Temporal and spatial mating-system variation in fragmented populations of Banksia cuneata, a rare bird-pollinated long-lived plant

Abstract

Plant mating systems can vary significantly in both space and time, influencing a range of demographic and genetic processes critical for the persistence of plant populations. Spatial and temporal mating-system variations were investigated in Banksia cuneata (A. S. George), a rare bird-pollinated shrub occurring in a highly fragmented landscape. Substantial variation in the mating system was observed, with the magnitude of temporal variation within a population often as high as the level of spatial variation among populations within a season. A significant reduction in outcrossing rates and increased temporal variation in both outcrossing rates and correlated paternity were observed in disturbed populations. Doubling of the paternal neighbourhood and a trend to increased outcrossing rate was found after augmentation of a disturbed population where population size was increased from 57 to 214 adult plants. A large increase in the fixation index for seeds compared with adults was observed in all populations, with the magnitude of the difference showing temporal and spatial uniformity. We suggest that temporal mating-system variation warrants increased consideration, not only in assessing the effects of habitat fragmentation on plant populations, but also in the design and establishment of successful translocation, augmentation and restoration programs.