Non-congruence among hotspots based on three common diversity measures in Yunnan, south-west China

Abstract

Background: Yunnan is one of the richest regions of the world in terms of plant diversity. As a result of increasing pressure from land use, it is in need of identifying priority areas for conservation. Aim: In this study, we aimed to identify hotspots for plant conservation based on different measures of diversity and to establish the degree of spatial congruence among the different measures of diversity. Methods: We compiled checklists of overall species richness, threatened species and plants endemic to Yunnan with the help of literature and experts. The values of these three measures were grid mapped and the highest 2.5% of all cells with respect to each of the three plant diversity measures were designated as hotspot cells. The grid maps were overlapped to examine the spatial congruence of three different types of hotspots. Diversity measures were related to climatic and geographical factors. Finally, a gap analysis was carried out to examine the relationship between the location of existing nature reserves and the identified hotspots. Results: The hotspots of endemic plants and those of overall species richness were mostly concentrated in north-west Yunnan, whereas those of threatened plants were mainly observed in south Yunnan. No congruence was observed across the three types of hotspots of plant diversity at the top 2.5% cut-off level. With the relaxation of the cut-off level, an increasing trend of congruence could be observed, indicated by a strong correlation between measures of diversity. No strong relationship was found between climatic and geographical factors, and values of diversity measures. The gap analysis showed that there were some nature reserves located within or in the proximity of each identified hotspot. Conclusions: We suggest that non-congruence across different types of hotspots highlights the importance of cut-off levels for hotspot selection for congruence across different types of hotspots. Different mechanisms may be responsible for the spatial patterns of species diversity of total richness, endemic plants, threatened plants and the hotspots of the three diversity measures. Climatic and geographical factors cannot satisfactorily explain spatial patterns of plant diversity over the whole study area because controlling factors differ in geographical dimensions. Conservation strategy should also be different for different parts of Yunnan. In north-west Yunnan (hotspots of overall richness and endemism), attention needs to be focused on the protection and maintenance of diverse habitats, whereas in south Yunnan (hotspots of threatened plants) conservation strategies should concentrate on the restoration of habitats and off-site conservation.