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"Fig wasp" is a broad term applied to chalcid
wasps (Chalcidoidea, Hymenoptera) that
exclusively breed in figs, the enclosed inflorescence of fig trees (Ficus,
Moraceae), but excludes those
chalcids that are parasitoids of facultative utilizers (such as lepidopteran,
coleopteran and dipteran
larvae) of the fig niche. From a taxonomic perspective the term "fig
wasp" encompasses
representatives of five chalcid families (Agaonidae, Pteromalidae, Ormyridae,
Eurytomidae and Torymidae) making up the assemblage of chalcidoid wasps associated with figs.
All species in the family Agaonidae breed in figs, but the Pteromalidae, Ormyridae,
Eurytomidae and Torymidae only have a very small
proportion of their total species associated with figs.
Fig
wasps were previously all united
under the Agaonidae incorporating six distinct taxa at subfamily level (Epichrysomallinae,
Otitesellinae, Sycoryctinae, Sycoecinae and Sycophaginae) (Bouček
1988). Subsequent morphological and molecular studies indicated that the
Agaonidae as defined by Bouček was not monophyletic (Machado
et
al. 1996; Kerdelhué 1997;
Rasplus et al. 1998). Recent
molecular investigations of DNA sequences showed that the different groups of
fig wasps are not closely related, suggesting that the fig niche has been
colonised on a number of separate occasions by different wasp lineages over
evolutionary time. The precise classificatory position of these groups of
non-pollinators is currently under investigation through both morphological and molecular appraisals of their evolutionary
relationships. The Sycoecinae,
Otitesellinae and Sycoryctinae have been reassigned to the Pteromalidae, leaving
only the pollinating fig wasps in the Agaonidae (Rasplus et al. 1998;
Campbell
et al. 2000). Phylogenetic relationships of
the remaining two subfamilies (Sycophaginae and Epichrysomallinae) are still
unresolved, but they
do not belong in the Agaonidae.
From an ecological perspective most fig wasp species are
phytophagous and the remaining
species are inquilines or parasitoids of these gallers. The phytophagous species
gall the ovule to
provide a food resource for larval development. The relationship of the
pollinating fig wasps with
their host fig tree is an obligate mutualism: the tree relies on the wasps for
pollen dispersal and
pollination, and in turn the wasps can only reproduce in the florets within the
fig.
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