Character state transformations and the fit of phylogenies to the fossil record

Angielczyk, Kenneth D
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Bernard Price Institute for Palaeontological Research
There is only one true history of life, and the biostratigraphic record and the phylogenetic relationships of organisms provide the most important information regarding this history. Ideally, the historical signal preserved in each of the data sets should be the same, and several methods have been proposed to compare the fit of phylogenies to the fossil record. All of these techniques use stratigraphic data associated with taxa, but our ability to recognize taxa and reconstruct their phylogenetic relationships ultimately is based on patterns of character state distributions that we observe. This raises the question of whether character states can be used to measure the fit of a phylogeny to the fossil record. Here I argue that we can, if the order of appearance of character states is considered. Optimization of character states on a phylogeny results in a predicted order of appearance of character states; derived states must arise after basal states. This order can be compared to that predicted by the fossil record. Although a number of factors can affect the frequency at which derived character states are sampled before basal states in the fossil record, conflicts between the two data sets should be relatively rare. Phylogenies that imply a large number of character state transformations that are inconsistent with the fossil record may need to be reconsidered before the fossil record is criticized.
phylogeny , stratigraphy , character-based measures of fit , taxon-based measures of fit