Performance of Solanum carolinense populations in the native and introduced range in the USA and Japan
Solanum carolinense (Solanaceae - EPPO A2 List) is a weedy species in its native range (North America) where it can have a negative impact on agriculture and pastureland. It can reproduce both by seed and vegetatively; it can grow rapidly and thrives in a variety of biotic and abiotic conditions. In the EPPO region, it can invade a number of different crops where it can have localised negative impacts. In Japan, S. carolinense is considered a moderately invasive species and a study was conducted to assess if S. carolinense follows the predictions of the Enemy Release Hypothesis including (1) introduced plants leave behind their suite of natural enemies and (2) a reduction in natural enemies promotes invasiveness by releasing populations from constraints that limit population growth. Surveys were conducted in the USA and Japan to compare herbivore damage levels and ramet densities in populations of the plant. Although a similar level of herbivore abundance from across different taxonomic groups were found, lower levels of damage were shown in populations of S. carolinense in Japan compared to the USA. Ramet density was significantly higher in the introduced range (2 to 14 stems m-2) compared to the native range (0.2–3.7 stems m-2). Therefore, in Japan, S. carolinense follows the predictions set out in the Enemy Release Hypothesis, even though the species is currently not displacing native plants and is not considered as a highly invasive species.
Sources
Halpern SL, Ohgushi T, Utsumi S, Kim TN (2026) Enemy reduction on Solanum carolinense in introduced populations in Japan. Biological Invasions 28, 72. https://doi.org/10.1007/s10530-026-03789-4