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 flowe ring behaviour, which reduced autogamous pollination within the spadix and promoted outcrossing among spadices by Colocasiomyia sp. (Diptera, Drosophi lidae). Self-compatibility of this species allowed geitonogamous crossing b etween genetically homogeneous spadices from the same individual. Chemical dyes as pollen analogues were carried by Colocasiomyia flies bidirectionall y along the forest stream habitat, and their movements were significantly a ffected 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. Est imated neighborhood size (N-e) and area (A) showed positive and negative co rrelation with density, respectively. The range of pollen flow was estimate d at most within a river system.