Prediction of Potential Suitable Habitat of Dendrobium sinense, an Endemic Orchid Species in Hainan Tropical Rainforest

Abstract:

To explore the potential suitable distribution range of Dendrobium sinense, its current and future suitable habitat based on the distribution data of 25 field surveys, with climate variables and topographic variables as environmental predictors were predicted by using GIS technology and MaxEnt model. The results showed that the potential suitable habitat area of D. sinense in Hainan Island was approximately 403.4 km², accounting for 1.1% of the total area of Hainan Island. It was mainly distributed in the jurisdiction of Bawangling Branch, Yinggeling Branch, Jianfengling Branch, Diaoluoshan Branch and Wuzhishan Branch of Hainan Tropical Rainforest National Park, with scattered distribution in the jurisdiction of Limushan Branch, the southern part of Wuzhishan City, Qiongzhong County, Wanning City, Baoting County, and Sanya City. The suitable distribution area of D. sinense was extremely narrow, and the suitable habitat was patchy, showing more serious fragmentation. Altitude, coefficient of variation of precipitation seasonality, precipitation in the wettest quarter and maximum temperature in the warmest month were the main environment factors affecting the population distribution pattern of D. sinense. The most suitable habitat for D. sinense was at an altitude of 1 070-1 600 m, with the coefficient of variation of precipitation seasonality of 0.80-0.88, precipitation in the wettest quarter of 1 700-2 266 mm, and the maximum temperature of 18 ℃-25 ℃ in the warmest month. Compared with the current, the potential suitable habitat under RCP4.5 and RCP8.5 climate scenarios of D. sinense decreased by 19.1% and 19.5% in 2050, and 19.7% and 19.8% in 2070, respectively. From three evaluation indexes (AUC=0.997±0.003, Kappa coefficient= 0.990±0.03, TSS=0.990±0.03), the prediction model had good prediction ability. At present, Dendrobium sinense populations are mainly distributed in Hainan Tropical Rainforest National Park, so it is necessary to strengthen in situ conservation and epiphytic host tree protection. There are large areas of highly suitable habitat in the northeast and south of Mihouling, as well as south of Yinggeling, making them as focus region for investigating unknown D. sinense populations.