Variation in the outcome of plant-plant interactions is not related to abiotic gradients across fine scales in four different taxa

Abstract

Biotic interactions are key drivers of community composition, with the outcome of plant-plant interactions varying from positive (e.g. facilitative. to negative (e.g. competitive., even across short distances and/or time periods. Such variation in the outcomes of interactions may be explained by the stress gradient hypothesis (SGH. which posits that there is a shift from more negative to increasingly positive interactions with increasing environmental stress. Examining the interaction between the cushion plant Azorella selago and species from four co-occurring taxonomic groups on a single scoria cone on sub-Antarctic Marion Island revealed that, as observed in other studies, vascular plant richness was higher in association with the cushion plant. However, in contrast to the predictions of the SGH, the cushion plant had a negative impact on the richness non-vascular taxa, and the outcome of A. selago’s interaction with all of the taxa was not related to any measures of abiotic stress. These results suggest that the SGH, at least in its current form, may not be useful for predicting the impact of plant-plant interactions on non-vascular taxa or across very short spatial extents. - Abstract as displayed in the - Abstract booklet. The presentation on the day may differ from the - Abstract.