Germination niche of co-occurring threatened native and alien species: a case study in Lindernia procumbens and L. dubia

Plant invasions have a negative impact on biodiversity and lead to species loss. Although studies on traits promoting invasiveness have been largely developed, comparative studies on germination traits of closely related native versus alien invasive species, which also take into account threatened species, are lacking. We analysed the germination requirements of two congeneric Lindernia species inhabiting paddy field in Northern Italy. Germination tests were conducted exposing seeds of both species across a broad range of temperature and conditions (i.e., cold-wet stratification, dark condition, alternate temperature, gibberellic acid). The invasive L. dubia showed higher and faster germination, occurring over a broader range of temperatures compared to the native threatened L. procumbens, along with a lighter non-deep physiological dormancy. These results show a competitive advantage of the alien species already in the early stages of plant regeneration and provide a comprehensive overview of the germination requirements, necessary for the development of future conservation and management plans.