Genetic diversity in Banksia and Dryandra (Proteaceae) with emphasis on Banksia cuneata, a rare and endangered species

Abstract

Random amplified polymorphic DNA (RAPD) markers were investigated as a tool for estimating genetic diversity within 33 species of Banksia and three species of Dryandra. Three primers were used on DNA from 10 seeds per species, and band data were pooled to give between 52 and 89 bands per species, most of which were polymorphic. Genetic diversity was calculated using six published metrics on three species, for which allozyme data were also available. Based on between-method consistency, three metrics were chosen for analysis of the full data set. Levels of genetic diversity in Banksia and Dryandra ranged from 0.59 to 0.90. Based on this information, a detailed study was conducted on all 10 known populations of B. cuneata, a rare and endangered species, with a restricted geographical distribution in south-western Australia. Estimates of genetic diversity ranged from 0.65 to 0.74, which is high for a rare and endangered species. Analysis of molecular variance (AMOVA) was used to partition RAPD variation within and between populations. Nearly all of the variation was attributable to individuals within populations, indicating a lack of population divergence. It is suggested that the combination of bird pollination and high outcrossing rates in B. cuneata maintain genetic diversity and cohesion between the populations.