Effects of grazing disturbance on the reproduction of a perennial herb, Cypella herbertii (Lindl.) Herb. (Iridaceae)

A recent study in a natural grassland in Argentina revealed that grazing strongly reduced the available pollinators for a population of Cypella herbertii. Comparing grazed and fenced areas (exclosures) we tested the hypothesis that self-incompatibility would be selected against in a pollinator-poor environment leading to changes in breeding system. No differences in breeding system were found between populations from inside and outside exclosures. However, we detected: (i) C. herbertii clearly exhibits a mixed-mating system but has a remarkably low spontaneous fruit formation; (ii) this species though highly self-compatible expresses a significant decay at seed set stage when self-pollinated. We conclude that grazing impact on pollinators together with C. herbertiis high dependence on pollinators should be considered when assessing the risk of extinction of this species.