What are the main causes of mortality and how do they differ along the altitudinal gradient?
The species Silene ciliata Poiret grows in cushions of up to 2 cm in height and 15 cm in diameter. The flowering period begins in late June and lasts about 8 weeks. Flowering stems reach 15 cm in height and bear 1 5 protandrous flowers (Giménez-Benavides et al., 2006). Hand-crossing pollination experiments indicate that S. ciliata is a self-compatible species (Giménez-Benavides, 2006). Mean flower number per plant in the study area ranges from 4·5 to 13·7 across populations, whereas mean fruit set in the studied populations is 0·32 ± 0·34. Fruit capsules contain up to 100 viable seeds of 1·53 ± 0·49 mm in diameter and 0·59 ± 0·06 mg in weight. Mean seed set is 0·24 ± 0·19 (Giménez-Benavides et al., 2006). These capsules open at the top when ripe, and seeds are soon dispersed by stalk vibration. Seed collection and description of the sowing sites Three populations were selected along the local altitudinal gradient in Sierra de Guadarrama (Madrid, Spain, 40°N, 3°W). Silene ciliata popula
