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 'equalization' strategy is only one of several possible strategies. Under certain conditions, a strategy emphasizing 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 summarize 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 towards 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 'equalization' 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 emphasize 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.

• Keywords
• Carbon, clonal plants, development, light, nitrogen, physiological integration, stable isotopes, translocation,
• MeSH
• Models, Biological MeSH
• Nitrogen metabolism   MeSH
• Ecosystem MeSH
• Fragaria * growth & development   genetics   physiology   MeSH
• Reproduction, Asexual MeSH
• Carbon metabolism   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Nitrogen MeSH
• Carbon MeSH

Exotic plant invaders pose a serious threat to native plants. However, despite showing inferior competitive ability and decreased performance, native species often subsist in invaded communities. The decline of native populations is hypothesized to be halted and eventually reversed if adaptive evolutionary changes can keep up with the environmental stress induced by invaders, that is, when population extinction is prevented by evolutionary rescue (ER). Nevertheless, evidence for the role of ER in postinvasion persistence of native flora remains scarce. Here, I explored the population density of a native forb, Veronica chamaedrys, and evaluated the changes in the shade-responsive traits of its populations distributed along the invasion chronosequence of an exotic transformer, Heracleum mantegazzianum, which was replicated in five areas. I found a U-shaped population trajectory that paralleled the evolution of plasticity to shade. Whereas V. chamaedrys genotypes from intact, more open sites exhibited a shade-tolerance strategy (pronounced leaf area/mass ratio), reduced light availability at the invaded sites selected for a shade-avoidance strategy (greater internode elongation). Field experiments subsequently confirmed that the shifts in shade-response strategies were adaptive and secured postinvasion population persistence, as indicated by further modeling. Alternative ecological mechanisms (habitat improvement or arrival of immigrants) were less likely explanations than ER for the observed population rebound, although the contribution of maternal effects cannot be dismissed. These results suggest that V. chamaedrys survived because of adaptive evolutionary changes operating on the same timescale as the invasion-induced stress, but the generality of ER for postinvasion persistence of native plants remains unknown.

• Keywords
• biological invasions, evolutionary rescue, phenotypic plasticity, shade-response strategies,
• MeSH
• Biological Evolution * MeSH
• Heracleum growth & development   radiation effects   MeSH
• Ecosystem MeSH
• Extinction, Biological * MeSH
• Phenotype MeSH
• Plant Leaves growth & development   radiation effects   MeSH
• Plants * radiation effects   MeSH
• Sunlight MeSH
• Veronica * growth & development   radiation effects   MeSH
• Introduced Species * MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH