Sequoia (genus)

Sequoia is a genus of redwood coniferous trees in the subfamily Sequoioideae of the family Cupressaceae. These are tall trees that grow cones on their branches. The genus is part of a larger group of plants that includes many evergreen trees.

Only one extant species of the genus is alive today: Sequoia sempervirens. It grows in the Northern California coastal forests ecoregion of Northern California and Southwestern Oregon in the United States. Two other genera in the same subfamily, Sequoiadendron and Metasequoia, are closely related to Sequoia. The genus includes the tallest trees in the world, and also the heaviest.

Scientists have also named several extinct species from fossils. These include Sequoia affinis, found in Western North America, and Sequoia magnifica, which was identified from petrified wood in the Yellowstone National Park area.

Etymology

In 1847, Austrian botanist Stephan Endlicher first published the name Sequoia for this group of trees. He did not explain why he chose it, and no record shows that anyone asked him.

Starting in the 1860s, some people said the name came from the Latin word for "sequence." They thought the tree followed or was left over from huge, long-gone ancient kinds of trees.

Later writers have questioned this idea. In 2012, Gary Lowe argued that Endlicher probably saw the tree as completing a morphological sequence of species, based on the number of seeds per cone scale. In this view, the tree was not the successor to a fossil sequence. In 2017, Nancy Muleady-Mecham suggested a link between the name and Sequoyah, the inventor of the Cherokee writing system. However, her idea has clear limits. The link only works if the names sound alike in English, and Endlicher could not have known how Sequoyah's name was pronounced in Cherokee. The name was probably taken from the Latin verb sequor, not from a verb form.

Paleontology

Sequoia jeholensis is the oldest known member of the genus Sequoia. Sequoia portlandica is also listed as an old member, but scientists are not sure what this name refers to, so it is a nomen dubium. Fossils of these trees have been found in the Jiufotang Formation (Lower Cretaceous) and the Jiulongshan Formation (Middle Jurassic) of China. By the late Cretaceous, the ancestors of sequoias lived in Europe, parts of China, and western North America. Comparing fossils with modern trees suggests that these ancestors already had wider tracheid cells. This helped them grow very tall, as the modern Sequoia sempervirens (coast redwood) and Sequoiadendron giganteum (giant sequoia) do.

Sequoia ancestors did not dominate the cold northern regions. There, Metasequoia, a redwood that is deciduous (it loses its leaves), did better in an environment with 3 months of continuous darkness. Sequoia and Metasequoia may have shared their range for a long time. This could have led to crossbreeding that produced the modern hexaploid Sequoia sempervirens.

As the climate cooled during the late Eocene and Oligocene, the northern range of ancestral Sequoia became smaller. By the end of the Miocene and the beginning of the Pliocene, Sequoia fossils looked the same as the modern Sequoia sempervirens. Further cooling in the Pliocene caused Sequoia to die out in Europe and Asia, where the frost was too harsh for it. In western North America, it spread south along the coast of Oregon and California, where plenty of rain and mild seasons helped it survive. Mountain building during the Sierra Nevada orogeny further separated Sequoia groups, because snowy mountain peaks blocked them from spreading east. The Pleistocene and Holocene distributions were likely almost the same as the modern S. sempervirens distributions.

Some fossil trees that were first named as Sequoia species have since been placed in other genera:

• †Sequoia chinensis China – Moved to Metasequoia chinensis
• †Sequoia couttsiae Europe – Moved to Quasisequoia couttsiae
• †Sequoia dakotensis South Dakota (Maastrichtian) – Moved to Sequoites dakotensis (possibly a species of Metasequoia)
• †Sequoia langsdorfii Europe – Moved to Metasequoia langsdorfii
• †Sequoia reichenbachi Europe – Moved to Metasequoia reichenbachii