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

Seed production in several populations of Stellaria media fromdifferent types of habitat was examined. Two populations, onefrom a flower garden and the other from a herring gull colonywere compared in detail by growing them at three soil fertilitylevels under similar conditions in a greenhouse. Three important differences between the two populations independentof soil fertility emerged: the garden plants flowered on averageeleven weeks earlier, they produced much smaller seeds, andthey produced more seeds per capsule. Other differences were influenced by soil fertility: at highfertility the garden plants produced about 50 per cent moreseeds than the gull colony plants, but on a seed weight basis,the gull colony plants were the more productive. However forboth populations at high fertility the proportion of shoot biomassallocated to seed production was similar. Some of these differences can be accounted for in terms of conditionsoccurring in the two habitats, in particular the relative importanceof disturbance and competition at the sites. Chickweed, Stellaria media (L.) Vill., ecotypic differentiation, time to flowering, seed production, resource allocation