Building an Integrative and Testable Hypothesis on How Edaphic Factors Ultimately Influence the Occurrence and Quality of Ophiocordyceps Sinensis, the Vegetable Caterpillar

Abstract

BackgroundThe yield of commercially harvested “vegetable caterpillar” Ophiocordyceps sinensis has dramatically plummeted in the last few decades, while market demand has increased. Besides controlling the obvious overexploitation of this species, understanding how edaphic factors influence this system may improve the chances of successful cultivation and thus support the conservation of O. sinensis in the wild. Our study investigates how the presence/absence and the quality of O. sinensis may be linked to a series of edaphic factors pertinent to its microhabitat, including enzyme activity, nutrients, moisture, pH and nematode population. In order to provide a preliminary hypothesis on the relationships among edaphic factors and their influence on O. sinensis, we performed a principal component analysis and structural equation modelling despite limited replication. ResultsSoil samples containing O. sinensis were more moist and contained a higher concentration of nutrients and enzyme activity than control samples collected nearby, where the species was absent. Preliminary analyses indicated that enzyme activity may be crucial and appeared to be affected by a number of other soil factors. We found that O. sinensis would occupy microhabitats with a relatively higher soil fertility and a more persistent enzyme activity, where the values of total nitrogen and catalase are especially important. Otherwise, with the exception of organic matter and enzyme activity, mean values did not suggest any other factors potentially corresponding to a better quality of O. sinensis.ConclusionsBased on these preliminary findings and a further literature review, we formulated the first integrative hypothesis (network of interactions) on how soil factors may influence each other and O. sinensis. Finally, we indicate how this hypothesis may be tested in the future, in order to increase the chances for successful cultivation and thus promote the conservation and sustainable harvesting of O. sinensis.