Editing Prunus (section)

===Classification===

==== Evolutionary history ====
{{update|section|date=September 2021}}

The oldest fossils confirmed to belong to ''Prunus'' date to the [[Eocene]], and are found across the Northern Hemisphere. Older potential Late Cretaceous records are unconfirmed.<ref>{{Cite journal |last1=Li |first1=Ya |last2=Smith |first2=Thierry |last3=Liu |first3=Chang-Jiang |last4=Awasthi |first4=Nilamber |last5=Yang |first5=Jian |last6=Wang |first6=Yu-Fei |last7=Li |first7=Cheng-Sen |date=April 2011 |title=Endocarps of ''Prunus'' (Rosaceae: Prunoideae) from the early Eocene of Wutu, Shandong Province, China |journal=Taxon |volume=60 |issue=2 |pages=555–564 |doi=10.1002/tax.602021|bibcode=2011Taxon..60..555L }}</ref>

The earliest known fossil ''Prunus'' specimens are wood, drupe, seed, and a leaf from the middle Eocene of the [[Princeton Chert]] of British Columbia, Canada.<ref name="stockeywehr">{{Cite encyclopedia |year=1996 |title=Life in Stone: a Natural History of British Columbia's Fossils |publisher=UBCPress |place=Vancouver |editor-last=Ludvigson |editor-first=Rolf |pages=234, 241, 245 |isbn=978-0-7748-0578-0 |last2=Wehr |first2=Wesley C. |first1=Ruth A. |last1=Stockey |contribution=Flowering Plants in and around Eocene Lakes of the Interior}}</ref> Using the known age as calibration data, a partial [[phylogeny]] of some of the Rosaceae from a number of [[nucleotide sequence]]s was reconstructed.<ref>{{cite journal |last=Oh |first=Sang-Hun |author2=Potter, Daniel |year=2005 |title=Molecular phylogenetic systematics and biogeography of tribe Neillieae (Rosaceae) using DNA sequences of cpDNA, rDNA, and LEAFY1 |journal=American Journal of Botany |volume=92 |issue=1 |pages=179–192 |doi=10.3732/ajb.92.1.179 |pmid=21652396}}</ref> ''Prunus'' and its sister clade [[Maloideae]] (apple subfamily) has been suggested to have diverged {{ma|44.3}} which is within the [[Lutetian]], or older middle [[Eocene]].{{efn|A date of 76 mya is given for Rosaceae, which is within the late [[Cretaceous]].}} Stockey and Wehr report: "The Eocene was a time of rapid evolution and diversification in [[Angiosperm]] families such as the Rosaceae ...."<ref name="stockeywehr" /> The oldest fossil species is ''[[Prunus cathybrownae]]'' from the [[Klondike Mountain Formation]].<ref>{{Cite journal |last1=Benedict |first1=John C. |last2=DeVore |first2=Melanie L. |last3=Pigg |first3=Kathleen B. |date=May 2011 |title=Prunus and Oemleria (Rosaceae) Flowers from the Late Early Eocene Republic Flora of Northeastern Washington State, U.S.A. |url=https://www.journals.uchicago.edu/doi/10.1086/660880 |journal=International Journal of Plant Sciences |language=en |volume=172 |issue=7 |pages=948–958 |doi=10.1086/660880 |bibcode=2011IJPlS.172..948B |issn=1058-5893}}</ref>

The Princeton finds are among a large number of angiosperm fossils from the [[Okanagan Highlands]] dating to the late early and middle Eocene. ''[[Crataegus]]'' is found at three locations: the [[McAbee Fossil Beds|McAbee Fossil Beds, British Columbia]]; the [[Klondike Mountain Formation]] around [[Republic, Washington]], and the [[Allenby Formation]] around [[Princeton, British Columbia]], while ''Prunus'' is found at those locations plus the [[Coldwater Beds]] of [[Quilchena|Quilchena, British Columbia]] and [[Chu Chua Formation]] around Chu Chua, British Columbia. A review of research on the [[Eocene Okanagan Highlands]]<ref name="Dillhoff">{{Cite journal |last=Dillhoff |first=Richard M. |author2=Leopold, Estella B. |author3=Manchester, Steven R. |date=February 2005 |title=The McAbee flora of British Columbia and its relation to the Early-Middle Eocene Okanagan Highlands flora of the Pacific Northwest |url=http://www.evolvingearth.org/learnearthscience/mcabeefeb2005cjes.pdf |url-status=dead |journal=Canadian Journal of Earth Sciences |volume=42 |issue=2 |pages=151–166 |bibcode=2005CaJES..42..151D |citeseerx=10.1.1.452.8755 |doi=10.1139/e04-084 |archive-url=https://web.archive.org/web/20160303184613/http://www.evolvingearth.org/learnearthscience/mcabeefeb2005cjes.pdf |archive-date=3 March 2016 |access-date=2 September 2007}}</ref> reported that the Rosaceae were more diverse at higher altitudes. The Okanagan highlands formations date to as early as 52 mya, but the (approximate) 44.3 mya date{{citation needed|date=September 2021}} might still apply. The authors state that "the McAbee flora records a diverse early middle Eocene angiosperm-dominated forest."<ref name="Dillhoff" />{{rp|165}}

====Linnean classification====
In 1737, [[Carl Linnaeus]] used four genera to include the species of modern ''Prunus''—''Amygdalus, Cerasus, Prunus'', and ''Padus''—but simplified it to ''Amygdalus'' and ''Prunus'' in 1758.<ref>{{cite book |author=Linnaeus Carolus |editor=Sprengel, Curtius |title=Genera Plantarum Editio Nona |trans-title=Plant Categories, Ninth Edition |year=1830 |location=Gottingen |publisher=Dieterich |pages=402–403 |url=https://books.google.com/books?id=8RoAAAAAQAAJ}}</ref> Since then, the various genera of Linnaeus and others have become subgenera and sections, as all the species clearly are more closely related. [[Liberty Hyde Bailey]] said: "The numerous forms grade into each other so imperceptibly and inextricably that the genus cannot be readily broken up into species."<ref name=Bailey>{{cite book |last=Bailey |first=Liberty Hyde |author-link=Liberty Hyde Bailey |title=Sketch of the Evolution of Our Native Fruits |url=https://archive.org/details/sketchevolution00bailgoog |year=1898 |location=New York |publisher=The MacMillan Company |page=[https://archive.org/details/sketchevolution00bailgoog/page/n210 181]}}</ref>

==== Traditional classification ====
Historical treatments break the genus into several different genera, but this segregation is not currently widely recognised other than at the subgeneric rank. The [[Integrated Taxonomic Information System|ITIS]] recognises just the single genus ''Prunus'', with an open list of species,{{efn|Do a search in the ITIS database on the scientific name ''Prunus'' for its current list.}} all of which are given at [[List of Prunus species]].{{efn|Other species appear, as well, which for whatever reasons are not yet in ITIS.}}

One treatment of the subgenera derives from the work of [[Alfred Rehder]] in 1940. Rehder hypothesized five subgenera: ''Amygdalus, Prunus, Cerasus, Padus'', and ''Laurocerasus''.<ref name="leewen">{{cite journal|doi=10.2307/2657135|first1=Sangtae |last1=Lee|first2=Jun |last2=Wen|title=A phylogenetic analysis of Prunus and the Amygdaloideae (Rosaceae) using ITS sequences of nuclear ribosomal DNA|journal=American Journal of Botany|year=2001|volume=88|pages=150–160|pmid=11159135|issue=1|jstor=2657135|doi-access=free}}</ref> To them C. Ingram added ''Lithocerasus''.<ref>{{cite encyclopedia |chapter=Stone Fruits |first=William |last=Okie |title=Encyclopedia of Fruits and Nuts |date=July 2003 |editor1-last=Janick |editor1-first=J. |editor2-last=Paulii |editor2-first=R.E. |publisher=C A B Intl |publication-date=2008}}</ref> The six subgenera are described as follows:
* Subgenus ''Amygdalus'', almonds and peaches: axillary buds in threes (vegetative bud central, two flower buds to sides); flowers in early spring, sessile or nearly so, not on leafed shoots; fruit with a groove along one side; stone deeply grooved; type species: ''[[Prunus dulcis]]'' (almond)
* [[Prunus subg. Prunus|Subgenus ''Prunus'']], plums and apricots: axillary buds solitary; flowers in early spring stalked, not on leafed shoots; fruit with a groove along one side, stone rough; type species: ''[[Prunus domestica]]'' (plum)
* [[Prunus subg. Cerasus|Subgenus ''Cerasus'']], true cherries: axillary buds single; flowers in early spring in corymbs, long-stalked, not on leafed shoots; fruit not grooved, stone smooth; type species: ''[[Prunus cerasus]]'' (sour cherry)
* [[Prunus sect. Microcerasus|Subgenus ''Lithocerasus'']], bush cherries: axillary buds in threes; flowers in early spring in corymbs, long-stalked, not on leafed shoots; fruit not grooved, stone smooth; type species: ''[[Prunus pumila]]'' (sand cherry)
* [[Prunus subg. Padus|Subgenus ''Padus'']], bird cherries: axillary buds single; flowers in late spring in racemes on leafy shoots, short-stalked; fruit not grooved, stone smooth; type species: ''[[Prunus padus]]'' (European bird cherry), now known to be polyphyletic<ref>{{cite journal |last1=Liu |first1=Xiao-Lin |last2=Wen |first2=Jun |last3=Nie |first3=Ze-Long |last4=Johnson |first4=Gabriel |last5=Liang |first5=Zong-Suo |last6=Chang |first6=Zhao-Yang |date=14 December 2012 |title=Polyphyly of the ''Padus'' group of ''Prunus'' (Rosaceae) and the evolution of biogeographic disjunctions between eastern Asia and eastern North America |journal=Journal of Plant Research |volume=126 |issue=3 |pages=351–361 |doi=10.1007/s10265-012-0535-1 |pmid=23239308 |s2cid=5991106 }}</ref>
* [[Prunus subg. Padus#Laurocerasus|Subgenus ''Laurocerasus'']], cherry laurels: mostly evergreen (all the other subgenera are deciduous); axillary buds single; flowers in early spring in racemes, not on leafed shoots, short-stalked; fruit not grooved, stone smooth; type species: ''[[Prunus laurocerasus]]'' (European cherry-laurel)

==== Phylogenetic classification ====
An extensive phylogenetic study based on different chloroplast and nuclear sequences divides ''Prunus'' into three subgenera:<ref name="Shi-2013">{{Cite journal |last1=Shi |first1=Shuo |last2=Li |first2=Jinlu |last3=Sun |first3=Jiahui |last4=Yu |first4=Jing |last5=Zhou |first5=Shiliang |title=Phylogeny and classification of ''Prunus sensu lato'' (Rosaceae) |journal=Journal of Integrative Plant Biology |date=2013 |volume=55 |issue=11 |pages=1069–1079 |doi=10.1111/jipb.12095 |pmid=23945216 |bibcode=2013JIPB...55.1069S |issn=1744-7909}}</ref>
* [[Prunus subg. Padus|Subg. ''Padus'']]: In addition to species of ''Padus'' (bird cherries), this subgenus also includes species of ''Maddenia'' (false bird cherries), ''Laurocerasus'' (cherry laurels) and ''Pygeum''.
* [[Prunus subg. Cerasus|Subg. ''Cerasus'']]: This subgenus includes true cherries such as [[sweet cherry]], [[sour cherry]], [[mahaleb cherry]] and [[Japanese flowering cherry]].
* [[Prunus subg. Prunus|Subg. ''Prunus'']]: This subgenus includes the following sections:
** [[Prunus sect. Prunus|Sect. ''Prunus'']]: Old World plums
** [[Prunus sect. Prunocerasus|Sect. ''Prunocerasus'']]: New World plums
** [[Apricot|Sect. ''Armeniaca'']]: apricots
** [[Prunus sect. Microcerasus|Sect. ''Microcerasus'']]: bush cherries
** [[Prunus sect. Amygdalus|Sect. ''Amygdalus'']]: almonds
** [[Prunus sect. Persica|Sect. ''Persica'']]: peaches
** [[Prunus sect. Emplectocladus|Sect. ''Emplectocladus'']]: desert almonds