Taxonomic Keys

Taxonomic keys are used to identify animals and plants. These are defined devices comprising a set of contradictory or contrasting statements or even propositions, which necessitate the identifier to compare and make decisions given the statements in the key and associated with the entity to be identified.

This process aids in the quick identification of an entity that is unknown. It always provides a choice to select between two conflicting statements wherein one is accepted, and the other is rejected. A couplet is a single pair of contradictory characters, while each of the statements in the couplet is referred to as the lead. At each of the levels, if a correct choice is made, one can reach and arrive at the accurate name of the plant or entity unknown.

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How To Use Keys?

• Read the introductory comments carefully
• Keys should be aptly selected from the manuals, floras, handbooks, monographs etc. For instance, the cultivated plants are not typically given in the floras, in this case, manuals are used
• Before you make a choice, carefully read and understand both the leads. At times, the second lead seems to be more appropriate than the first
• With the help of a glossary, check the meaning of unknown terms
• Many specimens/materials would be required to measure when measurement of fruit, leaves are used
• Refrain from making decisions on the basis of a single observation
• Verify and validate results after reading description, equating specimens and the illustration or with that of an authentic herbarium specimen

How are Keys Constructed?

• Use constant characters, always. Do not use variables
• Use of positive terms always. For instance, use – “petiole is present”. Avoid specifying “petiole is not present”
• Make correct and accurate measurements, refrain from using terms such as small/large
• Use characters that are available always instead of opting for seasonal ones
• Make it a point to start both choices of a pair with the same word. For instance – flower zygomorphic, flower actinomorphic (symmetry of flowers)
• Try to start different pair of choices using different words

What are some demerits of using Taxonomic keys?

While taxonomic keys may assist in the quick identification of unknown entities, it does have certain disadvantages too, they are –

• The key that is used may not be all-inclusive of all the properties/variations that a species exhibits. In other words, just a word or a few words may not be able to specify all the characteristics the species possesses – variations of species may not be effectively covered
• It can be based on the traits which are not seen in the season
• It could happen that all the species of interest or desired species are not included
• There is a tendency to commit mistakes while making a choice, with just one wrong decision, hence arriving at the wrong interpretation

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