An introduction to biological systematics
An introduction to biological systematics

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An introduction to biological systematics

2.4 What does relationship mean in systematics? E. Mayr

Activity 3

Timing: 0 hours 5 minutes

Dr. Patterson looks at the second of his three systematists, Ernst Mayr. Mayr’s answer to the meaning of ‘relationship’ in systematics comes from the point of view of an evolutionist. This clip refers to a diagram from a 1974 paper written by Mayr’s (Figure 5).

Figure 5 Relationships according to 'inferred percentual difference from ultimate ancestor (A)', following Mayr, E. (1974) Cladistic analysis or cladistic classification?, Z. Zool. Syst. Evolut.-forsch., 12, 94–128, Figure 1 (redrawn). Mayr states, 'Taxon C is more closely related to B than to D, even though it shares a more recent common ancestor with D'
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Dr. Colin Patterson
The second answer to the question, "What does ‘relationship’ mean?" comes from Ernst Mayr. Here's a quotation from his 1969 book ‘Principles of Systematic Zoology’ … "To the evolutionist, ‘relationship’ means “inferred genetic similarity, as determined both by distance from branching points and subsequent rate of divergence," end quote.
Again, we can understand Mayr's concept better with the help of a diagram. It comes from a 1974 paper by Mayr, and it shows four species - an ancestral species A, and three descendants, B, C, and D. The numbers show the genetic difference of each species from the ancestor: C differs from A by only 10%, B differs by 15%, and D has diverged very rapidly, and differs from A by 70% of its genome.
Mayr says, "Taxon C is more closely related to B than to D, even though it shares a more recent common ancestor with D".
So that's Mayr's solution - relationship means genes in common, or genetic similarity.
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