Plant invasions have harmful, even devastating, impacts on the local biotic communities and ecosystems, and as such they are considered a major threat to native biodiversity around the world. Soil nematodes, which are the important component of soil ecosystem, could also be significantly affected by invasive plants. Moreover, previous studies have indicated that the effects of plants on soil nematodes are often regulated by aboveground herbivores in the natural environment. However, little is known about whether the effects of invasive plants on soil nematodes are mediated by aboveground herbivores since invasive plants are not completely released from herbivores in the introduced range. 

Supervised by Prof. DING Jianqing and Prof. HUANG Wei, LIU Jia, PhD from Wuhan Botanical Garden, conducted a greenhouse experiment to examine the effects of invasive plant Alternanthera philoxeroides under different herbivory treatments (no insect herbivores, specialist Agasicles hygrophila, and generalist Cassida piperata) on soil nematode communities and how these effects changed with time. 

They found that aboveground herbivory significantly increased the abundance of soil nematodes of A. philoxeroides, such as plant feeder nematodes, after insect herbivores were removed immediately. However, such impacts waned with time and there was no significant difference at later stages. In addition, the regulatory influences of specialist A. hygrophila and generalist C. piperata were similar.  

Studies on the impacts of plant invasions on soil nematodes may provide a novel perspective from belowground communities for better understanding and exploring the mechanisms of plant invasions. Furthermore, the results in this study highlight the importance of aboveground herbivores in examining the effects of invasive plants on belowground biotic communities. 

This work was supported by the National Key Research and Development Program of China and the National Natural Science Foundation of China. Relevant research results have been published in Journal of Plant Ecology entitled “Aboveground herbivory increases soil nematode abundance of an invasive plant”.  

Variations of nematode abundance of Alternanthera philoxeroides under different herbivory treatments with time after removal of herbivores (Image by LIU Jia)