Paleobotany in the Post-Genomics Era
Gandolfo, Maria .
How to choose a fossil as a calibration point.
IN the last decade, there has been a rise in the interest of the plant fossil record. Fossils potentially provide additional information to assess homology and evolutionary change – e.g. the popular “missing link” phenomenon, may provide character evidence that affects phylogenetic conclusions and thus our understanding of modern relationships, provide evidence of past distributions that can aid in understanding biogeographic histories, and can provide estimates of minimum ages of the clades to which they belong. Lately, many molecular biologists have used fossils in their analyses as a way of providing a calibration point for evolutionary models used to approximate dates for the nodes of phylogenetic trees. However, there has been little if any discussion of the criteria by which calibration fossils can be selected for these studies. A quick examination of these papers suggests that many fossils of questionable identity have been used in this manner, and others that are more confidently identified have been ignored in some cases. When considering the use of a fossil as a calibration point, it is critical to take in account the quality of preservation, the method and details of identification (reliability of the taxonomic placement), and accuracy of the published age. In this presentation I will explore these aspects with the goal of providing basic criteria for the use of fossils to calibrate molecular evolutionary models. These approaches not only provide better primary estimates for ages of clades, but also provide more reliable sources for those molecular biologists wishing to clean up their molecular clocks.
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1 - Cornell University, LH Bailey Hortorium, Dept. Plant Biology, 228 Plant Science Building, Ithaca, New York, 14853, USA
Presentation Type: Symposium or Colloquium Presentation
Date: Wednesday, August 2nd, 2006
Time: 3:30 PM