The avoidance of self-interference in the Tuscan endemic spring geophyte Crocus etruscus Parl. (Iridaceae)

Spatial separation between sexes within hermaphrodite flowers (herkogamy) is widespread among angiosperms and is traditionally viewed as an adaptation that reduces the likelihood of self-pollination. While different degrees of herkogamy have been reported for Crocus, the relationship between sexual organ positions and reproductive fitness has not been explored yet, and studies of the breeding system within natural populations remain scarce within the genus. We analyzed the effects of different breeding systems (spontaneous self-pollination, facilitated self-pollination and cross-pollination) and of herkogamy degree on female reproductive success of the Tuscan endemic Crocus etruscus. Results showed that C. etruscus is monomorphic for style length and self-incompatible (SCI = 0.29). We also detected a significant negative effect of herkogamy on seed set of open-pollinated flowers. Thus, we conclude that the species avoids self-fertilization by self-incompatibility, but interestingly shows also a certain degree of spatial separation of male and female reproductive structures within the same flower. This floral trait could be useful to avoid self-interference thus reducing ovule discounting and pollen loss on its own stigma.