Mixed Mating in Banksia brownii Baxter ex R. Br. (Proteaceae)

Abstract

Mating system parameters of the rare and endangered species Banksia brownii were estimated for two populations using both the mixed mating and effective selfing models. Estimates of outcrossing rate were similar in both populations for both models (mixed mating t Pop. 1=0.68, Pop. 2=0.75; effective selfing t Pop. 1=0.65, Pop. 2=0.73) and were among the lowest reported for undisturbed Banksia populations. Banksia brownii is killed by fire and the high level of selfing found may be associated with this trait. Multilocus and minimum variance mean i estimates were similar and the covariance of selfing with gene fixation (D) was not significantly different from zero indicating that populations were not structured and that most of the inbreeding was the result of self-fertilisation. The absence of structure was attributed to gene dispersal through pollen disperse by birds, and selection against inbred seed. It is suggested that several entire, large populations of this species together with habitat sufficient to support pollinators be reserved to conserve this species.