Phenetic method or Numerical taxonomy
This method involves clustering or grouping of individuals of a taxon or several taxa. Based on overall similarity, identifications are being made. The desired size of the clusters or groupings is called the operational taxonomic unit (OTU).
The identification method involves measurement of taxon to taxon similarity or dissimilarity. It is measured using a scale of 0 to 1. ‘1’represents perfect identity. ‘-1’designates dissimilarity between taxa. In this method enormous amount of data are collected for related groups. Analyses are made, using statistical tools and computers.
The characterization and identification of a cell’s complete chromosome set is referred to as karyotyping. It is the first stage in the process of using chromosomes in taxonomy.
Karyotypes within interbreeding populations of a species are usually constant. Between species there may be variation in chromosome number and size. Final stages of chromosomal aberrations such as inversions and translocations can give clues regarding intermediary stages.
Chemotaxonomy refers to the use of information about small molecules produced by the action of enzymes. Protein fractions in electrophoretic techniques, identification of amino acids in chromatography, prevalence of isoenzymes in tissue materials are all tools employed in chemotaxonomy. The occurrence of specific pheromones, colour pigments, toxins also help as keys in taxonomy.
This method depends on identification and dating of fossils. Availability of a good complete fossil provides better chance for identification. In several fossils, their sections taken through laborious processes have provided the identification features.
The fossils are normally studied along with other accompanying fossils, its geographic location and other factors. Even though it is possible to assign a fossil to a genus or other higher level, fixing the species is not always possible.