The formation and maintenance of the extremely high species diversity of Orchidaceae plants is subject to the interaction of many factors, of which the complex and diverse pollination methods are important factors. The emergence of deceptive pollination such as foodborne deception, sexual deception, and spawning site mimicry, or the coexistence of mimesis and reward, promotes the evolution and adaptation of orchid diversity. In the deceptive pollination of orchids, an important trend in pollination systems is that orchids use tiny diptera insects to pollinate. Small dipterans usually refer to small flylets with a body length of less than 5 mm, including Ceratopogonidae, Chloropidae, and Mycetophilidae. The pollinated orchids of these tiny dipteran insects are concentrated in the neotropical axillary orchid subfamily (Pleurothallidinae) and the Australian diurideae. In the two-tailed orchid family, some species feed on fungi, or micro-small flies or mushrooms that lay eggs on the fungus as pollinators, and in addition, orchids with gill-like markings on the lip flaps may mimic fungi to attract insects. However, most of the species in these taxa lack pollination ecology studies, so the importance of small dipterans in pollination of orchids is underestimated.
Corybas Salisb.) belongs to the Orchidoideae and Diurideae families. The genus is distributed from the Himalayas to Southeast Asia, New Guinea, New Zealand, Australia and some of its islands, all of which belong to about 140 species; There are 6 species in China, which is the northern boundary of the distribution of this genus. The plants of this genus have small flowers, about 1 cm, and have a small distribution and population in the wild; Its flowers resemble mushrooms, are speculated to be mimetic fungi, and pollinate the mushrooms, but due to the extremely small size of the mushroom, about 2-5 mm, the flight trajectory is difficult to capture, the frequency of flower visits is extremely low, and it is currently only seen in the photos of the pollination of the genus by the fungus mosquito taken by Australian orchid enthusiast Rudie H. Kuiter, and the pollination ecology of the genus lacks empirical support, and the hypothesis of the mushroom mimesis fungus is unsolved. Recently, the Wang Hong Special Group of the Kunming Institute of Botany of the Chinese Academy of Sciences carried out field work in the southern section of Gaoligong Mountain, and discovered the new distribution of the genus Corybas geminigibbus in China, and investigated the biconvex orchid and C. c. shanlinshiensis) habitat, flowering period and flower morphology characteristics, and carried out field pollinator observation and breeding system studies.
Typically, fungus gnat insects include at least 6 families (i.e. Sciaridae, Diadocidiidae, Ditomyiidae, Keroplatidae, Bolitophilidae, and Mycetophilidae). The study observed and collected Phthinia sp. of the Mycetophilidae family in the wild. (female 1) and Exechia sp.) (2 females and 1 male), pollinators of biconvex orchid and Shanlinxi orchid, respectively, are the first to be reported in the tropical and subtropical northern hemispheres. Combined with breeding system detection, pollinator sex identification, flower visit behavior and flower odor analysis, studies have shown that both species are inbred affinity, but cannot self-inbrance, relying on mushroom pollination and fruiting. No nectar was found in the orchid pitch, nor was it found that the mosquitoes lay eggs in the flowers, but the possibility of spawning place mimesis or foodborne mimicry (fungal mimic) could not be ruled out. In addition, observations have found that the flowers of the orchid provide temporary shelter for the fungus mosquito, and there is also habitat mimicry. The study suggests that three mimic modes of spawning site mimicry, fungal mimicry and habitat mimicry may coexist, but more in-depth study is needed.
Publications on the pollination and breeding systems of two Corybas species (Diurideae; Orchidaceae) by fungus gnats (Mycetophilidae) in southwestern Yunnan, China, published in BMC Plant Biology. The research work is supported by the Strategic Pilot Science and Technology Special Project of the Chinese Academy of Sciences (Category B), the Special Project of the Basic Resources Survey of the Ministry of Science and Technology, the National Natural Science Foundation of China, the Natural Science Foundation of Yunnan Province and the Yunling Scholars Project of Yunnan Province.
Fig. 1. Biconvex orchid: habitat, flower morphology and pollinators. A, habitat, B, small crisp mushroom distributed in the same domain, C, female mushrooms rest on the middle sepals, D, flower morphology, E, female Femoris mosquitoes carrying pollen clusters.
Fig. 2. Mushrooms and mushrooms in the biconvex orchid colony. A, the fruiting body of the milk bolete liver fungus, B, the secretions on the back of the liver bacteria of the milk boletus, C, the mushroom mosquito and its eggs, D, the mushroom eggs.
Fig. 3.Shanlinxi orchid: habitat, flower characteristics and pollinators. A, habitat, B, flower morphology, C, pollination process, D, female Edophea mosquitoes carry pollen clumps.
Source: Kunming Institute of Botany, Chinese Academy of Sciences