Spatial variation in seed production among and within sites and within individuals ofThalictrum thalictroides(Ranunculaceae)

摘要

Spatial variation in seed and ovule numbers and percent seed set is described for three populations of the perennial herbThalictrum thalictroides. Total ovule number of an individual was positively correlated with its seed number, but correlations between ovule number and percent seed set were negative or nonsignificant. Ovule and seed numbers, and to some extent percent seed set, varied among flower positions and inflorescences within plants. Within sites, log-normal distributions of total seed number indicate that a few individuals contributed a large number of seeds relative to the rest of the population. At two sites high values of percent seed set suggest that factors that determine ovule number can be at least as critical to variation in seed number as other factors acting later on. Quadrat reproductive means were not correlated from one year to the next, implying that the relative favorability of certain quadrats is not consistent among years. Sites varied in their reproductive means as well as in their frequency distribution of percent seed set, indicating that the importance of initial ovule number to final seed number per plant not only varies among species as is commonly observed but within as well.