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Table 2 Comparison of published skills and skill systems

From: Understanding the tree of life: an overview of tree-reading skill frameworks

Halverson and Friedrichsen (2013)

Novick and Catley (2016)

Skills by other authors

Core idea

Level 1: no use of representation

  

Naïve handling

Level 2: superficial use of representation

Students base interpretations of phylogenetic trees on superficial features of the representation without connection to the underlying meanings of the phylogenetic relationships illustrated

  

Level 3: simplified use of representation

Interpretations of phylogenetic trees are based on the idea of a main branch, with taxa branching off from a main branch and later branching off from one another

  

Level 4: symbolic use of representation

Students at this level understand the symbolic elements associated with parts of phylogenetic trees; however, they overemphasize nodes when interpreting and comparing phylogenetic representations (often engage in node-counting)

 

Halverson (2011): reading and understanding

Identifying structures

Level 5: conceptual use of representation

Phylogenetic trees are viewed as 2-D illustrations of 3-D representations and their branches as being able to rotate around nodes without altering the relationships represented. However, students at this level do not make connections between their interpretations of phylogenetic trees and the evolutionary history represented

Reason about common relationships in the face of changing subsets of taxa. (J)

Halverson (2011): identification and use

Handling apomorphies

Rotating cladogram branches around their nodes does not change the relationships among the affected taxa, even though the adjacency relations among the taxa do change. (K)

Level 6: scientific use of representation

Students are able to scientifically interpret the relationships illustrated within the topology of a phylogenetic tree based on represented common ancestry, monophyletic patterns, and implied apomorphies separating taxa. These students consistently compare phylogenetic representations based on patterns of clades regardless of the style of the representation

Identify a synapomorphy that two or more taxa share due to inheritance from their MRCA. (A)

Meir et al. (2007) Skill A: reading traits from trees

Halverson (2011): identification and use

Identifying relationships

Identify a set of taxa that share a certain character. (B)

Identify the sequential order of appearance of characters on a designated evolutionary path. (H)

Recognize that characters that appear on multiple branches of a cladogram are indicative of convergent evolution. (I)

Evaluate whether a given set of taxa compromise a clade. (C)

Blacquiere and Hoese (2016) Knowledge of most recent common ancestors

Halverson (2011): identification and use

Comparing trees

Mark all nested clades in a cladogram. (D)

Assess relative evolutionary relatedness when three taxa are resolved (i.e., compromise a three-taxon statement). (E)

Assess relative evolutionary relatedness when three taxa compromise a polytomy (i.e., no two of the taxa share a more recent common ancestor with each other than with the third taxon). (F)

Level 7: expert use of representation

This level is reserved for describing experts in the field of systematics and is not applicable for beginning students. These scientists can quickly interpret representations on the underlying phylogenetic meanings that trees represent. At this level, multiple representations are used and generated consistently to solve phylogenetic problems, explain evolutionary phenomena, and make predictions

Use the information depicted in a cladogram to make an inference based on phylogenetic relationship. (G)

Meir et al. (2007) Skill B: deducing ancestral traits

Halverson (2011): evidentiary support

Arguing and inferring

  1. All skills in this table are arranged following the hierarchy of Halverson and Friedrichsen. The last column summarizes the core ideas of the corresponding skills