Origin matters for level of resource sharing in the clonal herb Aegopodium podagraria

Resource sharing in heterogeneous environments has been shown to increase growth and survival of clonal plants. In addition, plants in harsh climates have been suggested to have higher levels of resource sharing than plants in milder climates. We experimentally investigated the level of resource sharing in plants from garden and forest habitats from two regions with contrasting climates. The clonal herb Aegopodium podagraria reaches its northern distribution limit in central Sweden. South of that it grows in both patchy and dynamic light climate, as a natural component of deciduous forest, as well as in more homogeneous light climates as a garden weed. Since heterogeneity and habitat harshness have both been suggested to increase resource sharing, we hypothesized (1) integration and sharing of resources to be higher in plants from forest than in plants from garden habitats and (2) integration and sharing of resources to be higher in plants from the northern region that encounter a harsher climate than in plants from the southern region. Clonal fragments of A. podagraria were collected and multiplied in the greenhouse. Ramet pairs were then planted in adjacent pots, with one ramet shaded. Rhizome connection was either left intact or severed to prevent resources sharing. Plants from forest habitats were more negatively affected by the severance treatment than plants from garden habitats. Although region alone had no significant effect on biomass, the interaction between rhizome severing, shading and regional origin was close to significance. We conclude that A. podagraria from forests are more dependent on resource sharing than those from gardens. These results concur with previous studies that suggest that local adaptation for different degrees of resource sharing can occur in clonal plants.