投影片 1

UPMGA Tree

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OTU

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11.5

8.5

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A-C

OTU

Dist. fr A-C to B = 8 + 9 = 8.5 = (A to B) + (C to B)
2 2

Dist. fr A-C to D = 12 + 11 = 11.5 = (A to D) + (C to D)
2 2

Dist. fr A-C-B to D = 12 + 14 + 11 = 12.33333

= (A to D) + (B to D) + (C to D)
3

First node unites A & C with branch lengths of 7/2 = 3.5

Second node unites the A-C clade with B with branch length of 8.5/2 = 4.25

Third node unites A-C-B with D with branch length of 12.33/2 = 6.17

Internode distances can be calculated by subtraction

Node 1 to Node 2 = (Node 2 to B) - ("Height" of Node 1)
= 4.25 - 3.5 = 0.75

"Height" of Node 1 can be taken from EITHER branch length 1-A or 1-C because branch lengths from any node to tip are equal by definition

Node 2 to Node 3 = (Node 2 to D) - ("Height of Node 2)
= 6.17 - 4.25 = 1.91667