Rhododendron diversity patterns and priority conservation areas in China

Aim: To predict Rhododendron diversity patterns and identify Rhododendron hotspots and priority areas for their conservation.

Location: China.

Methods: We predicted the distribution of 212 Rhododendron species by applying a spatially explicit species assemblage modelling (SESAM) framework on a 10 × 10 km grid across China. We evaluated Rhododendron diversity based on species richness, β-diversity and weighted endemism (also known as range-size rarity), and then identified hotspots formed by the top 1%, 5%, 25% and 50% of record-containing grid cells for each diversity metric separately and for the combination of the three diversity metrics. We determined the priority conservation areas for Rhododendrons by overlaying the hotspots with the map of the 2139 nature reserves existing in China, and calculated the percentage of hotspots that is protected. The same analysis was also applied to threatened Rhododendron species.

Results: Rhododendron species richness, β-diversity and weighted endemism decrease within China from the south-west to the north-east, mainly along mountain ranges. In total, 12 general hotspots for Rhododendron species are detected, covering 1.4% of China's land area. Five separately discerned hotspots (i.e. southern Chongqing, south-eastern Tibet, north-western Yunnan, south-western Sichuan and northern Guangdong) comprising threatened Rhododendron species largely overlap (86.3%) with the general hotspots, and form priority areas for conservation. However, the remaining hotspots, especially southern Zhejiang and north-eastern Guizhou, need more protection.

Main conclusions: To the best of our knowledge, this is the first comprehensive study of Rhododendron diversity patterns across the whole of China in terms of species richness, β-diversity and weighted endemism, thereby offering a sound basis for the conservation of Rhododendrons in China. We demonstrate that as much attention should be paid to the small hotspots in south-western and south-eastern China, as to the largest hotspot (i.e. Mt Hengduan), to achieve conservation of Rhododendrons.