Pollen movement in a natural population of Arisaema serratum (Araceae), a plant with a pitfall-trap flower pollination system.

Arisaema serratum possesses a pitfall-trap flower pollination system. However, little is known about the efficiency and pattern of pollen movement in A. serratum. Thus, the aims of this study are to (1) determine the paternal parents of the seeds and (2) elucidate pollen movement in a natural population. Paternity analysis using microsatellite markers was performed. Seeds were collected from a natural population of A. serratum in 2001 at Horigane, Japan. Small midges became trapped in female spathe tubes during the flowering period. We found that (1) seeds in a fruit were fertilized by multiple sires; (2) seeds sired by a paternal parent were either clumped, exclusively, or randomly distributed on the spadix, depending on the parent; (3) to a great extent, a few males contributed as sires; (4) distance from a female was not a factor in the inequality of reproductive success among males; (5) male reproductive success was not correlated with its size. We conclude that pollen carryover and the trap-flower pollination system are likely to result in multiple paternity and inequality in male success.