Physiological integration and morphological plasticity in extensive clonal plants

Sammanfattning: Clonal plants show a large variation in physiological integration, i.e. the translocation of resources among ramets within the clone. As resource transport is costly, we hypothesized that plants from poor sites should be more highly integrated than plants from rich sites and that plants would benefit if they were plastic in their degree of integration. Tracers were used to study the transport of water, mineral nutrients and carbohydrates in plants from contrasting habitats using field or green house experiments. As opposed to our hypothesis, plants from poor habitats changed their patterns of physiological integration in response to resource availability, while plants from rich sites maintained the same pattern. The number of integrated ramets did not change in response to nutrient level, but the absolute distance of translocation, the amounts that were shared between ramets and the direction of translocation was affected. Proposed costs of physical connections between ramets are high risks of pathogen spread and a lower morphological plasticity in integrated ramets, resulting in a less efficient foraging strategy. Extensive rhizome growth was an efficient strategy to escape soil-borne pathogens. Although morphological plasticity was similar in the two Carex species (C. arenaria and C. disticha), one species was more integrated than the other. I propose that the responses in the patterns of physiological integration provide clues to understand the evolution from the ancestral, fully integrated ramets to the derived trait of ramet independence found in many present-day species.