Orchids are found in almost all terrestrial ecosystems except polar and extremely arid desert regions and are the "flagship" group in plant conservation. However, the conservation of orchids is impeded by a lack of biodiversity surveys. To date, systematic analysis of orchids along elevation gradients and their relationships with host trees has never been reported. 

In a study published in Global Ecology and Conservation, researchers from the Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences and their collaborators present the first systematic analysis of the diversity and distribution patterns of orchids along elevation gradients on Mount Victoria, Myanmar. 

The researchers investigated the species richness, abundance, and environmental conditions of epiphytic and terrestrial orchids along an elevation gradient (600-3,000 m) on Mt. Victoria, the third-highest mountain and a famous eco-tourism site in Myanmar. The researchers then structured a binary species-based network between epiphytic orchids and their hosts to further address the effect of hosts on orchid distribution. 

They recorded 94 orchid species on Mt. Victoria, including 58 epiphytic and 36 terrestrial orchids. Species richness of epiphytic orchids showed a hump-shaped pattern (peaking at about 2,200 m), while terrestrial orchids showed a monotonic decreasing trend with increasing elevation. Both elevation and slope significantly influenced the species composition and diversity of epiphytic and terrestrial orchids, while terrestrial orchids were also influenced by herb coverage. 

Furthermore, the network between epiphytic orchids and their hosts showed low connectivity and significant nestedness, with high levels of modularity and specialization. Network interactions were heterogeneously distributed among hosts. Four tree species hosted abundant orchid species and thus played a critical role in maintaining the orchid diversity. 

In addition, 20 orchid species were associated with specific host species, indicating a high risk of extinction under disturbance. 

"Effective forest management and conservation in Mt. Victoria should focus on tree species. Protecting suitable habitat, i.e., the large-sized host trees and the unspoiled forests in which they can survive, is the most important measure to conserve the endemic species," said SONG Liang of XTBG. 

Mt. Victoria, Myanmar. (Image by LIU Qiang)  

Vegetation type of Mt. Victoria at the elevation of 2,200 m. (Image by LIU Qiang)