By land and by tree: Pollinator taxa diversity of terrestrial and epiphytic orchids

There are approximately 30,000 species in the family Orchidaceae, with some species growing terrestrially and others growing as epiphytes. Though the pollination biology of many of these species is not well known, there has been a diversity of taxa recorded as orchid pollinators. Insects, birds, and even a record of a mammal species have been documented as successful pollinators, while some orchids are able to reproduce without the use of a pollen vector. The goal of this review is to provide an overview of orchid pollination tactics, with references to more specific studies of each, and to analyze a large subset of publications to determine differences in pollinator taxa and specificity between epiphytic and terrestrial orchid genera. This review examines pollination data from over 400 orchid species, including 74 epiphytic and 83 terrestrial orchid genera. Two pollinator taxa, Coleoptera and Hymenoptera (Class: Insecta), were found to pollinate significantly more terrestrial than epiphytic orchid genera, while other taxa showed no significant differences. Hymenoptera were the dominant taxa of pollinator in regards to the overall number of species recorded; however, based on species interaction webs that were built, the Lepidoptera (Class: Insecta) have stronger interactions with the orchid species they pollinate, suggesting a more specific relationship between the two.