Cost of reproduction in Viscaria vulgaris (Caryophyllaceae): a field experiment [Lychnis viscaria]

An increase in reproductive effort is often associated with a cost which may affect future reproductive success. I analysed cost of reproduction in Viscaria vulgaris plants where either a) all flowers were hand-pollinated with an excessive number of conspecific pollen grains to increase cost of reproduction, or b) the flower number of inflorescences was reduced to decrease cost of reproduction, or c) plants were unmanipulated, thus acting as naturally pollinated controls. In 1990, the same plants were not manipulated but surveyed for the same traits as in 1989 and in addition, for the number of inflorescences produced. A random sample of untreated plants was also analyzed for ovule number and fruit set. The position of analyzed flowers within the inflorescence was always noted. Number of seeds per capsule, seed set, and seed weight were all affected by experimental treatment, but these differences did not occur during the following year when no experiment was performed. Hand pollination increased seed number and seed set over that of the reduction treatment and control. Plants with reduced flowers had significantly heavier seeds than control plants, hand-pollinated plants had the lightest seeds. During both years, position within the inflorescence affected flower number, fruit set, ovule number, seed number, and seed set. Individual flowers of Viscaria vulgaris are temporarily pollen limited, but high reproductive effort does not influence the following years' performance. It regulates flower production, ovule development, seed set, and seed size, probably in response to current available resources.