Under the supervision of Dr. Jianqing Ding, Xinmin Lu (Ph. D) and Yan Sun (M.Sc) of the Invasion Biology and Biocontrol Lab, studied on the response of the invasive plant alligator weed Alternanthera phioxeroides to defoliation by its biological control agent, the host-specific flea beetle, Agasicles hygrophila. Their results indicated that alligator weed response differently to herbivory in terrestrial and aquatic habitats and recovered the potential mechanism. Their findings provided new insight for biological control against invasive plants. 

Native to South America, alligator weed is a world-wide noxious weed and is one of the most important invasive species in China, causing great loss in agriculture and threatening biodiversity. The weed widely distributes in the warm temperate and subtropical regions of China. Agasicles hygrophila was introduced to control this noxious weed in America, Australia, and China, but has only been successful in aquatic habitats and has no or only limited control in terrestrial habitats, though it can reach high densities in terrestrial habitats. Understanding the reasons for failure of biological control is crucial for improving its efficiency. 

Lu & Sun carried out greenhouse and common garden experiments to compare compensatory ability of alligator weed to artificial and actual herbivory at different plant densities and in differing habitats. Their results indicated that in terrestrial habitat alligator weed can compensate herbivory more intensively than in aquatic habitat. In response to herbivory, plants in terrestrial habitat allocate more resource to below-ground, whereas flooding may inhibit the root growth and resource allocation between above and below-ground. Their results also indicated that con-specific association may increase plant compensatory ability to cope with intense damage at certain plant densities. Therefore, to improve the efficiency of biological control against alligator weed, it is crucial to find a way to suppress plant root growth. 

These results have been published in international journals, Biological Invasions, Plant Biology and Biological Control. The work was funded by the Knowledge Innovation Program of the Chinese Academy of Sciences and National Natural Sciences Foundation of China (NSF).