Sequoioideae

Sequoioideae, commonly referred to as redwoods, is a subfamily of coniferous trees within the family Cupressaceae. It includes the largest and tallest trees in the world. The subfamily achieved its maximum diversity during the Jurassic and Cretaceous periods.

"Redwood" redirects here. For other uses, see Redwood (disambiguation). "Redwood Tree" redirects here. For the song, see Redwood Tree (song).

Sequoioideae
Temporal range:
Sequoiadendron giganteum
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Gymnosperms
Division: Pinophyta
Class: Pinopsida
Order: Cupressales
Family: Cupressaceae
Subfamily: Sequoioideae
Genera

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][4]

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.

Taxonomy and evolution

Multiple studies of both morphological and molecular characters have strongly supported the assertion that the Sequoioideae are monophyletic.[5][6][7][8] Most modern phylogenies place Sequoia as sister to Sequoiadendron and Metasequoia as the out-group.[6][8][9] 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.[8]

Cladistic tree

A 2006 paper based on non-molecular evidence suggested the following relationship among extant species:[10]

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.[11]

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.[12] 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.[8]

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.

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.[9]

Extant species

Paleontology

Sequoioideae is an ancient taxon, with the oldest described Sequoioideae species, Sequoia jeholensis, recovered from Jurassic deposits.[13][14] A genus Medulloprotaxodioxylon, reported from the late Triassic of China supports the idea of a Late Triassic Norian origin.[15]

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.[16] A general cooling trend beginning in the late Eocene and Oligocene reduced the northern ranges of the Sequoioideae, as did subsequent ice ages.[17] 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.

The extinct genus Austrosequoia is known from the Late Cretaceous-Oligocene of the Southern Hemisphere, including Australia and New Zealand.[18]

Young but already tall redwood trees (Sequoia sempervirens) in Oakland, California

Conservation

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).

See also
  • Temperate cloud forest of North America Westcoast (Sequoia forests)

References
  1. "Prescribed Fire at Redwood National and State Parks - Redwood National and State Parks (U.S. National Park Service)".
  2. "The Threats to the Redwoods".
  3. "Why redwood burl poaching is so destructive". Christian Science Monitor. 5 March 2014.
  4. Kurland, Justin; Pires, Stephen F; Marteache, Nerea (2018). "The spatial pattern of redwood burl poaching and implications for prevention". Forest Policy and Economics. 94: 46–54. doi:10.1016/j.forpol.2018.06.009. S2CID 158505170.
  5. Brunsfeld, Steven J; Soltis, Pamela S; Soltis, Douglas E; Gadek, Paul A; Quinn, Christopher J; Strenge, Darren D; Ranker, Tom A (1994). "Phylogenetic Relationships Among the Genera of Taxodiaceae and Cupressaceae: Evidence from rbcL Sequences". Systematic Botany. 19 (2): 253. doi:10.2307/2419600. JSTOR 2419600.
  6. Gadek, P.A.; Alpers, D.L.; Heslewod, M.M.; Quinn, C.J. (2000). "Relationships Within Cupressaceae Sensu Lato: A Combined Morphological and Molecular Approach". American Journal of Botany. 87 (7): 1044–57. doi:10.2307/2657004. JSTOR 2657004. PMID 10898782.
  7. Takaso, T.; Tomlinson, P.B. (1992). "Seed cone and ovule ontogeny in Metasequoia, Sequoia and Sequoiadendron (Taxodiaceae-Coniferales)". Botanical Journal of the Linnean Society. 109: 15–37. doi:10.1111/j.1095-8339.1992.tb00256.x.
  8. Yang, Z.Y.; Ran, J.H.; Wang, X.Q. (2012). "Three Genome-based Phylogeny of Cupressaceae s.l: Further Evidence for the Evolution of Gymnosperms and Southern Hemisphere Biogeography". Molecular Phylogenetics and Evolution. 64 (3): 452–470. doi:10.1016/j.ympev.2012.05.004. PMID 22609823.
  9. Mao, K.; Milne, R.I.; Zhang, L.; Peng, Y.; Liu, J.; Thomas, P.; Mill, R.R.; Renner, S.S. (2012). "Distribution of Living Cupressaceae Reflects the Breakup of Pangea". Proceedings of the National Academy of Sciences. 109 (20): 7793–7798. Bibcode:2012PNAS..109.7793M. doi:10.1073/pnas.1114319109. PMC 3356613. PMID 22550176.
  10. Schulz; Stützel (August 2007). "Evolution of taxodiaceous Cupressaceae (Coniferopsida)". Organisms Diversity & Evolution. 7 (2): 124–135. doi:10.1016/j.ode.2006.03.001.
  11. Stull, Gregory W.; Qu, Xiao-Jian; Parins-Fukuchi, Caroline; Yang, Ying-Ying; Yang, Jun-Bo; Yang, Zhi-Yun; Hu, Yi; Ma, Hong; Soltis, Pamela S.; Soltis, Douglas E.; Li, De-Zhu (August 2021). "Gene duplications and phylogenomic conflict underlie major pulses of phenotypic evolution in gymnosperms". Nature Plants. 7 (8): 1015–1025. doi:10.1038/s41477-021-00964-4. ISSN 2055-0278. PMID 34282286. S2CID 236141481.
  12. Soltis, D.E.; Buggs, R.J.A.; Doyle, J.J.; Soltis, P.S. (2010). "What we still don't know about polyploidy". Taxon. 59 (5): 1387–1403. doi:10.1002/tax.595006. JSTOR 20774036.
  13. Ma, Qing-Wen; K. Ferguson, David; Liu, Hai-Ming; Xu, Jing-Xian (2020). "Compressions of Sequoia (Cupressaceae sensu lato) from the Middle Jurassic of Daohugou, Ningcheng, Inner Mongolia, China". Palaeobiodiversity and Palaeoenvironments. 1 (9): 1. doi:10.1007/s12549-020-00454-z. S2CID 227180592. Retrieved 9 March 2021.
  14. Ahuja M. R. and D. B. Neale. 2002. Origins of polyploidy in coast redwood (Sequoia sempervirens) and relationship of coast redwood (Sequoia sempervirens) to other genera of Taxodiaceae. Archived 2 January 2014 at the Wayback Machine Silvae Genetica 51: 93–99.
  15. Wan, Mingli; Yang, Wan; Tang, Peng; Liu, Lujun; Wang, Jun (2017). "Medulloprotaxodioxylon triassicum gen. Et sp. Nov., a taxodiaceous conifer wood from the Norian (Triassic) of northern Bogda Mountains, northwestern China". Review of Palaeobotany and Palynology. 241: 70–84. doi:10.1016/j.revpalbo.2017.02.009.
  16. Chaney, Ralph W. (1950). "Revision of Fossil Sequoia and Taxodium in Western North America Based on the Recent Discovery of Metasequoia". Transactions of the American Philosophical Society. Philadelphia. 40 (3): 172–236. doi:10.2307/1005641. ISBN 978-1422377055. JSTOR 1005641. Retrieved 1 January 2014.
  17. Jagels, Richard; Equiza, María A. (2007). "Why did Metasequoia disappear from North America but not from China?". Bulletin of the Peabody Museum of Natural History. 48 (2): 281–290. doi:10.3374/0079-032x(2007)48[281:wdmdfn]2.0.co;2. S2CID 129649877.
  18. Mays, Chris; Cantrill, David J.; Stilwell, Jeffrey D.; Bevitt, Joseph J. (28 May 2018). "Neutron tomography of Austrosequoia novae-zeelandia e comb. nov. (Late Cretaceous, Chatham Islands, New Zealand): implications for Sequoioideae phylogeny and biogeography". Journal of Systematic Palaeontology. 16 (7): 551–570. doi:10.1080/14772019.2017.1314898. ISSN 1477-2019.
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