The Tree of Life aims high. Its goal is to provide a virtual representation of past and present life on earth, complete with bibliographic references and peer review. Needless to say, the site is huge, consisting of almost 1,400 individual pages distributed over 20 computers in four countries (according to the introduction page). Pages on particular groups of organisms are contributed by researchers who may in turn serve as coordinators for pages about subsidiary groups. The project as a whole is organized by David R. Maddison, known within the systematic biology community as the author of MacClade, a computer program for manipulating phylogenetic trees.
This cooperative organization means that the information presented comes from acknowledged experts, but also means that there is a lack of consistency in the treatment of various groups ‐ based largely on the willingness of an authority to take the time to author pages. The cellular slime molds, for instance, still await a Web champion, while Maddison’s own group, the Coleoptera (beetles), boasts a presence almost in accordance with their showing on the real tree. The better‐developed pages include morphological descriptions, discussions of relationships, extensive lists of references, links to external pages relating to the group, photographs of representative organisms, and abundant links to subsidiary groups (see, for instance, Kathleen M. Pryor and Alan R. Smith’s pages on ferns and those on bats by Nancy B. Simmons and Tenley Conway). Other pages are simply placeholders with an unlinked phylogeny, a couple of pictures, and little else. As the home page points out, the real tree took three billion years to grow.
The navigation of the site is extremely simple. Users may either choose to begin at the root of the tree or may skip to a page of “popular groups.” The latter option is handy for those who wish to avoid clicking through pages of bacteria on their way to some “higher” group. There is also an effective and easy‐to‐use search engine, although, given the organization of the site, it hardly seems necessary. When a user clicks on a linked terminal taxon of one tree, s/he is taken to a page for that taxon, which may lead to other pages, etc. In some cases, the chain of links may extend all the way to the level of individual species, although this seems to be rare.
One of the greatest credits to this site is its acknowledgement of controversy. At the root of the tree, for instance, we are presented with two possible phylogenies reflecting different opinions regarding the Archaea (methanogenic bacteria, etc.). Many pages for major groups feature a “Discussion of Phylogenetic Relationships” section in which differing theories are discussed. This improves the content of the site and makes the point that systematic biology is very much a vital and changing science.
In addition to the tree proper, the site contains many pages of supplemental information, including a detailed site map, a glossary, pages about contributors, and discussions of the project itself and a bit of the theory behind the study of phylogeny and classification. Many of the “concepts” pages are still under construction. A peer review process has recently been added, although few pages bear the “peer reviewed” icon. This not only ensures quality control, but may also raise the prestige associated with electronically published documents, thereby providing an incentive for tenure‐track faculty to contribute pages. Another interesting concept which is in its infancy are “tree houses” ‐ pages about certain groups with information aimed at children. Currently, the beetles maintain the only treehouse.
A feature which would be helpful is some description of which branches of the tree are well‐developed and which need work, perhaps in the form of pie graphs which compare the number of pages devoted to a group on the tree with the number of known taxa. This would provide both a broad picture of biological diversity and a measure of how close the tree comes to reflecting that diversity. It might also encourage researchers to adopt under‐represented groups.
The Tree of Life is highly recommended for use in all academic libraries, from high school up, and is definitely a site to watch as it develops.
