Ptree is a secondary source: an independently edited tree of life reference that assembles, interprets and visualizes published biological evidence. For a specific measurement or biological claim, follow Ptree's source links and cite the underlying publication or dataset, just as you would follow a reference from Wikipedia.
Cite Ptree for its visualizations, comparisons and synthesis. A tree of life visualization on a lecture slide is a good example. The evidence behind each property identifies its contributing sources; Sources & licenses provides the full reference list.
Suggested reference
Dayah, Michael. Ptree: Interactive Tree of Life Explorer. https://ptree.org/. Accessed 6 October 2026.
Use the date you consulted the site. For a specific visualization, include the full exploration URL and name the scientific tree and property. Ptree is updated over time; an access date identifies when you observed a result.
Linking an exploration
The address preserves the scientific tree, property, location, view, fossil setting and open branches, together with the active article, interaction subject or comparison. Use Share in the explorer or copy the full address from your browser.
A shared URL restores the exploration against the available data. It does not freeze a historical data release. For published research, record the underlying source versions or dates as well as the Ptree URL and access date, and retain the evidence or figure supporting your result.
Classroom slides, figures and videos
You may use screenshots, annotated figures and recordings of Ptree in lessons, classroom slides and educational videos without asking permission. Credit Ptree.org, keep its branding and source credits visible, and link to the exploration so your audience can investigate for themselves.
The press page supplies images for coverage of Ptree. For inclusion of original Ptree material in textbooks, commercial courseware or products for sale, contact Michael Dayah for permission.
Photographs and source data
Credit the contributing provider for the data or image. Photographs, silhouettes, maps and articles retain their own licenses, including when they appear within a screenshot or recording. Preserve their credits and follow the terms linked at the point of use and in Sources & licenses.
For material under CC BY 4.0, give appropriate credit, link to the license and indicate changes you made. Other source licenses may impose additional conditions. Ptree's attribution identifies the source terms; inclusion in the explorer does not change them.
Embedding and redistribution
You may link to Ptree or embed the live site in an iframe. Use the full exploration URL to open a prepared example directly.
Redistributing the Ptree application or its source code, hosting a copied version, or repackaging it as another product requires written permission. These conditions govern Ptree's original work; the underlying source material remains available under its respective licenses.