Variation and Evolution in the Genus Flindersia (Rutaceae). II. Review of Methods for Geographic Variation Analysis of Volatile Oil Data

Abstract

The genus Flindersia is currently being studied as it provides an ideal system for the investigation of variation and evolution in a group of tropical tree species. The first stage in this investigation is to study the pattern of geographic variation present within each species in turn. The appropriate methods are considered in detail with particular reference to the sampling regime, the use of leaf volatile oils and the use of numerical analysis. Sampling is on a population basis, so the problems of sample size and density are discussed. The use of leaf volatile oils in the study of geographic variation is explained, with reference to the advantages and disadvantages, including the possible problems of ontogenetic variation, temporal (seasonal and diurnal) variation and environmentally induced variation, and to the phenomenon of chemical forms. The array of available numerical techniques is also covered, with reference to significance tests, contour mapping, differential systematics, distance matrix, clustering, ordination, partial clustering, minimum spanning tree, networks and multiple discriminant analysis. Finally, a standard procedure is drawn up for the subsequent geographic variation analysis of the various species of Flindersia.