Taxonomic Study of the Chalcidoid Wasps Sycoscapter Saunders (Hymenoptera: Pteromalidae) Associated with Monoecious Ficus in Taiwan, with Description of Four New Species.

As a prominent group of nonpollinating fig wasps widely distributed in the paleotropics, Sycoscapter Saunders has been subject to limited taxonomic attention. This study presents the first comprehensive taxonomic investigation of Sycoscapter wasps associated with five Taiwanese monoecious fig species, employing both molecular and morphological methods. Phylogenetic analyses using COI and COI+28S data revealed the presence of five species associated with monoecious figs in Taiwan and neighboring regions: Sycoscapter gajimaru (Ishii), Sycoscapter piceoscapus Chou & Tzeng sp. nov., Sycoscapter monticola Chou & Tzeng sp. nov., Sycoscapter ishiianus Chou & Tzeng sp. nov., and Sycoscapter littoralis Chou & Tzeng sp. nov. Morphologically, these five Sycoscapter species possessed distinctive characteristics, including the male head shape, which distinguished them from related species. Furthermore, males of all five species exhibited rudimentary wing vestiges, commonly found in wasps associated with monoecious figs but absent in those associated with dioecious figs. Overall, this study enriches our understanding of chalcidoid fauna in Taiwan and provides insight into the mechanisms that sustain intricate ecosystems.