REVERSIBLE ANTHER OPENING IN LILIUM PHILADELPHICUM (LILIACEAE): A POSSIBLE MEANS OF ENHANCING MALE FITNESS

Studies of Lilium philadelphicum on Isle Royale National Park, Lake Superior, show that thecae (pollen-containing sacs) of dehisced anthers close in the rain, thus protecting the pollen and prolonging the pollen donor phase of the flower. To our knowledge, this is the first report of anthers with longitudinal dehiscence reclosing after opening. Individual flowers of L. philadelphicum are long lived (8–11 d), do not shorten their flowering period in response to successful fertilization of the ovules, and are primarily pollinated by butterflies. Butterflies do not forage in the rain and may first visit a flower several days after anthesis. Under such circumstances, strong selection may exist to protect pollen during unfavorable weather conditions in order to prolong the pollen donor phase. Flowers with long pollen donor phases are likely to contribute more offspring to the next generation than flowers with short pollen donor phases.