No abstract

Abstract. Lysergol, elymoclavine and three other van Urk-positive alkaloids were identified by 2D chromatography in the seed extract of Ipomoea parasitica.The presence of the same ergoline alkaloids was also demonstrated in vegetative tissue of L parasitica. Heliothis virescens larvae reared on a diet containing an alkaloid extract of I. parasitica showed an increase in the consumption index and a reduction in the effiency of conversion of food. No difference was observed in the approximated digestibility. The percentages of pupation and emergence were reduced and the malefemale ratio was altered in insects fed on a diet containing the alkaloid extract of L parasitica or lysergol. The increases in the concentration of ergoline alkaloids in L parasitica at the seedling stage and at flowering support the theory that these compounds play a defensive role against herbivory in the plant.Key words, allelochemical effect -herbivory -chemical defence -ontogenetic variation -ergoline alkaloids -lysergol -elymoclavine -Ipomoea parasitica- Heliothis virescensIn spite of the considerable physiological activity of the ergoline alkaloids and of their use in pharmacology, little attention has been paid to their ecological role in the higher plants where they are present. However, some researchers have recently investigated the effect of ergoline alkaloids from endophyte (ergot)-infected grasses on certain arthropods. Yates et al. (1989) investigated the effect of ergoline alkaloids from endophyteinfected grasses on the milkweed bug Oncopeltus fasciatus. These authors found that a fraction containing simple lysergic acid amides, N-formylloline and related alkaloids was highly toxic while a fraction containing ergopeptine alkaloids proved to be relatively non-toxic, although commercial ergopeptines were toxic. Clay & Cheplick (1989) found that the ergoline alkaloids ergonovine, ergotamine, ergocryptine, agroclavine and elymoclavine but not lysergol reduce larval weight and/or leaf area consumption in the fall armyworm Spodoptera fugiperda.In this paper the possible ecological role of the ergoline alkaloids in L parasitica is discussed on the bases of their effect on H. virescens and their ontogenetic and organ variation.