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Early evidence of xeromorphy in angiosperms: stomatal encryption in a new eocene species of Banksia (Proteaceae) from Western Australia


Carpenter, RJ and McLoughlin, S and Hill, RS and McNamara, KJ and Jordan, GJ, Early evidence of xeromorphy in angiosperms: stomatal encryption in a new eocene species of Banksia (Proteaceae) from Western Australia, American Journal of Botany, 101, (9) pp. 1486-1497. ISSN 0002-9122 (2014) [Refereed Article]

Copyright Statement

Copyright 2014 Botanical Society of America

DOI: doi:10.3732/ajb.1400191


Premise of the study: Globally, the origins of xeromorphic traits in modern angiosperm lineages are obscure but are thought to be linked to the early Neogene onset of seasonally arid climates. Stomatal encryption is a xeromorphic trait that is prominent in Banksia, an archetypal genus centered in one of the world’s most diverse ecosystems, the ancient infertile landscape of Mediterranean-climate southwestern Australia.

Methods: We describe Banksia paleocrypta, a sclerophyllous species with encrypted stomata from silcretes of the Walebing and Kojonup regions of southwestern Australia dated as Late Eocene.

Key results: Banksia paleocrypta shows evidence of foliar xeromorphy ∼20 Ma before the widely accepted timing for the onset of aridity in Australia. Species of Banksia subgenus Banksia with very similar leaves are extant in southwestern Australia. The conditions required for silcrete formation infer fluctuating water tables and climatic seasonality in southwestern Australia in the Eocene, and seasonality is supported by the paucity of angiosperm closed-forest elements among the fossil taxa preserved with B. paleocrypta. However, climates in the region during the Eocene are unlikely to have experienced seasons as hot and dry as present-day summers.

Conclusions: The presence of B. paleocrypta within the center of diversity of subgenus Banksia in edaphically ancient southwestern Australia is consistent with the continuous presence of this lineage in the region for ≥40 Ma, a testament to the success of increasingly xeromorphic traits in Banksia over an interval in which numerous other lineages became extinct.

Item Details

Item Type:Refereed Article
Keywords:Banksia, Eocene, Proteaceae, sclerophylly, silcrete, southwestern Australia, stomatal crypt, xeromorphy, climate change
Research Division:Biological Sciences
Research Group:Evolutionary biology
Research Field:Biogeography and phylogeography
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the environmental sciences
UTAS Author:Carpenter, RJ (Dr Raymond Carpenter)
UTAS Author:Jordan, GJ (Professor Greg Jordan)
ID Code:98528
Year Published:2014
Funding Support:Australian Research Council (DP110104926)
Web of Science® Times Cited:22
Deposited By:Plant Science
Deposited On:2015-02-18
Last Modified:2017-11-01

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