cladistically

Cladistically is an adverb describing actions, analyses, or interpretations that follow the principles of cladistics. Cladistics is a method of biological classification based on common ancestry, in which groups are defined as clades—lineages that include a common ancestor and all its descendants. In a cladistic framework, taxa are evaluated using synapomorphies, shared derived traits that diagnose clades, and the evolutionary relationships are typically represented as a cladogram.

When one says that a grouping is cladistically justified or that an analysis was conducted cladistically, they mean that the grouping or the inferred relationships are defined by patterns of shared derived characters rather than overall similarity (phenetics). Cladistically informative traits are those that help resolve branching order and monophyly; outgroup comparison helps polarize character states.

Historically, cladistics emerged from the work of Willi Hennig in the mid-20th century and became a standard framework in systematics. The term "cladistically" is used to emphasize adherence to this framework, regardless of whether data come from morphology, molecules, or both.

Limitations and debates: cladistic analyses can be sensitive to character choice, coding, and homoplasy (convergent evolution or reversals). In modern practice, cladistics often integrates molecular data and uses computational methods such as maximum parsimony, maximum likelihood, and Bayesian inference within a cladistic paradigm.

Related topics include cladistics, phylogenetics, monophyly, and synapomorphy.