Differentiation of spring emerging and autumn emerging ecotypes in Galium spurium L. var. echinospermon.

Ecotypes of Galium spurium L. var. echinospermon with distinct germination phenologies were found to occur in two adjacent plots of a grassland nature reserve with different management histories: a spring-germinating population is present in a winter-burnt plot, and an autumn-germinating type in an unburnt plot. These ecotypes share common flowering and fruiting phenologies, and disperse their seeds in early summer. Markedly contrasting thermal dormancy/germination characteristics were demonstrated for their seeds in systematic laboratory tests performed after several types of seed storage including storage in the field. The primary dormancy of seeds of the spring germinator was removed by moist-chilling or field winter-chilling, while that of the autumn germinator was removed by moist storage at 25°C or field summer temperatures. Biseasonal seedling emergence of the species appears to be due to a local differentiation of distinct ecotypes.