ALLOZYME VARIABILITY WITHIN AND AMONG POPULATIONS OF THE EPIPHYTIC MOSS LEUCODON (LEUCODONTACEAE, MUSCI)

Enzyme electrophoresis was used to estimate genetic variability within and among populations of five species of the genus Leucodon (L. atrovirens, L. luteus, L. nipponicus, L. sapporensis, and L. temperatus). All of these perennial, dioecious plants are epiphytic on tree trunks and produce numerous spores that are released in winter. Gene diversity within populations (H-S) was low (0.070) in L. nipponicus, which grows in disturbed habitats, and high (0.169-0.202) in the other four species, which inhabit stable environments. Gene diversity between populations relative to total diversity (G(ST)) was low in L. temperatus (0.042) and L. luteus (0.043), suggesting that extensive gene flow occurs among populations. G(ST) was moderate in L. sapporensis (0.104) and L. atrovirens (0.114); these values are still less than those previously reported for terrestrial mosses. Since epiphytes could disperse their spores effectively by the wind, low genetic divergence among populations may be related to the epiphytic habit of the species. On the other hand, high G(ST) value (0.208) was found in L. nipponicus. It is probably explained by the genetic differentiation of populations by genetic drift, for the species forms geographically and ecologically isolated populations with small number of individuals. We also observed incongruity between morphological and genetic similarity among species.