1: Species diversity and genetic diversity are fundamental components of biodiversity. A primary goal of biodiversity studies is to explain the distribution of species and alleles in space and time. A new challenge is to cross discipline boundaries and explore the relationship between these two scales of diversity. 2: In the biodiverse northern sandplain shrublands of south-western Australia, the woody shrub Banksia attenuata occurs on patchily distributed sand dunes, and coexists with B. hookeriana, B. menziesii, and two small tree species, Eucalyptus todtiana and Xylomelum angustifolium, which together comprise a plant functional group of large shrubs/small trees.3: Genetic variation (alleles per locus and heterozygosity) between 736 B. attenuata individuals on 27 discrete dunes was assessed using 11 polymorphic microsatellite markers. For each dune, the physical properties of area and height, and species diversity (richness and evenness) of the functional group, were measured.4: Synthesis. Genetic diversity of B. attenuata covaried positively with species diversity, which in turn covaried strongly with dune height rather than dune area. The positive relationship between species and genetic diversity demonstrated here supports the theory of common environmental, rather than neutral, processes acting directly or indirectly on both scales of diversity, and suggests the possibility of predicting one component of diversity on the basis of the other.