A revision of Acacia Mill. in Queensland (concluded)

Abstract

Bentham's classification of Acacia with six series has usually been followed, with minor modifications. Recent studies in the chemistry of the heartwood, morphology of pollen and seedlings, and several taximetric studies have resulted in re-appraisals of Bentham's classification. Three subgenera with ten sections are recognised here. Of these sections Alatae (Benth.) Pedley and Lycopodiifoliae Pedley are new, and the names Spiciflorae DC. and Phyllodineae DC. replace the more familiar Vulgares (Benth.) Taub, and Uninerves (Benth.) Maiden & Betche respectively. Lectotypes for some infrageneric taxa are chosen. Characters useful in identification and classification are discussed. The arrangement of phyllodes, their shape, size, venation, indumentum and the position and structure of their glands enable a large proportion of species to be identified. The succession of bipinnate seedling leaves and their retention on older plants are discussed and it is suggested that the Botrycephalae and the Racemosae group of the Phyllodineae are related. Juvenile phyllodes of some species differ markedly from those of mature plants and some species retain them throughout their lives. The nature of the inflorescence (heads or spikes) and their arrangement are useful in defining groups of related species. Flowers show little variation in size and structure and are of limited value in classification and identification. Flower colour is more or less constant for each species. There is a great diversity of pods though only one-fifth of specimens examined included pods. Delimitation of species is discussed briefly. Naturally occurring hybrids are rare. Most species have a diploid complement of 26 chromosomes. Polyploids are more common in subg. Acacia than they are in other subgenera. Acacias are scarce or absent only in rainforest and grassland. Edaphic factors determine the ranges of many species. Most favour coarse-textured well-drained soils, but some wideranging, economically important species are confined to clays. Others are associated with deeply weathered rocks on scarps. Regeneration of most species is from seed, particularly after fires, but A. harpophylla and A. argyrodendron sucker from the roots. Their seeds lack an impervious testa. The abundance and geographic ranges of some species have been affected by man's activities. Though data are lacking dispersal by animals is probably insignificant. A key to the identification of 234 species and descriptions, essential synonymy, citation of some specimens, and notes on distribution, ecology and taxonomy for all species are given. A. nilotica (Asia), A. baileyana, A. decurrens (south-eastern Australia) and A. saligna (Western Australia) are naturalized. Taxa described as new are: A. ditricha (suibg. Acacia); A. jackesiana, A. spania, A. striatifolia, A. tenuinervis, A. hyaloneura, A. longispicata suibsp. velutina, A. oligophleba, A. leiocalyx subsp. herveyensis, A. crassa subsp. longicoma, A. grandifolia, (Juiiflorae); A. microcephala, A. maranoensis, A. ammophila, A. melvillei, A. melleodora, A. excelsa subsp. angusta, A. fleckeri, A. hyalonoma, A. legnota, A. leptoloba (Plurinerves); A. johnsonii, A. islana, A. burbidgeae, A. tindaleae, A. hockingsii, A. lauta, A. calant ha, A. deuteroneura, A. everistii, A. holotricha, A. polifolia, A. buxifolia subsp. pubiflora (Phyllodineae); and A. albizoides (subg. Aculeiferum). A. caroleae (Juiiflorae), A. ixodes and A. per angust a (Phyllodineae) are new species based on A. doratoxylon var. angustifolia, A. gnidium var. latifolia, and A. flmbriata var. perangusta respectively. Acknowledgements, bibliography and an index to collections in the Queensland Herbarium (BRI) are given.