The New Zealand orchid flora comprises 25 genera and over 100 species. Most of the species are terrestrial and are found throughout the country. Terrestrial orchids are the most threatened group within the family. We studied the pollination ecology of four terrestrial orchids: Gastrodia cunninghamii, Thelymitra longifolia, Pterostylis a lobule, and P. patens. Reproduction of these orchids relies on contrasting reproductive strategies. Thelymitra longifolia is predominantly self-pollinated, whereas both Pterostylis species are cross-pollinated and have an absolute dependence on pollinators. Hand-pollination treatments showed T. longifolia, P. alobula, and P. patens to be self-compatible. Results for G. cunninghamii were unclear and need further study. Insect flower visitation is uncommon in these species and was observed only in G. cunninghamii and P. alobula. Aphids were usually found inside the flowers of G. cunninghamii, but the role they may have as pollinators is undetermined. In P. a lobule, male fungus gnats of Zygomyia (Mycetophilidae: Diptera) were considered pollinators. Hypotheses on the attraction system(s) used by these greenhood orchids are discussed. These two species are more likely to be affected by disruption of the plant-pollinator mutualism because of the specialist nature of the plant-pollinator interaction.
