Study On Orchids Diversity In Northern Hainan Island And Pollination Biology Of Dendrobium Loddigesii

Orchidaceae is one of the four major flowering plant families in the world. Because of co-evolution with the pollinators, there is special flower structure in the family. It is the most evoluted and advanced family in the phylogeny of the plant kingdom. The growth and propagation of orchidaceae need special environmental conditions which are more harsh to the family than other plants. There are only a dozen kilometers from our research region (the volcanic lava region Northern Hainan Island) to Haikou city. Because of the impacts of human life, economic activities, and even ingoing of city, orchid plants are dramaticly reducing. Their habitat is destroyed and even lost, and orchidaceae is endangered plant. Therefore, it is urgent to investigate the status of their germplasm resources in order to understand the endangered mechanism of population and explore measurement of germplasm conservation.Based on field experiment, conservation biology and collecting of document, wild orchidaceae germplasm resources, the host and concomitants plants from the Northern Hainan Island are studied in the research. The pollination biology of Dendrobium loddigesii help to understand the endangering mechanism of the family. And the protection measurement and constructive advice for sustainable management are proposed for the orchid plants in the region. The main results and conclusions are summarized as the following:·There are 9 wild orchids genera including 13 species in Northern Hainan Island volcanic lava region. Among them, four kinds occur only in Hainan Island and two kinds are limited distributed in Northern Hainan Island volcanic lava area. The richness of species is low while the endemic distribute species are high, so it is valuable to conservation in the region. Orchid plants belong to tropical flora with a single type. Because of invasion of agriculture, the habite of orchid plants is a macular distribution.·Among the 13 orchids species, ten are epiphytic orchids (76.9%) and three are terrestrial orchids (23.1%) in Northern Hainan Island volcanic lava region. The hosts of epiphytic orchids show a huge diversity. The same species of orchid might choose different genera and even family plants as the host while different orchid plants can also be born of the same species tree and even a tree with the same location. But the same genera is apt to choose the same host. Basalt and fruit trees such as longan, litchi, guava are very important hosts to the orchidaceae. And the plasticity and orientation for the hosts provides an important measurement of artificial cultivation.·The human life and economic activities such as reclamation orchards, fruit tree species turnover, man-made felling, development and construction, mining volcanoes, and alien species invasion led to reduction of habitats, hosts and the associated species with orchids.·Under natural condition, there is only a 0.48% fruit setting in the species.Even with hand pollination, there is still a low fruit setting. The long time drought may be the main reason. Another reason is rare the pollinator. In our field observation, self- pollination is approved to affinity.·Ctenoplecta florisomnis, a species of Apoidea is the sole pollinator for the D. loddigesii. The morphology correspondence between the D. loddigesii and C. florisomnis is the power proof co-evolution of the pollinator and plant.The relationship between the dynamics of looking for food in the pollinators and flower character such as structure, colour, scent and honeydew is an important ligament of pollination biology research. According to the behavior of the pollinator, there is not sex deceptive. Tenoplecta most of them collect floral oil only for food, but the influence of potpourri , colour to the action of pollinator deserves further research. Well-prepared field works and elaborate experiment plans will help to understand the natural pollination mechanism and mating system. In conclusion, the human life, economic activities and alien species invasion led to reduction of habitats, hosts and the associated species with orchids, accelerate the decreasing speed of the arethusa which its habitat have been fragmented already. The rare pollinator lead to low fruit setting under natural condition. Therefore, the destroyed habitats and rare pollinators are the inhibition for the develop and propagate of the orchidaceae in Northern Hainan Island, and even lead it to be endangered.