Evolution and Biodiversity Laboratory Systematics and Taxonomy

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the tree. In our example, we could hypothesize that OTU 6 is actually more closelyrelated to OTU 1 than to OTU 4. However, this would require that character g (fusedeyes) had evolved once, and then secondarily lost in both OTUs 4 and 6. This is lessparsimonious than stating fused eyes evolved only once, in OTU 1 only.Figure 8. A cladogram based on synapomorphies in Caminalcules 1 - 8.Cladistics and Linnaean ClassificationGiven an hypothesis of evolutionary relationships, the second step in biosystematicendeavor is to erect a classification that faithfully reflects those relationships. Becausethe results of a cladistic analysis (i.e., the cladogram) are heirarchical, they can easilybe incorporated into the Linnaean hierarchy, as shown in Figure 9. (RememberLinnaeus? If not, go back to page one.)In cladistic analysis, all taxa must be monophyletic, meaning that they must includethe common ancestor (almost always hypothetical) and all descendants of that commonancestor. Thus, in the cladogram above, OTUs 2 and 7 together with their commonancestor (at the branch point just below them) constitute a monophyletic genus, as doOTUs 1,4,6 and 8 and their common ancestor (at the branch point just above theappearance of character d).A Family consisting of only OTUs 2 and 7 would not be monophyletic, because itdoes not include all the descendants of the common ancestor (at the branch point justbelow character d). Such a group would be considered paraphyletic (containing some,but not all, of a particular ancestor's descendants).A Family consisting of OTUs 2 and 7 plus OTUs 3 and 5 would be consideredpolyphyletic (consisting of species derived from more than one most recent commonancestor). This is because such a taxon would be made up of groups descended fromboth the ancestor just below the appearance of character h, and the one just below theappearance of characters c and e.systematics-18
Order Caminalcula:Family 1Genus 1Species 2Species 7Genus 2Species 1Species 4Species 6Species 8Family 2Genus 3Species 3Species 5Figure 9. Incorporated results of a cladistic analysis showing Linnaeanrelationships among the OTUs.Exercise: Constructing a Cladogram Based on SynapomorphiesUsing the Caminalcules in the packet at your lab station, go through the steps ofsample cladistic analysis we did for the Caminalcules in Figure 7. Use the Tables 5 and6 to list shared, derived characters that help you group the OTUs into taxa that reflecttheir (hypothetical) evolutionary relationships. Finally, in the space provided, draw acladogram of your Caminalcules, showing the appearance of each character, as inFigure 9. Is it rooted or unrooted? Be careful!Outgroup Analysis: Rooting the TreeAs you may already realize, your phylogenetic tree of Caminalcules should beunrooted because you have no way to know which character states are derived. Oneis tempted to automatically assume that a more complex form is the more derived state.However, there is always the chance that a taxon has lost an ancestral character (orcharacter state). (Can you think of any examples in our own species?)To root your tree, you will need to consider the character states in an outgroup. Buthow? Fortunately, we have some for you right here in the lab.Once you have completed your initial analysis and your cladogram has beenexamined and approved by your laboratory instructor, select a member of your team togo to the front desk and randomly select a card from the envelope labeled “outgroups.”Each card has an illustration representing one individual of a species ofCaminalcules related to yours, but not in the same taxa. Use this outgroup to root yourtree. Note that the rooted tree may be quite different from your unrooted one.systematics-19
Page 1 and 2: Evolution and Biodiversity Laborato
Page 3 and 4: 3. The taxon's content. All the stu
Page 5 and 6: Exercise II. Creating a Taxonomic K
Page 7 and 8: 2. Symplesiomorphies vs. Synapomorp
Page 9 and 10: Now list five homologous characters
Page 11 and 12: Figure 1. A phylogenetic tree. The
Page 13 and 14: Figure 3a. Phylogeny of Primates. T
Page 15 and 16: Figure 5. Representative vertebrate
Page 17: Step One. Select a series of charac
Page 21 and 22: A Rooted Cladogram of Caminalcules:
Page 23 and 24: 1. ProtistsThese are the simplest o
Page 25: Now consider the list of organisms

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