Although Darwin figured out that natural selection was general force driving evolution, he knew there were many difficult puzzles left to solve. For example, he called the sudden appearance of flowering plants in the fossil record an “abominable mystery.” Popular accounts of evolution tend to focus on the animal kingdom, but Darwin, throughout his life, looked equally to plants for insights into the diversification of species.
The New York Botanical Garden recently produced a special exhibition that includes a self-guided tour of plants representing major developments in our planet’s biological prehistory. Parts of the exhibition, including a re-creation of Darwin’s own garden, have already closed, but the Web site, Darwin’s Garden: An Evolutionary Adventure continues to have information on the exhibit, including audio recordings from the two-part symposium with leading Darwin scholars, hosted in conjunction with the American Museum of Natural History.
Other botanical gardens around the world have permanent sections, with “living fossils,” plants that trace their lineage back hundreds of millions of year, highlighting the major advances in green evolution, such as club mosses, true mosses, ferns, horsetails, cycads, ginko trees, conifers, and flowering plants. In the Brooklyn Botanical Garden’s Steinhardt Conservatory, you can walk their Trail of Evolution to see plants representing ancient floras. San Diego State University has a Geology Park with a similar theme. In Los Angeles, I have visited the Huntington Gardens’ Rose Hills Foundation Conservatory for Botanical Sciences, which has interactive live plant exhibits, some of which focus on evolution. In England, the Royal Botanical Gardens in Kew has an Evolution House (http://www.kew.org/collections/evolu.html), and the Sheffield Botanical Garden has an Evolution Garden.
If you are interested in cultivating your own garden with an evolutionary theme, you might start ferns, with the Cultivation of Horsetails or perhaps a rare Wollemi pine, a tree known from 90-million-year-old fossils that was thought extinct until it was discovered in 1994 in Australia. Only a hundred or so are alive in the wild, but as of this summer you can buy a sapling via the National Geographic Society.
Many Web pages give an overview of plant evolution, but a good place to start is the University of California Museum of Paleontology’s Introduction to the Plantae. Perhaps knowing that most people interested in paleontology have an animal bias, the site reminds us that “when we think of a particular landscape, it is the plants which first come to mind. Try to picture a forest without trees, or a prairie without grasses. It is the plants which produce and maintain the terrestrial environment as we know it.” Click on the “Systematics” button to learn more about the relationships of the earliest land plants. Here, I learned that charophytes are the branch of green algae from which land plants evolved. It is a great place to get ideas for an evolution garden. Elsewhere at the site, The Virtual Paleobotanical Laboratory allows you to explore the intricacies of plant evolution.
Other sites with a focus on early plants are Toby White’s Palaeos and W. P. Armstrong’s Plants of Jurassic Park, with emphasis on cycads and other dinosaur-era vegetation. Hans Steur in the Netherlands has put together Hans’ Paleobotony Pages, which is well illustrated and organized by geologic periods.