Suppression of ancestor-descendant information in classification
Richard Zander
Tuesday, 17 February 2009 17:01 UTC
The analysis of sister-group relationships involving parsimony and other tools has given systematics much evolutionary information for classification purposes. Unfortunately, phylogeneticists commonly insist on classifications that reflect strict phylogenetic monophyly, in my opinion, solely as homage to the method. Ancestor-descendant relationships involving unique evolutionary directions (major autapomorphies) are not flagged at taxonomic levels the same as those of sister groups exhibiting the same degree of evolutionary change. All of us have seen perfectly good evolutionary taxa that have been split apart or synonymized as sacrifices to the sister-group relationship analytic method. Yet enforcing strict phylogenetic monophyly (holophyly) divorces systematics from other fields informed by classification (biodiversity, evolution, law) by eliminating information on descent with modification of taxa (as opposed to traits). Phylogenetics is in the process of destroying more information on evolution than creationism or intelligent design has or will ever do.
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Replies
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Hi, Dr. Zander,
Your post is pretty interesting. I’m not sure if I understand you completely. What is meant by “good evolutionary taxa that have been split apart or synonymized as sacrifices to the sister-group relationship analytic method”? Also, are you saying that taxa with unique autapomorphies have been synonomized with its sister groups?
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Zhang II:
A good evolutionary taxon in the context of phylogenetic classification is one that has NOT been split or lumped SOLELY because it is autophyletic (with evolutionarily unique traits but embedded in a paraphyletic group) or which has NOT been split into two SOLELY because it appears in two different molecular lineages. That is, a traditional taxon for which lumping or splitting will create discordant or very weak new taxa based on expressed traits.This is particularly common when taxa with unique autapomorphies are synonymized with a paraphyletic group, not a sister group. For more information see recent publications on my reprint page:
http://www.mobot.org/plantscience/ResBot/Repr/1Reprints.htmThe key is that phylogenetic methods can only create trees of sister-group relationships, not of ancestor-descendant relationships of taxa, and this is why strict holophyly is enforced on phylogenetic classification: the idea that any other classification method is “unscientific” even though an entire class of evolutionary information is excised from phylogenetic classifications.
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