Patterns of morphological variation within Acacia suaveolens (Mimosaceae)

Abstract

Acacia suaveolens shows a considerable degree of morphological variability throughout its range in eastern Australia. Multivariate morphometric analyses of data from 375 herbarium specimens suggest that there are five polythetically distinct forms within this species. The morphological boundaries between these forms are somewhat arbitrary but are closely related to a number of environmental variables. Discrimination between these forms is possible only on the basis of a combination of attributes. In all cases, the distinctions between the forms are maintained in offspring plants grown under controlled environmental conditions, indicating that these morphological differences are genetically fixed. These forms are taxonomically treated as new subspecies. Apart from the typical form (subsp. suaveolens), which is widespread, the following morphological forms have been identified: a form with narrower phyllodes, restricted to the Holocene sand dunes in the Myall Lakes region (subsp. myallensis D. Morrison & A.J. Rupp); a form with wider phyllodes and longer pulvinus, and longer and thicker seeds, occurring in areas with an altitude above 300 m (subsp. montana D. Morrison & A.J. Rupp); a form with wider phyllodes, more flower heads per raceme, thicker seeds, and a small rootstock, restricted to the Grampians region (subsp. grampianensis D. Morrison & A.J. Rupp); and a form with shorter phyllodes, shorter internodes, shorter fruits, thicker seeds and a prostrate habit, occurring on windswept coastal headlands (subsp. prostrata D. Morrison & A.J. Rupp).