Variability in flavonoid compounds of four Tribulus species: Does it play a role in their identification by desert locust Schistocerca gregaria?

We examined how variability in phenolic metabolism of four closely related Tribulus taxa might affect palatability to Schistocerca gregaria. Plants were collected in the Mauritanian breeding areas of the locust. Eighteen Ravonoids (caffeoyl derivatives, quercetin glycosides, including rutin, and kaempferol glycosides) were detected with high-performance liquid chromatography in leaf extracts. Principal component analysis (PCA) differentiated relative abundance of flavonoids of Tribulus terrestris from T. longipetalus, T. ochroleucus, and T. bimucronatus. Flavonoid content of T. terrestris leaves varied between northern and southern Mauritanian sites. Dual choice tests with plants whose flavonoid profiles had been determined previously were analyzed by multiple regression. The data suggest that the desert locust prefers T. terrestris plants rich in quercetin glycosides.