Glossary

Phylogenetic analysis

Inferring the evolutionary relationships between organisms or gene sequences and representing them as a branching tree.

Phylogenetic analysis infers the evolutionary relationships between organisms, populations, or gene sequences, typically represented as a branching tree in which closer branch points indicate a more recent common ancestor.

It starts from a sequence alignment across the sequences being compared, then applies a tree-building method, ranging from simple distance-based clustering to more computationally intensive maximum-likelihood or bayesian inference approaches, that searches for the tree topology best supported by the pattern of similarities and differences in the data.

Phylogenetic analysis is used to trace the origin and spread of infectious disease outbreaks, reconstruct species' evolutionary history, and study how genes or traits evolved over time, and outbreak tracing in particular has turned it into a real-time public health tool rather than a purely historical one; it also builds directly on the differences identified through variant calling when comparing many samples. Pitfalls include that different genes within the same organisms can support conflicting trees, a real biological signal from processes like recombination rather than analytical error, and that the "best-supported" tree from any method remains a statistical estimate rather than a proven history, which is why results are reported with confidence measures instead of certainty.

Last reviewed September 22, 2026

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Related terms

Sequence alignment Arranging DNA, RNA or protein sequences to identify regions of similarity that may reflect shared function or ancestry. Variant calling Identifying positions where a sequenced sample's DNA differs from a reference genome. Bayesian inference A statistical approach that updates the probability of a belief as new evidence arrives, starting from a prior assumption. Clustering An unsupervised technique that groups data points so items within a group are more similar to each other than to items outside it.