Costs of Flower and Fruit Production in Tipularia Discolor (Orchidaceae)

Abstract

The cost of reproduction may be an important constraint on the evolution of life history traits, yet it has seldom been adequately measured in plants. To demonstrate a net cost of reproductive structures one must show that their production has a negative effect on future growth. Using a summer—deciduous orchid, we compared subsequent growth of plants with no inflorescence, no fruits, few fruits (<10), or many fruits (>10). Greater investment in reproduction led to increasingly negative effects on future corm size and leaf area. The cost of an inflorescence without fruits was about one—half the cost of an inflorescence with few fruits. Each fruit cost the plant °2% of its total leaf area the next year. Natural pollination resulted in a mean of seven fruits per plant. Hand—pollination led to a dramatic increase in fruit set (up to 25 fruits per plant), and a large decrease in subsequent growth. Plants with many fruits were less likely to propagate vegetatively than those with few fruits. Also, plants with many fruits were less likely to flower the following year, probably because they were smaller than those with few fruits. The potential benefits of greater pollinator visitation are unclear because larger "clutch size" may not result in greater lifetime fecundity.