Systematics/Phytogeography / Taxonomie/ Section
Wurdack, Kenneth .
Evolution and biogeography of Picrodendraceae: saga of the spiny-pollen spurges.
Picrodendraceae is a small family of ca 24 genera and 90 species that were formerly classified in Euphorbiaceae s.l. subfamily Oldfieldioideae and distinguished by echinate pollen. They have a great diversity of form from ericoid desert shrubs to tropical trees and simple or compound leaves. In recent Malpighiales ordinal phylogenies Picrodendraceae are sister to Phyllanthaceae, another euphorb segregate. Both families share a suite of gynoecial and fruit features including 2 ovules/locule and explosive fruits. My combined molecular phylogeny samples nearly 50 taxa and 6 genes (plastid infA, ndhF, rbcL, and trnL-F; and nuclear ITS and low-copy EMB2765) and is fairly congruent with previously published results based on morphological and pollen characters. Notably different are the exclusion of Croizatia (to Phyllanthacaeae) and Paradrypetes (to Rhizophoraceae) that had traditionally been considered primitive members of the group, and a new placement for Hyaenanche. Podocalyx from Amazonian South America is sister to the rest of the family and has links to Phyllanthaceae (i.e., ecarunculate seeds and wood structure). The family contains 2 major subclades, (1) Caletieae with an Australasian radiation, and (2) Picrodendreae with American and African members, including Hyaenanche previously misplaced in Caletieae. Oldfieldia and Picrodendron also belong with the latter despite sometimes being excluded from the family due to aberrant seed anatomy. The possibly horizontally transferred mt cox1 intron is present in 3 genera (Podocalyx, Piranhea, and Tetracoccus) and missing in the rest.
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1 - Smithsonian Institution, Botany Department, PO Box 37012, NMNH, MRC-166, Washington, DC, 20013-7012, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Wednesday, July 30th, 2008
Time: 2:00 PM