Wildlife Wednesday: Pollinators by demise
Fungus gnats are a large family of insects that are numerous in forests. Often overlooked because of their inconspicuous stature, fungus gnats are a group in the order Diptera, or the flies. These insects are mycophagous which is Latin for “mushroom eater”. Therefore, when plants emit smells reminiscent of the decomposers, fungus gnats follow.
Photographs left to right: Leia bivittata (credit: Sequoia Janirella Wrens) and Leptomorphus subcaeruleus (credit: @sebastienbenoit)
Such is the case for our target species Jack-in-the-Pulpit (Arisaema triphyllum), which attracts these flies with the fake promises of fungi. Upon receiving this phony signal, the fungus gnats will travel to the flower of the plant. The flower consists of a spadix, a long cone-like structure with reproductive organs, and the spathe, a leaf covering the spadix. Upon arrival, they will end up becoming trapped in the bottom of the spathe, the walls too slick to free themselves and boxed in by the overhanging spathe.
Gnat survival is all dependent on one factor: the sex of the flower. In male flowers, the gnats can escape through a small hole at the bottom of the spathe, in which they will carry pollen to female flowers when they escape. In female flowers, however, there is no hole, and gnats will eventually meet their deaths.
Photographs left to right: Jack-in-the-pulpit flower, unripe fruit (credit: Claire O’ Neill), ripe fruit (@vickiebell)
Scientists are still trying to determine the evolutionary benefit of this trap, and until they do, it will remain a mysterious and treacherous journey for fungus gnats in eastern forests. So next time you see a flowering (May-June), or fruiting (July-Semptember) Jack-in-the pulpit appreciate the complexity and mystery of it, take an observation, and consider the fungus gnats.
Sources and further reading:
Suetsugu, K., & Sato, M. (2020). It's a trap! Frontiers in Ecology and the Environment, 18(4), 187. https://doi.org/10.1002/fee.2202
https://www.fs.usda.gov/wildflowers/plant-of-the-week/arisaema_triphyllum.shtml
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Very cool, I had no idea that these plants were so complex!
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