Cladelevel

Cladelevel is a term used in discussions of phylogenetic classification to refer to the relative depth or scope of a clade within a hierarchical, clade-based taxonomy. It denotes how broadly or narrowly a clade is defined within a tree, independent of traditional Linnaean ranks such as class or order. As such, cladelevel is a descriptive, not formal, label used primarily in theoretical or educational contexts to compare clades without invoking rank-based terminology.

Because cladelevel depends on the particular phylogeny and definitions adopted, it can vary across studies. A basal or early-diverging clade would typically be described as having a lower cladelevel, whereas a more derived or crown-group clade would have a higher cladelevel in the same framework. The concept is often discussed in relation to the shift toward clade-based nomenclature under systems like the PhyloCode, which names clades by relationships rather than fixed ranks.

However, cladelevel is not an official taxonomic rank and is not codified in major nomenclatural codes. Because there is no universal standard, its use can be ambiguous and lead to confusion if not accompanied by precise clade definitions and clear phylogenetic context.

In practice, scientists rely on established clade names (for example, crown groups or total groups) and, when useful, describe relative depth informally with terms such as basal or derived in connection with clade names. Cladelevel serves as a conceptual aid rather than a formal criterion for naming.

See also: clade, crown group, total group, monophyly, PhyloCode, taxonomy.