| The overall aim of the project is to investigate if presence of the invasive plant Lupinus polyphyllus affects pollination success of native grassland species in road verges. Invasive plants can have either competitive or facilitative effects on native pollination. The mechanism behind these effects can be mediated either by impacts on pollinator population sizes, e.g. by causing a rise in population growth, or by impacts on pollinator behaviour, e.g. by attracting pollinators to or away from natives. Even though studies of the impact of invasive plants on native pollination interactions starts to accumulate, there is no investigation of effects via pollinator populations and most studies of pollinator behaviour lack a spatial perspective. The latter is of concern, because within an invaded area the facilitation/competition effects on pollinator behaviour may be distance-dependent. If groups of plants compete for pollinators and the invasive is highly attractive to pollinators the net effect on native pollination success should depend on the combined outcome of intra versus inter-group effects. Such hierarchical components of competition/facilitation effects are neglected in studies of invasive plants and pollinator behaviour.
I will perform large-scale field experiments using potted plants of two native self-incompatible grassland herbs. Plants have already been grown from a common seed source and been planted in standardized soil to prevent genetic and recourse effects on reproductive success. Two experiments will be performed: (i) A full size study investigating hierarchical effects on pollinator behaviour within an invaded area by placing pots of the target species close by, at 10 m distance, and at 200 m distance from Lupinus. (ii) A pilot study investigating effects on native reproduction success via influences on pollinator population sizes. Reproductive success of target plants will be monitored before, during and after the flowering of Lupinus, at invaded and non-invaded sites separated by a distance larger than the pollinators feeding range. The experiments will run for one field season.
Maintenance of pollination services is of crucial importance for the conservation of biodiversity, and the aim of this project is to improve our understanding of pollination interactions in invaded habitats. The novelty of the project lies in incorporation of spatial scale and hierarchical competition/facilitation effects and the attempt to estimate effects mediated via changes in pollinator population sizes. Lupinus is an aggressive invader in the study regions and the results from this study will provide a basis for decision-making concerning eradication of Lupinus.
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