Hesperocyparis

Hesperocyparis (western cypress)^[1] is a genus of trees in the family Cupressaceae, containing North American species otherwise assigned to the genus Cupressus.^[2] They are found throughout western North America. Only a few species have wide ranges, with most being restricted-range endemics.

Hesperocyparis
Hesperocyparis macrocarpa, Monterey cypress
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Gymnospermae
Division:	Pinophyta
Class:	Pinopsida
Order:	Cupressales
Family:	Cupressaceae
Subfamily:	Cupressoideae
Genus:	Hesperocyparis Bartel & R.A. Price
Type species
Hesperocyparis macrocarpa (Hartweg ex Gordon) Bartel & Price
Species
See text
Synonyms
Neocupressus de Laub. nom. superfl.

Taxonomy

Members of Hesperocyparis were and still are placed in Cupressus by many authorities, but phylogenetic evidence supports a different affinity. A 2021 molecular study found Hesperocyparis to be the sister group to the genus Callitropsis (containing only the Nootka cypress), with this clade being sister to the Asian genus Xanthocyparis, containing only the Vietnamese golden cypress. The clade comprising all three genera was found to be sister to a clade containing Juniperus and Cupressus sensu stricto.^[3] If Hesperocyparis and the other smaller genera were reunited with Cupressus it may also require them to be merged into a larger genus including Juniperus.^[4]

As of 2024 Hesperocyparis is listed as the correct classification by Plants of the World Online,^[5] World Flora Online,^[6] and the Gymnosperm Database.^[7] There is disagreement about this classification, with some scientists continuing to use Cupressus in preference to Hesperocyparis.^[8][9]

At the species level there is also uncertainty as to the number of species. In part this is because the north west of Mexico has not been sufficiently surveyed to give enough information to definitively determine if a number of species there and in the southwestern United States are fully separate species or part of a species complex.^[7]

Phylogeny

Stull et al. 2021[10][11]

Juniperus Cupressus s.l. Cupressus s.s. Xanthocyparis vietnamensis Farjon & Nguyên Callitropsis nootkatensis (Don) Oersted Hesperocyparis H. bakeri (Jepson) Bartel (Modoc cypress) H. macnabiana (Murray) Bartel (Macnab’s/Shasta cypress) H. goveniana (Gordon) Bartel (Gowen cypress) H. macrocarpa (Hartweg ex Gordon) Bartel (Monterey cypress) H. sargentii Jepson (Sargent cypress) H. glabra (Sudworth) Bartel (Smooth Arizona cypress) H. arizonica (Greene) Bartel (Arizona cypress) H. guadalupensis (Watson) Bartel (Guadalupe cypress) H. montana (Wiggins) Bartel (San Pedro Martir cypress) H. forbesii (Jepson) Bartel (Tecate cypress) H. lusitanica (Miller) Bartel (Mexican cypress) H. stephensonii (Jepson) Bartel (Cuyamaca cypress)

Additional species:^[5]

• Hesperocyparis abramsiana (C. B. Wolf) Bartel (Santa Cruz cypress)
• Hesperocyparis benthamii (Endl.) Bartel
• Hesperocyparis nevadensis (Abrams) Bartel (Piute cypress)
• Hesperocyparis pygmaea (Lemmon) Bartel (Mendocino cypress)
• Hesperocyparis revealiana (Silba) Silba

References

1. NRCS. "Hesperocyparis". PLANTS Database. United States Department of Agriculture (USDA). Retrieved 14 May 2015.
2. Robert P. Adams, Jim A. Bartel & Robert A. Price (2009). "A new genus, Hesperocyparis, for the cypresses of the Western Hemisphere" (PDF). Phytologia. 91 (1): 160–185.
3. 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 (July 19, 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 232282918.
4. Christenhusz, Maarten J. M.; Fay, Michael F.; Chase, Mark W. (2017). Plants of the world : an illustrated encyclopedia of vascular plants. Richmond, Surrey, UK & Chicago, Illinois: Kew Publishing, Royal Botanic Gardens, Kew & The University of Chicago Press. p. 84. ISBN 978-1-84246-634-6. Retrieved 18 February 2024.
5. "Hesperocyparis Bartel & R.A.Price". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 30 January 2024.
6. "Hesperocyparis Bartel & R.A.Price". World Flora Online. Retrieved 30 January 2024.
7. Earle, Christopher J. "Hesperocyparis (New World Cypresses) description". The Gymnosperm Database. Retrieved 30 January 2024.
8. Michalet, Richard; Carcaillet, Christopher; Delerue, Florian; Domec, Jean-Christophe; Lenoir, Jonathan (19 December 2023). "Assisted migration in a warmer and drier climate: less climate buffering capacity, less facilitation and more fires at temperate latitudes?". Oikos. doi:10.1111/oik.10248. S2CID 266410521. Retrieved 13 February 2024.
9. Raddi, Paolo; Della Rocca, Gianni; Danti, Roberto (8 January 2020). "Cupressus glabra". In Stimm, B.; Roloff, A.; Lang, U.M.; Weisgerber, H. (eds.). Enzyklopädie der Holzgewächse: Handbuch und Atlas der Dendrologie /begründet von Peter Schütt. Andreas Roloff; Horst Weisgerber; Ulla M. Lang; Bernd Stimm. Weinheim: Wiley-VCH. ISBN 9783527321414.
10. 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 (July 19, 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.
11. Stull, Gregory W.; et al. (2021). "main.dated.supermatrix.tree.T9.tre". Figshare. doi:10.6084/m9.figshare.14547354.v1.