Phylogeny or an Evolutionary Tree

For generations, learning how to interpret an evolutionary tree has been one of the many basics for a young budding biologist. Here is a 5-step quick guide on the basics of phylogeny interpretation.

How to Interpret a phylogenetic evolutionary tree? 5 quick easy basics

1. Descendants are at the tips.

   

2. The earliest ancestor is at the root of the tree.

   

3. A speciation event occurs where a lineage splits. In other words, the speciation event occurs at the spot where a branching gives rise to two or more new lineages.

   

4. The unique history of species <Fill in the Blank> is the line that follows up to its current descendant but does not touch or share with another species’ lineage.

   

   Let’s give an example. As shown in the figure above, the orange line is the unique history of Species D. The red one is the unique history of Species C, and the blue one for B, and purple one for A. Notice the dashed green line – this represents the shared history of Species C and Species D.
5. Each lineage has its ancestors. These ancestors could be unique to only that specific species or common with other species.

   

   The purple circle indicates the common ancestor of Species C and Species D. Hypothetically, if the purple circle was extended slightly upwards near the tip of Species D, then this would indicate a unique ancestor of Species D. The orange circle represents the common ancestor of Species B and Species D, but also Species B, C, and D. The red circle represents the common ancestor of Species A and B, but again also Species A, B, C, and D.

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