Introduction

Plants on tropical and subtropical islands are not only speciation paradigms but are well known because many of them are on the verge of extinction (Whittaker & Fernández-Palacios, 2007). About one in six vascular plant species grows on oceanic islands, and one in three of all endangered plants is an insular endemic (World Conservation Monitoring Centre, 1992). One of the most extraordinary features of islands is that they harbor a high number of endemics within a very small area (Kruckeberg & Rabinowitz, 1985). It is, therefore, not surprising that 10 of the 34 biodiversity hotspots are islands (Mittermeier et al., 2004).

Despite their biological importance and conservation priority, there is an urgent need for floristic inventories of islands (Campbell & Hammond, 1989). Major insular systems from the tropics, such as the Caribbean Islands, Philippines, Madagascar, and Indonesia do not have recent comprehensive floras, or even checklists of their endemic species. We are aware that developing comprehensive floras for these islands can be a Herculean task requiring massive resources. However we argue, that by preparing checklists of insular endemics we are paving the way for more extensive floristic studies and practical conservation investments. Checklists can help in establishing conservation actions and priorities and provide a framework for additional floristic surveys and treatments. More importantly, checklists of endemics can be instrumental in increasing conservation awareness among those directly involved in the management of plant biodiversity on these islands and can provide educational and research tools for environmental biologists and educators.

In this study, we compiled a checklist of endemic seed plants from Hainan Island. In a separate paper in this issue of Botanical Review (Francisco-Ortega et al., in press) we discuss the patterns of endemism on Hainan. Hainan is the second largest island of China and represents the most important insular element in the Indo-Burma Biodiversity Hotspot. The island has the most extensive and best preserved tropical forests in China and therefore is a major priority for conservation (Deng et al., 2008; Zang & Ding, 2009).

We prepared an initial list of seed plants endemic to Hainan based on the checklist developed for the indigenous flora of the island by Wu et al. (1994) (see Francisco-Ortega et al. (In press) for a more extensive discussion of the history of floristic accounts for Hainan). Consequently we updated the initial list by using several bibliographic/taxonomic data base resources, including the Catalogue of Life, China (The Biodiversity Committee of the Chinese Academy of Sciences, 2008), the Kew Bibliographic Database (Royal Botanic Gardens – Kew, 2009), the International Plant Name Index (IPNI, 2009), the ISI Web of Knowledge (Thomson Reuters, 2009), the World Checklist of Selected Plant Families (World Checklist of Selected Plant Families, 2009), and the International Legume Database & Information Service (ILDIS, 2009). We also consulted relevant taxonomic treatments and available volumes of the Flora of China, including unpublished family drafts posted on the Flora of China website (Flora of China, 2009). Additionally, we circulated early drafts of the final checklist among plant taxonomists who are actively working with Chinese plants (see acknowledgement section below). The resulting checklist of seed plants endemic to Hainan is presented in Appendix 1. The checklist also contains information concerning conservation status, the occurrence of Hainan endemics in four protected areas, and available molecular phylogenies. We found that many of the species regarded as endemic to Hainan by Wu et al. (1994) also occur on the mainland or have since then been merged with other, more widespread taxa. An additional checklist of the species that were until recently thought to be endemic to Hainan, but are no longer considered to be, and the reason for their exclusion, is presented in Appendix 2. Among those species previously thought to be endemic, 23 of them are reported to be in Vietnam, but not in mainland China.