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Endymion Dante CooperSupervisors Dr Murray Henwood and Dr Matthew Pye (Univ. of Sydney), and Dr Elizabeth Brown Degree PhD University University of Sydney Project title Systematics of the Lepidoziaceae Limpr.: understanding relationships, biogeography and morphological evolution in this hyper-diverse family of hepatics. Keywords Liverworts, Lepidoziaceae, Telaranea, Lepidozia, phylogeny, biogeography, morphological evolution Project details The Lepidoziaceae is a very large, putatively Gondwanan family of leafy liverworts. Despite being widespread, morphologically and ecologically diverse, phylogenetic relationships of and within the family remain poorly understood. Revision of taxonomic groups at all taxonomic levels is essential to our understanding of the evolution of this important group of plants. As currently circumscribed the Lepidoziaceae is comprised of 27-30 genera and some 1000 species (Schuster 2000, Heslewood and Brown 2007). Of these, 13 genera and about 100 species are recognised from Australia (McCarthy 2003). This represents approximately 12% of Australia’s liverwort species. Since first described by Limpricht in 1877 the Lepidoziaceae has been divided into no less than six separate families (Evans 1939, Fulford 1966, 1968). These were reunited by Schuster in 1969 who then divided the family into subfamilies. Schuster (1972), however, emphasised that definition of subfamilies was 'exceedingly difficult'. Despite his conclusion that division of the family into two or more natural units 'must fail' (Schuster 1972) he continues to recognise eight subfamilies (Schuster 2000). Characteristic of the family is a strongly conserved sporophyte generation coupled with extreme variability in the gametophyte. Variation in gametophyte characters such as leaf insertion, leaf form and branch ontogeny, elsewhere fixed at the family level, has resulted in a range of interpretations and generic limits continue to be fluid (Heslewood and Brown 2007). Cladisitic methods have been widely employed in systematics and have greatly assisted in the resolution of difficult taxonomy. Yet there have been only two attempts to apply cladistic methods to the Lepidoziaceae. These studies used different data sources and arrived at markedly different conclusions. Engel and Smith Merrill (2004) used 32 morphological characters to reconstruct the phylogeny of Telaranea. Their phylogenetic hypothesis indicated that Telaranea was polyphyletic and they broadened its definition to include elements of Arachniopsis and Kurzia. Heslewood and Brown (2007) used three molecular markers to reconstruct the phylogeny of the Lepidoziaceae. Their phylogeny placed Telaranea in a well supported clade with Lepidozia; Kurzia (including those species transferred to Telaranea by Engel and Smith Merrill) was placed in a separate clade with members of the Lembidioideae. The relationship between these two clades was unresolved. The conflict between these two results, neither of which agree with Schuster’s (2000) classification, indicates that further work is required. As currently circumscribed (on morphological characters) the Lepidozioideae includes a number of genera, i.e. Kurzia, Megalembidium, Sprucella and Psiloclada (Schuster 2000). Monophyly of this subfamily is not supported by the molecular data (Heslewood and Brown 2007), but the strong morphological association of Telaranea and Lepidozia (Schuster 2000) is supported. Existing morphological and molecular evidence suggest that the definition of Lepidozioideae should be narrowed to include only Telaranea and Lepidozia (and probably Sprucella which is morphologically very close to these genera) but the circumscription of subfamilies will be further investigated in the course of this study. There is considerable intrageneric variation in the morphological characters which separate genera and the molecular phylogeny suggests that many genera, e.g. Telaranea, are paraphyletic (Heslewood and Brown 2007). The morphological and genetic basis for generic divisions needs re-investigation. The Lepidozioideae in this restricted sense (Telaranea and Lepidozia) is a major component of the liverwort flora of Australia. There are approximately 100 species and subspecific taxa recognised from Australia and New Zealand. This represents between half and two thirds of species assigned to these genera. Phylogenetic investigation of this subfamily will lead to an improved taxonomic knowledge of genera and subgeneric taxa. This project aims to resolve these issues by providing robust phylogenetic hypotheses for Lepidozia and Telaranea, and for backbone relationships in the Lepidoziaceae. These phylogenies will also provide an opportunity to investigate patterns of morphological evolution and biogeography. Contact details School of Biological Sciences Phone +61 (02) 9036 7182 |
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