Test of the colonization ability of the invasive alien plant Flaveria bidentis (Asteraceae) in southern China

The risk of invasion from exotic alien plants is enhanced by the increased global flow of humans and trade. Exploring the colonizing ability of invasive alien organisms in local areas is conducive to formulating prevention and control measures. At present, model prediction of potential distribution areas has been frequently used, while there are relatively few experimental tests. Yellow top [ Flaveria bidentis (L.) Kuntze] is a globally problematic invasive plant that has become wide-spread throughout northern China. Model predictions were controversial as to whether Flaveria bidentis will spread to southern China. In 2018, seven fitness traits were measured, and seeds were collected from individual plants in 31 populations (899 individuals) of Flaveria bidentis in northern China (invaded area). In 2019, the collected were sown in a common garden in southern China (uninvaded area) under two treatments: manual weeding and no manual weeding. Annual monitoring of the occurrence of Flaveria bidentis seedlings in a common garden in southern China was conducted from 2020 to 2022. Our results showed that in southern China, the 31 populations of Flaveria bidentis could all complete their life history in the common garden with manual weeding. However, in the common garden without manual weeding, the life cycle could not be completed and no surviving seedlings were found in the three-year survey. Compared with the values observed in northern China, the plant height, 1000-grain weight, germination vigor, germination rate and germinable seed number per plant were significantly decreased in the manually weeded common garden in southern China, but the seed number per plant was significantly increased, so the germinable seed number per plant could still reach 4104 ± 1026. Comparison of the phenotypic differentiation coefficient and phenotypic plasticity index showed that the phenotypic difference in different populations was mainly influenced by environmental differences. The above results showed that once Flaveria bidentis is free from biotic resistance from local plants in southern China, it can complete its life cycle and produce abundant offspring, thus achieving colonization, and strong phenotypic plasticity is conducive to its adaptation and diffusion. Therefore, in southern China, monitoring of Flaveria bidentis should be strengthened to prevent it from producing seeds, and the native plant cover is conducive to inhibiting the germination of seeds that may be contained in the soil and seedling growth.