ANALYSES OF DIGITISED LEAF IMAGES OF THE DODONAEA VISCOSA COMPLEX IN AUSTRALIA

Summary Dodonaea cuneata, D. angustissima and D. viscosa form the Dodonaea viscosa complex in Australia. An electronic digitiser was used to trace outlines of leaves of the D. viscosa complex, and the digitised images were stored on computer thus allowing rapid data access and retrieval. Characters usually measured by hand were derived from the stored images, along with a number of characters which are difficult to measure manually (such as area, curvature and indices of symmetry and shape). Multivariate analyses showed the full set of computer derived characters to be better in discriminating between and in clustering the 173 individuals than the hand measurable character set. However, the analysis showed that the differences between the three taxa of this complex are not sufficiently significant to warrant recognition at the species level, thus supporting the conclusions drawn from flower and fruit morphology. The advantages of the digitiser as a technique include fast data collection (1 minute to digitise each leaf), accessible and readily retrievable computer data, the potential for deriving and measuring more complex characters, and the ability to plot the leaf images for visual interpretation.