Polytomy

Definition

A polytomy is a section of a phylogenetic tree where a single ancestral lineage splits into three or more descendant lineages simultaneously. It often indicates unresolved evolutionary relationships among those lineages.

5 Must Know Facts For Your Next Test

1. Polytomies are depicted as nodes in a phylogenetic tree with more than two branches.
2. They represent uncertainty in the evolutionary relationships between lineages.
3. Hard polytomies suggest simultaneous divergence events, while soft polytomies indicate insufficient data to resolve branching order.
4. Polytomies can result from rapid speciation events or lack of distinguishing morphological or genetic data.
5. Resolving polytomies often requires additional data such as molecular sequences or fossil records.

Review Questions

Related terms

Phylogenetic Tree: A diagram that depicts the evolutionary relationships among various biological species based upon similarities and differences in their physical or genetic characteristics.

Node:

A point on a phylogenetic tree where a single ancestral lineage splits into two or more descendant lineages.

Clade: A group of organisms that includes an ancestor and all its descendants, forming a single branch on the tree of life.