Sexual Dimorphism of Dormancy and Survivorship in Buried Seeds of Silene Latifolia

Abstract

1 To test for differences in survivorship between buried male and female seeds in the dioecious perennial, Silene latifolia (Caryophyllaceae), the behaviour of large numbers of seeds buried under field conditions and unearthed after 5 and 10 months was compared with unburied seeds. 2 After 5 months of burial there was significant mortality of seeds and a large fraction of the remaining seeds displayed induced dormancy, i.e. they did not germinate under glasshouse conditions. The sex ratio of germinating seeds was not significantly different from the sex ratio of seeds germinated without burial (0 months). 3 Seed survivorship was constant from 5 to 10 months. However, by 10 months levels of dormancy had decreased so that most seeds germinated when unearthed and tested in a growth chamber. Furthermore, the proportion of females in germinating seed was significantly higher after 10 months than after 5 months. 4 Sex differences in mortality were therefore only revealed after 10 months, when dormancy had been broken. This result suggests that female seeds were more likely to become dormant during the first 5 months of burial, whereas males suffered greater mortality. Thus, sex differences in both survivorship and dormancy of buried seeds affected the sex ratio of germinating seeds over time. Such sexual dimorphism in seed bank dynamics may have an important effect on sex ratio variation in natural populations of dioecious plants.