Editing Pine (section)

=== Taxonomy ===

{{Main list|List of Pinus species |l1=List of ''Pinus'' species}}

Pines are [[gymnosperm]]s. The genus is divided into two subgenera based on the number of [[Vascular bundle|fibrovascular bundles]] in the needle, and the presence or absence of a resin seal on the scales of the mature cones before opening. The subgenera can be distinguished by cone, seed, and leaf characters:
*[[Pinus subg. Pinus|''Pinus'' subg. ''Pinus'']], the yellow, or hard pine group, with cones with a resin seal on the scales, and generally with harder wood; the needle fascicles mostly have a persistent sheath (two exceptions, ''[[Pinus leiophylla]]'' and ''[[Pinus lumholtzii]]'', have deciduous sheaths).<ref name="RHSD"/> The subgenus has also been called ''diploxylon'', on account of its two fibrovascular bundles.<ref name="Mirov">{{cite book |last1=Mirov |first1=N. T. |title=The Genus ''Pinus'' |date=1967 |publisher=Ronald Press |location=New York}}</ref>
*[[Strobus|''Pinus'' subg. ''Strobus'']], [[synonym (biology)|syn.]] ''Pinus'' subg. ''Ducampopinus'', the white, or soft pine, and pinyon pine groups, with cones without a resin seal on the scales, and usually have softer wood; the needle fascicles mostly have a deciduous sheath (one exception, ''[[Pinus nelsonii]]'', has a persistent sheath).<ref name="RHSD"/> The subgenus has also been called ''haploxylon'', on account of its single fibrovascular bundle.<ref name="Mirov"/>

Phylogenetic evidence indicates that both subgenera have a very ancient divergence from one another.<ref name=Stull>{{Cite journal |last1=Stull |first1=Gregory W. |last2=Qu |first2=Xiao-Jian |last3=Parins-Fukuchi |first3=Caroline |last4=Yang |first4=Ying-Ying |last5=Yang |first5=Jun-Bo |last6=Yang |first6=Zhi-Yun |last7=Hu |first7=Yi |last8=Ma |first8=Hong |last9=Soltis |first9=Pamela S. |last10=Soltis |first10=Douglas E. |last11=Li |first11=De-Zhu |display-authors=5 |date=July 19, 2021 |title=Gene duplications and phylogenomic conflict underlie major pulses of phenotypic evolution in gymnosperms |url=https://www.nature.com/articles/s41477-021-00964-4 |journal=Nature Plants |volume=7 |issue=8 |pages=1015–1025 |doi=10.1038/s41477-021-00964-4 |pmid=34282286 |bibcode=2021NatPl...7.1015S |s2cid=236141481 |issn=2055-0278 |access-date=January 10, 2022 |archive-date=January 10, 2022 |archive-url=https://web.archive.org/web/20220110174725/https://www.nature.com/articles/s41477-021-00964-4/ |url-status=live}}</ref> Each subgenus is further divided into sections and subsections.<ref name="Gernandt López García 2005">{{cite journal |last=Gernandt |first=David S. |last2=López |first2=Gretel Geada |last3=García |first3=Sol Ortiz |last4=Liston |first4=Aaron |title=Phylogeny and classification of Pinus |journal=Taxon |volume=54 |issue=1 |date=2005 |doi=10.2307/25065300 |doi-access=free |pages=29–42 |url=https://rc.upr.edu.cu/jspui/bitstream/DICT/2586/1/Geada-LopezTAXON2005.pdf}}</ref>

Many of the smaller groups of ''Pinus'' are composed of closely related species with recent divergence and history of hybridisation. This results in low morphological and genetic differences. This, coupled with low sampling and underdeveloped genetic techniques, has made taxonomy difficult to determine.<ref>{{cite journal |last1=Flores-Rentería |first1=Lluvia |last2=Wegier |first2=Ana |last3=Ortega Del Vecchyo |first3=Diego |last4=Ortíz-Medrano |first4=Alejandra |last5=Piñero |first5=Daniel |last6=Whipple |first6=Amy V. |last7=Molina-Freaner |first7=Francisco |last8=Domínguez |first8=César A. |display-authors=5 |title=Genetic, morphological, geographical and ecological approaches reveal phylogenetic relationships in complex groups, an example of recently diverged pinyon pine species (Subsection Cembroides) |journal=Molecular Phylogenetics and Evolution |volume=69 |issue=3 |pages=940–9 |date=December 2013 |pmid=23831459 |doi=10.1016/j.ympev.2013.06.010 |bibcode=2013MolPE..69..940F }}</ref> Recent research using large genetic datasets has clarified these relationships into the groupings often accepted today.<ref name="Gernandt López García 2005"/>