LAUSR

・Genus Asarum (Aristolochiaceae) shows diverse floral morphology and is hypothesised to be diversified as a result of pollinator mediated selection. Yet most aspects of their reproductive ecology including pollinators remain unclear. This study focuses on A. costatum and A. minamitanianum in Japan, a sister species pair but showing remarkable difference in a calyx lobe length (10-20 mm and 70-180 mm, respectively). The objectives of this study are to reveal multiple aspects of reproductive ecology of the two species and to obtain evolutionary insights into floral organ elongation. ・We adopted combined approaches, including field observations, molecular analyses, and cultivation experiments such as pollinator observation for three years, fine-scale spatial genetic analysis of 769 individuals, paternity analysis based on 566 seeds over four years, and control pollination experiments. ・Both species showed strong spatial genetic structures indicating confined seed dispersal. Pollinator observation revealed that flies and ground-dwelling insects visited flowers of both species, and the pollinator fauna were differentiated between the species. The visitation rate of flies was extremely low, but was more than twice higher in the species with elongated floral appendage. Paternity analysis revealed A. minamitanianum conducted predominantly outcrossing, while A. costatum showed a wide range of selfing rates among fruits. ・The two Asarum species are likely to be adapted to fly pollination in the shady forest understory, where available pollinator fauna is limited. In addition, although its function remains unclear, the elongated calyx lobe of A. minamitanianum could have evolved for effective pollen dispersal by attracting flies.