Chen, Iju , Manchester, Steven R. .
Comparative analyses of modern and fossil seeds of Vitaceae.
Seeds of the Vitaceae (grape family) can be easily distinguished from those of other plant families by a pair of ventral infolds and a dorsal chalaza. Abundant fossil seeds from various Tertiary localities have been assigned to this family. An extensive seed survey of Vitaceae was conducted to refine the phylogenetic placement of the fossil seeds. Seeds representing all 15 living genera (including Leea, separated as Leeaceae by some authors), and about one third of the species (250/750) of this family, were investigated using principle component analysis. The results showed that seeds of the same genus usually share a set of diagnostic characters. The relative length and orientation of the ventral infolds and the shape and position of the chalaza are important characters to distinguish basic seed types that correspond to clades recognizable from other morphological and molecular characters. Most of the fossils appear to conform with modern morphological groupings, suggesting that they can be used for identification to particular extant clades and/or genera. The genera with tetramerous flowers—Cayratia, Cissus, Cyphostemma, and Tetrastigma—typically have a linear or elongate chalaza; the genera with pentamerous flowers—Ampelopsis, Ampelocissus, Parthenocissus, and Vitis—frequently have round or oval chalaza. The seed types of Ampelopsis, Ampelocissus, Parthenocissus, and Vitis are frequently found associated together in the same localities in the North Hemisphere. The majority of fossil seeds, including the oldest known specimens from the Paleocene of Europe and North America have oval chalazas. Fossil vitaceous seeds with linear chalaza are so far known only from the Eocene of Peru, Oligocene of Australia, Oligocene of Europe, and Miocene of Africa. Although fossil flowers of this family have not been recovered, the fossil seed remains indicate that both the tetramerous and pentamerous clades, and several of the extant genera, were established by the Eocene.
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1 - University of Florida, Florida Museum of Natural History, Dickinson Hall, PO Box 117800, Gainesville, Florida, 32611-7800, US
2 - University of Florida, Department of Botany, Florida Museum of Natural History, P.O. Box 117800, Gainesville, Florida, 32611-7800, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 28th, 2008
Time: 10:45 AM