The mating system and patterns of genetic variation in Banksia cuneata A. S. George (Proteaceae)

Abstract

The mating system and patterns of genetic variation were studied in the rare and geographically restricted species Banksia cuneata. Nine out of 20 allozyme loci analysed were polymorphic and six were considered suitable for estimating mating system parameters. Estimates of the outcrossing rate ranged from t = 0.67 to t = 0.95 and the effective selfing rate from E = 0.14 to E = 0.25, and showed significantly lower levels of outcrossing in two populations than reported for other Banksia species. This appeared to be due to increased biparental inbreeding associated with high plant density and reduced or altered pollinator activity associated with habitat disturbance. The six populations were clearly divided into two population groups (D̄, between groups = 0.088) with significant gene flow estimated among populations within groups but not amoung groups. Although B. cuneata has an extremely restricted geographical range and is largely bird-pollinated, significant differentiation has occurred between some populations over relatively small geographical distances. The differentiation correlates with certain ecological features of the region and is a likely result of the dissected population structure and relatively small sized populations found in this species.