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University of Tasmania.
Swedish Museum of Natural History, Department of Paleobiology.ORCID iD: 0000-0001-6723-239X
University of Adelaide.
University of Cambridge.
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2014 (English)In: American Journal of Botany, ISSN 0002-9122, E-ISSN 1537-2197, Vol. 101, no 9, 1486-1497 p.Article in journal (Refereed) Published
Abstract [en]

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 fl uctuating 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.

Place, publisher, year, edition, pages
2014. Vol. 101, no 9, 1486-1497 p.
Keyword [en]
Banksia ; Eocene; Proteaceae; sclerophylly; silcrete; southwestern Australia; stomatal crypt; xeromorphy
National Category
Other Earth and Related Environmental Sciences
Research subject
The changing Earth; Diversity of life; Ecosystems and species history
URN: urn:nbn:se:nrm:diva-983DOI: 10.3732/ajb.1400191OAI: diva2:769693
Swedish Research Council, 2010-3931
Available from: 2014-12-08 Created: 2014-12-08 Last updated: 2015-12-02

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