A living fossil Tetrapus fig wasp (Hymenoptera: Agaoninae) developing in extant Neotropical fig species (Moraceae: Ficus, section Pharmacosycea)
It has been assumed that Tetrapus female wasps (Agaonidae s.s.), the pollinators of the figs of the New World, section Pharmacosycea, are mainly characterized by the presence of one mandibular appendange only, and that it is the most ancestral clade of extant Agaonidae s.s., and the males are tetrapodous. The main objective of this work was to study five Tetrapus morphotypes, whose females have two mandibular appendages and the males are hexapodous, their fig host association and phylogenetic position to the family Agaonidae. The question of which group of fig pollinating wasps and associated figs are the sister to the rest of the pollinating agaonids, and figs respectively remain open. I report a group of New World extant Tetrapus morphotypes (Agaonidae: Agaoninae) provisionally assigned to Hexapus subg. nov. in preparation. Currently, Tetrapus appears as the sister taxon to all other fig pollinating taxa. Howeveer, morphologically, ecologically, geographically and historically Hexapus seems to be the ancestral clade of the extant Agaoninae. Hexapus morphotypes develop in fig species of subsection Petenenses (section Pharmacosycea). In the known extant Tetrapus, the females have one mandibular appendage and the males have reduced one or two short-lobe atrophied non-functional midlegs (tetrapodous). Hexapus females have two free mandibular appendages, and the males have five segmented functional mid-legs (hexapodous). Molecularly Hexapus seems to be the ancestral clade of extant Agaoninae; e.g., a Tetrapus sp. of Ficus crassivenosa was placed by other author as the ancestral clade of 101 wasp species, representing 19 worldwide Agaoninae genera, including four Tetrapus species. In Tetrapus sp. of Ficus crassivenosa, the female has two mandibular appendages and the male is hexapodous. The females of T. apopnus and T. delclosi, preserved in Early to mid-Miocene amber from the Dominican Republic, also have two mandibular appendages and the general morphology of extant Hexapus. I suggest that Hexapus stands up as a living fossil and the sister clade of Tetrapus s.s. The presence of extant Hexapus; as well as extant Tetrapus and their fig host species, especially in South America supports a Southern Gondwanaland origin for both of them, but not a trans-Pacific migrating connection with tropical America for section Pharmacosycea (the host of Tetrapus and Hexapus), a long oceanic dispersal, high levels of stem extinction of Tetrapus or Atlantic land connections, as proposed by other authors. However, lastly it has been assumed that figs and their pollinators arose simultaneously in Eurasia during early Tertiary and spread southwards from it. Most of the morphological and molecular studies of the fig biology of Agaoninae and Ficus, did not include Hexapus morphotypes and their fig hosts, and assumed that Tetrapus is the most ancestral clade of the extant fig pollinating wasps.