Following some links on other blogs I’ve recently seen an excellent article by T. Ryan Gregory called “Understanding Evolutionary Trees”. It introduces and explains evolutionary (phylogenetic) trees and highlights the importance of tree thinking. It even has a section on how NOT to read evolutionary trees, outlining common misunderstandings, misconceptions and misinterpretations. I wish I had had this available a few months ago when I was giving my introductory phylogenetics lectures. I think this will be compulsory reading for my students in next year’s course.

T. Ryan Gregory (2008) Understanding Evolutionary Trees. Evolution: Education and Outreach doi:10.1007/s12052-008-0035-x
Abstract: Charles Darwin sketched his first evolutionary tree in 1837, and trees have remained a central metaphor in evolutionary biology up to the present. Today, phylogenetics—the science of constructing and evaluating hypotheses about historical patterns of descent in the form of evolutionary trees—has become pervasive within and increasingly outside evolutionary biology. Fostering skills in “tree thinking” is therefore a critical component of biological education. Conversely, misconceptions about evolutionary trees can be very detrimental to one’s understanding of the patterns and processes that have occurred in the history of life. This paper provides a basic introduction to evolutionary trees, including some guidelines for how and how not to read them. Ten of the most common misconceptions about evolutionary trees and their implications for understanding evolution are addressed.