Third-Party Parasitism

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Science  04 Apr 2008:
Vol. 320, Issue 5872, pp. 21
DOI: 10.1126/science.320.5872.21a

For more than 50 million years, Agaonidae wasps have laid their eggs in the ovules of the enclosed flowers, or syconia, of fig trees. The grubs stimulate the formation of a small gall and feed on the plant's tissue. The payback for the loss of reproductive power to the fig tree occurs when the young wasps emerge and carry their host's pollen to other trees. Fortunately for the trees, wasps don't lay eggs in every ovule in a syconium, even though in evolutionary terms this might seem a good strategy for the wasp; rather than being deterred by the tree itself, the fig wasps are in fact preyed on by another wasp. The parasitoid's ovipositor is just long enough to penetrate the wall of the fig and reaches only the outermost ovules. Dunn et al. show that thanks to the packing architecture of the ovules within the syconium, the fig wasps predominantly use inner ovules that are out of range of the parasitoid, allowing the other ovules to mature into fig seeds and thereby stabilizing this mutualism. — CA

PLoS Biol. 6, e59 (2008).

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