Integrated niche and dispersal modeling reveals global expansion patterns and invasion risks of Tithonia diversifolia under CMIP6 climate scenarios

Biological invasions have become one of the most serious threats to global biodiversity, and this issue has grown increasingly severe under the combined influence of climate change and human activities. As one of the most invasive alien plant species, Tithonia diversifolia has spread rapidly to more than 70 regions of the world. Its large geographic ranges indicate that this species possesses strong adaptability and dispersal capabilities. Therefore, understanding the ability of invasive species to establish and expand their distribution range is critical for predicting their potential invasion risk in new environments. The Centroid Shift, Overlap, Unfilling, and Expansion (COUE) framework and the n-dimensional hypervolume (NDH) framework were used to compare the niche shifts between native and invasive populations. Species distribution models (SDMs) were calibrated using datasets of native, invasive, and worldwide species (including both native and invasive areas) to predict potential distribution. Finally, land use cover data and dispersal models were integrated to forecast invasion risk. Our results showed that although the niche equivalency was not supported, the ecological niche of T. diversifolia exhibits strong conservatism, with limited expansion occurring in drier, high elevation and high levels of human disturbance. The worldwide SDM outperformed other SDM in predicting both current and future potential distributions. The potential distribution for T. diversifolia showed a general decrease but fragmented expansion occurred at the peripheral regions of China, Southeast Asia, and Central America under future climate scenarios. Dispersal model showed that there was significant colonization credit, with potentially over 40-fold increases in occupied areas. These results suggest that T. diversifolia presents serious threats to global ecosystems and socio-economic development, emphasizing the need for integrated management strategies and reinforcement of early prevention measures necessary for deterring the potential hazards of this invasion. • Niche expansion targets dry climates, higher elevations, and disturbed landscapes. • Climate change and human disturbance drive global spread of T. diversifolia . • Dispersal–land-use integration reveals large colonization credit and hidden invasion risks.