Phylogenetic studies of eucalypts: fossils, morphology and genomes

Abstract

The eucalypt group includes seven genera: Eucalyptus, Corymbia, Angophora, Eucalyptopsis, Stockwellia, Allosyncarpia and Arillastrum. Knowledge of eucalypt phylogeny underpins classification of the group, and facilitates understanding of their ecology, conservation and economic use, as well as providing insight into the history of Australia’s flora. Studies of fossils and phylogenetic analyses of morphological and molecular data have made substantial contributions to understanding of eucalypt relationships and biogeography, but relationships among some genera are still uncertain, and there is controversy about generic circumscription of the bloodwood eucalypts (genus Corymbia). Relationships at lower taxonomic levels, e.g. among sections and series of Eucalyptus, are also not well resolved. Recent advances in DNA sequencing methods offer the ability to obtain large genomic datasets that will enable improved understanding of eucalypt evolution.

Chloroplast variation is incongruent with classification of the Australian bloodwood eucalypts (genus Corymbia, family Myrtaceae)

“…The nrDNA analyses here ( Fig 6 ), for instance, using only ITS data, show 71% BS for the nesting of Angophora in Corymbia in the MP analysis but <50% support in the ML analysis, leaving open the possibility that Angophora might be sister to a monophyletic Corymbia . More thorough assessment of relationships will require analysis of more substantial datasets, for which there are now good prospects using HTS methods [ 37 ].…”

“…The most notable differences between the groups are in the flowers, which in Angophora have free sepals and petals, in contrast to the calyptrate/operculate perianth of Corymbia ( Fig 2 ). Despite such morphological differences, molecular phylogenetic analyses have presented conflicting signals regarding monophyly of Corymbia [ 37 ], with some resolving the genus as monophyletic (e.g. [ 6 , 27 , 38 , 39 ]), while others resolve it as paraphyletic, with Angophora nested within it [ 28 , 29 , 30 , 31 , 40 ].…”

Molecular relationships of Campomanesia xanthocarpa within Myrtaceae based on the complete plastome sequence and on the plastid ycf2 gene

“…versity is the wet tropics, predominantly in South America, Australia, and tropical Asia (Grattapaglia et al, 2012). Evolutionary and phylogenetic trends within this family have been studied using single and combined plastidial genes, as well as by complete plastome sequencing (Steane, 2005;Bayly et al, 2013Bayly et al, , 2016Jo et al, 2016;Eguiluz et al, 2017;Machado et al, 2017).…”

52 million years old Eucalyptus flower sheds more than pollen grains

“…Dating molecular phylogenies has become essential to comprehend the evolution of taxa, but to produce robust calibrated phylogenies, it is necessary to have reliable calibration points. Even though there are several eucalypt calibrated phylogenies, the estimated age of the tribe Eucalypteae (the eucalypts) is still controversial (see Bayly, 2016; Hill et al, 2016, and citations therein). Crisp et al (2005) argued that for eucalypts calibration can be “problematic because no well‐dated fossil that can be placed accurately on a tree is known.” Ladiges et al (2003) and Crisp et al (2004) suggested that the eucalypts originated at least in the Late Cretaceous (~70 Ma) whereas Thornhill et al (2015, 2019) and Macphail and Thornhill (2016) disagreed with those authors and proposed the divergence time of the tribe was early‐to‐early late Early Eocene (~55.2–51.2 Ma).…”

“…Dating molecular phylogenies has become essential to comprehend the evolution of taxa, but to produce robust calibrated phylogenies, it is necessary to have reliable calibration points. Even though there are several eucalypt calibrated phylogenies, the estimated age of the tribe Eucalypteae (the eucalypts) is still controversial (see Bayly, 2016;Hill et al, 2016, and citations therein). Crisp et al (2005) argued that for eucalypts calibration can be "problematic because no well-dated fossil that can be placed accurately on a tree is known. "…”