Differences in Seed Production Between Stellaria media Populations from Different Habitat Types

Abstract

Seed production in several populations of Stellaria media from different types of habitat was examined. Two populations, one from a flower garden and the other from a herring gull colony were compared in detail by growing them at three soil fertility levels under similar conditions in a greenhouse. Three important differences between the two populations independent of soil fertility emerged: the garden plants flowered on average eleven weeks earlier, they produced much smaller seeds, and they produced more seeds per capsule. Other differences were influenced by soil fertility: at high fertility the garden plants produced about 50 per cent more seeds than the gull colony plants, but on a seed weight basis, the gull colony plants were the more productive. However for both populations at high fertility the proportion of shoot biomass allocated to seed production was similar. Some of these differences can be accounted for in terms of conditions occurring in the two habitats, in particular the relative importance of disturbance and competition at the sites.