Doyle, James A. , Pirie, Michael D. .
Fossil data and ages of clades in Annonaceae (Magnoliales).
A phylogenetic evaluation of the oldest fossil records of Annonaceae and other Magnoliales illustrates general problems encountered in placing fossils in phylogenetic trees of living taxa and provides specific insights on the time of origin and diversification and the geographic history of this major tropical family. Perichalazal seeds with all three basic types of endosperm rumination occur in the London Clay (Early Eocene), indicating that the four major clades in the family (Anaxagorea, ambavioids, SBC, LBC) had diverged and entered Laurasia by 50 Mya. Maastrichtian (latest Cretaceous) seeds with lamelliform ruminations might suggest presence of the LBC (inaperturate clade) around 70 Mya, but because of ambiguity in character optimization they only provide a minimum age for the whole crown group of Annonaceae. The crown group is pushed back further by the discovery of Futabanthus in the Coniacian of Japan (89 Mya), which appears to attach near the base the clade including all Annonaceae except Anaxagorea. Archaeanthus, a flower with magnoliaceous features from near the Albian-Cenomanian bounday in Kansas, has been used to assign a minimum or fixed age of 98-100 Mya to the node connecting Annonaceae and Magnoliaceae, and its relationship to Magnoliaceae is confirmed by phylogenetic analysis. However, Endressinia, from the late Aptian of Brazil, appears to belong in or below the clade including Annonaceae and their closest outgroups (Eupomatia, Degeneria, Galbulimima), which pushes the age of the Annonaceae-Magnoliaceae node back to at least 112 Mya. Use of fixed calibrations based on either Futabanthus or Endressinia results in similar molecular dates within Annonaceae, but because there are no strong calibrations or maximum ages lower in the angiosperm tree, it is important to realize that these internal dates are essentially minimum ages.
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1 - University of California, Davis, Department of Evolution and Ecology, One Shields Ave., Davis, California, 95616, USA
2 - University of Stellenbosch, Department of Biochemistry, Private Bag X1, Matieland 7602, Stellenbosch, South Africa
Presentation Type: Oral Paper:Papers for Sections
Location: 552A/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 9:30 AM