Experimental ramet aggregation in the clonal plant Agrostis stolonifera reduces its competitive ability

Spatial models predict that long-distance dispersal of offspring provides competitive superiority in open environments. We tested this prediction by artificially aggregating ramets of the spreading clonal species Agrostis stolonifera in an undisturbed environment and in an environment where flooding increased open space. We compared the competitive response of this manipulated Agrostis with both the natural ramet distribution of Agrostis and with the naturally aggregated clonal species Alopecurus pratensis. Our phenotypic manipulation of ramet dispersal significantly increased aggregation of clonal offspring, without altering the number of offspring, and thus provided an adequate test of spatial effects. Regardless of flooding, both Alopecurus and the aggregated Agrostis were more suppressed in species mixtures than the natural dispersed form of Agrostis. This demonstrates that long distance dispersal of ramets enhances competitive ability, at least in early stages of succession.