Contributions to the Cenozoic macrofossil record of the Myrtaceae in South Eastern Australia

Abstract

The Myrtaceae are a large and diverse Angiosperm family, containing iconic groups of plants such as the Eucalypts, Lily Pillys, Melaleucas, Ti-Trees, Guavas, Feijoas and Bottlebrushes. The Myrtaceae are a key family in the vegetation of the Southern Hemisphere, and in Australia are often a dominant component of virtually all terrestrial ecosystems, from rainforest to sclerophyll heath. Despite the importance of the family, their macrofossil record is historically poorly studied. In this thesis, the macrofossil record of the Myrtaceae is reviewed, and it is found that the majority of published records of Myrtaceae fossils are poorly identified or equivocal. In the subsequent chapters, macrofossils of myrtaceous affinity from several Cenozoic sites in South Eastern Australia are identified, taking advantage of recent advances in molecular phylogenetic studies of the family, as well as recent fundamental botanical work, to identify fossils in a rigorous phylogenetic framework. Fossils of the capsular-fruited genus Metrosideros, one of the most widely distributed woody, flowering plant genera in the Pacific, are described in Chapters 3 and 4 from Eocene to Oligo-Miocene deposits in Tasmania, including Hasties, Little Rapid River, and the newly discovered Golden Fleece locality. These fossils provide the first evidence of this capsular-fruited genus in Australia, and demonstrate that its absence from the continent is the result of extinction, rather than failure of dispersal. In Chapter 5, fossil leaves of the fleshy-fruited genus Syzygium are described from Miocene sediments of Kiandra, New South Wales, which may provide the first confident identification of non-Eucalypt fossil Myrtaceae leaves using cuticle micromorphological characters. The fossils described in this thesis are among the best described Myrtaceae macrofossils from anywhere in the world, and pose significant advances in the understanding of the fossil record of these key genera within the family, as well a providing a framework upon which the identification of future Myrtaceae macrofossils might be based.