Reciprocal and coincident patchiness of multiple resources differentially affect benefits of clonal integration in two perennial plants

Abstract

Summary 1. The modules of plants experience different levels of resources, and clonal plants can integrate resource heterogeneity. However, no studies have tested whether the benefits of clonal integration depend on patterns of heterogeneity in multiple resources, like high levels of above-ground and below-ground resources in the same patches (‘coincident patchiness’) or different patches (‘reciprocal patchiness’). 2. We hypothesized that the benefits of clonal integration can vary depending on whether patchiness is reciprocal or coincident, and that clonal species experience greater benefits from integration when qualitative patterns of resource heterogeneity are more like those likely to occur in their habitats. To test these hypotheses, we grew pairs of connected ramets of Cynodon dactylon and Potentilla reptans under high and low levels of light and of water and soil nutrients, and measured the growth and physiological traits of the plants. 3. Consistent with the hypotheses, connection between ramets in contrasting patches increased final dry mass of Cynodon by 30% compared with connection between ramets within the same type of patch when resource patchiness was coincident, whereas connection decreased mass by 60% when patchiness was reciprocal. Inconsistent with the hypotheses, between-patch connection increased mass of Potentilla by 70% over within-patch connection whether patchiness was reciprocal or coincident; although the species did grow accumulate more mass when patchiness was reciprocal. 4. In Cynodon, treatments had little effect on allocation of mass to roots or specific leaf area; analysis of mass of ramets within pairs suggested that constraints on translocation may have underlain differential effects of reciprocal and coincident patchiness on performance. In Potentilla, treatments affected all measured characteristics, suggesting a higher degree of clonal integration that may have allowed clones to benefit strongly from integration regardless of pattern of resource patchiness. 5. Synthesis. The ability of some plant species to benefit from clonal integration can depend strongly on whether resource heterogeneity is coincident or reciprocal, while other species may benefit equally from integration under both resource patterns. Our results provide an initial indication that the ecological range of some clonal species may be linked to patterns of resource patchiness via traits of clonal integration.