Gnetum is a genus of gymnosperms, the sole genus in the family Gnetaceae within the Gnetophyta. They are tropical evergreen trees, shrubs and lianas. Unlike other gymnosperms, they possess vessel elements in the xylem. Some species have been proposed to have been the first plants to be insect-pollinated as their fossils occur in association with extinct pollinating scorpionflies. Molecular phylogenies based on nuclear and plastid sequences from most of the species indicate hybridization among some of the Southeast Asian species. Fossil-calibrated molecular-clocks suggest that the Gnetum lineages now found in Africa, South America and Southeast Asia are the result of ancient long-distance dispersal across seawater. Their leaves are rich in bioactive compounds such as flavonoids and stilbenes. Of the species studied so far, Gnetum have photosynthetic and transpiration capacities which are considerably lower than those of other seed plants, due to the absence of multiple chloroplast genes essential for photosynthesis, a trait they seem to share with the other living members of Gnetophyta, Ephedra and Welwitschia, as well as conifers. There are over 50 different species of Gnetum. Species There are over 50 different species of Gnetum. Gnetum sect. Gnetum Gnetum subsect. Gnetum - 2 species of trees; Southeast Asia, Pacific Islands Gnetum gnemon - Tibet, Yunnan, Assam, Indochina, Nicobar Islands, Malaysia, Indonesia, Philippines, New Guinea, Melanesia, Micronesia Gnetum costatum - New Guinea, Solomon Islands Gnetum subsect. Micrognemones - 2 species of lianas; tropical west Africa Gnetum africanum - central Africa from Cameroon to Angola Gnetum buchholzianum - central Africa from Nigeria to Zaire Gnetum subsect. Araeognemones - 9 species of lianas; tropical South America and Central America - Ituá Gnetum camporum - Venezuela Gnetum leyboldii - Costa Rica, Panama, Venezuela, Colombia, Ecuador, Peru, Amazonian Brazil Gnetum nodiflorum - Guianas, Venezuela, Colombia, Ecuador, Peru, northwestern Brazil Gnetum paniculatum - Guianas, Venezuela, northwestern Brazil Gnetum schwackeanum - Amazonas State of southern Venezuela, northwestern Brazil Gnetum urens - Guianas, Venezuela, Peru, northwestern Brazil Gnetum venosum - Bolívar State of southern Venezuela, northwestern Brazil Gnetum sect. Scandentia [Gnetum sect. Cylindrostachys] - about 20 species of lianas; southern Asia Gnetum subsect. Stipitati Gnetum arboreum - Luzon in Philippines Gnetum contractum - southern India Gnetum edule - southern India Gnetum gracilipes - Yunnan + Guangxi in China Gnetum latifolium - Assam, much of Southeast Asia, New Guinea, Bismarck Archipelago Gnetum montanum - Himalayas, southern China, northern Indochina Gnetum oblongum - Bangladesh, Myanmar Gnetum pendulum -