High self-pollen transfer and low fruit set in buzz-pollinated Dianella revoluta (Phormiaceae)

Abstract

We used pollinator observation, flower manipulation, controlled pollination and pollen-tube analysis to better understand the reproductive ecology of Dianella revoluta R.Br., a common species known to have depressed fruit set at fragmented sites. This buzz-pollinated species was found to receive large quantities of self-pollen even during a single pollinator visit, but is only partially self-compatible. This may be the first direct demonstration of pollinator-facilitated, autogamous self-pollen transfer accounting for a significant proportion of stigmatic pollen load. Frequent high self-pollen transfer may account for the observed low rate of fruit development in open-pollinated flowers. Self-pollen tubes reached the base of the style in comparable numbers and at the same rate as outcross pollen tubes, with no sign of pollen-tube competition favouring outcross pollen. Barriers to greater self-fertility occur late, probably through early abortion of selfed ovules. We also investigated what impact overlapping distribution with D. longifolia may have on D. revoluta pollination and reproduction. Although these species shared pollinators, they differed in terms of frequency of visits. There was also separation of floral phenology within the course of a day.