Suggestions to improve the Taxonomy Index (T-Index) introduced by Valdecasas (2011).

In the original description of the index, S i is the number of taxa in the given clade and rank after the study. The meaning of “number of taxa” must be the number of valid taxa in this context. This suggests that the number of taxa can only be higher after the taxonomic revision. However, synonyms are abundant in most taxonomic groups in various proportion (May & Nee 1995; Patterson 1996). Synonymising taxa, and thus, decreasing the number of valid taxa is frequent in many taxonomic revisions. A lower number of taxa after a taxonomic revision results in an even higher T-Index than the number of taxa treated (see Table 1).