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

In the annual species, Crepis sancta (L.) Bornm., peripheral and central florets of the capitulum yield achenes that differ in mass, colour, morphology, and in the presence-absence of pappus. To examine the consequences of seed dimorphism on dispersal in time in this species, I compared the viability of central and peripheral achenes stored for up to 5 years. Both the germination 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 independent experiments showed that peripheral achenes have reduced dispersal ability, whereas the pappus unit of central achenes confers greater dispersal ability. These differences between achene types may explain the persistence of this colonizing species in communities dominated by perennial species, which is a major ecological feature of C. sancta.