Ramet specialization allows similar performance of the invasive macrophyte Hedychium coronarium under different light and intraspecific competition levels

Abstract Invasive species can affect ecosystems functioning by forming dense monospecific stands and outcompeting native plants. However, the performance of the invader depends on its plastic responses to abiotic attributes of invaded communities. Understanding the interplay between intraspecific competition and environmental conditions is important to elucidate the domain and aggressive potential of invasive species. Here, we assessed the performance of the invasive Hedychium coronarium in two levels of intraspecific competition created through rhizome density under full light and partial shade. We tested the influence of light, density and their interaction on ramet length and number of ramets during the first three months after planting (phase 1) and after 22 months (phase 2), and on rhizome dry weight and the ramet/rhizome biomass ratio in phase 2. In both phases, ramets were longer under shade and the number of ramets was higher under low rhizome density indicating lower intraspecific competition. In phase 2, there was a negative effect of rhizome density on ramet length, but it was restricted to shade, probably due to the aggravation of competition for light. Rhizome dry weight was greater under shade conditions and it was not affected by rhizome density, and ramet/rhizome ratio did not differ between treatments. Our results supported a large phenotypic plasticity of H. coronarium ramets, which allowed similar performances despite variations in environmental conditions and population densities. We suggest that this mechanism of energy allocation enhances the success of this invasive plant in varied habitats, such as open and closed, forested sites.