Phylogenetics

Apart from utilizing cladistic analyses in order to infer relationships among fossil and extant anthropoids, I am interested in exploring possible improvements to available methodology.

Chronobiogeographic analysis

In 2006, I collaborated with Erik Seiffert in an attempt to develop a method that would allow researchers to incorporate biogeographic information into phylogenetic analyses. The inspiration for this was the recognition that the changes in geographic distribution implied by competing phylogenetic hypotheses sometimes seemed highly asymmetrical in terms of plausibility. This plausibility was also highly dependent upon the time frame of the purported range change (vicariance, expansion, or dispersal). Accordingly, we had to develop a method that would also incorporate chronostratigraphy. The result (Rossie & Seiffert, 2006) was our "chronobiogeographic" character, which operated in a manner similar to the stratocladistic technique developed by Fisher (1992).

Examples illustrating the calculation of character and chronobiogeographic parsimony debt for two competing hypotheses using the step matrix from figure 1. Schematized land masses A-D are arranged as in figure 1. Taxa W, X, Y, and Z are found in A₁, D₃, B₁, and D₂, respectively. The cladistic hypotheses differ in their interpretation of the morphological state ‘0’ in taxon X. Chronobiogeographic analysis finds it more parsimonious to consider this state a reversal in taxon X, while cladistic analysis of the two morphological characters alone interprets it as a symplesiomorphy. Note that as in Fox et al. (1999) morphological (“morph”) debt is the number of homoplasies (annotated as ‘r’ for the reversal in 2b), not the total number of state changes (annotated as hash marks).

Rossie, J. B. & Seiffert, E. R. (2006) Continental paleobiogeography as phylogenetic evidence. In: Lehman, S.M. and J. Fleagle (Editors) Primate Biogeography. New York: Plenum/Kluwer Press.