Competitiveness of generalist plant populations at a mine site

Abstract

Plants inhabiting extremely stressful mine site environments tend to be specialized and localized, where they express lowerperformance than nonmine site plants from adjacent areas. However, such a cost may be concealed. In a previous study at a mine site, wefound mine and adjacent nonmine plants of multiple species expressed similar performances in the absence of competition. However,a lower competitive ability may be a concealed driver. We aim to test whether costs under competition could explain specialization. Ina glasshouse experiment, we measured the performance (i.e. vegetative and reproductive growth) of mine and nonmine potted plantsunder competition. The 6 herbaceous species tested were Anagallis arvensis L., Cirsium vulgare (Savi) Ten., Conyza sumatrensis Retz.,Echium vulgare L., Oxalis chnoodes Lourteig, and Senecio diaschides D.G.Drury. We exposed individuals to interspecific competitionusing a local grass (Polypogon monspeliensis), as well as to intraspecific competition. Plants were grown alone for the control group.For all treatments, the mine plants expressed similar performances to the nonmine plants, except for mine site O. chnoodes, whichhad lower performance under intraspecific competition. Mine plants of A. arvensis and C. sumatrensis had higher performance thannonmine plants. Overall, there was no evidence of specialization in the mine site plants. These results indicate that, under somecircumstances, inhabiting a stressful metal habitat does not promote specialization in multiple species. Future research may focuson assessing the environmental conditions and population genetics that promote the evolution of generalists that inhabit extremelystressful environments.