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Branching diagram with curved lines, basic features

This style is often used in textbooks and popular publications. The tree with curved lines shown here depicts the relationships among ants, flies, butterflies, and beetles. This diagram has the following basic features:

• An arrow showing that evolutionary time flows from the bottom root of the tree (earlier times) towards the top tips (more recent times).
• A root at the bottom from which the other branches emanate. The root represents the ancestor that all the lineages on the tree have in common.
• A branching pattern. The branching pattern of this tree shows two branches emanating from the root of the tree leading upwards.  The left branch leads to ants at the top of the tree.  The right branch splits into two branches leading upwards.  The right branch of these leads to beetles at the top of the tree.  The left branch of these splits into two branches leading upwards. The left branch of these leads to flies at the top of the tree.  The righthand branch of these leads to butterflies at the top of the tree. The branching pattern represents evolutionary relationships. It tells you how closely related different groups are. Here, flies and butterflies are more closely related to each other than either is to beetles because their branches join more recently than either joins the beetles’ branch. All the insect groups are related to one another, but some are more closely related than others.
• Branching points. Branching points represent the ancestor that all the lineages whose branches join at that point have in common. Three branching points on the tree are highlighted. Point 1 appears over the point at which the fly and butterfly branches meet.  When you click it, that point and the two branches emanating upwards from it (the fly and butterfly branches) are highlighted. Point 2 appears over the point at which the beetle branch connects to the shared ancestral branch of flies and butterflies. When you click it, that point and all the branches emanating upwards from it (including the fly, butterfly, and beetle branches) are highlighted. Point 3 appears over the point at which the ant branch connects to the shared ancestral branch of flies, butterflies, and beetles. When you click it, that point and all the branches emanating upwards from it (including the ant, fly, butterfly, and beetle branches) are highlighted. Here, point 1 is the most recent ancestor that flies and butterflies have in common. Point 2 is the ancestor that flies, butterflies, and beetles have in common. Point 3 is the ancestor that all the lineages have in common.
• Tips represent groups of organisms. On the tree, the icons depicting ants, flies, butterflies, and beetles are each highlighted. Here, each tip is a major group of insects.

Buttons at the bottom are labeled “Advanced tree features” and “animated video.” A button at the top is labeled “select a tree.”

Branching diagram with curved lines, advanced features

This style is often used in textbooks and popular publications. The tree with curved lines shown here depicts the relationships among 11 unspecified groups. The tree has a vertical timescale running from 200 million years ago at the root of the tree to 0 million years ago at the top of the tree. This diagram has the following basic features:

• Highlighted group or name on a lineage. “Name of group” is boxed, highlighted in yellow, and appears on a branch of the tree. Also, two terminal branches are circled at the top, labeled “name of group”, and are highlighted. When a name is written on or above lineages, it indicates that those lineages belong to the same named group.
• Labeled branch mark. One lineage on the tree has a short line on it that is labeled “dark wings evolve.” This indicates that a particular feature (such as having dark- instead of light-colored wings) evolved and was inherited by the descendent lineages, the lineages that have that ancestor in common.
• A polytomy is represented by three or more lineages coming from the same branching point. A branching point from which three branches all directly emanate (one going to the left, one going up, and one going to the right) is highlighted, along with those descendant lineages. A polytomy indicates that scientists are uncertain about which of those lineages are more closely related.
• Differently colored branches. Three terminal lineages and the branching point at which they meet are colored red, instead of black as the rest of the branches on the tree are. This usually indicates that a particular feature evolved and was inherited by the highlighted lineages. It can also mean that the highlighted branches share the same name.
• Images near different branches. Three segments of the tree have drawings of a beetle near them, which are highlighted. The lowest beetle is the largest and the beetle highest on the tree is the smallest. This can indicate hypotheses about what ancestors looked like or what traits they had.
• Varying branch length with timescale. Two branches with different lengths are highlighted. Varying branch length with a timescale indicates when different lineages split or extinction events occurred. When a timescale is not present, varying branch length just reflects the graphic design of the tree and does not indicate anything about the evolutionary history of the group.

Buttons at the bottom are labeled “Basic tree features” and “animated video.” A button at the top is labeled “select a tree.”

Animated video

An animated video shows these different styles of branching diagram morphing into another. Each diagram depicts the relationships among ants, flies, butterflies, and beetles. All evolutionary trees, no matter what they look like, represent the same thing: evolutionary relationships.

Buttons at the bottom are labeled “basic tree features” and “advanced tree features.” A button at the top is labeled “select a tree.”

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