DISPERSAL ECOLOGY OF NUPHAR-LUTEUM (L) SIBTHORP AND SMITH - ABIOTIC SEED DISPERSAL MECHANISMS

Nuphar luteum (Nymphaceae) is a water lily indigenous to the glacial l akes of the Rocky Mountains of the western United States. The seeds ar e negatively buoyant, but are dispersed across the water surface in tw o different manners: (1) within the floating fruits, and (2) within a buoyant, but water-soluble matrix that surrounds the seeds. Seed dispe rsal via fruits results in a clumped distribution, while seed dispersa l mediated by the buoyant matrix results in scattered seed distributio ns. Experimental release of tagged fruits and seeds in nature show tha t fruit and seeds can travel up to 80 m/h on the water surface. Althou gh seeds only neat for about 72 h, this is adequate time for dispersal , especially in small glacial lakes that are connected via streams. By comparing historical lake-specific population distributions of N. lut eum using aerial photographs taken over a 36 year period we found litt le change in the overall intralake distribution of each population. We believe these historical patterns to be related to the mechanisms of fruit and seed dispersal. (C) 1995 The Linnean Society of London