Fig-fig wasp mutualism is getting even more complex

I don’t think anything in biology requires as much time and patients as do behavioral studies do. It’s still a manageable task when you’re dealing with mammals since we undoubtedly experience the world similarly. In contrast, little creatures, like insects, experience the environment very differently, rendering natural history observations challenging.

In light of this, it was delightful to receive an email this morning, informing me of a new study on the behavior of fig rove beetles:

Frank, J. H. & H. Nadel. 2012. Life cycle and behaviour of Charoxus spinifer and Charoxus major(Coleoptera: Staphylinidae: Aleocharinae), predators of fig wasps (Hymenoptera: Agaonidae). Journal of Natural History, 46(9-10): 621-635.

The genus Charoxus are a truly fascinating genus of rove beetles, that I think really bring home how ecologically diverse the rove beetles can be. Charoxus are large aleocharine staphylinids (~ 3 mm) with large anteriorly directed mandibles and a cylindrical body, presumably adapted for squeezing into figs and feeding on fig wasps inside.

Figs themselves are pollinated and parasitized by various groups of parasitic wasps; some of these fig-wasp relationships being mutualistic . For fig-pollinating Agaonidae wasps, the females bite their way through the fruit’s ostiole, which essentially shuts out all other visitors – parasitic wasps, therefore, must drill through the fruits exterior. Agaonidae wasps reproduce and mate within the fruit and males open a passageway out of the fruit, where the female wasps exit and Charoxus individuals enter. By now (fig fruit stage D), many of the wasps have left but there is enough of a fauna left that Charoxus are able to almost complete an entire life cycle inside the figs. Charoxus adults lay several eggs within a formally parasitized fig flower and the 3rd instar larvae drop to the ground to pupate, with essentially all necessary feeding appearing to occur within the fig fruit.

Figs themselves are en ecologically important element of many subtropical and tropical biomes. The trees themselves often live parasitically on other plants, and the fruits are important food sources for vertebrates. But to scale this ecological prominence down to the efforts of minute mutualistic wasps, and to further expand this ecological interaction to parasitoids and predators of fig-wasps blows my mind. Charoxus truly adds another element of complexity to the fig and fig-wasp mutualist story.


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