tree-logo.gif (7741 bytes) Plant Taxonomy (BIOL308)  -  Stephen G. Saupe, Ph.D.; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321;;

Sham Plants:  Evolutionary Classification

    In our previous exercise, we tried to determine the number of genera and species represented by Dr. Warren Wagner's "Sham Plants."  Now, we will assume that each diagram represents a separate species and that these are grouped into three genera (see table below).

Genus Diagram Number (s) Abbreviation
Bulbosa 13, 14 B13, B14
Crassicaulon 5, 6, 12 C5, C6, C12
Dendrogramma 7, 11, 16 D7, D11, D16
Macrosepala 8 M8
Sympetala 1, 2,3,4,9,10, 15,17 S1, S2,...S17
Zygomorpha 18 Z18

    Work out the most probable pattern of evolutionary  relationships for the six genera of sham plants.  In other words, create a phylogenetic tree, bush or other diagram to represent the relationships among these taxa.  Your diagram may be similar to that of Cronquist, Thorne or other.  Then, once you've developed a classification for the genera, insert the species (use the designations - S1, S2 and so on).  Remember the process for constructing evolutionary classifications:  collect evidence →  weight (primitive/advanced) → develop classification to reflect degree and extent of divergence from a common ancestor.  As you develop your classification, consider the following questions:

  1. Which characters are primitive?  advanced (specialized)?  Justify your choices.
  2. Which is the most primitive genus/species?  most advanced? 
  3. Are any of the taxa the immediate common ancestor of the family?  Or is the immediate common ancestor extinct?  If so, what would it look like?

Be prepared to present to the class and defend your answer.

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Last updated:  08/20/2007 / � Copyright by SG Saupe