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A New Method for Cladistic Analysis—Median Elimination Series (MES)

Li Chao-Luan   

  1. (Chengdu Institute of Biology, Academia Sinica, Chengdu, 610015)
  • Received:1900-01-01 Revised:1900-01-01 Online:1990-01-10 Published:1990-01-10
  • Contact: Li Chao-Luan

Abstract:

The use of parsimony (or the principle of simplicity) in phylogenetic infere-
nce is reviewed.  The major problem in using parsimony for phylogenetic reconstruction is
that neither a single solution for a given set of data nor the most parsimonious tree could be
provided.  Therefore, based on recognition and judgement of similarity of organisms by Hen-
nig's advanced character (1965) and some particular principles from evolutionary theory of
Darwinism accepted by many systematists as general truths (Bonde 1977; Wiley 1975; Gaffrey
1979), the author has developed a new method, Elimination Series through Median Selection
(Median Elimination Series, MES for short), for phylogenetic analysis. In addition to using
the advanced characters for understanding the relationships between taxa, MES emphasizes that
the mosaic characters including both primitive and advanced in an array of characters play
an important part in determining the nodes or branches and  distinguishing the taxa.The
author considers median units as ancestors in a phylogenetic tree like Farris, but the concept
and algorithm of “median” differ from Farris' (1970) in: (1) The author's median involves
the top taxon and unplaced one, but Farris' median does the top taxon, its ancestor as well as
unplaced one;  (2) The median taken by the author is of common value or the least one
among the associated characters of two taxa.  However, the median taken by Farris is median
numerical value among the three (3) The median or median unit called by the author is the
numerical value of the relatively primitive character or taxon between the advanced characters
or the taxa stood apart from the original position. Farris' one is the median position or num-
ber in the center of three taxa or its associated characters.  The author recognizes that rever-
sion of characters is possible and obtains the knowledge of it from observation and analysis
of characters of organisms or scientific experiment and distinguished through analysis of mor-
phocline and co-variation in a series of taxa, but not from induction only by mathematical
model based on the principle of simplicity.  The author divides co-variation into 4 types:
     1.  Progressive co-variation.  Transformation series of characters A and a is as follows:
                                                   A → A'
                                                   a → a'
          reversed co-variation.  Transformation series of characters A and a is as follows:
                                                   A ← A'
                                                   a ← a'
     3.  Progression-reversion co-variation.  Transformation series of characters A and a is
follows:
                                                   A → A'
                                                   a ← a'
     4.  Reversion-progression co-variation.  Transformation series of characters A and a is as
follows:
                                                   A ← A'
                                                   a → a'
The characters next to the arrows should be advanced.   Co-variation for most of the species
of Cissus from China belongs to the type 1 and that for C. repanda Vahl. to the type 3, without
types 2 and 4.  In determining the progressive co-variation, reverse evolution of   character
could be distinguished through the analysis of morphocline and co-variation.  The author has
recognized two types of cyclic polarity, including unidirectional and bidirectional ones.  For
the former, the character may return back to the original state through more than one step.  In
fact, this is a complex reversion.  For the latter, the character may reach a advanced state from
the original one via two different ways.  In fact, this is special progressive transformation se-
ries and it may often occur in complex reticulate evolution as a small net, for example, in evo-
lution of leaf fragment and others of angiosperms (Meyen 1973).  The cyclic polarity in C.
repanda Vahl. is bidirectional (see transformation series 11 of the characters in Cissus). Trans-
formation series of All the characters have been determined on the basis of analysis of  mor-
phocline, co-variation and cyclic polarity.   In this  paper, the three steps of understanding
phylogenetic system are developed: (1) recognition of homologous characters; (2) discovery of
internal relationships between homologous characters in order to obtain transformation series
or phylogeny of homologous characters; (3) discovery of internal relationships between phylo-
genies of homologous characters in order to get a phylogenetic system of organisms or approa-
ching understanding essence of evolution.  The result inferred by MES is based on some prin-
ciples of evolution from Darwin and Hennig but not judged by the principle of simplicity or
parsimony from Popper (1960, 1968).  The statement in this paper attempts to show that if a
dilemma in modern cladistics could be solved, its principles must be reconsidered.

Key words: Cissus, Cladistic analysis, Co-variation, Median Elimination Series, Reverse evolution

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