NUMERICAL TAXONOMY

            A. INTRODUCTION

            Numerical taxonomy is a branch of modern approach to taxonomy or synthetic taxonomy in which the analysis of various types of taxonomic data is done by mathematical or computerized methods. It is also referred as ‘Taximatrics’. In numerical taxonomy, the numerical evaluation of similarities or affinities between taxonomic units is counted, and the arrangement of these units into taxa is done on the basis of their affinities.

            Adenson (1767), a French Botanist was the first to put forward a plan for assigning numerical values to the similarity between organisms. He tried to use as many as characters as possible for classification. And as such classification is known as ‘Adensonian classification’. Adensonian principles have developed several new methods in taxonomy during recent years, particularly after 1960, and all these methods are included in numerical taxonomy.

            The use of modern electronic data processing technique and several other methods of the numerical taxonomy have helped in the evolution of several new classifications of plants.

            B. ADVANTAGES OF NUMERICAL TAXONOMY

Sneath and Sokal (1973) have mentioned the following advantages of numerical taxonomy –

1. In comparison with the classical taxonomy, the data in numerical taxonomy are collected from more variety of sources, such as morphology, physiology, phytochemistry, cytology, proteins, etc.

2. Through numerical taxonomy, much taxonomic work can be done by less highly skilled workers.

3. Numerically coded data may be used easily for the creation of keys, maps, descriptions, catalogues, etc. with the help of existing electronic data processing system in herbaria and other taxonomic institutions.

4. Because the numerical methods are more sensitive in delimiting taxa, they provide better keys and classification systems in comparison to classical taxonomic methods.

5. The quality of classical taxonomy is improved by numerical taxonomy as more and better described characters are used in the later.

6. Numerical taxonomy has suggested several fundamental changes in the classical principles of taxonomy in general and classification system in particular.

7. Number of existing biological concepts has been reinterpreted in the light of numerical taxonomy.

 C. APPLICATION OF NUMERICAL TAXONOMY

Some of the examples of the application of numerical taxonomy are as follows –

1. Numerical methods are used considerably to study the similarities and dissimilarities in bacteria, and other micro-organisms.

2. Numerical taxonomy is used for delimiting of several angiospermic genera like – Solanum, Oryza, etc.

3. Several angiospermic taxa are re-classified using numerical methods.

           4. Sneath and Sokal (1973) have mentioned several examples of of the application of numerical taxonomy in several angiospermic genera like – Apocynum, Crotolaria, Cucurbita, Chenopodium, Oenothera, Salix, Zinnia, Barley cultivars, Maize cultivars, Wheat cultivars, etc.

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