Editing Coregonus (section)

=== Species diversity ===
There is much uncertainty and confusion in the classification of the many species of this genus. Particularly, one extreme view of diversity recognises just two main species in Northern and Central Europe, the [[common whitefish]] ''C. lavaretus'' and the [[Coregonus albula|vendace]] ''C. albula'', whereas others would divide these into numerous, often narrowly distributed species. A drastic increase in number of recognized species occurred in 2007, when a review advocated that more than 50 local European populations should be considered as distinct based on [[Morphology (biology)|morphological]] differences.<ref name="Kottelat_2007">{{cite book | vauthors = Kottelat M, Freyhof J |title=Handbook of European Freshwater Fishes |date=2007 |publisher=Publications Kottelat |location=Cornol, Switzerland |isbn=978-2-8399-0298-4}}</ref> It has been estimated that several of them are very young, having separated from each other less than 15,000 years ago.<ref name="Hudson_2016">{{cite journal | vauthors = Hudson AG, Lundsgaard-Hansen B, Lucek K, Vonlanthen P, Seehausen O | title = Managing cryptic biodiversity: Fine-scale intralacustrine speciation along a benthic gradient in Alpine whitefish (''Coregonus'' spp.) | journal = Evolutionary Applications | volume = 10 | issue = 3 | pages = 251–266 | date = March 2017 | pmid = 28250810 | pmc = 5322408 | doi = 10.1111/eva.12446 | bibcode = 2017EvApp..10..251H }}</ref> Many of these were primarily defined based on number of [[gill raker]]s. Although this largely is [[hereditary]], the number is highly variable (even within single populations and species), can change relatively fast in response to changes and [[Genetics|genetic]] studies have shown that they often are of limited use in predicting relationships among populations (a large difference in gill raker number does not necessarily equal a distant relationship).<ref name="Ostbye_2005">{{cite journal | vauthors = Østbye K, Bernatchez L, Naesje TF, Himberg KJ, Hindar K | title = Evolutionary history of the European whitefish Coregonus lavaretus (L.) species complex as inferred from mtDNA phylogeography and gill-raker numbers | journal = Molecular Ecology | volume = 14 | issue = 14 | pages = 4371–4387 | date = December 2005 | pmid = 16313599 | doi = 10.1111/j.1365-294X.2005.02737.x | bibcode = 2005MolEc..14.4371O | s2cid = 21487510 }}</ref><ref name="Jacobsen_2012">{{cite journal | vauthors = Jacobsen MW, Hansen MM, Orlando L, Bekkevold D, Bernatchez L, Willerslev E, Gilbert MT | title = Mitogenome sequencing reveals shallow evolutionary histories and recent divergence time between morphologically and ecologically distinct European whitefish (Coregonus spp.) | journal = Molecular Ecology | volume = 21 | issue = 11 | pages = 2727–2742 | date = June 2012 | pmid = 22509795 | doi = 10.1111/j.1365-294X.2012.05561.x | bibcode = 2012MolEc..21.2727J | s2cid = 4499697 }}</ref><ref>{{cite journal | vauthors = Ozerov MY, Himberg M, Aykanat T, Sendek DS, Hägerstrand H, Verliin A, Krause T, Olsson J, Primmer CR, Vasemägi A | display-authors = 6 | title = Generation of a neutral FST baseline for testing local adaptation on gill raker number within and between European whitefish ecotypes in the Baltic Sea basin | journal = Journal of Evolutionary Biology | volume = 28 | issue = 5 | pages = 1170–1183 | date = May 2015 | pmid = 25877003 | doi = 10.1111/jeb.12645 | s2cid = 13189069 | doi-access = free }}</ref> Genetic differences between several of the recently proposed species, even ones that are relatively distinct morphologically, are very limited and sometimes they are not [[monophyletic]].<ref name="Ostbye_2005" /><ref name="Jacobsen_2012" /> Various ''Coregonus'', whether regarded as separate species or not, readily interbreed with each other.<ref>{{cite web | publisher = U.S. Fish and Wildlife | orig-date = 2011 | date = 2017 | url = https://www.fws.gov/fisheries/ans/erss/highrisk/Coregonus-maraena-ERSS-FINAL-Sept-2017.pdf | title = Maraena Whitefish (Coregonus maraena). | access-date = 12 April 2018 }}</ref> A review of whitefish in the United Kingdom found that the [[identification key]] provided in 2007 did not match most individuals and that solid evidence for more than one species in that region is lacking.<ref>{{cite journal | vauthors = Etheridge EC, Adams CE, Bean CW, Durie NC, Gowans AR, Harrod C, Lyle AA, Maitland PS, Winfield IJ | display-authors = 6 | title = Are phenotypic traits useful for differentiating among a priori Coregonus taxa? | journal = Journal of Fish Biology | volume = 80 | issue = 2 | pages = 387–407 | date = February 2012 | pmid = 22268437 | doi = 10.1111/j.1095-8649.2011.03189.x | doi-access = free | bibcode = 2012JFBio..80..387E }}</ref>

Many European lakes have more than one ''Coregonus'' [[Polymorphism (biology)|morph]] differing in ecology and morphology (especially gill rakers).<ref name="Bhat_2014">{{cite journal | vauthors = Bhat S, Amundsen PA, Knudsen R, Gjelland KØ, Fevolden SE, Bernatchez L, Præbel K | title = Speciation reversal in European whitefish (Coregonus lavaretus (L.)) caused by competitor invasion | journal = PLOS ONE | volume = 9 | issue = 3 | pages = e91208 | date = 2014 | pmid = 24626131 | pmc = 3953381 | doi = 10.1371/journal.pone.0091208 | bibcode = 2014PLoSO...991208B | doi-access = free }}</ref> Such morphs are sometimes partially [[Reproductive isolation|reproductively isolated]] from each other, leading to suggestions of recognizing them as separate but [[Cline (biology)|clinal]] species.<ref name="Hudson_2016" /> The morphs or clinal species may rapidly disappear (in 15 years or less, equalling three ''Coregonus'' [[Biological life cycle|generations]]) by merging into a single in response to changes in the habitat.<ref name="Bhat_2014" /> A similar pattern can be seen in North America where the [[ciscoes]] of the ''[[Coregonus artedi]]'' [[Species complex|complex]] in the [[Great Lakes]] and elsewhere comprise several, often co-occurring morphs or ecotypes, whose taxonomic status remains controversial.<ref>{{cite journal | vauthors = Turgeon J, Estoup A, Bernatchez L | title = Species Flock in the North American Great Lakes: Molecular Ecology of Lake Nipigon Ciscoes (Teleostei: Coregonidae: Coregonus). | journal = Evolution; International Journal of Organic Evolution | volume = 53 | issue = 6 | pages = 1857–1871 | date = December 1999 | pmid = 28565465 | doi = 10.1111/j.1558-5646.1999.tb04568.x | s2cid = 12144534 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Turgeon J, Bernatchez L | title = Reticulate evolution and phenotypic diversity in North American ciscoes, Coregonus ssp.(Teleostei: Salmonidae): implications for the conservation of an evolutionary legacy. | journal = Conservation Genetics | date = January 2003 | volume = 4 | issue = 1 | pages = 67–81 | doi = 10.1023/A:1021860910719 | bibcode = 2003ConG....4...67T | s2cid = 35532451 }}</ref><ref name="Eshenroder_2016">{{cite report | vauthors = Eshenroder RL, Vecsei P, Gorman OT, Yule D, Pratt TC, Mandrak NE, Bunnell DB, Muir AM | display-authors = 6 | title = Ciscoes (Coregonus, subgenus Leucichthys) of the Laurentian Great Lakes and Lake Nipigon. | collaboration = Great Lakes Fishery Commission | publisher =  United States Geological Survey | date = 2016 | url = https://pubs.er.usgs.gov/publication/70179454 }}</ref><ref>{{cite report | vauthors = Boguski DA, Murray L, Pratt TC, Johnson JD, Reist JD | title = Patterns of Morphological Diversity in Ciscoes Distributed Within Three of Manitoba's Glacial Relict Lakes with Reference to Shortjaw Cisco (Coregonus Zenithicus) | work = Canadian Science Advisory Secretariat = Secrétariat canadien de consultation scientifique | date = January 2014 | url = http://waves-vagues.dfo-mpo.gc.ca/Library/352585.pdf }}</ref>