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Patterns in Tree Balance among Cladistic, Phenetic, and Randomly Generated Phylogenetic Trees
Stephen B. Heard
Vol. 46, No. 6 (Dec., 1992), pp. 1818-1826
Published by: Society for the Study of Evolution
Stable URL: http://www.jstor.org/stable/2410033
Page Count: 9
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I examine patterns in tree balance for a sample of 208 cladograms and phenograms from the recent literature. I provide an expression for expected imbalance under a simple, uniformrate random speciation model, and I estimate variances by simulation for the same model. Imbalance decreases with tree size (number of included taxa) in both theoretical and literature trees. In contrast to previous suggestions, I find cladistic trees to be no more imbalanced than phenetic trees when confounding variables are appropriately controlled. The degree of imbalance found in literature trees is inconsistent with the uniform-rate speciation model; this is most likely a result of variability in speciation and extinction rates among real lineages. The existence of such variation is a necessary (but not sufficient) condition for the operation of the macroevolutionary processes of species sorting and species selection.
Evolution © 1992 Society for the Study of Evolution