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Rahier, Martine

Nom
Rahier, Martine
Affiliation principale
Fonction
Professeure ordinaire
Email
Martine.Rahier@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/99

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  • Publication
    Accès libre
    Distribution of autogenous and host-derived chemical defenses in Oreina leaf beetles (Coleoptera: Chrysomelidae)
    (1995)
    Pasteels, Jacques M.
    ;
    Dobler, Susanne
    ;
    Rahier, Martine 
    ;
    Ehmke, Adelheid
    ;
    Hartmann, Thomas
    ;
    Pasteels, Jacques M.
    ;
    Dobler, Susanne
    ;
    Ehmke, Adelheid
    ;
    Hartmann, Thomas
    The pronotal and elytral defensive secretions of 10 Oreina species were analyzed. Species feeding on Apiaceae, i.e., O. frigida and O. viridis, or on Cardueae (Asteraceae), i.e., O. bidentata, O. coerulea, and O. virgulata, produce species-specific complex mixtures of autogenous cardenolides. O. melanocephala, which feeds on Doronicum clusii (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. O. cacaliae 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 O. elongata, O. intricata, and O. speciosissima, 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 O. elongata and O. speciosissima, 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.
  • Publication
    Accès libre
    A comparison between allozyme data and phenotypic distances from defensive secretion in Oreina leaf-beetles (Chrysomelinae)
    (1994)
    Rahier, Martine 
    ;
    Pasteels, Jacques M.
    The genetic relationships between five Oreina species (Chrysomelidae, Coleoptera) were studied. Of these species, four (O. bifrons, O. gloriosa, O. speciosa, O. variabilis) feed on Apiaceae and secrete mixtures of autogenous cardenolides from defensive glands, whilst the other (O. speciosissima) feeds on Asteraceae and is able both to produce cardenolides and to sequester pyrrolizidines N-oxides (PAs). A dendrogram based on the different mixtures of cardenolides produced by the different species agreed with these genetic relationships. In other words, cardenolide mixtures are good taxonomic markers, since the clustering method based on chemical defense produces a branching pattern similar to that based on genetic relationships.
  • Publication
    Accès libre
    Chemical defences in leaf beetles and their larvae: The ecological, evolutionary and taxonomic significance
    (1984)
    Pasteels, Jacques M.
    ;
    Rahier, Martine 
    ;
    Braekman Jean-Claude
    ;
    Daloze, Désiré
    The chemical defences of the Chrysomelinae are reviewed. Defensive glandular secretions have evolved independently in larvae and adults, and faster than the morphology of the glands. Both characters are used in a phylogenetic study of the Chrysomelini, disclosing suprageneric affinities. First, a close relationship between the Chrysomelina and Phratora is proposed. Secondly, Leptinotarsa and Gonioctena are probably more closely related to the Chrysolinina than to the Chrysomelina and Phratora. The qualitative and quantitative composition of larval and adult secretions sometimes differs between geographically isolated populations of the same species, which are therefore probably genetically distinct. The host plant shows an influence which explains discrepancies between the current classification and the chemical nature of the secretions. Some beetles sequester secondary plant metabolites or use them as precursors for their own defences. The original biosynthetic pathway has been lost in these species. Other factors which could affect the chemical diversity of the secretions are discussed: random events such as neutral mutations and genetic drift, conditioning or adaptation of predators to specific defensive mixtures, and the diversity of potential predators. The latter could help to explain the divergence in the chemical nature of the larval and adult secretions. The volatile irritants produced by the larvae are well suited to repel small arthropods, such as ants, whereas poisons associated with aposematic coloration in the adults could be directed against small vertebrates, such as birds.