Oldest record of Metrosideros (Myrtaceae): Fossil flowers, fruits, and leaves from Australia

Abstract

This research establishes the presence of Metrosideros (aff. subg. Metrosideros) in the Eocene-Oligocene (∼40-30 mya) of Tasmania, Australia. This is the first fossil record of Metrosideros in Australia, as well as the oldest conclusive fossil record, and may provide evidence for an Australian origin of the genus. It is also yet another example of extinction in the Tertiary of a group of plants on the Australian mainland that is only found today on nearby Pacific landmasses.

Heterogeneity in global vegetation and terrestrial climate change during the late Eocene to early Oligocene transition

“…In our analysis we only used plant microfossils (pollen and spores) rather than an approach integrating all plant fossil data (such as has been used in refs 20 , 21 , 82 ), due to the statistical grouping applied to the data. Fossil pollen and spore taxa and macrofossil taxa, do not share a common taxonomy and assigning a fossil pollen grain and a fossil leaf to a parent species is a difficult prospect, except in the rare instances that multiple articulated plant parts are preserved together 83 . Therefore, if plant macrofossils had been included in the statistical analysis there would have been no shared similarity between the two.…”

Two fossil species of Metrosideros (Myrtaceae) from the Oligo‐Miocene Golden Fleece locality in Tasmania, Australia

“…As such, it might be considered that they are not as well adapted for long-distance dispersal as some species in subgenus Metrosideros . Discovery of fossils of subgenus Mearnsia in Australia, in conjunction with the subgenus Metrosideros fossils previously described by Tarran et al (2016) , might then be considered further evidence of an Australian origin for the genus.…”

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Recently described fossils of Metrosideros , with affi nities to subgenus Metrosideros from the Late Eocene to Early Oligocene of Australia, have helped us understand one of the great biogeographic puzzles of the capsular-fruited Metrosidereae, namely the absence of this tribe from Australia despite a widespread distribution around the Pacifi c ( Fig. 1 ) , and a clear adaptation for long-distance dispersal in at least subgenus Metrosideros ( Tarran et al, 2016 ). Th ese fossils contribute to an interpretation of the current absence of the Metrosidereae from Australia as being a result of extinction, rather than an absence of dispersal from some other landmass, such as New Zealand.While these fossils contribute to our understanding of the paleobiogeography of the group, other pertinent questions still remain surrounding (1) the geographic origin of the genus, (2) the deep infrageneric relationships within Metrosideros , and (3) the poorly resolved relationships with the other closely related tribes Backhousieae, Kanieae, Myrteae, Syzygieae, and Tristanieae ( Pillon et al, 2015 ).

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“…Recently described fossils of Metrosideros , with affi nities to subgenus Metrosideros from the Late Eocene to Early Oligocene of Australia, have helped us understand one of the great biogeographic puzzles of the capsular-fruited Metrosidereae, namely the absence of this tribe from Australia despite a widespread distribution around the Pacifi c ( Fig. 1 ) , and a clear adaptation for long-distance dispersal in at least subgenus Metrosideros ( Tarran et al, 2016 ). Th ese fossils contribute to an interpretation of the current absence of the Metrosidereae from Australia as being a result of extinction, rather than an absence of dispersal from some other landmass, such as New Zealand.…”

The Evolution and Fossil Record of Parasitism

“…15). Other examples of cuticle alterations interpreted as a host response include Metrosideros leunigii (Myrtaceae) leaves from the Eocene-Oligocene of Australia that appear to have produced cuticle thickenings to divert the growth of the hyphae of a fungal parasite (Tarran et al 2016: fig. 8A).…”