Genetic Determination of Erect and Prostrate Growth Habit in Five Shrubs From Windswept Headlands in the Sydney Region

Abstract

In the Sydney region, many plants from populations on windswept headlands have a more prostrate growth habit compared with plants from populations of the same species occurring away from the coast. To determine whether these different growth habits are genetically determined, plants from four populations of each of five species (Acacia rnyrtifolia, Acacia suaveolens, Banksia ericifolia, Casuarina distyla, Hakea teretifolia) were grown under uniform glasshouse conditions. Multivariate analyses of six morphological characteristics indicate that, for four of these species, the offspring are similar to their maternal parent; we thus conclude that the habit differences are genetically fixed in these populations. The same trend is apparent for <I.C. distyla , although significant variation occurs in the offspring. Univariate analyses indicate that different characteristics reflect the habit differences in different species. For conservation biology, the implications of this intra-specific variation are that attempts should be made to conserve viable populations of all genetically isolated taxa within a species.