Systematics Section / ASPT
Mathews, Sarah .
The positions of Ceratophyllum and Chloranthaceae inferred from phytochrome data.
PHYLOGENETIC analyses of data from three phytochrome genes, PHYA, PHYB, and PHYC, in 105 taxa suggest that Ceratophyllum and Chloranthaceae diverge early, above ANITA (Amborella, Nymphaeales, Austrobaileyales) but before other angiosperms. MP and ML bootstrap support values and Bayesian posterior probabilities for the divergence of both taxa before monocots, magnoliids, and eudicots range from 52% to 89%, depending on the data partition and analytical approach. In most trees, Ceratophyllum diverges first, followed by Chloranthaceae, supported by MP bootstrap values from 67 to 85%. Optimal ML trees have the same topology. The positions of Chloranthaceae and Ceratophyllum were largely stable in 17 analyses that differed by analytical approach, rate class of sites analyzed, and the inclusion or exclusion of Amborella and water lilies. There were four exceptions, none of which received support above 50%: Ceratophyllum + Chloranthaceae were sister to a clade of monocots, magnoliids, and eudicots (105 taxa, ML without fastest of 8 rate classes); Ceratophyllum + Chloranthaceae were sister to eudicots (105 taxa, MP without rate classes 7 & 8); Ceratophyllum was sister to monocots and Chloranthaceae still diverged above ANITA (105 or 101 taxa, MP without rate classes 6, 7 & 8). Also consistent across analyses was a clade of monocots + eudicots (MP/ML boostrap values from 50-80%, posterior probability of 100%). The position of Ceratophyllum has remained enigmatic, with limited evidence available from sources other than nucleotide data. However, the early divergence of Chloranthaceae in phytochrome trees is consistent with the presence of fossil pollen assignable to Hedyosmum in the early Cretaceous and with trees inferred from morphological data.
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1 - Harvard University, Arnold Arboretum, Harvard University Herbaria, 22 Divinity Avenue, Cambridge, Massachusetts, 02138, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 144/Performing Arts Center
Date: Tuesday, August 1st, 2006
Time: 11:15 AM