| Fig wasps | |
|---|---|
| Blastophaga psenes | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Hymenoptera |
| Suborder: | Apocrita |
| Superfamily: | Chalcidoidea |
| Family: | Agaonidae |
| Subfamilies | |
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Fig wasps are wasps of the family Agaonidae which pollinate figs or are otherwise associated with figs, a coevolutional relationship that has been developing for at least 80 million years.[1] They have been seen to fly farther than any known pollen-bearing insect, and in some regions of the world where wind can gust at up to 30 kilometres per hour (19 mph), they can travel downwind approximately 100 miles in their 48-hour lifespan.[2]
The family as presently defined is polyphyletic, including several unrelated lineages whose similarities are based upon their shared association with figs; efforts are underway to resolve the matter, and remove a number of constituent groups to other families, particularly the Pteromalidae and Torymidae. Thus, the number of genera in the family is in flux. Probably only the Agaoninae should be regarded as belonging to the Agaonidae, whilst the Sycoecinae, Otitesellinae and Sycoryctinae should be included in the Pteromalidae. Placement of the Sycophaginae and Epichrysomallinae remains uncertain.
Among the Agaonidae, the female is a normal insect, while the males are mostly wingless. The males' only tasks are to mate with the females while still within the fig syconium and to chew a hole for the females to escape from the fig interior. This is the reverse of Strepsiptera and the bagworm, where the male is a normal insect and the female never leaves the host.
Most fig inflorescences contain three kinds of flowers: male, short female, and long female. Female fig wasps can reach the ovaries of short female flowers with their ovipositors, but not long female flowers. Thus the short flowers grow wasps, whereas the long flowers become seeds. In figs of this sort, the crunchy bits in the fruit contain both seeds and wasps. However, there are several commercial and ornamental varieties of fig that are self-fertile and do not require pollination; these varieties are not visited by fig wasps.
Pollinating fig wasps (Agaoninae) are specific to specific figs. The common fig Ficus carica is pollinated by Blastophaga psenes.
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The life cycle of the fig wasp is closely intertwined with that of the fig tree it inhabits. The wasps that inhabit a particular tree can be loosely divided into two groups; pollinating and non-pollinating. The pollinating variety forms a mutually beneficial symbiosis with the tree, whereas the non-pollinating variety is parasitic. Both life cycles, however, are very similar.
Though the lives of individual species differ, a general fig wasp life cycle is as follows. In the beginning of the cycle, a mature female pollinator wasp enters the "fruit" (actually a stem-like structure known as a syconium) through a small natural opening, the ostiole, which is covered in male flowers, and deposits her eggs in the cavity, which is covered in female flowers. Forcing her way through the ostiole, she often loses her wings and most of her antennae. To facilitate her passage through the ostiole the underside of the female's head is covered with short spines that provide purchase on the walls of the ostiole.[3] In depositing her eggs, the female also deposits pollen she picked up from her original host fig. This pollinates some of the female flowers on the inside surface of the fig and allows them to mature. After the female wasp lays her eggs and follows through with pollination, she dies, allowing the fig to consume her corpse. After pollination, there are several species of non-pollinating wasps which deposit their eggs before the figs harden. These wasps act as parasites to either the fig or the pollinating wasps. As the fig develops, the wasp eggs hatch and develop into larvae. After going through the pupal stage, the mature male’s first act is to mate with a female. The males of many species lack wings and are unable to survive outside the fig for a sustained period of time. After mating, a male wasp begins to dig out of the fig, creating a tunnel for the females to escape through.
Once out of the fig, the male wasps quickly die. The females find their way out, picking up pollen as they do. They then fly to another tree of the same species where they deposit their eggs and allow the cycle to begin again.
The fig-wasp mutualism originated between seventy and ninety million years ago as the product of a unique evolutionary event. [4] [5] [6] Since then cocladogenesis and coadaptation on a coarse scale between wasp genera and fig sections has been supported by both morphological and molecular studies. [7] [8] This illustrates the tendency towards coradiation of figs and wasps. [9] Such strict cospeciation should result in identical phylogenetic trees for the two lineages [10] and recent work mapping fig sections onto molecular phylogenies of wasp genera and performing statistical comparisons has provided strong evidence for co-speciation at that scale. [11]
Groups of genetically well defined pollinator wasp species coevolve in association with groups of genetically poorly defined figs. [12] The constant hybridization of the figs promotes the constant evolution of new pollinator wasp species. Host switching and pollinator host sharing may contribute to the incredible diversity of figs. [13]
Genera currently included in Agaonidae according to the Universal Chalcidoidea Database:
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