Adaptation analysis of two Asteraceae invasive plants in Lhasa, Tibet

Invasive plants pose a major threat to global ecosystems, especially in ecologically fragile high-altitude regions. Due to its unique geographical and climatic conditions, the Tibetan Plateau is considered highly susceptible to biological invasions. This study investigates the germination capacity and early growth performance of two invasive species, Bidens pilosa and Tagetes minuta, under the natural climatic conditions of Lhasa, Tibet. We assessed how seed burial depth, geographical provenance, and climatic variables affect their establishment potential. The results showed that B. pilosa exhibited the highest germination rate in shallow soil layers, especially for seeds originating from Kunming (KM). However, seeds from the same source that matured in Lhasa following one local growing season (LS), showed a significant reduction in germination capacity, indicating the negative effects of high-altitude stress on maternal seed quality. Seeds from different altitudes displayed varied adaptive performance, with high-altitude provenances showing greater plant height in Lhasa's cold, dry environment. Although T. minuta exhibited generally low germination rates across all burial depths, the individuals that successfully emerged demonstrated vigorous early growth, particularly under deeper burial conditions. This suggests that once established, the species may possess strong potential for rapid population expansion and severe invasion. Climate data over the past three years showed that the growing season from May to October in Lhasa-characterized by increased temperature and precipitation-provided a favorable climate window for both species. Our findings suggest that the ongoing warming and humidification trend on the Tibetan Plateau, driven by global climate change, may further facilitate the expansion and establishment of these invasive species. This study provides essential insights for risk assessment and management of invasive plants in Lhasa and other high-altitude regions, emphasizing the importance of long-term monitoring and targeted early-warning strategies in response to shifting environmental conditions.