There are many very good references that explain in much more details this methodology than I will do. The ones I have used a lot to learn and practice are:
- Darly P. and Tassy P., La reconstruction phylogénétique: concepts et méthodes, 1993 (http://sfs.snv.jussieu.fr/pdf/Darlu_Tassy_online.pdf)
- Lipscomb D.L., Basics of Cladistics Analysis, 1998, (http://www.gwu.edu/~clade/faculty/lipscomb/Cladistics.pdf)
- Wiley, E.O., Siegel-Causey, D., Brooks, D.R. and Funk, V.A., The Compleat Cladist: A Primer of Phylogenetic Procedures, 1991 (http://www.archive.org/details/compleatcladistp00wile)
I simply want to give enough material here to help understand cladistics and see how it can work in astrophysics.