Advantages of Clonal Growth in Heterogeneous Habitats: An Experiment with Potentilla Simplex

Abstract

1 The ability to share resources between modules (ramets) is considered to be a benefit of the clonal growth habit. This type of physiological integration may buffer the entire clone against locally adverse conditions resulting from the patchy distribution of resources. The hypothesis that physiological integration is most advantageous in a heterogeneous habitat was tested using the clonal, perennial species Potentilla simplex (Rosaceae). 2 Five artificial habitat types differing in nutrient status were constructed in the glasshouse and the performance of intact and disconnected clones (clones in which all ramets were severed from each other following the establishment of roots) growing in them was compared. The habitat types ranged from homogeneously poor via three levels of spatial heterogeneity in nutrient supply to homogeneously rich. 3 Intact clones growing in the heterogeneous habitats weighed significantly more than their disconnected counterparts, supporting the hypothesis. The benefits of resource sharing were enhanced with increasing patchiness of the habitat. No differences in biomass between intact and disconnected clones appeared in the homogeneous settings. 4 Parent ramets supported their offspring at a large cost in biomass to themselves, but the offspring ramets benefited from clonal integration irrespective of the quality of the patches they occupied. 5 Across all habitats, intact stolons elongated more than the severed ones. This increased mobility of intact clones implies that clonal integration may allow this species to escape from unfavourable patches. The enhanced performance of connected ramets rooted in rich patches shows that clonal integration also enables clones to exploit resource-rich microhabitats, thereby maximising foraging ability and resource acquisition, particularly when resources are distributed in patches. 6 The cumulative effects of parent and offspring biomass and offspring ramet number appear to explain the trend in performance of intact and disconnected clones observed in the homogeneous and heterogeneous habitats.