BIOGEOGRAPHY OF FERNS - DISPERSAL AND VICARIANCE

A local fern flora consists of species with a variety of systematic and chorological relationships. Thus the biogeography of a flora is a composite of species-specific biogeographies. However, large-scale environmental changes affect the biogeography of a flora as a whole. The eastern Asian-eastern North American disjunct distribution pattern in some recently revised fern taxa may have arisen by a layering of many climatic and geological events. The fern flora of Seram Island, east Malesia, is most closely related to New Guinea. Together with geological evidence, this suggests that the Seram fern flora originated largely by dispersal from New Guinea. From the systematic relationship of Taenitis, it is assumed that the present distribution pattern of the genus has been primarily caused by westward dispersal with allopatric or parapatric speciation in Malesia. In the cladistic biogeography of Drynarioideae and Pyrrosia both dispersal and vicariance were assumed to have been involved. As molecular approaches have been initiated in the systematics and biogeography of ferns, usefulness of the method is stressed.