Home/Cladogram vs phylogenetic tree

Cladogram vs phylogenetic tree

The short answer: a cladogram shows only the order in which lineages split. A phylogenetic tree can show that and use branch lengths to represent how much change or how much time is involved.

The difference in one line

Every cladogram is a phylogenetic tree, but not every phylogenetic tree is a cladogram. "Phylogenetic tree" is the umbrella term; a cladogram is the version where branch lengths carry no meaning.

A cladogram. The tips are aligned because branch length carries no meaning here; only the branching order is being shown.

A phylogram of the same tree. Branch lengths are now drawn to scale, so the tips end unevenly and a scale bar is added.

Side by side

	Cladogram	Phylogram	Chronogram
Branch length means	Nothing	Amount of evolutionary change	Time
Tips aligned?	Usually yes	No, they end wherever the data puts them	Yes, at the present day
Shows branching order	Yes	Yes	Yes
Needs a scale bar	No	Yes	Yes (a time axis)
Typically built from	Shared derived characters	Sequence or trait data with rates	Molecular clocks, fossil calibration

How to tell which one you're looking at

Tips all flush in a neat line? Almost certainly a cladogram.
Tips ending at ragged, uneven positions? A phylogram, the lengths are carrying information.
A scale bar or an axis in millions of years? A chronogram.

If a diagram has no scale bar, assume its branch lengths mean nothing. Reading time or amount of change into a plain cladogram is the most common misinterpretation of these diagrams.

Which should you use?

Use a cladogram when the question is who is related to whom. It's the right choice for coursework, for reasoning from a character matrix, and whenever you want the relationships to be read without distraction. It's also the honest choice when you don't have rate or timing data, drawing branch lengths you can't justify implies precision you don't have.

Use a phylogram when you have data on how much change occurred along each lineage, typically from molecular sequences. Use a chronogram when you have dated nodes and want to show when splits happened.

Related terms you'll meet

Dendrogram, any branching diagram, including ones with nothing to do with evolution (clustering results, for instance).
Phylogeny, the evolutionary history itself, as opposed to the diagram of it.
Cladistics, the method of grouping organisms strictly by shared derived characters.
Taxonomy, naming and classifying organisms, which today usually tries to follow clades.

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Frequently asked questions

Is a cladogram a phylogenetic tree?

Yes. 'Phylogenetic tree' is the general term for any diagram of evolutionary relationships. A cladogram is the specific case where branch lengths aren't meaningful and only the branching order is being claimed.

Can a cladogram show time?

No. If you need to show when splits happened you want a chronogram, where branch lengths are scaled to time and nodes are dated from fossils or molecular clocks.

What is a phylogram?

A phylogenetic tree whose branch lengths are proportional to the amount of evolutionary change along each lineage, so tips typically don't line up.

Which one do I need for a biology assignment?

Almost always a cladogram. Coursework that gives you a character matrix and asks for a diagram of relationships is asking for branching order, not branch lengths.

Can the same data give different trees?

Yes. Conflicting characters can support different arrangements, which is why parsimony, preferring the tree needing the fewest evolutionary changes, is used to choose between them.