Flora of subtropical China: Ancient, rich, and threatened

Abstract

China is one of the richest countries in the world in terms of plant diversity. The estimated number of vascular plant species is about 33,000 (30,000 angiosperms, 250 gymnosperms, and 2,600 pteridophytes). In agreement with this, four of the world biodiversity hotspots are located totally or partially within China. The endemic component of the Chinese flora is considerable: ~240 genera and over 17,000 plant species are probably endemic to China, a substantial part of them being relict elements. Most of these relict taxa belong to lineages that were widely distributed along the Northern Hemisphere at the Miocene but that at present are restricted to small and isolated ranges along the mountains of central and southern China; conspicuous examples include Cathaya argyrophylla, Eucommia ulmoides, Ginkgo biloba, Glyptostrobus pensilis, Metasequoia glyptostroboides, and Taiwania cryptomerioides. Although multiple reasons are responsible for this relict, highly endemic, and rich flora, reduced extinction rates during the late Cenozoic global cooling—thanks to the existence of large refugia—is certainly the main driving factor. Since early 2000s, a growing body of research (including studies aimed to identify centres of endemism, studies on phylogeography/genetic diversity, and ecological niche modelling) has revealed the existence of large refuge areas in China, which were mostly concentrated in the current subtropical region. Instead of a single refugium, the mountains of subtropical China followed a pattern of “refugia-within-refugia” (that is, plant species often had multiple refugia, sometimes even within the same mountain range). Unfortunately, subtropical China, like the rest of the country, is facing enormous threats directly related to the global change and China’s burgeoning economic and population growth (some of the major concentrations of population of China are within the subtropical area, such as the Sichuan Basin, Wuhan’s region and the Yangtze Delta region). At national level, nearly 4,000 plant species have been listed as endangered, and at least 200 taxa having already become extinct since the 1950s. To avoid further losses, a series of conservation measures should be urgently implemented, which may include: increasing the research in any aspect of plant biology, especially for rare and threatened species, expanding the lists of protected plants to all the endangered species of China, improving the eficiency of the already established protected areas, setting up new protected areas in the loristically richest regions (hotspots), ensuring that all endemic and threatened plants are well represented in otanical gardens and germplasm banks, stressing upon enforcement of environmental laws, promoting the sustainable use of wild plant resources, strengthening the environmental awareness and education of Chinese society