Phylogeny and classification of Eucalyptus subgenus Eudesmia (Myrtaceae) based on nuclear ribosomal DNA, chloroplast DNA and morphology

Abstract

Abstract. Phylogenetic analysis of Eucalyptus subgenus Eudesmia is presented on the basis of the following three datasets: sequences of the internal transcribed spacer (ITS) and the external transcribed spacer (ETS) regions from nuclear rDNA, sequences of the psbA-trnH intergenic spacer region from chloroplast DNA, and morphological characters, including stamen bundling, operculum development, seeds and trichomes. Studies of floral development were essential for understanding the morphology of mature flowers and interpretation of synapomorphy and homoplasy. A summary phylogeny was constructed from a maximum parsimony analysis of those nodes coded as characters that had support in the molecular trees together with morphological characters. A revised infra-subgeneric classification is presented on the basis of the summary phylogeny, and compared with classifications of Johnson (1998) andBrooker (2000). Differences relate to relationships between clades and taxonomic rank (sections, series and subseries) and valid names of Brooker (2000) are conserved where possible. One main clade of 14 species (section Limbatae), many of mallee growth form, was found in all analyses; this clade is distributed in the South-West of Western Australia and adjacent Interzone and desert areas. A second main clade (section Complanatae) occurs in the northern and eastern tropical and subtropical regions of Australia, including Kimberley, Arnhem, Queensland and New South Wales. This section includes E. tetrodonta, previously treated as an isolated taxon in a monotypic section; however, this species is related to E. baileyana, E. similis, E. lirata and series Miniatae. The hypothesised phylogeny provides a framework for further analyses of biogeography and ecology, including functional traits.

Population genetic analysis and phylogeny reconstruction in Eucalyptus (Myrtaceae) using high-throughput, genome-wide genotyping

“…In general, the DArT analyses (of the whole data set or of subsets of taxa) produced trees that were congruent with existing phylogenies from DNA sequence data Gibbs et al DArT data provided more resolution than ITS sequence data within subgenus Eucalyptus.…”

“…1), a position that was incongruent with other data (Gibbs et al 2009) and probably due to a high level of missing data for that species.…”

“…Furthermore, there are many copies of ribosomal RNA genes in a genome and this introduces a risk of comparing paralogous loci (Bayly and Ladiges 2007). Despite the limitations of ribosomal and chloroplast DNA for resolution of species-level relationships, Gibbs et al (2009) successfully used ITS, ETS and cpDNA sequence data in combination with morphological characters to resolve relationships among species within subgenus Eudesmia. Although none of the data sets in isolation produced a well-resolved phylogeny of the eudesmids there were elements of congruence in a combined analysis that provided the basis of a sound system of subdivision for that subgenus.…”

Progress in Myrtaceae genetics and genomics: Eucalyptus as the pivotal genus

“…4), only Eudesmia appeared to be monophyletic (see also Gibbs et al 2009). The previously recognized small subgenus Minutifructus (subgenus Telocalyptus of Pryor and Johnson (1971) comprising four tropical boxes species (including the extra-Australian E. deglupta) was a grouping of diverse lineages nested within Symphyomyrtus, and its over-ranking was confirmed with a subsequent cpDNA phylogeny (Whittock et al 2003); see also Ladiges and Udovicic (2005).…”

“…Harrington and Gadek (2004) Phylogenetic relationships within the Eucalyptus sections Below the sectional level in Eucalyptus, molecular phylogenies using ITS (Table 4) are poorly resolved (e.g., subgenus Symphyomyrtus section Maidenaria; Steane et al 1999Steane et al , 2002. Enhanced resolution was achieved by integrating ITS, ETS, and chloroplast sequence with morphological data in a recent phylogeny of subgenus Eudesmia (Gibbs et al 2009). At these phylogenetic levels, more variable and robust marker systems are required to avoid problems with duplication (paralogy), recombination, single gene bias, and lack of sequence variability.…”