Editing Platanus (section)

==Phylogeny==
There are two subgenera, subgenus ''Castaneophyllum'' containing the anomalous ''[[Platanus kerrii|P. kerrii]]'', and subgenus ''Platanus'', with all the others; recent studies in Mexico<ref name="Nixon-2003">{{Cite journal |last1=Nixon |first1=Kevin C. |last2=Poole |first2=Jackie M. |year=2003 |title=Revision of the Mexican and Guatemalan Species of Platanus (Platanaceae) |journal=Lundellia |language=en |volume=6 |issue=1 |pages=103–137 |doi=10.25224/1097-993X-6.1.4 |s2cid=90869751 |issn=1097-993X|doi-access=free }}</ref><ref name="Grimm-2010">{{Cite journal |last1=Grimm |first1=Guido W. |last2=Denk |first2=Thomas |year=2010 |title=The reticulate origin of modern plane trees (''Platanus'', Platanaceae): A nuclear marker puzzle |url=https://onlinelibrary.wiley.com/doi/10.1002/tax.591014 |journal=[[Taxon (journal)|Taxon]] |language=en |volume=59 |issue=1 |pages=134–147 |doi=10.1002/tax.591014}}</ref><ref name="De Castro-2013">{{Cite journal |last1=De Castro |first1=Olga |last2=Di Maio |first2=Antonietta |last3=Lozada García |first3=José Armando |last4=Piacenti |first4=Danilo |last5=Vázquez-Torres |first5=Mario |last6=De Luca |first6=Paolo |year=2013 |title=Plastid DNA sequencing and nuclear SNP genotyping help resolve the puzzle of central American Platanus |journal=[[Annals of Botany]] |language=en |volume=112 |issue=3 |pages=589–602 |doi=10.1093/aob/mct134 |issn=1095-8290 |pmc=3718222 |pmid=23798602}}</ref> have increased the number of accepted species in this subgenus. Within subgenus ''Platanus'', evidence from both [[Chloroplast DNA|chloroplast]]<ref name="De Castro-2013" /><ref name="Feng-2005">{{Cite journal |last1=Feng |first1=Yun |last2=Oh |first2=Sang-Hun |last3=Manos |first3=Paul S. |date=2005-10-01 |title=Phylogeny and Historical Biogeography of the Genus Platanus as Inferred From Nuclear and Chloroplast DNA |url=http://www.ingentaselect.com/rpsv/cgi-bin/cgi?ini=xref&body=linker&reqdoi=10.1600/036364405775097851 |journal=Systematic Botany |language=en |volume=30 |issue=4 |pages=786–799 |doi=10.1600/036364405775097851|s2cid=86021109 }}</ref> and [[nuclear gene]]<ref name="Grimm-2010" /><ref name="De Castro-2013" /><ref name="Feng-2005" /><ref name="Grimm-2007">{{Cite journal |last1=Grimm |first1=Guido W. |last2=Denk |first2=Thomas |date=2007-12-18 |title=ITS Evolution in Platanus (Platanaceae): Homoeologues, Pseudogenes and Ancient Hybridization |url=http://dx.doi.org/10.1093/aob/mcm305 |journal=Annals of Botany |volume=101 |issue=3 |pages=403–419 |doi=10.1093/aob/mcm305 |issn=1095-8290 |pmc=2701810 |pmid=18089582}}</ref> sequences suggests that the ''P. racemosa'' [[species complex]] in [[Western North America]] (including ''[[Platanus racemosa|P. racemosa]], [[Platanus gentryi|P. gentryi]], [[Platanus wrightii|P. wrightii]]'') is more closely related to the [[Eurasian]] ''P. orientalis'' than it is to the other North American species (''[[Platanus mexicana|P. mexicana]]'' [[sensu lato]], including up to four species: ''P. chiapaensis, P. lindeniana, P. [×] mexicana'' [[sensu stricto]], ''P. oaxacana; [[Platanus occidentalis|P. occidentalis]]'' [[Platanus occidentalis|s.l.]] with two [sub]species: ''P. occidentalis, P. palmeri''; ''[[Platanus rzedowskii|P. rzedowskii]]'').<ref name="Nixon-2003" /><ref name="Grimm-2010" /><ref name="De Castro-2013" /> The two groups form [[Genetics|genetically]] and [[Morphology (biology)|morphologically]] distinct [[Lineage (evolution)|evolutionary lineages]] ([[sister clades]]), informally called the “ANA clade” (Atlantic North American lineage) and “PNA-E clade” (Pacific North American-European lineage).<ref name="Grimm-2010" /> Both lineages have been affected by [[reticulate evolution]]ary processes in the past (ancient or [[recent]] [[Hybridization (biology)|hybridization]] and [[introgression]]):<ref name="Grimm-2010" /><ref name="De Castro-2013" /><ref name="Grimm-2007" />
* ''Platanus palmeri'' (= ''P. occidentalis'' [[Variety (botany)|var.]] ''palmeri'') – forming the southwesternmost populations of ''P. occidentalis'' s.l.<ref name="Grimm-2010" /><ref name="De Castro-2013" /> – carries nuclear [[intron]] sequences (second intron of the [[Leafy|Leafy gene]]) of PNA-E origin.<ref name="Grimm-2010" /> It lacks the plastid haplotype specific for the northeastern populations (''P. occidentalis'' s.str.)<ref name="De Castro-2013" />
* The [[internal transcribed spacer]]s of the nuclear-encoded [[Ribosomal DNA|rRNA genes]] of ''P. occidentalis'' s.l. and ''P. rzedowskii'' include ANA-specific variants with functional [[5.8S ribosomal RNA|5.8S rDNA]] as well as PNA-E-specific variants showing signs of [[Pseudogene|pseudogeny]].<ref name="Grimm-2007" /> The latter are shared with ''P. gentryi'', the PNA-E species closest to the ANA clade area and the northern/ interior populations of ''P. mexicana'' s.l. This indicates that already the [[common ancestor]] of ''P. rzedowskii'' and ''P. occidentalis'' s.l. had been in contact with a member of the PNA-E clade.
* Likewise, ''[[Platanus rzedowskii|P. rzedowskii]]'' from [[Nuevo León]] is a genetic mosaic, and may have originated from earlier hybridization within the ANA clade, between southernmost ''P. occidentalis'' s.l. (''P. palmeri'') and ''P. mexicana'' s.l., or their ancestors.<ref name="Grimm-2010" /> Today the ranges of ''P. occidentalis'' s.l. and ''P. mexicana'' s.l. are mutually exclusive. ''Platanus rzedowskii'' is geographically and morphologically intermediate between ''P. occidentalis'' s.l. and ''P. mexicana'' s.l.<ref name="Nixon-2003" /><ref name="De Castro-2013" />
* Morphological reinvestigation including the originally collected material revealed that the interior populations of ''P. mexicana'' (northern [[Querétaro]] and northern [[Hidalgo (state)|Hidalgo]]; ''P. mexicana'' var. ''interior'' according Nixon & Poole) mark the [[hybrid zone]] between ''P. rzedowskii'' and ''P. mexicana'' s.l. and the (former) contact zone to the species of the PNA-E clade (''P. gentryi'', ''P. wrightii''). Since the [[holotype]] of ''P. mexicana'' is from this zone and shows the characteristical intermediate morphology, ''P. mexicana'' s.str. would represent a [[nothospecies]]: ''P. × mexicana''.<ref name="Denk-2012">{{Cite journal |last1=Denk |first1=Thomas |last2=Grimm |first2=Guido W. |last3=Röseler |first3=Anne-Katrin |year=2012 |title=When field botany meets history: taxonomy of Platanus mexicana in Mexico |url=https://bioone.org/journals/willdenowia/volume-42/issue-1/wi.42.42113/When-field-botany-meets-history--taxonomy-of-Platanus-mexicana/10.3372/wi.42.42113.full |journal=Willdenowia |volume=42 |issue=1 |pages=99–115 |doi=10.3372/wi.42.42113 |s2cid=84804295 |issn=0511-9618}}</ref> The remaining populations of ''P. mexicana'' s.l., ''P. lindeniana'', show no sign of introgression from either ''P. rzedowskii, P. occidentalis-palmeri'' or the Western North American species (''P. racemosa'' species aggregate),<ref name="Grimm-2010" /><ref name="De Castro-2013" /> with the exception of one [[Zygosity|heterozygotic]] ''P. oaxacana'' population from northcentral [[Oaxaca]].<ref name="De Castro-2013" />
[[File:PlatanusNuclearEvolution.png|thumb|Sorting and evolutionary history of three different [[Noncoding strand|noncoding]] nuclear [[Locus (genetics)|loci]] contributing to the [[gene pool]] of modern-day species of ''Platanus'' (after<ref name="Grimm-2010" />)]]

The genus ''Platanus'' exemplarily illustrates the concept of a [[Coral of life|Coral of Life]], a species network. Its modern-day species are not only the product of evolutionary [[Dichotomy|dichotomies]] ([[cladogenesis]]), the splitting of an ancestral lineage into two ([[Tree of life (biology)|Tree of Life]] metaphor) but also evolutionary [[Anastomosis|anastomoses]]: hybridization and introgression.

The fossil record of leaves and fruit identifiable to ''Platanus'' begins in the [[Paleocene]].<ref name="MissisippiMiocene">{{cite journal |author1=McNair, D.M. |author2=D.Z. Stults |author3=B. Axsmith |author4=M.H. Alford |author5=J.E. Starnes |title=Preliminary investigation of a diverse megafossil floral assemblage from the middle Miocene of southern Mississippi, USA |journal=[[Palaeontologia Electronica]] |date=2019 |volume=22 |issue=2 |doi=10.26879/906 |url=https://palaeo-electronica.org/content/pdfs/906.pdf|doi-access=free }}</ref> Despite the geographic separation between North America and Old World, species from these continents will cross readily resulting in fertile [[Hybrid (biology)|hybrid]]s such as the London plane, which is an anthropogenic hybrid ([[cultivar]]) between the North American ''P. occidentalis'' [[sensu stricto]] (ANA clade) and the [[Mediterranean Basin|Mediterranean]] ''P. orientalis'' (PNA-E clade). Widely used as a park tree across the Northern Hemisphere, it frequently [[backcrossing|backcrosses]] with both its parents.<gallery widths="200" heights="200" mode="packed">
File:Skhtorashen176.jpg|The {{age|-20}}-year-old ''Platanus orientalis'' tree [[Tnjri]] in [[Nagorno-Karabakh]].
File:Platanus dissecta USNM P38122 img3.jpg|Miocene ''[[Platanus dissecta]]'' leaf, [[Latah Formation]]
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