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Is ACCTRAN better than DELTRAN? Ingi Agnarssona,b

Summary: Is ACCTRAN better than DELTRAN?
Ingi Agnarssona,b
* and Jeremy A. Millerc
Institute of Biology, Scientific Research Centre of the Slovenian Academy of Sciences and Arts, Novi trg 2, PO Box 306, SI-1001 Ljubljana, Slovenia;
Department of Biology, University of Akron, Akron, OH 44325-3908, USA; c
Department of Entomology, California Academy of Sciences, 875 Howard
Street, San Francisco, CA 94103, USA
Accepted 15 May 2008
When parsimony ancestral character reconstruction is ambiguous, it is often resolved in favour of the more complex character
state. Hence, secondary loss (secondary ``absence'') of a complex feature is favoured over parallel gains of that feature as this
preserves the stronger hypothesis of homology. We believe that such asymmetry in character state complexity is important
information for understanding character evolution in general. However, we here point out an inappropriate link that is commonly
made between this approach and the accelerated transformation (ACCTRAN) algorithm. In ACCTRAN, changes are assigned
along branches of a phylogenetic tree as close to the root as possible. This has been taken to imply that ACCTRAN will minimize
hypotheses of parallel origins of complex traits and thus that ACCTRAN is philosophically better justified than the alternatives,
such as delayed transformation (DELTRAN), where changes are assigned along branches as close to the tips as possible. We
provide simple examples to show that such views are mistaken and that neither ACCTRAN nor DELTRAN consistently minimize


Source: Agnarsson, Ingi - Department of Biology, Universidad de Puerto Rico


Collections: Biology and Medicine