Thermal acclimation fails to confer a carbon budget advantage to invasive species over natives

Both native and invasive plants can adjust photosynthesis and respiration when exposed to warmer temperatures. However, it is uncertain if invasive plants are more plastic and exhibit higher acclimation to rising temperatures than native ones, a trait that could contribute to their invasive behavior in novel environments.

We compared the capacity of a highly invasive palm in central Europe (Trachycarpus fortunei) and two native co-occurring species (Ilex aquifolium and Tilia cordata) to acclimate photosynthesis and respiration to air temperature changes using a two-year-long transplant experiment across Europe (mean temperatures ranging from 8.4 to 21.8°C). We measured the optimal temperature of photosynthesis (T_opt), the assimilation at optimal temperature (A_opt), the thermal breath of photosynthesis (T₈₀), the respiration at 25°C (R₂₅), the temperature sensitivity of respiration (Q₁₀), and simulated the whole-plant carbon budget.

For all species, T_opt, A_opt, and T₈₀ increased with warming, while R₂₅ decreased in the native species and Q₁₀ decreased in the invasive species only. Consequently, acclimation enhanced the carbon budget of the invasive and native plants in the warm and hot sites. The invasive palm had a similar or lower acclimation capacity than other species and a lower but constant carbon budget across the European temperature gradient. Our work reveals that not all invasive plants exhibit greater photosynthetic plasticity than native ones, suggesting that temperature-driven enhancement of their carbon budget may play a limited role in future invasion processes.