Editing American chestnut (section)

==Evolution and ecology==
Chestnuts are in the Fagaceae family along with [[beech]] and [[oak]].<ref>{{cite journal |last1=Kremer |first1=Antoine |last2=Abbott |first2=Albert G. |last3=Carlson |first3=John E. |last4=Manos |first4=Paul S. |last5=Plomion |first5=Christophe |last6=Sisco |first6=Paul |last7=Staton |first7=Margaret E. |last8=Ueno |first8=Saneyoshi |last9=Vendramin |first9=Giovanni G. |title=Genomics of Fagaceae |journal=Tree Genetics & Genomes |date=June 2012 |volume=8 |issue=3 |pages=583–610 |doi=10.1007/s11295-012-0498-3|s2cid=16005843 |doi-access=free }}</ref> Chestnuts are not closely related to the [[Aesculus|horse chestnut]], which is in the family [[Sapindaceae]].<ref>{{cite journal |last1=Krahulcová |first1=Anna |last2=Trávníček |first2=Pavel |last3=Krahulec |first3=František |last4=Rejmánek |first4=Marcel |title=Small genomes and large seeds: chromosome numbers, genome size and seed mass in diploid Aesculus species (Sapindaceae) |journal=Annals of Botany |date=8 January 2017 |volume=119 |issue=6 |pages=957–964 |doi=10.1093/aob/mcw261|pmid=28065925 |pmc=5604552 }}</ref> [[Phylogenetic]] analysis indicates a westward migration of [[Extant species|extant]] ''Castanea'' species from Asia to Europe to North America, with the American chestnut more closely related to the Allegheny chinquapin (''Castanea pumila'' v. ''pumila'') than to European or Asian [[clades]]. The [[genomic]] range of chestnuts can be roughly divided into a [[Cline (biology)|clinal]] pattern of northeast, central, and southwest populations, with southwest populations showing greatest diversity, reflecting an [[evolutionary bottleneck]] likely caused by [[Quaternary glaciation]].<ref>{{cite journal |last1=Sandercock |first1=Alexander M. |last2=Westbrook |first2=Jared W. |last3=Zhang |first3=Qian |last4=Johnson |first4=Hayley A. |last5=Saielli |first5=Thomas M. |last6=Scrivani |first6=John A. |last7=Fitzsimmons |first7=Sara F. |last8=Collins |first8=Kendra |last9=Perkins |first9=M. Taylor |last10=Craddock |first10=J. Hill |last11=Schmutz |first11=Jeremy |last12=Grimwood |first12=Jane |last13=Holliday |first13=Jason A. |title=Frozen in time: rangewide genomic diversity, structure, and demographic history of relict American chestnut populations |journal=Molecular Ecology |date=26 July 2022 |volume=31 |issue=18 |pages=4640–4655 |doi=10.1111/mec.16629|pmid=35880415 |bibcode=2022MolEc..31.4640S |s2cid=251068122 |doi-access=free }}</ref> Two lineages of American chestnut have been identified, one a hybrid between the American chestnut and the Allegheny chinquapin from the southern Appalachians. The other lineage shows a gradual loss of genetic diversity along a northward vector, indicating possible expansion of range following the most recent glacial maximum during the [[Wisconsin glaciation]].<ref>{{cite journal |last1=Dane |first1=Fenny |last2=Wang |first2=Zhuoyu |last3=Goertzen |first3=Leslie |title=Analysis of the complete chloroplast genome of Castanea pumila var. pumila, the Allegheny chinkapin |journal=Tree Genetics & Genomes |date=February 2015 |volume=11 |issue=1 |page=14 |doi=10.1007/s11295-015-0840-7|s2cid=18860364 }}</ref> [[Castanea ozarkensis|Ozark chinkapin]] (''C. ozarkensis''), which is typically considered either a distinct species or a subspecies of the Allegheny chinquapin (''C.&nbsp;pumila'' subsp. ''ozarkensis''), may be ancestral to both the American chestnut and the Allegheny chinquapin.<ref>{{Cite journal|last1=Huang|first1=Hongwen|last2=Hawkins|first2=Leigh K.|last3=Dane|first3=Fenny|date=1999-11-01|title=Genetic Variation and Population Structure of Castanea pumila var. ozarkensis|journal=Journal of the American Society for Horticultural Science|language=en-US|volume=124|issue=6|pages=666–670|doi=10.21273/JASHS.124.6.666|issn=2327-9788|doi-access=free}}</ref><ref>{{Cite web |url=https://www.nationalgeographic.com/environment/article/saving-chestnut-trees-ozarks |first=Robert |last=Langellier |archive-url=https://web.archive.org/web/20190626124603/https://www.nationalgeographic.com/environment/2019/06/saving-chestnut-trees-ozarks/|url-status=live|archive-date=June 26, 2019|title=A legendary Ozark chestnut tree, thought extinct, is rediscovered|date=2019-06-24|website=National Geographic |access-date=2019-07-28}}</ref> A natural hybrid of ''C.&nbsp;dentata'' and ''C.&nbsp;pumila'' has been named [[Castanea × neglecta|''Castanea'' × ''neglecta'']].{{r|powo49294-2}}

The American chestnut population was reduced to 1–10% of its original size as a result of the chestnut blight and has not recovered.<ref>{{cite journal |last1=Van Drunen |first1=Stephen G. |last2=Schutten |first2=Kerry |last3=Bowen |first3=Christine |last4=Boland |first4=Greg J. |last5=Husband |first5=Brian C. |title=Population dynamics and the influence of blight on American chestnut at its northern range limit: Lessons for conservation |journal=Forest Ecology and Management |date=September 2017 |volume=400 |pages=375–383 |doi=10.1016/j.foreco.2017.06.015|bibcode=2017ForEM.400..375V }}</ref> The surviving trees are "frozen in time" with shoots re-sprouting from survivor [[rootstock]] but almost entirely undergoing blight-induced dieback without producing chestnuts. Unexpectedly, American chestnut appears to have retained substantial genetic diversity following the population bottleneck, which is at odds with the limited incidence of blight resistance/tolerance in extant populations.<ref>{{cite journal |last1=Stoltz |first1=Sophia S. |last2=Husband |first2=Brian C. |title=High genetic diversity in American chestnut (Castanea dentata) despite a century of decline |journal=Conservation Genetics |date=10 November 2022 |volume=24 |pages=25–39 |doi=10.1007/s10592-022-01473-3|s2cid=253470197 }}</ref>

The pre-blight distribution was restricted to moist, well-drained, steep slopes with acidic [[loam]] soils.<ref>{{cite journal |last1=Tulowiecki |first1=Stephen J. |title=Modeling the historical distribution of the American chestnut (Castanea dentata) for potential restoration in western New York State, US |journal=Forest Ecology and Management |date=April 2020 |volume=462 |page=118003 |doi=10.1016/j.foreco.2020.118003|bibcode=2020ForEM.46218003T |s2cid=212766961 }}</ref><ref name="Pre-Blight Distribution of Castanea">{{cite journal |last1=Russell |first1=Emily W. B. |title=Pre-Blight Distribution of Castanea dentata (Marsh.) Borkh |journal=Bulletin of the Torrey Botanical Club |date=April 1987 |volume=114 |issue=2 |pages=183–190 |doi=10.2307/2996129|jstor=2996129 }}</ref> According to [[Palynology|analysis of old forest dust]] data, the tree was rare or absent in [[New England]] prior to 2,500 years before present<ref>{{cite journal |last1=Paillet |first1=Frederick L. |title=Chestnut: history and ecology of a transformed species |journal=Journal of Biogeography |date=October 2002 |volume=29 |issue=10–11 |pages=1517–1530 |doi=10.1046/j.1365-2699.2002.00767.x|bibcode=2002JBiog..29.1517P |s2cid=53319372 }}</ref> but rapidly established dominance in these forests, becoming a common tree over a range from [[Maine]] and [[southern Ontario]] to [[Mississippi]], and from the [[Atlantic]] coast to the [[Appalachian Mountains]] and the [[Ohio Valley]]. Within its range, the American chestnut was the dominant timber of mountain ridges and sandstone soils. Along the [[Blue Ridge Mountains]] of North Carolina, it dominated the area above the range of the [[Tsuga canadensis|Eastern hemlock]] and below 1,500 meters.<ref>{{cite book |isbn=978-1-332-06695-7 |orig-date=1905 |title=Report on an Examination of a Forest Tract in Western North Carolina (Classic Reprint) |last1=Reed |first1=Franklin W. |date=July 28, 2015 |publisher=FB&C Limited }}</ref> In [[Western Maryland]], it comprised 50% of ridge timber and 36% of forested slopes.<ref>Dorsey, Clarence Wilbur, George Curtis Martin, Oliver Lanard Fassig, Hugh M. Curran, Edwin G. Paul, and Henry Albert Pressey. Garrett County. Vol. 2. Johns Hopkins Press, 1902.</ref><ref name="Pre-Blight Distribution of Castanea"/>

The tree's abundance was the result of a combination of rapid growth, relative fire resistance, and a large annual nut crop, in comparison to oaks, which do not reliably produce sizable numbers of acorns every year. Historically, the mean fire return interval was 20 years or less in chestnut-predominant ecologies, with a forest stand pattern that was more open than is currently the case.<ref>{{cite journal |last1=Kane |first1=Jeffrey M. |last2=Varner |first2=J. Morgan |last3=Stambaugh |first3=Michael C. |last4=Saunders |first4=Michael R. |title=Reconsidering the fire ecology of the iconic American chestnut |journal=Ecosphere |date=October 2020 |volume=11 |issue=10 |doi=10.1002/ecs2.3267|bibcode=2020Ecosp..11E3267K |s2cid=224943591 |doi-access=free }}</ref>

The American chestnut was an important tree for wildlife, providing much of the fall [[mast (botany)|mast]] for species such as [[white-tailed deer]], [[wild turkey]], [[Allegheny woodrat]] and (prior to its extinction) the [[passenger pigeon]]. [[American black bear|Black bears]] were also known to eat the nuts to fatten up for the winter. The tree contains more [[nitrogen]], [[phosphorus]], [[potassium]] and [[magnesium]] in its leaves than other trees that share its habitat, so they return more nutrients to the soil which helps with the growth of other plants, animals, and microorganisms.<ref name=blight>{{cite magazine |last=Jabr |first=Ferris |url=https://www.scientificamerican.com/article/chestnut-forest-a-new-generation-of-american-chestnut-trees-may-redefine-americas-forests/ |title=A New Generation of American Chestnut Trees May Redefine America's Forests |magazine=[[Scientific American]] |date=March 1, 2014 |access-date=September 22, 2015 }}</ref> The American chestnut is preferred by some avian seed hoarders and was particularly important as a food source during years where the oak mast failed.<ref>{{cite journal |last1=Wright |first1=James R. |last2=Matthews |first2=Stephen N. |last3=Pinchot |first3=Cornelia C. |last4=Tonra |first4=Christopher M. |title=Preferences of avian seed-hoarders in advance of potential American chestnut reintroduction |journal=Forest Ecology and Management |date=May 2022 |volume=511 |page=120133 |doi=10.1016/j.foreco.2022.120133|s2cid=247469499 |doi-access=free |bibcode=2022ForEM.51120133W }}</ref> The functional extinction of the American chestnut may have resulted in the extinction of some of the tree's host-specialist insect associates, including the [[Curculio caryatrypes|Greater Chestnut Weevil]].<ref>{{cite journal |last1=Charles |first1=Michael A. |last2=McKenna |first2=Duane D. |title=Did the Functional Extinction of the American Chestnut, Castanea dentata, Result in the Extinction of the Greater Chestnut Weevil, Curculio caryatrypes? |journal=Northeastern Naturalist |date=2 January 2024 |volume=30 |issue=4 |doi=10.1656/045.030.0413}}</ref>