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Abstract Detail

Evolution and Diversification in the Sapindales

Renner, Susanne S [1], Grimm, Guido W. [2], Schneeweiss, Gerald M. [3], Stuessy, Tod F. [4], Robert, Ricklefs [5].

Rooting and dating maples via Bayesian evolutionary analyses: Implications for Asian/North American range disjunctions.

Acer comprises c. 124 species and is genetically barely distinct from Dipteronia (two species in SW China), judging from nuclear ITS (606 sequences) and 6 chloroplast loci (6600 bp) sequenced for 74 species and subspecies. Acer has thousands of leaf, fruit, and pollen fossils from the Paleocene onward, but assigning these to extant clades has rarely been possible. Analyses of the 6600-bp data under Bayesian relaxed clocks calibrated with oldest Aesculus fossils (60-63 my old) suggest that Acer diverged from Dipteronia 60 my ago, fitting with both groups' oldest fossils. Similar results are obtained from rbcL data for 128 or 98 Sapindales (incl. 47 or 18 Acer), constrained with Ailanthus, Biebersteinia, Toona, and/or Aesculus fossils. Strict clocks with either data set yield ages of 24-31 my, pointing to rate heterogeneity. Chronograms from clocks relying on uncorrelated rate models (BEAST) and an LTT plot (anchored on the 124 contemporary species) suggest a change in diversification rate at about 35 my ago, fitting with a dip in megafossils at that time (Boulter et al. 1996). Given that the mutual monophyly of Acer and Dipteronia is weakly supported, we tested BEAST clocks as root finders: Relaxed clocks yielded a monophyletic Dipteronia nested in Acer, while strict clocks yielded the opposite. Accepting a mid-Eocene age of the Acer crown group, NE American A. spicatum and A. pensylvanicum became isolated from Asian relatives in the Lower Oligocene and Upper Miocene, respectively; the Eastern A. rubrum/A. saccharinum in the Oligocene/Miocene (and from each other 3-4 my ago); the NW American A. macrophyllum and A. circinatum in the Upper Eocene and mid-Miocene; and A. saccharum in the Lower Miocene; the isolated A. negundo and A. glabrum lines may date back to the Eocene.

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Related Links:
A Nuclear Ribosomal DNA Phylogeny of Acer - open access at Evolutionary Bioinformatics

1 - University of Munich, Biology, Menzingerstr. 67, Munich, Germany
2 - University of Tuebingen, Institute of Geosciences, Sigwartst. 10, Tuebingen, 72076, Tuebingen
3 - University of Vienna, Institute for Botany, Department of Plant Biogeography, Rennweg 14, Vienna, A 1030, Austria
4 - University of Vienna, Institute for Botany, Dept. of Higher Plant Systematics and Evolution, Rennweg 14, Vienna, A-1030, Austria
5 - University of Missouri-St. Louis, Biology, 8001 Natural Bridge Rd., St. Louis, MO, 63121, U.S.A.

Asian/North American disjunctions
Bayesian relaxed clock
Diversification rate
Molecular clock.

Presentation Type: Symposium or Colloquium Presentation
Session: C01
Location: Boulevard B/Hilton
Date: Tuesday, July 10th, 2007
Time: 8:15 AM
Number: C01002
Abstract ID:1177

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