Endeavour to reconstruct the characters of each hypothetical ancestor.

If a node has a degree greater than three then that node is a polytomy

Typically polytomies are treated as ‘soft’ That multiple lineages would diverge at exactly the same time; however, if lineages diverge rapidly in time relative to the rate of character evolution.

The node closest to the root is the ancestor of the node. A rooted tree has a node identified as the root from which ultimately all other nodes descend.   The node closest to the root is the ancestor of the node. Unrooted trees lack a root, and hence do not specify evolutionary relationships in quite the same way.

sister taxa or anscestor These ancestors are hypothetical, but some methods of phylogenetic reconstruction allow us to infer what they (or their sequence) may have looked like. sister taxa or anscestor

Gene tree and species tree

This is the point at which the two gene lineages coalesce and the time at which this occurs is the coalescence time.   Alleles 1 and 2 are both found in the same species, they are not each other’s closest relative.

Hypothetical example illustrates the problem of lineage sorting Hypothetical example illustrates the problem of lineage sorting. If the alleles present in a lineage prior to that lineage speciating are not monophyletic then the distribution and relationships of these alleles need not accurately reflect the phylogeny of the organisms themselves.

0.2795/2 + (0.3959-0.4525)/2 =0.1114 0.2795-0.1114=0.1682