Phenotypic plasticity of Alternanthera philoxeroides in response to shading: introduced vs. native populations.
It is still debated whether invasive plants have superior functional traits or the ability to display increased phenotypic plasticity in the introduced area. We conducted common garden experiments using five native populations and five invasive populations of Alternanthera philoxeroides to look for differences in phenotypic plasticity in response to shading of functional traits between introduced and native populations. We found both native and introduced plants showed significant phenotypic plasticity in response to shading, including reduction of biomass, root/shoot ratio (RSR) and branch biomass fraction (BBF), and increasing in specific stem length (SSL) and specific leaf area (SLA). The introduced populations (from the USA) showed higher plasticity in response to shading than the native Argentina population in traits such as RSR, BBF and SSL. Introduced plants also show significant reductions in RSR (-20.8%), BBF (-54.6%), SSL (-18.5%) and SLA (-8.8%). Our results suggest that A. philoxeroides has evolved a lower plastic response to shading in its introduced range, which might contribute to the establishment of dense populations with high persistence and resistance to colonization by sympatric native species.