Q.14 Which one of the following methods is used to test the significance of a
predicted phylogeny?
(A) Bootstrap
(B) Maximum likelihood
(C) Maximum parsimony
(D) Minimum evolution
Bootstrap: The Key Method for Testing Predicted Phylogeny Significance
Bootstrap serves as the primary statistical technique to evaluate the reliability of branches in a predicted phylogenetic tree. It assesses confidence by resampling data, making it essential for validating evolutionary relationships in biological research.
Correct Answer
The correct answer is (A) Bootstrap.
This method tests the significance of a predicted phylogeny by generating confidence values for tree branches through repeated resampling of the original dataset. High bootstrap values, typically above 70-95%, indicate robust support for specific clades.
Bootstrap Explained
Bootstrap involves resampling sequence data with replacement to create multiple pseudoreplicates, then reconstructing trees from each. Percentages at nodes show how often a clade appears across these replicates, providing a measure of statistical confidence. This non-parametric approach helps identify unstable branches in phylogenies derived from molecular data.
Maximum Likelihood Overview
Maximum likelihood (ML) constructs phylogenies by finding the tree that maximizes the probability of observing the data under an evolutionary model. While powerful for tree building, ML itself does not test significance; bootstrap or similar methods are applied post-construction to evaluate branch support.
Maximum Parsimony Details
Maximum parsimony seeks the tree requiring the fewest evolutionary changes (steps) to explain the data. It prioritizes simplicity but, like ML, requires bootstrap analysis to assess the significance of the resulting phylogeny.
Minimum Evolution Breakdown
Minimum evolution (often linked to neighbor-joining) builds trees by minimizing total branch lengths from a distance matrix. It focuses on tree estimation, not inherent significance testing, relying on bootstrap for validation.
| Method | Primary Role | Tests Significance? |
|---|---|---|
| Bootstrap | Resampling for confidence | Yes |
| Maximum Likelihood | Probabilistic tree building | No |
| Maximum Parsimony | Fewest changes tree | No |
| Minimum Evolution | Shortest total branch tree | No |
