Hainan tree ferns (Cyatheaceae): morphological, ecological and phytogeographical observations

Based on extensive field surveys and studies of numerous herbarium collections, a taxonomic revision on the tree ferns (Cyatheaceae) from Hainan Island, South China is made. Some formerly used diagnostic characters are critically reassessed, while others with taxonomic value are introduced for the first time. As a result, two genera and six species are recognized for the island. Alsophila denticulata is a new record for Hainan. Alsophila gigantea var. polynervata and Cyathea hainanensis are reduced to synonymy. A lectotype is designated for Alsophila podophylla. The habitat and geographical distribution of the Hainan tree ferns are briefly discussed. Their distribution patterns indicate affinities either to the fern flora of Malesia, the eastern Himalayas, or southern Japan.