Xanthocyparis

''Xanthocyparis'' is a genus of cypresses in the family Cupressaceae. , it has only one species, ''Xanthocyparis vietnamensis'', native to Vietnam and southeast China. It is commonly known as the Vietnamese golden cypress. The Nootka cypress, '' Cupressus nootkatensis'' or ''Callitropsis nootkatensis'', was also placed in the genus, but this has been rejected.

Taxonomy

In 2002, Aljos Farjon and others described the new genus ''Xanthocyparis'' to accommodate the new Vietnamese species '' X. vietnamensis'' and another species, the Nootka cypress, which had been formerly included in the genus ''Chamaecyparis'' as ''C. nootkatensis''. This was based in part on the discovery that ''C. nootkatensis'' was more closely related to the genus ''Cupressus'' than to ''Chamaecyparis''.

In 2004, Damon Little and others, while confirming the above relationship with further evidence, pointed out that as circumscribed by Farjon ''et al.'', ''Xanthocyparis'' included the type species of ''Callitropsis'' (''Cupressus nootkatensis'', a synonym of ''Chamaecyparis nootkatensis'' and ''Xanthocyparis nootkatensis''). ''Callitropsis'' had been described by Anders Sandøe Ørsted in 1864, but this name had been overlooked by Farjon and most other authors; under the rules of the International Code of Botanical Nomenclature, ''Callitropsis'' as the earlier-published name had nomenclatural priority over ''Xanthocyparis'' if that genus included ''Cupressus nootkatensis''. Little ''et al.'' therefore recognized ''Xanthocyparis'' as a synonym of ''Callitropsis''. The name ''Xanthocyparis'' was proposed for conservation over ''Callitropsis'', a decision that was ratified at the International Botanical Congress in 2011.

Little ''et al.'' also presented evidence that ''Cupressus'' is paraphyletic with respect to ''Juniperus'' and ''Xanthocyparis'', with the North American species of ''Cupressus'' being more closely related to ''Xanthocyparis'' than they are to the European and Asian ''Cupressus'' species. These species were transferred to ''Callitropsis'' by Damon Little in 2006, although this transfer was not universally accepted. In 2009, most of the North American species previously included in ''Callitropsis'' were placed in a separate genus, '' Hesperocyparis''.

A 2021 molecular study found ''Xanthocyparis'' to be sister to a clade comprising '' Hesperocyparis'' and ''Callitropsis'', with the clade containing all three being sister to a clade comprising ''Juniperus'' and ''Cupressus sensu stricto''.

Distribution

''Xanthocyparis vietnamensis'' was originally described as endemic to Vietnam, being native only to the karst limestone mountains of the Hà Giang Province in northern Vietnam. It has since also been recorded in Cao Bằng and Tuyên Quang provinces in Vietnam, as well as southeast China (Guangxi).

References

{{Taxonbar, from1=Q133623, from2=Q145841, from3=Q50840138, from4=Q17165388

Cupressaceae
Monotypic conifer genera
Taxa named by Aljos Farjon
Taxa named by Tiên Hiêp Nguyên
Plants described in 2002