Strategies of resource sharing in clonal plants: A conceptual model and an example of contrasting strategies in two closely related species.

Background and aims: Clonal growth is widespread among herbaceous plants, and helps them to cope with environmental heterogeneity through resource integration via connecting clonal organs. Such integration is considered to balance heterogeneity by translocation of resources from rich to poor patches. However, such an 'equalisation' strategy is only one of several possible strategies. Under certain conditions, a strategy emphasising acropetal movement and exploration of new areas or a strategy of accumulating resources in older ramets may be preferred. The optimal strategy may be determined by environmental conditions, such as resource availability and level of light competition. We aimed to summarise possible translocation strategies in a conceptual analysis and to examine translocation in two species from different habitats.

Methods: Resource translocation was compared between two closely related species from different habitats with contrasting productivity. The study examined the bidirectional translocation of carbon and nitrogen in pairs of mother and daughter ramets grown under light heterogeneity (one ramet shaded) at two developmental stages using stable-isotope labelling.

Key results: At the early developmental stage, both species translocated resources toward daughters and the translocation was modified by shading. Later, the species of low-productivity habitats, Fragaria viridis, translocated carbon to shaded ramets (both mother and daughter), according to the 'equalisation' strategy. In contrast, the species of high-productivity habitats, Potentilla reptans, did not support shaded mother ramets. Nitrogen translocation remained mainly acropetal in both species.

Conclusions: The two studied species exhibited different translocation strategies, which may be linked to the habitat conditions experienced by each species. The results indicate that we need to consider different possible strategies. We emphasise the importance of bidirectional tracing in translocation studies and the need for further studies to investigate the translocation patterns in species from contrasting habitats using a comparative approach.