Editing Prunus (section)

==== 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}}