Calibrating phylogenies: are we using the right fossils?

2011 REU Project:

A critical contribution of the fossil record to our understanding of evolution is to provide ages for when taxa and their distinguishing features arose. Few studies broadly integrate information from the fossil record with that for living organisms, and fewer yet take into account the biases inherent to either, leading to conflicting results from the two disciplines. For example, fossil record dates for evolutionary events clash with those extrapolated from molecular phylogenies for many major clades. One possible reason for this may be incongruent scales of resolution between the fossil record and molecular divergence estimates. In order to test how compatible these two sources of age information are, age estimates and variances for evolutionary branching events will be compared to statistical measures of fossil record quality for a diverse sample of clades. These analyses will determine whether confidence intervals on fossil ages of overlap corresponding molecular age estimates, and whether their magnitude is greater or smaller than the variances on the extrapolated molecular ages of these groups. They will also inform us as to whether fossils chosen for calibration tend to come from taxa and ages with relatively good fossil records or not. Results may shed light on causes for discrepancies between the two sources of temporal information and provide criteria for improved choice of fossils for calibration purposes.

Research methods and techniques: The participant will be given an introduction to the theoretical background for methods of measuring completeness of the fossil record and techniques for reconstructing divergence ages from molecular data, as well as instruction on paleontological  methods for analyzing the fossil record (simple gap analysis) and sources for temporal information on fossils (e.g. www.paleodb.org).  The project will cover several taxonomic groups (e.g. birds, mammals, arthropods), and the undergraduate participant will gather information on the fossil record of these groups, run analyses to determine the confidence intervals on their group and its constituent clades, and compare results to the published predictions of molecular phylogenies using appropriate statistics. Candidates with programming/bioinformatics skills are preferred.

Curator/Advisor: Dr. Peter Makovicky, Dept. of Geology