The Yule tree graph
The Yule tree is a graph with one edge coming in and two edges coming out of each branch-point. The branches represent the time periods between the evolution of new species. If the branch leads to a branch-point, it means a new species evolved. If the branch leads to a leaf, it marks an extinction.
The leaves represent the species present today.The graph also features “cherries,” which represent two present species that are the closest to each other in evolutionary terms, and “pendants,” which represent the evolutionary connection to another species that is slightly further from them in evolutionary terms.
Counting the number of different types of cherries and pendants helps determine the particular dependence on the phenotype of new species being created or going extinct.
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