n African Entomology - Evidence that (Hymenoptera: Eulophidae) is the only gall inducer among four hymenopteran species associated with seed capsules of (Myrtaceae) in South Africa

Volume 23, Issue 1
  • ISSN : 1021-3589



Three chalcidoid wasp species, Grissell (Torymidae), Girault (Eulophidae) and Kim & La Salle (Eulophidae), have each been described independently as gall inducers associated with species (Myrtaceae). The finding that at times they emerge together from seed capsules of river red gum ( Dehnhardt) collected at the same site in South Africa, cast doubt on the accuracy of these earlier interpretations. The current study examined the gall inducing abilities of each of the three wasp species. During geographical surveys, all three species coexisted in seed capsules at 16 of the 61 sites sampled. A study of the seasonal emergence pattern of the three species, together with a fourth, locally abundant gall associate, sp., showed that and emerge during early summer, while the remaining two species emerge in smaller numbers throughout the year. Oviposition trials on sleeved branches of , from which all insects had previously been excluded, verified that had the ability to induce galls, while both and failed to do so. Only one type of gall of characteristic structure was encountered, which repudiates the possibility of a second gall inducer, and no indication of inquilinism was found. and sp. are thus more likely to be parasitoids. DNA sequences were obtained for the adults of all four these species. By matching the DNA of identified adults with that of juvenile hymenopterans in the galls, it was confirmed that all four hymenopterans species developed within the seed-capsule galls of . Regrettably, this technique failed to give a clear indication of the exact host relationships between the various gall inhabitants. By dissecting seed capsules at different stages of gall development, the origin of the gall was proven to be in the placenta of one of the locules of a flower bud, and not in a seed or ovule, as previously reported.

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