Cladistics tests whether traditional taxa match evolutionary relationships, revealing when similar morphology results from convergence rather than shared ancestry alone.
Coverage 2018–2018 · Updated 15 Jul 2026
Cladistics tests whether a traditional taxonomic group corresponds to evolutionary relationships by comparing its membership with a tree built from independent evidence.
Traditional classifications often emphasized morphology, but similar traits can evolve independently. Conserved gene sequences can reveal that a familiar family is not one clade, prompting species to be transferred between families.
In the figwort-family case, chloroplast sequence comparisons produced clades that conflicted with the traditional morphology-based Scrophulariaceae. The classification was revised so named families more closely matched common ancestry.
When several gene sequences consistently place a plant outside its traditional family, researchers can reclassify it rather than preserving a grouping based on convergent flower form.
Students need the logic of testing and revision, not memorized details of every transferred plant. A new tree remains a testable hypothesis that can change with better sampling or evidence.
This objective is assessed through multiple choice.
Build the answer around this relationship: Cladistics can test whether traditional taxa reflect evolutionary ancestry.
Representative question
The figwort family is a large one consisting of many flowering plants that look similar. For what reason have some members of the family been reclassified into a new family?
Cladistic analysis shows the differences in flower structure to be fewer than the shared similarities.
DNA analysis shows the similarities in flower shape to be a product of convergent evolution.
DNA analysis shows some of the families to have suffered recent mutations in only one gene.
DNA analysis shows the similarities between the seed dispersal strategies to be a product of divergent evolution.
A3.2 exam answers are strongest when they sound like evidence arguments. Classification organizes diversity, but fixed ranks and morphology can mislead. Evolutionary classification should match phylogeny using monophyletic clades supported by synapomorphies. Molecular clocks estimate divergence time from calibrated sequence differences. Cladograms are built from aligned sequence data and interpreted by nodes, not tip positions. Cladistics can reclassify old taxa, and rRNA evidence supports the three-domain system.
