Temporal patterns of seed set and decelerating fitness returns on female allocation in Zigadenus paniculatus (Liliaceae), an andromonoecious lily

I describe temporal patterns of seed production in the andromonoecious lily Zigadenus particulatus. Fruit set per flower and seed set per fruit declined through time within plants. Hand pollination experiments showed that this was not due to increasing pollen limitation. Nutrient supplementation had little effect on seed output, but leaf clipping reduced seed production, especially in late‐blooming flowers, and removal of early‐blooming flowers increased seed set by later flowers. Thus, the temporal pattern of seed output was due to declining availability of photosynthates. Plants with larger bulbs produced larger inflorescences, a greater proportion of hermaphrodite flowers, more fruits per hermaphrodite flower, and more seeds per fruit, but lost a greater fraction of their initial bulb mass as a consequence of fruiting. After controlling for the effects of bulb mass, plants with larger inflorescences produced a greater proportion of male flowers, and plants with more hermaphrodite flowers produced fewer fruits per hermaphrodite flower and fewer seeds per fruit. Thus, the female fitness gain curve was decelerating. The temporal decline in seed output provides a partial explanation for the parallel decline in allocation to pistils. However, a complete explanation for the pattern of gamete packaging requires an understanding of factors controlling male, as well as female, fitness.