Editing Oak (section)

== Ecology ==

[[File:Oak leafroller larvae.png|thumb|left|upright=0.8|Caterpillars of the North American oak leafroller, ''[[Archips semiferanus]]'', can defoliate oak forests.]]

Oaks are [[keystone species]] in a wide range of habitats from Mediterranean semi-desert to subtropical rainforest. They are important components of hardwood forests; some species grow in associations with members of the [[Ericaceae]] in [[oak–heath forest]]s.<ref>[http://www.dcr.virginia.gov/natural_heritage/ncTIIIe.shtml ''The Natural Communities of Virginia Classification of Ecological Community Groups'' (Version 2.3), Virginia Department of Conservation and Recreation, 2010] {{webarchive |url=https://web.archive.org/web/20090115181617/http://www.dcr.virginia.gov/natural_heritage/ncTIIIe.shtml |date=15 January 2009 }}. Dcr.virginia.gov. Retrieved 2011-12-10.</ref><ref>Schafale, M. P. and A. S. Weakley. 1990. ''Classification of the natural communities of North Carolina: third approximation''. North Carolina Natural Heritage Program, North Carolina Division of Parks and Recreation.</ref> Several kinds of [[truffle]]s, including two well-known varieties – black [[Tuber melanosporum|Périgord truffle]]<ref>{{cite web |url=http://www.thenibble.com/reviews/main/vegetables/truffle-glossary6.asp#glossary |title=Truffle Glossary: Black Truffles |publisher=thenibble.com |date=2010-07-01 |access-date=1 July 2010 |url-status=live |archive-url=https://web.archive.org/web/20100419130742/http://www.thenibble.com/reviews/main/vegetables/truffle-glossary6.asp#glossary |archive-date=19 April 2010}}</ref> and the white Piedmont truffle<ref name=r13>{{cite web |url=http://www.thenibble.com/reviews/main/vegetables/truffle-glossary8.asp#glossary |title=Truffle Glossary: White Truffles |publisher=thenibble.com |date=2010-07-01 |access-date=1 July 2010 |url-status=live |archive-url=https://web.archive.org/web/20100925140942/http://www.thenibble.com/reviews/MAIN/vegetables/truffle-glossary8.asp#glossary |archive-date=25 September 2010}}</ref> – have symbiotic relationships with oak trees. Similarly, many other fungi, such as ''[[Ramaria flavosaponaria]]'', associate with oaks.<ref name="Nirschl">{{cite web |last1=Nirschl |first1=Rick |title=Mushrooms of the Oak Openings |url=http://www.toledonaturalist.org/~naturalist/wp-content/uploads/2018/01/fungifinal3_sheet1.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.toledonaturalist.org/~naturalist/wp-content/uploads/2018/01/fungifinal3_sheet1.pdf |archive-date=2022-10-09 |url-status=live |access-date=19 July 2018 |website=Toledo Naturalists' Association |page=4}}</ref><ref name="Petersen">{{cite journal |last1=Petersen |first1=Ronald H. |author-link1=Ron Petersen |date=November 1985 |title=Notes on Clavarioid Fungi. XX. New Taxa and Distributional Records in ''Clavulina'' and ''Ramaria'' |journal=Mycologia |publisher=Taylor & Francis |volume=77 |issue=6 |pages=903–919 |doi=10.2307/3793302 |issn=0027-5514 |jstor=3793302 |oclc=7377077277}}</ref>

Oaks support more than 950 species of caterpillars, an important food source for many birds.<ref>{{cite web |last1=Bryant |first1=Tracey |date=April 2021 |title=Planting For the Planet |publisher=University of Delaware |url=https://www.udel.edu/udaily/2021/april/doug-tallamy-earth-day-oak-sustainable-ecosystem/}}</ref> Mature oak trees shed widely varying numbers of acorns (known collectively as mast) annually, with large quantities in [[Mast (botany)|mast years]]. This may be a [[predator satiation]] strategy, increasing the chance that some acorns will survive to germination.<ref name="Bogdziewicz Marino Bonal Zwolak 2018 pp. 2575–2582">{{cite journal |last1=Bogdziewicz |first1=Michał |last2=Marino |first2=Shealyn |last3=Bonal |first3=Raul |last4=Zwolak |first4=Rafał |last5=Steele |first5=Michael A. |title=Rapid aggregative and reproductive responses of weevils to masting of North American oaks counteract predator satiation |journal=Ecology |publisher=Wiley |volume=99 |issue=11 |date=2018-09-28 |issn=0012-9658 |doi=10.1002/ecy.2510 |pages=2575–2582|pmid=30182480 |bibcode=2018Ecol...99.2575B |s2cid=52156639 |doi-access=free }}</ref>

[[File:Eurasian jay (32648148027) (cropped).jpg|thumb|[[Jay]]s feed on acorns and help to [[Seed dispersal|disperse these seeds]].]]

Animals including [[squirrel]]s<ref name="Steele Yi 2020">{{cite journal | last1=Steele | first1=Michael A. | last2=Yi | first2=Xianfeng | title=Squirrel-Seed Interactions: The Evolutionary Strategies and Impact of Squirrels as Both Seed Predators and Seed Dispersers | journal=Frontiers in Ecology and Evolution | publisher=Frontiers Media SA | volume=8 | date=4 August 2020 | issn=2296-701X | doi=10.3389/fevo.2020.00259 | page= | doi-access=free }}</ref> and jays – [[Eurasian jay]]s in the Old World, [[blue jay]]s in North America – feed on acorns, and are important agents of [[seed dispersal]] as they carry the acorns away and bury many of them as food stores.<ref name="Mitrus Szabo 2020">{{cite journal | last1=Mitrus | first1=Cezary | last2=Szabo | first2=Josif | title=Foraging Eurasian Jays ''(Garrulus glandarius)'' prefer oaks and acorns in central Europe | journal=Ornis Hungarica | publisher=Walter de Gruyter GmbH | volume=28 | issue=1 | date=1 June 2020 | issn=2061-9588 | doi=10.2478/orhu-2020-0010 | pages=169–175| s2cid=220634002 | doi-access=free }}</ref><ref name="Enroth 2022">{{cite web |last1=Enroth |first1=Christopher |title=Of blue jays and pin oaks: How jays have shaped our oak forests around the world |url=https://extension.illinois.edu/blogs/good-growing/2022-03-04-blue-jays-and-pin-oaks-how-jays-have-shaped-our-oak-forests-around |publisher=University of Illinois Urbana-Champaign |access-date=14 October 2023 |date=4 March 2022}}</ref><ref name="Bossema 1979">{{cite journal | last=Bossema | first=I. | title=Jays and Oaks: an Eco-Ethological Study of a Symbiosis | journal=Behaviour | publisher=Brill | volume=70 | issue=1–2 | year=1979 | issn=0005-7959 | doi=10.1163/156853979x00016 | pages=1–116| url=https://research.rug.nl/en/publications/dc64a15d-a47b-459d-94d3-36ee96189986 }}</ref> However, some species of squirrel selectively excise the embryos from the acorns that they store, meaning that the food store lasts longer and that the acorns will never germinate.<ref name="Steele Yi 2020"/>

=== Hybridisation ===

[[File:Quercus stellata.jpg|thumb|left|upright=0.9 |A hybrid white oak, possibly ''[[Post oak|Quercus stellata]]'' × ''[[Chinkapin oak|Q. muehlenbergii]]'']]

[[Interspecific hybridization]] is quite common among oaks, but usually between species within the same section only,<ref>{{Cite journal |last=Valen |first=Leigh Van |year=1976 |title=Ecological Species, Multispecies, and Oaks |journal=Taxon |volume=25 |issue=2/3 |pages=233–239 |doi=10.2307/1219444 |issn=0040-0262 |jstor=1219444|bibcode=1976Taxon..25..233V }}</ref> and most common in the white oak group. White oaks cannot discriminate against pollination by other species in the same section. Because they are [[wind pollinated]] and have weak internal barriers to hybridization, hybridization produces functional seeds and fertile hybrid offspring. Ecological stresses, especially near habitat margins, can also cause a breakdown of mate recognition as well as a reduction of male function (pollen quantity and quality) in one parent species.<ref>{{Cite journal|last1=Williams |first1=Joseph H. |first2=William J. |last2=Boecklen |first3=Daniel J. |last3=Howard |year=2001 |title=Reproductive processes in two oak (''Quercus'') contact zones with different levels of hybridization |journal=Heredity |volume=87 |issue=6 |pages=680–690 |doi=10.1046/j.1365-2540.2001.00968.x|pmid=11903563 |doi-access=free |bibcode=2001Hered..87..680W }}</ref><ref>{{Cite book|last=Arnold |first=M. L. |year=1997 |title=Natural Hybridization and Evolution |publisher=Oxford University Press |location=New York |isbn=0-19-509974-5}}</ref>

Frequent hybridization among oaks has consequences for oak populations around the world; most notably, hybridization has produced large populations of hybrids with much [[introgression]] and the [[evolution]] of new species.<ref name=r2>{{Cite journal|last1=Conte |first1=L. |last2=Cotti |first2=C. |last3=Cristofolini |first3=G. |year=2007 |title=Molecular evidence for hybrid origin of ''Quercus crenata'' Lam. (Fagaceae) from ''Q-cerris'' L. and ''Q-suber'' L. |journal=Plant Biosystems |volume=141 |issue=2 |pages=181–193 |doi=10.1080/11263500701401463|bibcode=2007PBios.141..181C |s2cid=83882998 }}</ref> Introgression has caused different species in the same populations to share up to 50% of their genetic information.<ref name=r3>{{cite journal |last1=Gomory |first1=D. |last2=Schmidtova |first2=J. |year=2007 |title=Extent of nuclear genome sharing among white oak species (''Quercus'' L. subgen. ''Lepidobalanus'' (Endl.) Oerst.) in Slovakia estimated by allozymes |journal=Plant Systematics and Evolution |volume=266 |issue=3–4 |pages=253–264 |doi=10.1007/s00606-007-0535-0|bibcode=2007PSyEv.266..253G |s2cid=23587024 }}</ref> As a result, genetic data often does not differentiate between clearly morphologically distinct species, but instead differentiates populations.<ref name=r4>{{Cite journal |last1=Kelleher |first1=C. T. |first2=T. R. |last2=Hodkinson |first3=G. C. |last3=Douglas |first4=D. L. |last4=Kelly |year=2005 |title=Species distinction in Irish populations of ''Quercus petraea'' and ''Q. robur'': Morphological versus molecular analyses |journal=Annals of Botany |pmid=16199484 |volume=96 |issue=7 |pages=1237–1246 |doi=10.1093/aob/mci275|pmc=4247074 }}</ref> The maintenance of particular loci for adaptation to ecological niches may explain the retention of species identity despite significant gene flow.<ref>{{Cite journal |last1=Zhang |first1=Ruhua |last2=Hipp |first2=Andrew L. |last3=Gailing |first3=Oliver |date= October 2015 |title=Sharing of chloroplast haplotypes among red oak species suggests interspecific gene flow between neighboring populations |journal=Botany |volume=93 |issue=10 |pages=691–700 |doi=10.1139/cjb-2014-0261 |issn=1916-2790 |hdl=1807/69792 |hdl-access=free}}</ref>

The [[Fagaceae]], or beech family, to which the oaks belong, is a slowly-evolving [[clade]] compared to other [[angiosperm]]s,<ref>{{Cite journal|doi=10.1139/g93-089 |last1=Frascaria |first1=N. |first2=L. |last2=Maggia |first3=M. |last3=Michaud |first4=J. |last4=Bousquet |year=1993 |title=The RBCL Gene Sequence from Chestnut Indicates a Slow Rate of Evolution in the Fagaceae |journal=Genome |volume=36 |issue=4 |pages=668–671 |pmid=8405983|url=http://agritrop.cirad.fr/590955/1/1993_frascaria%20et%20al.pdf }}</ref><ref>{{cite journal |last1=Manos |first1=P. S. |first2=A. M. |last2=Stanford |year=2001 |title=The historical biogeography of Fagaceae: Tracking the tertiary history of temperate and subtropical forests of the Northern Hemisphere |journal=International Journal of Plant Sciences |volume=162 |pages=S77–S93 |issue=Suppl. 6 |doi=10.1086/323280 |bibcode=2001IJPlS.162S..77M |s2cid=84936653 }}</ref> and the patterns of hybridization and introgression in ''Quercus'' pose a significant challenge to the [[species concept|concept of a species]] as a group of "actually or potentially interbreeding populations which are reproductively isolated from other such groups."<ref name="Raven 2005"/> By this definition, many species of ''Quercus'' would be lumped together according to their geographic and ecological habitat, despite clear distinctions in morphology and genetic data.<ref name="Raven 2005">{{cite book |last1=Raven |first1=Peter H. |first2=George B. |last2=Johnson |first3=Jonathan B. |last3=Losos |first4=Susan R. |last4=Singer |title=Biology |url=https://archive.org/details/biology00pete |url-access=registration |edition=Seventh |publisher=McGraw Hill |location=New York |year=2005 |isbn=0-07-111182-4}}</ref>

=== Diseases and pests ===

[[File:Oak Mildew.JPG|thumb|Oak [[powdery mildew]] on pedunculate oak, caused by ''[[Erysiphe alphitoides]]'']]

Oaks are affected by a large number of pests and diseases. For instance, ''Q. robur'' and ''Q. petraea'' in Britain host 423 insect species.<ref name="Kennedy Southwood 1984">{{cite journal |last1=Kennedy |first1=Catherine E.J. |last2=Southwood |first2=T. Richard E. |year=1984 |title=The number of species of insect associated with British trees. A reanalysis |journal=[[Journal of Animal Ecology]] |volume=53 |issue=53 |pages=455–478 |jstor=4528 |doi=10.2307/4528|bibcode=1984JAnEc..53..455K }}</ref> This diversity includes 106 [[Macrolepidoptera|macro-moths]], 83 [[Microlepidoptera|micro-moths]], 67 [[beetle]]s, 53 [[cynipoidea]]n wasps, 38 [[heteroptera]]n bugs, 21 [[auchenorrhyncha]]n bugs, 17 [[sawfly|sawflies]], and 15 [[aphid]]s.<ref name="Kennedy Southwood 1984"/> The insect numbers are seasonal: in spring, chewing insects such as caterpillars become numerous, followed by insects with sucking mouthparts such as aphids, then by [[leaf miner]]s, and finally by gall wasps such as ''[[Neuroterus]]''.<ref>{{cite journal |last1=Southwood |first1=T. Richard E. |last2=Wint |first2=G.R. William |last3=Kennedy |first3=Catherine E.J. |last4=Greenwood |first4=Kennedy |year=2004 |title=Seasonality, abundance, species richness and specificity of the phytophagous guild of insects on oak (''Quercus'') canopies |journal=[[European Journal of Entomology]] |volume=101 |issue=101 |pages=43–50|doi=10.14411/eje.2004.011 |doi-access=free }}</ref> Several [[powdery mildew]]s affect oak species. In Europe, the species ''[[Erysiphe alphitoides]]'' is the most common.<ref>{{Cite journal |doi=10.1111/j.1439-0329.2008.00544.x |title=New insights into the identity and origin of the causal agent of oak powdery mildew in Europe |year=2008 |last1=Mougou |first1=A. |last2=Dutech |first2=C. |last3=Desprez-Loustau |first3=M.-L. |journal=Forest Pathology |volume=38 |issue=4 |page=275|bibcode=2008FoPat..38..275M }}</ref> It reduces the ability of leaves to photosynthesize, and infected leaves are shed early.<ref name="Hajji Dreyer 2009">{{Cite journal |title=Impact of ''Erysiphe alphitoides'' on transpiration and photosynthesis in ''Quercus robur'' leaves |year=2009|last1=Hajji |first1=M. |last2=Dreyer |first2=E. |last3=Marçais |first3=B. |journal=European Journal of Plant Pathology |volume=125 |issue=1 |pages=63–72 |doi=10.1007/s10658-009-9458-7 |bibcode=2009EJPP..125...63H |s2cid=21267431 |url=https://hal.archives-ouvertes.fr/hal-02103659/file/2009-EJPP-Hajji%26al.pdf}}</ref>
Another significant threat, the [[oak processionary]] moth (''Thaumetopoea processionea''), has emerged in the UK since 2006. The caterpillars of this species defoliate the trees and are hazardous to human health; their bodies are covered with poisonous hairs which can cause rashes and respiratory problems.<ref name=forestry>{{cite web |author=unspecified |title=Oak Processionary Moth - Tree pests and diseases |website=[[Forestry Commission|Forestry Commission (UK)]] |url=https://www.forestry.gov.uk/oakprocessionarymoth |date=11 September 2018 |access-date=31 January 2019 |archive-date=20 November 2018 |archive-url=https://web.archive.org/web/20181120133817/https://www.forestry.gov.uk/oakprocessionarymoth |url-status=dead }}</ref> A little-understood disease of mature oaks, [[acute oak decline]], has affected the UK since 2009.<ref>{{cite news |last=Kinver |first=Mark |date=28 April 2010 |title=Oak disease 'threatens landscape' |work=BBC News |url=http://news.bbc.co.uk/2/hi/science_and_environment/10089581.stm |url-status=live |access-date=29 April 2010 |archive-url=https://web.archive.org/web/20100429031402/http://news.bbc.co.uk/2/hi/science_and_environment/10089581.stm |archive-date=29 April 2010}}</ref> 
In California, goldspotted oak borer (''[[Agrilus auroguttatus]]'') has destroyed many oak trees,<ref name="Coleman 2008">{{cite web |last=Coleman |first=T. W. |url=http://www.fs.fed.us/r5/spf/fhp/socal/CnfOakMortalityBE080408.pdf |title=New insect evidence in continuing oak mortality |publisher=US Forest Service |date=4 August 2008}}</ref> while sudden oak death, caused by the [[oomycete]] pathogen ''[[Phytophthora ramorum]]'', has devastated oaks in California and Oregon, and is present in Europe.<ref name="Scientific Societies 2008">{{cite journal |title=Sudden oak death, ramorum leaf blight, ramorum shoot blight |journal=The Plant Health Instructor |publisher=Scientific Societies |year=2008 |issn=1935-9411 |doi=10.1094/phi-i-2008-0227-01 |last1=Parke |first1=J.L. |last2=Peterson |first2=Ebba K.}}</ref> Japanese oak wilt, caused by the fungus ''[[Raffaelea quercivora]]'', has rapidly killed trees across Japan.<ref name="Kuroda Yamada 1996">{{cite journal |last1=Kuroda |first1=K. |last2=Yamada |first2=T. |year=1996 |title=Discoloration of sapwood and blockage of xylem sap ascent in the trunks of wilting ''Quercus'' spp. following attack by ''Platypus quercivorus'' |journal=Journal of the Japanese Forestry Society |volume=78 |issue=1 |pages=84–88 |url=http://ci.nii.ac.jp/naid/110002830776/en}}</ref>

=== Gall communities ===

{{further|Gall|Gall wasp}}

Many [[galls]] are found on oak leaves, buds, flowers, and roots. Examples are [[oak artichoke gall]], [[oak marble gall]], [[oak apple]] gall, [[knopper gall]], and [[Neurotus quercus-baccarum|spangle gall]]. These galls are the handiwork of tiny wasps from the  [[Cynipidae]]. In a complex ecological relationship, these gall wasps become hosts to [[parasitoid wasp]]s—primarily from the order [[Chalcidoidea]]—which lay their larvae inside the gall wasps, ultimately leading to the hosts' demise. Additionally, [[inquiline]]s live [[Commensalism|commensally]] within the galls without harming the gall wasps.<ref>{{cite journal |last1=Askew |first1=Richard R. |last2=Melika |first2=George |last3=Pujade-Villar |first3=Juli |last4=Schönrogge |first4=Karsten |last5=Stone |first5=Graham N. |last6=Nieves-Aldrey |first6=Jose Luis |title=Catalogue of parasitoids and inquilines in cynipid oak galls in the West Palaearctic |journal=Zootaxa |date=30 April 2013 |volume=3643 |issue=3643 |pages=1–133 |doi=10.11646/zootaxa.3643.1.1 |pmid=25340198 |isbn=978-1-77557-147-6 |url=https://www.researchgate.net/publication/237007745}}</ref>

<gallery mode=packed>
File:Gallrazorback.jpg|Oak apple gall on ''[[Quercus garryana]]''
File:Oak apples on oak leaf and in cross section.JPG|Oak apples on oak leaf
File:Biorhiza pallida male.jpg|''[[Biorhiza pallida]]'' male, the cause of oak apple galls
</gallery>