Phylogeny of Australian Gnaphalieae (Asteraceae) Based on Chloroplast and Nuclear Sequences, the trnL Intron, trnL/trnF Intergenic Spacer, matK, and ETS

Abstract

The Gnaphalieae are a group of sunflowers that have their greatest diversity in South America, Southern Africa, and Australia. The objective of this study was to reconstruct a phylogeny of the Australian Gnaphalieae using sequence data from the trnL intron, trnL/trnF intergenic spacer, matK, and ETS. Included in this investigation are the Australian genera of the Gnaphalieae from the subtribes Cassiniinae, Gnaphaliinae, Angianthinae, and Loricariinae, and one to four genera from all tribes of the subfamily Asteroideae to serve as outgroups. Results indicate that the subtribes An- gianthinae and Cassiniinae are non-monophyletic as currently circumscribed. There is also some evidence to suggest that the genera Asteridea, Craspedia, Hyalosperma, Millotia ,a ndPodolepis are monophyletic, whereas Calocephalus, Gnephosis, Myri- ocephalus pro parte, Ozothamnus, Siloxerus, Trichanthodium ,a ndXerochrysum are non-monophyletic. A group of perennial shrubs and alpine cushion plants from southeastern Australia dominates the clade at the base of the Gnaphalieae. The more derived clades contain primarily herbaceous annual taxa, mainly from western Australia. Based on our results, it seems likely that initial colonization and diversification of the Australian Gnaphalieae occurred in the Bassian Floristic region in eastern New South Wales, Victoria, and Tasmania. Following diversification in eastern Australia, concurrent with the in- creasing aridity over the entire continent during the Miocene, a massive radiation in the Gnaphalieae occurred into the arid zone of South Australia and Western Australia. The Gnaphalieae (paper daisies or everlastings) are a group of sunflowers that have their greatest diversity in Australia, southern Africa, and South America. Phy- logenetic relationships among the currently recognized 187 genera of the Gnaphalieae have been hypothesized through a contemporary, morphology-based cladistic analysis (Anderberg 1991). Based on this analysis, An- derberg (1991) proposed that the tribe is composed of 11 monophyletic lineages, including six informal groups and five subtribes. The Australian flora con- tains approximately 84 endemic genera of Gnaphal- ieae, the majority of which (60 genera) reside within the endemic subtribe Angianthinae. The majority of the remaining genera (12 genera) are assigned to the subtribe Cassiniinae. The ubiquitous parallelisms in morphology that ex- ist within the tribe Gnaphalieae, and indeed Astera- ceae as a whole (Carlquist 1976), have made it difficult to find conservative, homogenetic characters that can be used reliably in phylogenetic reconstruction. Given the problems of non-homologous morphological simi- larities (homoplasies) in the group, we have chosen to explore these relationships with a molecular approach. The objectives of our work are: (i) to attempt to recon- struct the phylogeny of the Australian Gnaphalieae us- ing sequence data from two relatively short, non-cod- ing chloroplast DNA sequences, the trnL intron and trnL/trnF intergenic spacer, as well as the maturase en- coding plastid enzyme matK, and the external tran- scribed spacer (ETS) of nrDNA; and (ii) to test the monophyly of the Angianthinae and assess their phy- logenetic relationships to the other Australian genera of the Gnaphalieae.