Basic Applied Bioinformatics

CHAPTER 27Interpretation of Phylogenetic Trees

CS Mukhopadhyay and RK Choudhary

School of Animal Biotechnology, GADVASU, Ludhiana

27.1 INTRODUCTION

Phylogenetic trees are frequently encountered in research papers related to evolution, population diversity, microbial studies, and genetics. It is critical to infer the meaning of a given phylogenetic tree, as terms such as “cladogram”, “phylogram”, “phenogram”, etc. sound quite confusing to a novice. This chapter starts with such terminologies, and then the phylogenetic tree is explained to decipher the meaning depicted in general.

SOME TERMINOLOGIES USED FOR PHYLOGENETIC TREES

1. Dendrogram is a broad term used to represent a phylogenetic tree. More precisely, “dendrogram” is a generic term applied to any type of phylogenetic tree (scaled or unscaled).
2. Cladogram is a representation of the ancestor‐to‐descendant relationship through a branching tree. The length of a branch denotes nothing (neither genetic change nor time‐scale). A clade simply means a common ancestor and the descendants (here, species) of that common ancestor.
3. Phylograms are diagrammatic representations of molecular phylogeny, constructed by statistical analysis of molecular data. The tree shows the divergence of species from internal nodes, and the branch length signifies the degree of evolutionary change of the taxa. The common ancestor is shown only in rooted trees.
4. Phenograms are also statistically constructed trees which indicate only the degree of resemblance ...