cladograma

A cladograma is a branching diagram used in cladistics to represent hypothesized evolutionary relationships among organisms or other taxa based on shared derived characteristics. In a cladogram, the nodes denote common ancestors, and the branches indicate lineages emerging from those ancestors. The tips of the diagram correspond to the taxa being analyzed, such as species or genera. The arrangement emphasizes the order of branching events and common ancestry rather than the amount of change or the time elapsed.

Key features include its focus on monophyletic groups, or clades, which include an ancestor and all its descendants. Cladograms are constructed using information about synapomorphies, which are shared derived traits that define clades. Traits that are ancestral (plesiomorphies) or derived but not shared (autapomorphies) play different roles in interpretation.

Construction and interpretation: Researchers collect character data from morphology, molecules, or other sources and analyze them with methods such as parsimony, maximum likelihood, or Bayesian inference to identify trees that best reflect the observed similarities and differences. The result is a hypothesis about evolutionary relationships, not a direct record of time or the amount of change.

Distinctions: A cladogram primarily conveys branching order and relationships without implying branch length. If branch lengths are scaled to time or amount of change, the diagram is often called a chronogram or phylogram rather than a strict cladogram.

Limitations: Cladograms are hypotheses dependent on chosen characters and analytical methods; convergent evolution and incomplete sampling can mislead interpretations. They are continually refined as new data become available.