As with any exhibit, evaluation and testing can provide ideas for improving your trees once they are out in the world — or even before they are out in the world, if formative testing is within the scope of your project. Does your audience understand the tree? Did they get the message? Being willing to change your tree(s) based on audience response can make them much more effective.

You may have an in-house team for evaluation or funds to hire an outside firm. If you don’t and if you need help with evaluation and assessment, explore the following resources:

• InformalScience.org has a suite of resources including guides, tools, and a directory of evaluators.
• The NSF Handbook for Project Evaluation and The Institute of Museum and Library Services have guides to evaluation resources.
• Local experts, such as the education staff at a natural history museum or professors/graduate students in education, museum studies, or communication can offer advice.

Even if your trees do a great job at conveying your message, keep in mind that changes may be called for based on shifts in scientific understandings of evolutionary relationships. Of course, you should try to use the best-supported tree that is available at the time that you are designing the exhibit, and most major connections on the tree of life are well supported and are unlikely to change. But there is no guarantee that a branch or two on the tree won’t need to be moved as new data emerges.

When possible, it is a good idea to be willing to change your tree based on new evidence. But if this is not possible, the idea that trees can and do change makes for a great talking point about science. Citing the source and date of the information in your tree can give visitors an idea of how recently these relationships were worked out and a sense of the ongoing process of science.

To learn more about more about how others have developed trees for exhibits, explore the following case studies:

• Explore Oregon! Evolutionary trees in a local natural history exhibit— Elizabeth White, exhibitions designer, discusses the development of some complex tree graphics for the University of Oregon Museum of Natural and Cultural History.
• Evolving Planet: Communicating the entire Tree of Life— Richard Kissel, now Director of Public Programs at the Yale Peabody Museum of Natural History, discusses the development of an exhibition at The Field Museum that uses trees as a recurring theme.
• Horse Evolution: Updating natural history museum exhibits with trees — Teresa MacDonald, Associate Director of Public Programs at the University of Kansas Natural History Museum, discusses changes made to an exhibit from the 1950s to reflect our modern, scientific understanding of evolutionary relationships.
• Megalodon: Illustrating scientific uncertainty in an exhibit about sharks — Betty Dunckel, Program Director at the Florida Museum of Natural History, discusses an exhibit on shark biology and conservation that illustrates scientific uncertainty about evolutionary trees.
• Travels in the Great Tree of Life: A focus on evolutionary trees — Michael Donoghue, Curator of Botany at the Yale Peabody Museum of Natural History, and Jane Pickering, Executive Director of the Harvard Museums of Science and Culture, explain how a multidisciplinary team approached the content development and design for an entire exhibition about phylogenetic relationships.
• STEM Escape: Immersing urban and rural families in a biomedical mystery — Watch this traveling exhibit develop in real time as the University of California Museum of Paleontology, University of Kansas Natural History Museum, California Academy of Sciences, and Berkeley Public Library, build and evaluate a new, immersive game that hones tree-thinking skills.