Search

Background and Aims: The prevailing view from the areocladogenesis of molecular phylogenies is that the iconic South African Cape Proteaceae (subfamily Proteoideae) arrived from Australia across the Indian Ocean during the Late Cretaceous (100-65 million years ago, Ma). Since fossil pollen indicates that the family probably arose in North-West Africa during the Early Cretaceous, an alternative view is that it migrated to the Cape from North-West-Central Africa. The plan therefore was to collate fossil pollen records throughout Africa to determine if they are consistent with an African (para-autochthonous) origin for the Cape Proteaceae, and to seek further support from other palaeo-disciplines., Methods: We used palynology (identity, date and location of records), molecular phylogeny and chronogram preparation, biogeography of plate tectonics, and palaeo-atmospheric and ocean circulation models., Key Results: Our collation of the rich assemblage of Proteaceae palynomorphs stretching back to 107 Ma (Triorites africaensis) in North-West Africa showed its progressive overland migration to the Cape by 75-65 Ma. No key palynomorphs recorded in Australia-Antarctica have morphological affinities with African fossils but specific clade assignment of the pre-Miocene records is not currently possible. The Cape Proteaceae encompass three molecular-based clades (tribes) whose most recent apparent ancestors are sisters to those in Australia. However, our chronogram shows that the major Adenanthos/Leucadendron-related clade, originating 54-34 Ma, would have 'arrived' too late as species with Proteaceae affinities were already present ~20 million years earlier. The Franklandia/Protea-related clade arose 118-81 Ma so its distinctive pollen should have been the foundation for the scores of palynomorphs recorded at 100-80 Ma, but it was not. Also, the prevailing winds and ocean currents trended away from South Africa rather than towards, as the 'out-of-Australia' hypothesis requires. Based on the evidence assembled here, we list three points favouring an Australian origin and nine against; four points favouring an Antarctic origin and seven against; and nine points favouring a North-West-Central African origin and three against., Conclusions: We conclude that a gradual migration of the Proteaceae from North-West-Central Africa southeast→south→southwest to the Cape and its surroundings occurred via adaptation and speciation during the period 95-70 Ma. We caution that incorrect conclusions may be drawn from literal interpretations of molecular phylogenies that neglect the fossil record and do not recognize the possible confounding effects of selection under matched environments leading to parallel evolution and extinction of bona fide sister clades., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Unlabelled: •, 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., (© 2014 Botanical Society of America, Inc.)