The sole remaining species of the phylum Ginkgophyta is Ginkgo biloba. This classification group represents one of the most ancient and isolated lineages of seed plants. The phylum Ginkgophyta contains only one class, Ginkgoopsida, one order, Ginkgoales, one family, Ginkgoaceae, and one genus, Ginkgo, making the species G. biloba the only living representative across all these taxonomic levels.
The Sole Survivor: Ginkgo biloba
The species is formally known as Ginkgo biloba, which was assigned by Carl Linnaeus in 1771. The specific epithet biloba refers to the characteristic two-lobed structure often seen in its distinctive fan-shaped leaves. It is commonly recognized as Ginkgo or the Maidenhair Tree, a name derived from the resemblance of its foliage to the leaflets of the maidenhair fern.
This large, deciduous tree can reach heights of up to 40 meters, typically presenting a conical crown in its youth. While it is now cultivated and distributed globally, its native range is restricted to a small area in China. It was once thought extinct in the wild until small populations were rediscovered in remote regions of China, often in protected temple gardens.
A Lineage of Living Fossils
The lineage represented by Ginkgo biloba is one of the most famous examples of a “living fossil.” The order Ginkgoales has a fossil record stretching back to the Early Permian period, approximately 300 million years ago, predating the rise of the dinosaurs. This ancient group was a significant component of global flora during the Permian and Triassic periods.
The Ginkgophytes reached their peak diversity during the Jurassic period, with fossil evidence indicating at least 16 genera once existed. These ancient species were widespread across the Northern Hemisphere, found in locations such as Alaska, Greenland, and Siberia. The foliage of these prehistoric forms, often classified as Ginkgoites, shows great similarity to the modern species.
Diversity within the phylum began a long decline during the Late Cretaceous period, coinciding with the rapid diversification and ascendancy of flowering plants, or angiosperms. By the end of the Pliocene epoch, approximately 3 million years ago, all species of Ginkgoales except for those closely related to G. biloba had become extinct.
Evolutionary Bottleneck
The species persisted only in a small refuge in central China. This suggests that a combination of environmental changes and competition from newer plant groups drove the evolutionary bottleneck.
Distinctive Biological Features
The tree possesses a distinct combination of botanical traits. Unlike most gymnosperms, such as pines and firs, the Ginkgo is a deciduous tree, shedding its leaves in the autumn after they turn a striking golden-yellow color. The fan-shaped leaves are characterized by a primitive pattern called dichotomous venation, where veins repeatedly split into two, rather than forming the net-like network typical of flowering plants.
The tree is dioecious, meaning individual trees are either exclusively male or exclusively female. Male trees produce small pollen cones, while female trees produce paired ovules that develop into seeds encased in a fleshy outer layer called a sarcotesta. The mature seeds emit a foul odor due to the presence of butyric acid in the sarcotesta, a trait thought to have evolved to attract ancient seed-dispersing animals.
The tree is resistant to many modern environmental stressors, contributing to its widespread cultivation in urban settings. It shows a high tolerance for air pollution, pests, diseases, and fire, allowing it to thrive where many other trees struggle. This inherent hardiness is a result of its long evolutionary history.