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Distribution of autogenous and host-derived chemical defenses in <i>Oreina</i> leaf beetles (Coleoptera: Chrysomelidae)
Auteur(s)
Pasteels, Jacques M.
Dobler, Susanne
Ehmke, Adelheid
Hartmann, Thomas
Pasteels, Jacques M.
Dobler, Susanne
Ehmke, Adelheid
Hartmann, Thomas
Date de parution
1995
In
Journal of Chemical Ecology, Springer, 1995/21/8/1163-1179
Mots-clés
Résumé
The pronotal and elytral defensive secretions of 10 <i>Oreina</i> species were analyzed. Species feeding on Apiaceae, i.e., <i>O. frigida</i> and <i>O. viridis</i>, or on Cardueae (Asteraceae), i.e., <i>O. bidentata</i>, <i>O. coerulea</i>, and <i>O. virgulata</i>, produce species-specific complex mixtures of autogenous cardenolides. <i>O. melanocephala</i>, which feeds on <i>Doronicum clusii</i> (Senecioneae, Asteraceae), devoid of pyrrolizidine alkaloids (PAs) in its leaves, secretes, at best, traces of cardenolides. Sequestration of host-plant PAs was observed in all the other species when feeding on Senecioneae containing these alkaloids in their leaves. <i>O. cacaliae</i> is the only species that secretes host-derived PA N-oxides and no autogenous cardenolides. Differences were observed in the secretions of specimens collected in various localities, because of local differences in the vegetation. The other species, such as <i>O. elongata</i>, <i>O. intricata</i>, and <i>O. speciosissima</i>, have a mixed defensive strategy and are able both to synthesize de novo cardenolides and to sequester plant PA N-oxides. This allows a great flexibility in defense, especially in <i>O. elongata</i> and <i>O. speciosissima</i>, which feed on both PA and non-PA plants. Populations of these species were found exclusively producing cardenolides, or exclusively sequestering PA N-oxides, or still doing both, depending on the local availability of food-plants. Differences were observed between species in their ability to sequester different plant PA N-oxides and to transform them. Therefore sympatric species demonstrate differences in the composition of their host-derived secretions, also resulting from differences in host-plant preference. Finally, within-population individual differences were observed because of local plant heterogeneity in PAs. To some extent these intrapopulation variations in chemical defense are tempered by mixing diet and by the long-term storage of PA N-oxides in the insect body that are used to refill the defensive glands.
Identifiants
Type de publication
journal article
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