Many Flowers but few Fruits: Pollinator and Pollen Limitation in the Early-Spring Flowering Cold Desert Perennial Iris tenuifolia

Abstract

Most flowers of plants did not develop into fruits due to limitations of pollen and resources for plant growth, but few studies have investigated effects of the abiotic environment in relation to pollination on seed production. Here we examine the flowering biology, the effect of flower display, resources, pollen availability and weather conditions on reproductive success of Iris tenuifolia. Flowers of I. tenuifolia began to open in late March and mid – April, and it exhibited a concentrated flowering pattern. Four types of bees were effective pollinators of this species. Flowers of I. tenuifolia are self-incompatible and not capable of autonomous selfing, outcross pollination ensures reproductive success in natural population. Plants with high numbers of flowers are attractive to pollinators and received significantly more visits and more pollen than flowers with a low number of flowers, this increases fruit and seed set. Resource addition of water and fertilizer had no significant effect on seed production, but weather conditions affected pollinator activity and influence female reproduction through pollen availability. Our results indicated that the desert environment in early spring can reduce the visitation by pollinators, further reducing the outcrossing success of plants, which leads to low seed set in this self-incompatible species.