Building trees by juggling information and following rules: an expert interview study on tree-building and phylogenetic inference

Abstract Tree-thinking is a fundamental skill set for understanding evolutionary theory and, thus, part of biological and scientific literacy. Research on this topic is mostly directed towards tree-reading—the umbrella-term for all skills enabling a person to gather and infer information from a given tree. Tree-building or phylogenetic inference as the second complementary sub-skill-set, encompassing all skills which enable a person to build a phylogenetic tree from given data, is not understood as well. To understand this topic we conducted think-aloud-tasks with tree-building experts and conducted supplementary guided interviews with them. We used school-like character tables, as they are common in high schools for the experts to build trees and audio-recorded their speech while building the trees. Analyzing the transcripts of the tasks we could find a basic methodology for building trees and define a set of backbone-skills of tree-building. Those are based on an iterative cycle going through phases of organizing information, searching and setting taxa/characters, organizing and checking oneself. All experts used simple guidelines, either deploying maximum parsimony to arrive at a solution or relying heavily on their previous knowledge. From that, we were able to utilize our result to formulate a guideline and helpful suggestions especially for beginners and novices in the field of tree-building to develop a better understanding of this topic.