Time and taxonomy

Colin Groves

Resumen


A cladistic approach, attempting to reconstruct phylogeny, is the most objective way of depicting relationships; whole-genome comparisons, such as DNA-DNA hybridisation, show that genetic similarity really does increase with recency of common ancestry. But if we aim to represent taxonomically every dichotomy in the cladogram, more and more taxonomic division will be required, and this has led to the current trend towards unranked taxonomies. To preserve the undoubted advantages of a ranked system, I propose that we retain the modified Linnaean ranking system and its associated “subs” and “supers,” while inserting unranked taxa at whatever point in the system is required. Moreover, to introduce full objectivity, we should try to link at least the modified Linnaean ranks (order, family, tribe, genus), except for species, to time since common ancestry; these time slots can be determined by looking at available fossil and/or molecular information on separation times of mammalian taxa in general, and applying criteria that do least violence to widely accepted taxonomic ranks.

 

Key words: Morphological, molecular, cladistics, unranked taxonomies, linking time to taxonomic rank.

 


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Referencias


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