Chemical composition of the slippery epicuticular wax blooms on Macaranga (Euphorbiaceae) ant-plants

Claus Markstädter, Walter Federle, Reinhard Jetter, Markus Riederer, Bert Hölldobler

Research output: Contribution to journalArticlepeer-review

83 Scopus citations

Abstract

The stems of many Macaranga ant-plants (Euphorbiaceae) are covered by epicuticular wax crystals rendering the surface very slippery for most insects. These wax blooms act as selective barriers protecting the symbiotic ant partners, which are specialized "wax-runners", against the competition of other ants. Glaucous stems occur almost exclusively among the ant-plants of the genus Macaranga (Federle et al. 1997). We analyzed the cuticular lipids of 16 Macaranga species by GC-MS and investigated the wax crystal morphology using SEM. Presence of crystalline wax blooms was strongly correlated with high concentrations (52%-88%) of triterpenoids. In contrast epicuticular waxes of glossy Macaranga surfaces contained only 0% to 36% of these dominant components. Therefore we conclude that triterpenoids are responsible for the formation of the thread-like Macaranga wax crystals. In all Macaranga ant-plants investigated, the principal components were epitaraxerol and taraxerone accompanied by smaller portions of taraxerol, β-amyrin and friedelin. Only in the case of the non-myrmecophytic M. tanarius did β-amyrin predominate. Moreover, we found that only in M. tanarius, the dense wax crystal lacework is torn into large mosaic-like pieces in the course of secondary stem diameter growth. Both chemical and macroscopic differences may contribute to a reduced slipperiness of M. tanarius stems and appear to be functionally important. The distribution of wax crystals and their composition amongst different sections of the genus suggests that glaucousness is a polyphyletic character within Macaranga.

Original languageEnglish (US)
Pages (from-to)33-40
Number of pages8
JournalChemoecology
Volume10
Issue number1
DOIs
StatePublished - 2000
Externally publishedYes

Keywords

  • Ant-plants
  • Epicuticular waxes
  • Euphorbiaceae
  • Fine structure
  • Insect attachment
  • Macaranga
  • SEM
  • Triterpenoids

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Biochemistry

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