Three new species of Synergini wasps from same gall on Lithocarpus glaber (Thunb.) in Hunan, China (Hymenoptera, Cynipidae)

Three new species of the tribe Synergini (Hymenoptera, Cynipidae), i.e., Lithosaphonecrus arcoverticus Liu, Zhu et Pang, sp. n. Lithosaphonecrus decarinatus Liu, Zhu et Pang, sp. n. and Saphonecrus emarginatus Liu, Zhu et Pang, sp. n. are described from Hunan, China. The three species have emerged from the same galls collected on Lithocarpus glaber (Thunb.) in December, June, and April, respectively. Phylogenetic reconstruction of Synergini based on mtDNA COI and rRNA 28S D2 genes resolved two independent monophyletic clades exclusively associated with Lithocarpus plant hosts, i.e., the genus Lithosaphonecus and the lithocarpii species complex of Saphonecrus. The three species each have a sister relationship with a congener in Taiwan, an island off the southeastern coast of continental China. This recurrent disjunct distribution and relatively low COI sequence variation between the sister species in each species pair are considered attributable to the formation of the Taiwan Strait in Holocene ca 10,000 years ago. We also discussed the possible speciation mechanism for Lithosaphonecrus due to seasonality and topography in subtropical China. Finally, we addressed the need for conservation consideration in urbanization planning.