Contributions to Zoology, 79 (4) – 2010Michel Laurin: The subjective nature of Linnaean categories and its impact in evolutionary biology and biodiversity studies

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Conclusion

No objective criterion can be used to assign ranks to taxa, and even attempts at applying such a system have been rare and unsuccessful (Hennig, 1966, 1981). Ranks are devoid of objective reality and are ‘ontologically empty designations’ (Ereshefsky, 2002: S309); therefore, they should be dropped. Because RN is based on non‑existent ranks (and types, which fortunately are real), it should be replaced by a more natural system. This includes PN (De Queiroz and Gauthier, 1990, 1992), but also any other system that does not rely on subjective Linnaean categories (e.g. Papavero et al., 2001; Kluge, 2004: 6–13; Dubois, 2005a, Dubois 2005b; Béthoux, 2007). This was not done earlier because biological nomenclature must be regulated, or communication would be very difficult (Strickland et al., 1843), and until very recently, no viable alternative to RN existed. Such an alternative is now available: the ICPN (International Code of Phylogenetic Nomenclature; also known as the PhyloCode) is a complete, coherent implementation of PN. Drafts have been accessible on the Internet since 2000, and it has been updated regularly (the current version is 4c and dates from January 12, 2010). Development of the ICPN has been supervised by an international society (ISPN) inaugurated in 2004 (Laurin and Cantino, 2004). Since then, that society convened twice more (Laurin and Cantino, 2007; Laurin and Bryant, 2009) to fine-tune the ICPN. The ISPN is open to all systematists, and it recently joined the IUBS (International Union of Biological Sciences; http://www.iubs.org/), an organization to which the societies or organizations that produce the rank-based codes (ICZN, ICBN; International Commission for the Nomenclature of Cultivated Plants, etc.) also belong. Now, dropping ranks without generating nomenclatural chaos becomes possible, and the natural taxonomy that Linnaeus, Darwin and many others dreamt about is finally in sight.