Abstract:

Background and Aims Orchidaceae is one of the largest families of flowering plants, and China is one of its most important centers of diversity, with 171 genera and about 1 247 species. Wild species of this family are considered as a key group for plant conservation. Because we cannot preserve all biota in all areas of distribution, conservation priorities must be set and a minimum number of distribution areas needed to preserve the greatest amount of biodiversity possible must be evaluated. Hainan Island is considered as a typical area in China with a high diversity of wild orchids. Previous studies on Hainan Island have focused on investigations of wild orchid resources, but little information is available on their conservation. Analyses of species diversity and endemism patterns provide vital information for conservation planning. Our goal was to determine priority areas with a diverse wild orchid flora and the minimum number of distribution units needed to protect all wild orchid species on Hainan Island.

Methods The 19 administrative counties of Hainan province were treated as the distribution units. Using data on the distribution of the species obtained from the literature and herbarium specimens, we constructed a presence/absence matrix of 202 wild orchids recorded on Hainan Island. Parsimony analysis of endemicity (PAE) was used to identify hotspots of total diversity and endemism at the distribution unit level, and complementarity analyses were applied to show how the target set of species can be conserved with a minimum number of distribution units.

Key Results The database consisted of 1 182 records in the 19 distribution units. Based on this distribution matrix, the analysis generated 424 equally parsimonious trees, from which a strict consensus cladogram was obtained. According to the floristic similarities among the 19 distribution units based on 202 species of wild orchids, two areas were suggested as priorities: one located in southern Hainan Island, represented by Baoting, Sanya, Lingshui and Qiongzhong, and another in the southwest, represented by Changjiang and Ledong. Bootstrap values were 79% and 69%, respectively. Similar results were obtained by parsimony analysis of endemicity. Units with the most floristic similarities of endemisms were Baoting, Lingshui, Ledong, Sanya, Qiongzhong and Changjiang, but the bootstrap values were low, less than 50%. Complementarity analysis showed that at least ten distribution units are required to protect all wild orchid species; listed in descending order of cumulative numbers, they are Baoting, Sanya, Wuzhishan, Lingshui, Baisha, Ledong, Qiongzhong, Dongfang, Changjiang and Qiongshan. Six are needed to protect 30 endemic species: Lingshui, Baoting, Qiongzhong, Ledong, Sanya and Wuzhishan. These six are included in the ten needed to preserve all wild orchid species. The main difference is the hierarchical arrangement of the units. These results indicated that, at least at distribution unit level, the units important to protect all wild orchid species are also important to preserve the endemic species.

Conclusions An assumption of both parsimony and complementarity analyses is complete knowledge of the distribution of each species in a region, but this is unlikely for wild orchids on Hainan Island. Another problem with our study is that we chose the administrative counties of Hainan Island as the distribution units rather than units based on biogeographic criteria. Despite these limitations, our study provided a baseline set of protected areas for the conservation of wild orchid diversity on Hainan Island that can be supplemented to meet other conservation and socio-economic needs and objectives.

Key words: Parsimony analysis of endemicity, Complementarity analysis, Minimum number of distribution units, Priority areas, Biodiversity, Conservation