An introduction to biological systematics
An introduction to biological systematics

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An introduction to biological systematics

2.3 What does relationship mean in systematics? G.G. Simpson

Activity 2

Timing: 0 hours 5 minutes

Dr. Patterson continues to look at Simpson’s answer to the meaning of ‘relationship’ in systematics, and illustrates this by referring to a diagrams showing how the systematist viewed the relationship between phylogeny and higher and lower taxa (Figure 4).

Figure 4 The relationship between phylogeny and higher and lower taxa, according to Simpson, G. G. (1961) Principles of Animal Taxonomy, p. 190, Figure 19 (redrawn). (a) 'Phylogenetic tree with stems and branches incorrectly conceptualized as corresponding with taxa at different levels'. (b) 'Same correctly subdivided into taxa.'
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Dr. Colin Patterson
We can understand and criticise Simpson's solution better with the help of a diagram, which shows his idea of incorrect and correct ways of looking at a phylogenetic tree.
In the left hand tree, the successive levels are equated with taxa, and the result's a family containing two genera, each with two species. Now Simpson called this idea ‘flatly false’, and said that the correct classification is the one in the right hand diagram, where we have a family containing three genera - two living ones with two species, and a third ancestral genus with three species.
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