Sequoioideae

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Sequoioideae
Temporal range: Jurassic–Present
Dawn Redwood Metasequoia glyptostroboides Trunk 2448px.jpg
The trunk of a Metasequoia glyptostroboides
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Gymnospermae
Division: Pinophyta
Class: Pinopsida
Order: Cupressales
Family: Cupressaceae
Subfamily: Sequoioideae
Genera

Sequoioideae, commonly referred to as Redwoods, is a subfamily of coniferous trees within the family Cupressaceae, that range in the northern hemisphere. It includes the largest and tallest trees in the world. The trees in the subfamily are amongst the most notable trees in the world and are common ornamental trees. The subfamily was dominant during the Jurassic and Cretaceous periods.

Contents

Description

The three redwood subfamily genera are Sequoia from coastal California and Oregon, Sequoiadendron from California's Sierra Nevada, and Metasequoia in China. The redwood species contains the largest and tallest trees in the world. These trees can live for thousands of years. Threats include logging, fire suppression, [1] illegal marijuana cultivation, and burl poaching. [2] [3]

Only two of the genera, Sequoia and Sequoiadendron, are known for massive trees. Trees of Metasequoia , from the single living species Metasequoia glyptostroboides , are deciduous, grow much smaller (although are still large compared to most other trees) and can live in colder climates.[ citation needed ]

Taxonomy and evolution

Multiple studies of both morphological and molecular characters have strongly supported the assertion that the Sequoioideae are monophyletic. [4] [5] [6] [7] Most modern phylogenies place Sequoia as sister to Sequoiadendron and Metasequoia as the out-group. [5] [7] [8] However, Yang et al. went on to investigate the origin of a peculiar genetic component in Sequoioideae, the polyploidy of Sequoia—and generated a notable exception that calls into question the specifics of this relative consensus. [7]

Cladistic tree

A 2006 paper based on non-molecular evidence suggested the following relationship among extant species: [9]

Sequoioideae
Metasequoia

M. glyptostroboides (dawn redwood)

Sequoia

S. sempervirens (coast redwood)

Sequoiadendron

S. giganteum (giant sequoia)

Taxodioideae

A 2021 study using molecular evidence found the same relationships among Sequoioideae species, but found Sequoioideae to be the sister group to the Athrotaxidoideae (a superfamily presently known only from Tasmania) rather than to Taxodioideae. Sequoioideae and Athrotaxidoideae are thought to have diverged from each other during the Jurassic. [10]

Possible reticulate evolution in Sequoioideae

Reticulate evolution refers to the origination of a taxon through the merging of ancestor lineages. Polyploidy has come to be understood as quite common in plants—with estimates ranging from 47% to 100% of flowering plants and extant ferns having derived from ancient polyploidy. [11] Within the gymnosperms however it is quite rare. Sequoia sempervirens is hexaploid (2n= 6x= 66). To investigate the origins of this polyploidy Yang et al. used two single copy nuclear genes, LFY and NLY, to generate phylogenetic trees. Other researchers have had success with these genes in similar studies on different taxa. [7]

Several hypotheses have been proposed to explain the origin of Sequoia's polyploidy: allopolyploidy by hybridization between Metasequoia and some probably extinct taxodiaceous plant; Metasequoia and Sequoiadendron, or ancestors of the two genera, as the parental species of Sequoia; and autohexaploidy, autoallohexaploidy, or segmental allohexaploidy.[ citation needed ]

Yang et al. found that Sequoia was clustered with Metasequoia in the tree generated using the LFY gene but with Sequoiadendron in the tree generated with the NLY gene. Further analysis strongly supported the hypothesis that Sequoia was the result of a hybridization event involving Metasequoia and Sequoiadendron. Thus, Yang et al. hypothesize that the inconsistent relationships among Metasequoia, Sequoia, and Sequoiadendron could be a sign of reticulate evolution by hybrid speciation (in which two species hybridize and give rise to a third) among the three genera. However, the long evolutionary history of the three genera (the earliest fossil remains being from the Jurassic) make resolving the specifics of when and how Sequoia originated once and for all a difficult matter—especially since it in part depends on an incomplete fossil record. [8]

Extant species

Paleontology

Sequoioideae is an ancient taxon, with the oldest described Sequoioideae species, Sequoia jeholensis, recovered from Jurassic deposits. [12] [13] A genus Medulloprotaxodioxylon, reported from the late Triassic of China supports the idea of a Late Triassic Norian origin. [14]

The fossil record shows a massive expansion of range in the Cretaceous and dominance of the Arcto-Tertiary Geoflora, especially in northern latitudes. Genera of Sequoioideae were found in the Arctic Circle, Europe, North America, and throughout Asia and Japan. [15] A general cooling trend beginning in the late Eocene and Oligocene reduced the northern ranges of the Sequoioideae, as did subsequent ice ages. [16] Evolutionary adaptations to ancient environments persist in all three species despite changing climate, distribution, and associated flora, especially the specific demands of their reproduction ecology that ultimately forced each of the species into refugial ranges where they could survive.[ citation needed ]

The extinct genus Austrosequoia , known from the Late Cretaceous-Oligocene of the Southern Hemisphere, including Australia and New Zealand, has been suggested as a member of the subfamily. [17]

Young but already tall redwood trees (Sequoia sempervirens) in Oakland, California Redwood tree in Oakland California (person for comparison)IMG 4881.jpg
Young but already tall redwood trees ( Sequoia sempervirens ) in Oakland, California

Conservation

In 2024, it was estimated that there were about 500,000 redwoods in Britain, mostly brought as seeds and seedlings from the US in the Victorian era. [18] The entire subfamily is endangered. The IUCN Red List Category & Criteria assesses Sequoia sempervirens as Endangered (A2acd), Sequoiadendron giganteum as Endangered (B2ab) and Metasequoia glyptostroboides as Endangered (B1ab). In 2024 it was reported that over a period of two years about one-fifth of all giant sequoias were destroyed in extreme wildfires in California. [19]

See also

Related Research Articles

Sequoia, Sequoya or Sequoyah refers to a type of tree in the cypress family which includes the redwood trees. By extension the name may refer to:

<i>Sequoiadendron giganteum</i> Species of tree native to North America

Sequoiadendron giganteum, also known as the giant sequoia, giant redwood or Sierra redwood is a coniferous tree, classified in the family Cupressaceae in the subfamily Sequoioideae. Giant sequoia specimens are the most massive trees on Earth. They are native to the groves on the western slopes of the Sierra Nevada mountain range of California but are grown around the world.

<span class="mw-page-title-main">Pinales</span> Order of seed plants, also known as conifers

The order Pinales in the division Pinophyta, class Pinopsida, comprises all the extant conifers. The distinguishing characteristic is the reproductive structure known as a cone produced by all Pinales. All of the extant conifers, such as Araucaria, cedar, celery-pine, cypress, fir, juniper, kauri, larch, pine, redwood, spruce, and yew, are included here. Some fossil conifers, however, belong to other distinct orders within the division Pinophyta.

Taxodiaceae is a formerly recognized conifer family. It is today recognised as a paraphyletic grade of basal lineages within the Cupressaceae. It contains the following living genera:

<span class="mw-page-title-main">Gymnosperm</span> Clade of non-flowering, naked-seeded vascular plants

The gymnosperms are a group of seed-producing plants that includes conifers, cycads, Ginkgo, and gnetophytes, forming the clade Gymnospermae. The term gymnosperm comes from the composite word in Greek: γυμνόσπερμος, literally meaning 'naked seeds'. The name is based on the unenclosed condition of their seeds. The non-encased condition of their seeds contrasts with the seeds and ovules of flowering plants (angiosperms), which are enclosed within an ovary. Gymnosperm seeds develop either on the surface of scales or leaves, which are often modified to form cones, or on their own as in yew, Torreya, Ginkgo. Gymnosperm lifecycles involve alternation of generations. They have a dominant diploid sporophyte phase and a reduced haploid gametophyte phase which is dependent on the sporophytic phase. The term "gymnosperm" is often used in paleobotany to refer to all non-angiosperm seed plants. In that case, to specify the modern monophyletic group of gymnosperms, the term Acrogymnospermae is sometimes used.

<i>Metasequoia</i> Genus of conifers

Metasequoia, or dawn redwood, is a genus of fast-growing coniferous trees, one of three species of conifers known as redwoods. The living species Metasequoia glyptostroboides is native to Lichuan county in Hubei province, China. Although the shortest of the redwoods, it grows to at least 165 feet in height. Local villagers refer to the original tree from which most others derive as Shuǐshān (水杉), or "water fir", which is part of a local shrine. Since its rediscovery in 1944, the dawn redwood has become a popular ornamental, with examples found in various parks in a variety of countries.

<i>Metasequoia glyptostroboides</i> Species of conifer

Metasequoia glyptostroboides, the dawn redwood, is a fast-growing, endangered deciduous conifer. It is the sole living species of the genus Metasequoia, one of three genera in the subfamily Sequoioideae of the family Cupressaceae. It now survives in the wild only in wet lower slopes and montane river and stream valleys in the border region of Hubei and Hunan provinces and Chongqing municipality in south-central China, notably in Lichuan county in Hubei. Although the shortest of the redwoods, it can grow to 167 ft (51 m) in height.

<span class="mw-page-title-main">Cupressaceae</span> Cypress family of conifers

Cupressaceae is a conifer family, the cypress, with worldwide distribution. The family includes 27–30 genera, which include the junipers and redwoods, with about 130–140 species in total. They are monoecious, subdioecious or (rarely) dioecious trees and shrubs up to 116 m (381 ft) tall. The bark of mature trees is commonly orange- to red-brown and of stringy texture, often flaking or peeling in vertical strips, but smooth, scaly or hard and square-cracked in some species.

<i>Cupressus</i> Several genera of evergreen conifers

Cupressus is one of several genera of evergreen conifers within the family Cupressaceae that have the common name cypress; for the others, see cypress. It is considered a polyphyletic group. Based on genetic and morphological analysis, the genus Cupressus is found in the subfamily Cupressoideae. The common name "cypress" comes via the Old French cipres from the Latin cyparissus, which is the latinisation of the Greek κυπάρισσος (kypárissos).

<i>Taiwania</i> Genus of conifers

Taiwania, with the single living species Taiwania cryptomerioides, is a large coniferous tree in the cypress family Cupressaceae.

<i>Cunninghamia</i> Genus of conifers

Cunninghamia is a genus of one or two living species of evergreen coniferous trees in the cypress family Cupressaceae. They are native to China, northern Vietnam and Laos, and perhaps also Cambodia. They may reach 50 m (160 ft) in height. In vernacular use, it is most often known as Cunninghamia, but is also sometimes called "China-fir". The genus name Cunninghamia honours Dr. James Cunningham, a British doctor who introduced this species into cultivation in 1702 and botanist Allan Cunningham.

<i>Torreya</i> Genus of conifers

Torreya is a genus of conifers comprising six or seven species placed in the family Taxaceae, though sometimes formerly placed in Cephalotaxaceae. Four species are native to eastern Asia; the other two are native to North America. They are small to medium-sized evergreen trees reaching 5–20 m, rarely 25 m, tall. Common names include nutmeg yew.

<i>Athrotaxis</i> Genus of conifers

Athrotaxis is a genus of two to three species of conifers in the cypress family, Cupressaceae. The genus is endemic to western Tasmania, where they grow in high-elevation temperate rainforests.

<i>Sequoia sempervirens</i> Species of tree

Sequoia sempervirens is the sole living species of the genus Sequoia in the cypress family Cupressaceae. Common names include coast redwood, coastal redwood and California redwood. It is an evergreen, long-lived, monoecious tree living 1,200–2,200 years or more. This species includes the tallest living trees on Earth, reaching up to 115.9 m (380.1 ft) in height and up to 8.9 m (29 ft) in diameter at breast height. These trees are also among the longest-living organisms on Earth. Before commercial logging and clearing began by the 1850s, this massive tree occurred naturally in an estimated 810,000 ha along much of coastal California and the southwestern corner of coastal Oregon within the United States.

<i>Sequoia</i> (genus) Genus of conifers in the cypress family Cupressaceae

Sequoia is a genus of redwood coniferous trees in the subfamily Sequoioideae of the family Cupressaceae. The only extant species of the genus is Sequoia sempervirens in the Northern California coastal forests ecoregion of Northern California and Southwestern Oregon in the United States. The two other genera in the subfamily Sequoioideae, Sequoiadendron and Metasequoia, are closely related to Sequoia. It includes the tallest trees, as well as the heaviest, in the world.

<i>Sequoia affinis</i> Extinct species of conifer

Sequoia affinis is an extinct species of the genus Sequoia in the cypress family Cupressaceae.

<i>Sequoiadendron</i> Genus of conifers in the cypress family Cupressaceae

Sequoiadendron is a genus of evergreen trees, with two species, only one of which survives to the present:

<i>Metasequoia occidentalis</i> Extinct species of conifer

Metasequoia occidentalis is an extinct redwood species of the family Cupressaceae that is found as fossils throughout the Northern Hemisphere. It is one of three extinct species of Metasequoia that are currently recognized as valid.

<i>Metasequoia heerii</i> Extinct species of conifer

Metasequoia heerii is an extinct redwood species of the family Cupressaceae that is found as fossils throughout the Northern Hemisphere. It is one of several proposed extinct species of Metasequoia that were previously referred to Sequoia.

References

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