Read more about Xiao Sun and colleagues’ Journal of Ecology study on volatiles of compounds (VOCs) and the performance of herbivores…

The interactions of aboveground and belowground herbivory can determine species populations and community composition. The outcome of the interactions can differ between conspecific and heterospecific aboveground and belowground herbivores, with conspecific herbivores enhancing their performance through systemic changes in plant metabolism. However, mechanisms underlying these interactions are still unclear.

In our previous studies of the specialist flea beetle (Bikasha collaris), which has both aboveground and belowground feeding stages, we found that the aboveground adults increased the performance of belowground conspecific larvae (Huang et al., 2012) and that these interactive effects are mediated by changes in plant nitrogen and secondary chemicals (Huang et al., 2013). We then further showed that while conspecific aboveground adults facilitated their belowground larvae, some other aboveground herbivores appeared to avoid plants infested by the larvae (Huang et al., 2014). However, it is unknown whether changes in volatile emissions by B. collaris larvae drive these interactions. i.e., attracting conspecific adults and repelling heterospecific aboveground herbivores.

Bikasha collaris (Coleoptera: Chrysomelidae) is a multivoltine specialist flea beetle with adults that chew leaves and larvae that bore into roots of Chinese tallow tree Triadica sebifera (Euphorbiaceae).

In this study we examine how herbivore-induced changes in plant volatile emissions mediate above- belowground interactions by determining host plant colonization by different herbivores. We show that leaf volatiles induced by belowground herbivory attract conspecific aboveground adults and then increase folivory, which in turn benefits belowground larvae through manipulation of host plant. We found greater leaf consumption by conspecific adults increased root nutrients, decreased root defenses, and thereby increased root feeding larvae performance.

When Triadica sebifera plant was attacked by Bikasha collaris belowground larvae, plant systematic defense responses alter foliar volatiles, subsequently repelling aboveground heterospecifics and attracting aboveground conspecifics. Afterwards, B. collaris aboveground adults facilitate conspecific belowground larval survival, growth, and their reproductive output as adults likely by increasing root nitrogen concentration and decreasing root total phenolics.

Our results provide novel insights into understanding the mechanisms by which diverse aboveground and belowground species co-exist to shape community structure. To the best of our knowledge, our study is the first to report plant volatiles induced by belowground larvae attract their aboveground conspecific adults and repel heterospecific herbivores.

The functions of HIPVs in mediating aboveground and belowground conspecific and/or heterospecific species interactions revealed by our study, shed light on the role of volatiles in determining species populations, community composition, and possibly biological diversity. These findings have important implications for understanding mechanisms underlying above and belowground species coexistence and community assembly.

Xiao Sun, Henan University, China

Read the full paper: Root feeding larvae increase their performance by inducing leaf volatiles that attract aboveground conspecific adults