Functional traits of a facultative metallophyte from tropical Africa: population variation and plasticity in response to cobalt

- Shoot height and leaf size diverged between non-metallicolous and metallicolous populations of Anisopappus chinensis.
- Foliar nutrient composition did not diverge between non-metallicolous and metallicolous populations of A. chinensis.
- Plasticity patterns in response to Co were often trait and population specific.
- Homeostasis of the majority of functional leaf traits in response to Co has been highlighted.
- Tolerance to Co would be achieved by the ability to limit foliar Co accumulation.

Divergence in functional traits and their plasticity can occur between metallicolous and non-metallicolous populations, driven by the selective pressure of metal toxicity in metalliferous soils, which is often associated with other edaphic constraints. The intraspecific variation of functional traits and their plasticity in response to cobalt in the soil, among populations of Anisopappus chinensis - a broad-niched metallophyte from southeastern D. R. Congo - have been experimentally investigated. Divergence in shoot height and leaf size was observed according to the ecological status of populations, with higher values occurring in plants from non-metalliferous soils. No clear differentiation in SLA was found between non-metallicolous and metallicolous populations. Metallicolous populations did not diverge in their leaf mineral composition and plastic response, with the exception of a lower leaf Co concentration on Co-contaminated soils. Functional leaf traits seemed to exhibit a homeostatic response to Co, which may account for the broad niche of the species. Further studies should include populations from other metallicolous and non-metallicolous habitats and include root and reproductive traits, to better understand resource acquisition strategies and adaptive response to Co toxicity.