Ecological aspects of distribution and speciation in Old World tropical ferns

SynopsisThe number of fern species in various countries in the Old World tropics is examined and explanations for very rich and very poor fern floras are given. Borneo and New Guinea are the two richest areas, with an estimated 1000 and 2000 species respectively; the difference in number is probably due to the much greater area of land at high altitudes in the latter. Aspects of geographical and ecological speciation in the genus Grammitis within New Guinea are discussed, and the means by which such speciation may have been promoted are outlined.