Germination ecology of the perennial Centaurium somedanum, a specialist species of mountain springs

To improve understanding of how a rare endemic species of Centaur/urn adapts to a specialized ecological niche, we studied the germination ecology of the mountain spring specialist, C. somedanum, a perennial species restricted to an unusual habitat for this genus. We conducted laboratory experiments with fresh seeds collected from two populations for three consecutive years, to investigate: (1) the effect of temperature and light on germination; (2) the existence of seed dormancy; and (3) inter-population and inter-annual variation in germinability. Germination occurred only in the light and at relatively low temperatures (15-22 degrees C) with no differences between constant and alternating regimes, and a significant decrease at high temperatures (25 degrees C and 30 degrees C). We found non-deep simple morphophysiological dormancy and variation in seed germinability depending on the year of seed collection. C. somedanum diverged from the common germination characteristics of the genus in: (1) its germination at lower temperatures, which contrasts with what is generally expected in wetland species but could be adaptive in the spring habitat; and (2) its morphophysiological dormancy, which we report here for the first time in the genus and which could be an adaptation to its mountain habitat.