Numerical taxonomy

The numerical taxonomy or Phänetik is a classification system in biological systematics. The aim is to establish a biological taxonomy based on morphological features. It draws extensively on computer-assisted calculation procedures and in particular the cluster analysis. The concept of numerical taxonomy was founded in 1961 by Robert R. Sokal and Peter Sneath ( 1923-2011 ) developed in the book Principles of Numerical Taxonomy.

Motivation and practice

The morphological orientation of the numerical taxonomy was already in their development in contrast to the majority of the taxonomic theory and practice. The vast majority of biological systematics is based on the phylogenetic development. The knockout evolution of theoretical considerations, however, is explicitly desired by Sokal and Sneath. The aim is to develop a generally applicable, theory -free as possible taxonomical system that is equally binding on the various disciplines such as ecology, evolutionary biology or paleontology.

The numerical taxonomy based on a large number of morphological features which must be observable and quantifiable all. The extent is determined in the given them the characteristics of individuals. By means of complex, computer-based method as to an objective measure of similarity of individuals are found. The similarities can then be used as material for a taxonomic system.

Review and inclusion in the research

The numerical taxonomy has not been able to put in the biological system. On the one hand, a purely morphologically oriented taxonomy is rejected as unrealistic by evolutionary biologists. On the other hand there are serious epistemological objections to the phänetische conception of an objective taxonomy. Morphological species concepts have led in part subjective and often of available methodology and specific research interests due to the necessary selection and weighting of morphological features. Secondly, the majority of taxonomists today believe that the taxonomy should be guided by the phylogenetic criteria. Since the clustering algorithms used in numerical taxonomy does not distinguish between convergent and lineage same characteristics, they result in a variety of cases, no correct reconstruction of phylogenetic ( evolutionary ) processes. Convergent evolution often affects a variety of morphological features in common (for example, in a comparison of birds and bats ), so that a purely quantitative assessment is misleading.

However, the problems of numerical taxonomy not change the fact that it is being used successfully in some areas. This is especially true for areas where other species concepts are not applicable. This is for example the case in paleontology, where some of the biological species concept Ernst Mayr's often can not be applied, since usually no information about the reproductive options are available.

The claim to have presented a general taxonomic method, however, can be regarded as a failure. However, this does not exclude that the Phänetik could permanently have a place in a plurality of taxonomic systems.