Abstract: Conyza sumatrensis (Retz.) E. Walker, a member of Asteraceae, is a highly invasive species. However, its reproduction biology remains poorly known. To understand the role of reproductive traits in successful invasion of the species, we studied several traits of its reproductive system: the miniature capitulum and gynomonoecious sexual system, the biology and phenology of capitula and florets, pollen/ovule ratio, the mating system (self-compatibility), flower visitors, physical traits and dispersal potential of achenes, germination potential of achenes from manually pollinated capitula, and the association of these traits with invasiveness. Our study showed that the reproductive traits of autonomous seed production, versatile mating system of self- and cross-pollination, and generalized pollination system might contribute to the species' successful invasive capability. The invasiveness was further enhanced by the high and rapid production of achenes, as well as the high percentage, rapid germination rate and high dispersal capability of achenes. It was concluded that in annual or winter-annual weeds, autonomous seed production contributed significantly to the invasiveness of the species.

Key words: Asteraceae, Conyza sumatrensis, gynomonoecy, invasiveness, mating system, reproduction