How old are the eucalypts? A review of the microfossil and phylogenetic evidence

Macphail, Mike, and Thornhill, Andrew H. (2016) How old are the eucalypts? A review of the microfossil and phylogenetic evidence. Australian Journal of Botany, 64. pp. 579-599.

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Molecular age estimates for the Eucalypteae (family Myrtaceae) suggest that the eucalypts, possibly associated with fire, have been present for ~65 million years. In contrast, macrofossils and fossil pollen attributable to three important eucalypt genera (Angophora, Corymbia and Eucalyptus) in the Eucalypteae date to ~51–53 million years ago (mid-Early Eocene) in Patagonia, eastern Antarctica and south-eastern Australia. At present, there is no fossil evidence to show that eucalypts had evolved before this epoch, i.e. when Australia was part of eastern Gondwana, although this seems probable on the basis of molecular-dated phylogenetic analyses. The primary reason is the absence of macrofossils, whereas the earliest fossil eucalypt-type pollen recorded (Myrtaceidites tenuis) is attributed to Angophora and Corymbia, not Eucalyptus. This pollen type is recorded in Australia and Antarctica but not in New Zealand or South America. The only Myrtaceidites morphospecies found in UpperCretaceous and Paleocene depositsin Australia is M. parvus, whose affinitylies with multiple extant Myrtaceae groups other than the Eucalypteae. In the present paper, we review current phylogenetic and microfossil databases for the eucalypts and assess this evidence to develop a 'consensus' position on the origin and evolution of the eucalypts in the Australian region.

Item ID: 49218
Item Type: Article (Research - C1)
ISSN: 1444-9862
Keywords: ancestral state reconstruction, Angophora, Australia, Corymbia, Eucalyptus, evolution, Myrtaceae eucalypt, Myrtaceidites, palynology, palynostratigraphy, palaeobotany, phylogenetics.
Date Deposited: 07 Jun 2017 23:22
FoR Codes: 31 BIOLOGICAL SCIENCES > 3104 Evolutionary biology > 310499 Evolutionary biology not elsewhere classified @ 100%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960805 Flora, Fauna and Biodiversity at Regional or Larger Scales @ 100%
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