Evolutionary tree design

Evolutionary tree design: An exploratory study of the influence of linear versus branching format on visitors’ interpretation and understanding across age groups

University of Kansas, Lawrence, Kansas, USA, 2014

Teresa Elise MacDonald

Abstract from a thesis for the degree of Doctor of Philosophy

This exploratory study sought to investigate the influence of tree graphic design—specifically linear versus branching depictions of taxa—on visitors in three different age groups (aged 11-13, 14-18, adults) interpretation and understanding using a multiple-case study strategy. The findings from this research indicate that linear and branched depictions elicit qualitatively different narratives and explanations about the relationships between the taxa in all age groups. Branched tree graphics support scientifically appropriate explanations of evolutionary relationships, i.e. that taxa are related via shared or common ancestry; while linear representations reinforce intuitive interpretations of ancestor-descendant or anagenic relationships. Furthermore, differences in the language used for linear and branched trees suggests that there is a spectrum within an analogy of developmental change that is thought to serve as a transitional concept between intuitive and scientific understanding—with ‘evolved from’ for branched depictions of taxa representing a shift towards an interpretation of shared ancestry rather than an individual transformation from one thing into another.

In addition, branched graphics appear to support the correct reading and interpretation of shared or common ancestry in tree diagrams. Mixed reasoning was common and overall reasoning patterns were broadly similar among participants in all age groups, however, older youth (aged 14 to 18) and adults often provided more detail in their explanations and sometimes included references to evolutionary ideas such as variation, inheritance and selection.