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Abstract Detail


Thornhill, Andrew [1].

A dated molecular perspective of eucalypt evolution.

The eucalypts – Eucalyptus, Angophora, and Corymbia – are native to Australia and Malesia and include over 800 named species in a mixture of diverse and depauperate lineages. We calibrated phylogenies with over 700 species against time using penalized likelihood and constraints obtained from fossil ages. Based on these trees, most major eucalypt subgenera arose in the Late Eocene and Early Oligocene. All Eucalyptus clades with taxa occurring in south-eastern Australia have crown ages < 20 Ma. Several eucalypt clades display a strong present-day geographic disjunction, although these clades did not have strong phylogenetic statistical support. In particular the estimated age of the separation between the eudesmids (Eucalyptus subgenus Eudesmia) and monocalypts (Eucalyptus subgenus Eucalyptus) was consistent with extensive inland water bodies in the Eocene. Bayesian Analysis of Macroevolutionary Mixtures (BAMM) rates of net species diversification accelerated in five sections of Eucalyptus subg. Symphyomyrtus, all beginning 2–3 Ma and associated with semi-arid habitats dominated by mallee and mallet growth forms, and with open woodlands and forests in eastern Australia. This is the first time that a calibrated molecular study has shown support for the rapid diversification of eucalypts in the relatively recent past; most likely driven by changing climate and diverse soil geochemical conditions.

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1 - State Herbarium Of South Australia, Hackney Road, Adelaide, SA, 5000, Australia

molecular dating

Presentation Type: Oral Paper
Session: SYS2, Systematics II: Rosids part 1 to Asterids part 1
Location: Tucson G/Starr Pass
Date: Wednesday, July 31st, 2019
Time: 10:45 AM
Number: SYS2011
Abstract ID:929
Candidate for Awards:None

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