The effects of achene dimorphism on the dispersal in time and space in Crepis sancta (Asteraceae)

In the annual species, Crepis sancta (L.) Bornm., peripheral and central fl orets of the capitulum yield achenes that differ in mass, colour, morpholog y, and in the presence-absence of pappus. To examine the consequences of se ed dimorphism on dispersal In time in this species, I compared the viabilit y of central and peripheral achenes stored for up to 5 years. Both the germ ination percentage and the early seedling survival of both morphs decreased progressively with duration of storage. However, the loss in viability was lower for peripheral achenes than for central ones. Furthermore, two indep endent experiments showed that peripheral achenes have reduced dispersal ab ility, whereas the pappus unit of central achenes confers greater dispersal ability. These differences between achene types may explain the persistenc e of this colonizing species in communities dominated by perennial species, which is a major ecological feature of C. sancta.