European Journal of Entomology

It is speculated that the wasps that attack the seeds of gymnosperm trees (conifers) before they are fertilized can induce unfertilized seeds to accumulate storage material whereas those that attack after the seeds are fertilized selectively oviposit in fertilized seeds. Moreover, in the case of the wasps that oviposit after fertilization of seed, the presence of unfertilized seeds and seedless fruit may increase plant fitness via reduced parasitism of the viable seed. To determine the relationship between the two strategies, host manipulation or selective oviposition, and the time of fertilization of the seeds of angiosperm host plants, fertilized seed of Ilex integra Thunb. was dissected out of berries either immediately after the flight of the seed wasp Macrodasyceras hirsutum Kamijo in the field or the death of adults in the laboratory. The wasps oviposited mostly in fertilized seeds and rarely in unfertilized seeds. Unfertilized seeds, produced by flowers enclosed in pollen exclusion bags, and then exposed to wasps did not contain immature wasps or storage material, which indicates that the wasp did not oviposit in unfertilized seeds. These results support the above mentioned hypothesis and indicate that the substantial proportion of seedless berries do not function as an egg sink.

Address
Laboratory of Forest Zoology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan; e-mail: takagi@fr.a.u-tokyo.ac.jp

Keywords
Selective oviposition, Macrodasyceras hirsutum, Hymenoptera, Torymidae, seed parasitoid wasp, seed predation, Ilex integra, seed fertilization, GLMM