Spjut, Richard W. .
Biogeographical data on putative hybrids†for Species of Taxus (Taxaceae) in the Himalayas and†North America.
A geographical analysis of Taxus, based on study of leaf characters for 867 herbarium specimens collected throughout the range of the genus, is presented for two Himalayan species and two American species. Characters include the number of cells across the abaxial margin without papillae, the number of stomata rows in a stomata band, and the angle at which leaves diverge from twigs. Taxus contorta, a western-central Himalayan species, closely allied to the Euro-Mediterranean T. baccata, shows an increase in number of stomata rows in its eastern-most range, in contrast to T. wallichiana, a southwestern Chinese to central Himalayan species, that shows a decrease in number of stomata rows in the western part of its range. The higher and lower stomata counts, respectively, for each speciesówhere their ranges are sympatricómay be the result of hybridization. Further evidence for hybridization is presented based on the angle of leaf divergence in which leaves of T. contorta are shown to spread at increasingly wider angles going from west to east. In North America, T. globosa, and its relatives further north, show a decrease in number of stomata rows from south to north. At the northern-most range in Mexico are specimens of T. globosa that are not easily distinguished from the rare Florida yew. These are thought to be the result of former contact between the the two species. -DU
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Nomenclatural and Taxonomic Review of Three Species and Two Varieties of Taxus (Taxaceae) in Asia
Key to the Species of Taxus in North America
Taxus wallichiana Group In Asia
Taxus baccata Alliance
Taxus cuspidata Alliance
1 - World Botanical Associates, Po Box 81145, Bakersfield, California, 93380-1145, USA
naturally occurring hybrids in Taxus
leaf anatomical characteristics of Taxus
Presentation Type: Oral Paper:Papers for Topics
Location: 134/Performing Arts Center
Date: Wednesday, August 2nd, 2006
Time: 9:00 AM