinator visitation and reproductive success in early blooming co-occurring native plants, two-leaf squill (<i>Scilla</i> spp.) and snowdrop (<i>Galanthus nivalis</i> L.).<h4>Results</h4>The blue flowers of <i>Scilla</i> significantly outcompeted the abundant white flowers of <i>G. nivalis</i> for pollinator visits. These differences were further supported by the higher abundance of pollinators found on <i>G. nivalis</i> petals (detected using eDNA metabarcoding) in experimental plots where <i>Scilla</i> was removed compared to plots where <i>Scilla</i> and <i>G. nivalis</i> co-occurred. eDNA analysis showed that the presence of <i>Scilla</i> significantly reduced alpha diversity and taxonomic richness of the <i>G. nivalis</i> pollinator community. Furthermore, the plot with <i>Scilla</i> showed a significant shift in community composition, with <i>G. nivalis</i> dominantly visited by taxa such as Lepidoptera, which may provide different pollination services, while the scilla-free group showed a more balanced and diverse composition including key Hymenoptera and Diptera taxa. This superior attractiveness of <i>Scilla</i>, consistent across both field observations and controlled lab experiments, strongly supports its role as a magnet species. Flower fertility of <i>G. nivalis</i> from plots with <i>Scilla</i> present was significantly lower than from plots without <i>Scilla</i>.<h4>Discussion</h4>Overall, it appears that early flowering plant communities face strong competition for pollinators, which are scarce due to low spring temperatures. Magnet species may more significantly influence pollinator activity "in their favor" and potentially threaten the reproductive success of other, co-occurring species.