This thesis investigates the systematics and ecology of the eastern Australian species of Lepidosperma Labill. (Cyperaceae). The investigation sets the c. 33 eastern Australian species in context with the c. 76 described species found throughout Australia, New Zealand, New Caledonia and southern Asia.

We investigated the status of a putative new species of Lepidosperma from the mountains of south-western Tasmania using phenetic analysis on morphological/anatomical data (Chapter 2). Our results support the recognition of this species, here described as Lepidosperma monticola G.T.Plunkett & J.J.Bruhl. The distribution, habitat and conservation status are discussed.

The thickened and persistent perianth members of Lepidosperma diaspores are generally assumed to form a unique type of elaiosome. We tested whether these perianth members provide a food reward and improve the removal of diaspores by ants (Chapter 3). We measured the physical traits of diaspores, the lipid and fatty acid composition of the perianth, and the relative attractiveness to ants of the perianth of some species of Lepidosperma. We found that diaspores of Lepidosperma show traits consistent with myrmecochory, particularly the lipid content of perianth material and the presence of oleic acid in fruit and perianth of Lepidosperma. Diaspores of Lepidosperma and Acacia were equally attractive to ants. We concluded that the perianth members act as an elaiosome that provides a lipid-rich food reward and contains known ant attractants.

Lepidosperma viscidum R.Br. forms a highly diverse complex distributed across southeastern Australia. We utilised multiple sources of data to delimit species: phenetic analyses using morphology/anatomy; novel resin metabolic fingerprinting; and phylogenetic analyses via nuclear ribosomal (ETS) and chloroplast (trnL-F) gene sequencing (Chapter 4). Our results give strong support for a more condensed circumscription of L. viscidum s.s., and the recognition of at least three undescribed species.

Lepidosperma is taxonomically difficult for non-specialists and specialists; delimitation of many species of Lepidosperma has long been problematic. We used nuclear ribosomal (ETS) and chloroplast (trnL-F) gene sequence data from over 300 specimens for phylogenetic analysis and to test known and putative species. Overall, the analysis provides good resolution above the level of species, but little support for higher relationships within the genus. We found that most described species are well supported but the L. laterale R.Br. clade in particular continues to be unresolved. The analyses also provided support for the recognition of at least four further undescribed species and highlights avenues for future work.