The invasion mechanisms of the invasive clonal plant Wedelia trilobata

Background/Question/Methods Invasive species has caused huge ecological and economic losses at the global scale with affecting the structure and function of ecosystems, and also shifting the evolution of native species. The invasive clonal plant Wedelia trilobata, one of the 100 Worst Invasive Species in the World, is a representative clonal creeping herb with strong stolons. It reproduces with its rapid clonal growth, resulting in dense population canopy in the field and caused huge ecological effects on the structure and function of ecosystems in China^[1-3]. What are the successful invasion mechanisms of W. trilobata?

Results/Conclusions Based on the relatively high proportion of ent-kaurane diterpenes, which are gibberellin (GA) precursors in W. trilobata, and it grows rapid in invaded habitats, we found that the endogenous GA can facilitate its fast asexual colonization and dispersal in invaded habitats, and GA facilitates the growth of W. trilobata faster than that of its native congener W. chinensis^[4].  Our results also showed that the clonal growth characteristics of W. trilobata showed significant differences among the invaded sites on Hainan Island, suggesting that the species was able to adapt to different environments. The mean phenotypic plasticity index of W. trilobata was higher than that of other invasive plant species. The molecular variance in the genetic diversity of the population showed significant differences among the sites. The responses of plants grown from different sites to light treatment varied^[3]. The rapid growth of W. trilobata in the field caused dense litter layer and weak light transmittance under its populations, which might be two major factors lead to the failure of its seedling recruitment in the field^[2]. However, our results showed that litter layer of W. trilobata could increase the competitive abilities of W. trilobata by promoting its own ramet growth and inhibiting both invasive and non-invasive competitors’ growth^[5]. W. trilobata contained the Toll/Interleukin-1 receptor (TIR) and non-TIR subclasses nucleotide-binding sites (NBS) resistance genes (R-genes). Compared with the homologous non-invasive plants using the information in GenBank, the invasive plants showed a significantly greater evolutionary rate (d_N/d_S) for TIR NBS R-gene/RGAs, showing the former would suffer less selection stress from co-evolutionary specialist pathogens^[6]. 

Funding: National Natural Science Foundation of China (31170386, 31570414) , the Natural Science Foundation of Jiangsu (BK20150503, BK20150504), the Natural Science Research Project of Higher Education of Jiangsu (14KJB610005), the Jiangsu Planned Projects for Postdoctoral Research Funds (1501028B), and the College Students Scientific Research Project of Jiangsu University (Y14A109).