HIGH BENEFITS OF CLONAL INTEGRATION IN 2 STOLONIFEROUS SPECIES, IN RESPONSE TO HETEROGENEOUS LIGHT ENVIRONMENTS

1 In natural habitats, essential resources for plant growth are heterogeneously distributed in space, resulting in environmental patchiness with favourable and less favourable microhabitats. Clonal plants may benefit from their ability to share resources between connected ramets experiencing contrasting levels of resource supply. This hypothesis was tested with clones of Potentilla reptans and P. anserina, consisting of a mother rosette and a number of daughters on an attached stolen, grown under homogeneously high and low light conditions, as well as in spatially heterogeneous light environments in which either mother or daughters were shaded. Biomass data were used to carry out an analysis of the costs and benefits of clonal integration. 2 Both species showed high benefits of integration. In P. reptans, connections to unshaded clone-parts enhanced biomass production of the shaded part. In contrast to the prediction that clonal integration would result in costs to unshaded clone-parts connected to shaded parts, unshaded ramets of both species developed higher instead of lower dry weights when connected to a shaded part. Thus, unshaded ramets actually benefitted from integration. 3 It is hypothesized that these unexpected benefits of integration were due to mutual support of connected clone-parts growing in shaded and unshaded patches. The high evaporative demands of the unshaded clone-parts probably resulted in water being translocated from shaded to unshaded ramets while, at the same time, carbohydrates were translocated from unshaded to shaded ramets. 4 We discuss implications of this suggested bidirectional transport of two different resources for the ecological significance of physiological integration in clonal plants and for the notion of habitat heterogeneity.