Reproductive biology and pollen flow of a rheophytic aroid, Furtadoa sumatrensis (Araceae) in the Malesian wet tropics

 A rheophytic aroid, Furtadoa sumatrensis M. Hotta, showed protogynous flowering behaviour, which reduced autogamous pollination within the spadix and promoted outcrossing among spadices by Colocasiomyia sp. (Diptera, Drosophilidae). Self-compatibility of this species allowed geitonogamous crossing between genetically homogeneous spadices from the same individual. Chemical dyes as pollen analogues were carried by Colocasiomyia flies bidirectionally along the forest stream habitat, and their movements were significantly affected by the density of mature spadices in a population. This correlation was consistent among populations. In a population with higher density, the dye's movements were restricted to a smaller distance logarithmically. Estimated neighborhood size (N _e ) and area (A) showed positive and negative correlation with density, respectively. The range of pollen flow was estimated at most within a river system. Received March 7, 2000 Accepted January 23, 2001