Question

Which of the following is incorrect regarding the terminologies of phylogenetics?

(a) The branching pattern in a tree is called tree topology

(b) When all branches bifurcate on a phylogenetic tree, it is referred to as dichotomy

(c) In case of dichotomy, each ancestor divides and gives rise to multiple descendants

(d) An unrooted phylogenetic tree does not assume knowledge of a common ancestor

The question was posed to me in an international level competition.

Enquiry is from Phylogenetics Basics in section Molecular Phylogenetics of Bioinformatics

Answer 1

Correct answer is (c) In case of dichotomy, each ancestor divides and gives rise to multiple descendants

The explanation: Sometimes, a branch point on a phylogenetic tree may have more than two descendents, resulting in a multifurcating node. The phylogeny with multifurcating branches is called polytomy. A polytomy is an be a result of either an ancestral taxon giving rise to more than two immediate descendants simultaneously during evolution, a process known as radiation, or an unresolved phylogeny in which the exact order of bifurcations cannot be determined precisely.