Parallelism in secondary loss of sex from a heterogonic life cycle on different host plants in the Andricus mukaigawae complex (Hymenoptera: Cynipidae), with taxonomic notes

The Andricus mukaigawae complex consists of bivoltine heterogonic ( = cyclically parthenogenetic) and univoltine thelytokous (parthenogenetic) populations. The bivoltine heterogonic populations are divided into A. mukaigawae (2n = 12), which produces bur-shaped unisexual galls (producing only asexual females) on Quercus aliena, Q. mongolica, and Q. serrata; and A. kashiwaphilus (2n = 10), which produces flower-shaped unisexual galls on Q. dentata. The univoltine thelytokous populations have to date been treated as one species, A. targionii (s. lat.), but the population on Q. aliena produces bur-shaped galls and that on Q. dentata produces flower-shaped galls. I investigated the karyotype of the population of A. targionii (s. lat.) on Q. dentata. This population had the same karyotype as that of A. kashiwaphilus. The karyotype and shape of galls indicate that A. targionii (s. lat.) on Q. dentata is derived from A. kashiwaphilus, and that on Q. aliena is derived from A. mukaigawae through the parallel deletion of the bisexual (sexually reproducing) generation on different host plants. Since A. targionii (s. lat.) is thus shown to be polyphyletic, the name A. targionii (s. str.) should be applied to the univoltine thelytokous population on Q. aliena, and the univoltine thelytokous population on Q. dentata should be identified as A. pseudoflos comb. n., judging from the original descriptions.