Editing Viola (plant) (section)

==Taxonomy==
[[File:Linnaeus Viola.png|thumb|upright|[[Carl Linnaeus|Linnaeus]]' original description (1753)|alt=First page of Linnaeus' 1753 description of Viola]]

===History===
First formally described by [[Carl Linnaeus]] in 1753{{sfn|Linnaeus|1753}} with 19 species, the genus ''Viola'' bears his [[botanical authority]], L.{{sfn|WFO|2019}} When [[Antoine Laurent de Jussieu|Jussieu]] established the hierarchical system of families (1789), he placed Viola in the [[Cisti]] (rock roses),{{sfn|Jussieu|1789}} though by 1811 he suggested Viola be separated from these.{{sfn|Lindley|1853}} However, in 1802 [[Batsch]] had already established a separate family, which he called Violariae based on Viola as the [[type genus]], with seven other genera.{{sfn|Batsch|1802}}{{sfn|IPNI|2020}} Although Violariae continued to be used by some authors, such as [[Bentham and Hooker]] in 1862 (as Violarieae),{{sfn|Bentham|Hooker|1862}} most authors adopted the alternative name Violaceae, first proposed by [[de Lamarck]] and [[de Candolle]] in 1805,{{sfn|de Lamarck|de Candolle|1815}} and [[Frédéric Charles Jean Gingins de la Sarraz|Gingins]] (1823){{sfn|Gingins|1823}} and [[Augustin Saint-Hilaire|Saint-Hilaire]] (1824).{{sfn|Saint-Hilaire|1824}} However de Candolle also used Violarieae in his 1824 ''Prodromus''.{{sfn|Candolle|1824}}

===Phylogeny===
''Viola'' is one of about 25 genera and about 600 species in the large [[eudicot]] family [[Violaceae]], divided into subfamilies and tribes. While most genera are [[monotypic]], ''Viola'' is a very large genus, variously circumscribed as having between 500 and 600 species. Historically it was placed in subfamily Violoideae, tribe Violeae. But these divisions have been shown to be artificial and not [[monophyletic]]. [[Molecular phylogenetic]] studies show that ''Viola'' occurs in Clade I of the family, as ''Viola'', ''[[Schweiggeria]]'', ''[[Noisettia]]'' and ''[[Allexis]]'', in which ''Schweiggeria'' and ''Noisettia'' are monotypic and form a sister group to ''Viola''.{{sfn|Wahlert et al|2014}}{{sfn|Yockteng et al|2003}}{{sfn|Ballard et al|1998}}

===Subdivision===
''Viola'' is a large genus that has traditionally been treated in [[Sections (botany)|sections]].{{sfn|Yockteng et al|2003}} One of these was that of [[Frédéric Charles Jean Gingins de la Sarraz|Gingins]] (1823),{{sfn|Gingins|1823}} based on stigma morphology, with five sections (''Nomimium'', ''Dischidium'', ''Chamaemelanium'', ''Melanium'', ''Leptidium'').{{sfn|Yoo|Jang|2010}} The extensive taxonomic studies of [[Wilhelm Becker]], culminating in his 1925 conspectus, resulted in 14 sections and many infrasectional groups. The largest and most diverse, being section ''Viola'', with 17 subsections. In addition to subsections, [[Series (biology)|series]] were also described.{{sfn|Becker|1925}} Alternatively, some authors have preferred to subdivide the genus into subgenera. Subsequent treatments were by Gershoy (1934){{sfn|Gershoy|1934}} and Clausen (1964),{{sfn|Clausen|1964}} using subsections and series. These were all based on morphological characteristics. Subsequent studies using [[molecular phylogenetic]] methods, such as that of Ballard et al. (1998) have shown that many of these traditional divisions are not [[monophyletic]], the problem being related to a high degree of [[hybridization (biology)|hybridization]]. In particular section ''Nomimium'' was dismembered into several new sections and transferring part of it to section ''Viola''. Section Viola ''s. lat.'' is represented by four sections, ''Viola'' ''sensu stricto'', ''Plagiostigma'' ''s. str.'', ''Nosphinium'' ''sensu lato''. and the ''V. spathulata'' group. In that analysis, the S American sections appear to be the [[basal group]]s, starting with ''Rubellium'', then ''Leptidium''. However, the exact phylogenetic relationships remain unresolved, as a consequence many different taxonomic nomenclatures are in use, including groupings referred to as [[Grex (horticulture)|Grex]].{{sfn|Ballard et al|1998}} Marcussen et al. place the five S American sections, ''Andinium'', ''Leptidium'', ''Tridens'', ''Rubellium'' and ''Chilenium'' at the base of the phylogenetic tree, in that order. These are followed by the single Australian section, ''Erpetion'', as sister group to ''Chilenium'', the northern hemisphere sections and finally the single African section, ''V. abyssinica''. These sections are morphologically, chromosomally, and geographically distinct.{{sfn|Marcussen et al|2015}}{{sfn|Fan et al|2015}}{{sfn|Malobecki et al|2016}}

====Sections====
Seventeen sections are recognized, listed alphabetically (approximate no. species);{{sfn|Marcussen et al|2012}}{{sfn|Marcussen et al|2015}}{{sfn|Watson et al|2019}}

* Sect. ''Andinium'' <small>W.Becker</small> (113) S America{{sfn|Watson et al|2019}}
* Sect. ''Chamaemelanium'' <small>Ging.</small> ''[[s.lat.]]'' (61) N America, northeast Asia (includes ''Dischidium'', ''Orbiculares'')
** Subsect. ''Chamaemelanium''
** Subsect. ''Nudicaules''
** Subsect. ''Nuttalianae''
* Sect. ''Chilenium'' <small>W.Becker</small> (8) southern S America{{sfn|BioLib|2019}}
* Sect. ''Danxiaviola'' <small>W. B. Liao et Q. Fan</small> (1) China{{sfn|Fan et al|2015}}
* Sect. ''Delphiniopsis'' <small>W.Becker</small> (3) western Eurasia: southern Spain; Balkans{{sfn|CSIC|2020}}
* Sect. ''Erpetion'' <small>(Banks) W.Becker</small> (11–18) eastern Australia; Tasmania 
* Sect. ''Leptidium'' <small>Ging.</small> (19) S America{{sfn|Freitas|Sosa|2002}}
* Sect. ''Melanium'' <small>Ging.</small> (125) western Eurasia (pansies){{sfn|Yockteng et al|2003}}{{sfn|Magrini|Scoppola|2015}}
* Sect. ''Nosphinium'' <small>W.Becker</small> ''s.lat.'' (31–50) N, C and northern S America; Beringia; Hawaii{{sfn|Marcussen et al|2012}} 
* Sect. nov. A (''V. abyssinica'' group) (1–3) Africa: equatorial high mountains 
* Sect. nov. B (''V. spathulata'' group) (7–9) western and central Asia: northern Iraq to Mongolia{{sfn|Fan et al|2015}} 
* Sect. ''Plagiostigma'' <small>Godr.</small> (120) northern hemisphere (includes ''Diffusae''){{sfn|Ning|2012}}{{sfn|Zhou|2008}}{{sfn|Tikhomirov |2015}}
** Grex Primulifolia
* Sect. ''Rubellium'' <small>W.Becker</small> (3–6) S America: Chile{{sfn|Ballard et al|1998}}
* Sect. ''Sclerosium'' <small>W.Becker</small> (1–4) northeastern Africa to southwestern Asia{{sfn|Shahrestani et al|2014}}
* Sect. ''Tridens'' <small>W.Becker</small> (2) southern S America 
* Sect. ''Viola''  ''s.str.'' (''Rostellatae'' ''[[nom. illeg.]]'') (75) northern hemisphere (violets) (includes ''Repentes''){{sfn|Malobecki et al|2016}}
** Subsect. ''Rostratae'' <small>Kupffer (W.Becker)</small>{{sfn|Danihelka|2010}}
** Subsect. ''Viola''
* Sect. ''Xylinosium'' <small>W.Becker</small> (3–4) Mediterranean region

====Species====
The genus includes [[dog violet]]s, a group of scentless species which are the most common ''Viola'' in many areas, sweet violet (''[[Viola odorata]]'') (named from its sweet scent), and many other species whose common name includes the word "violet". But not other "violets": Neither [[Streptocarpus sect. Saintpaulia|''Streptocarpus'' sect. ''Saintpaulia'']] ("African violets", [[Gesneriaceae]]) nor ''[[Erythronium dens-canis]]'' ("dogtooth violets", [[Liliaceae]]) are related to ''Viola''.

=====List of selected species=====
{{Main list|List of Viola species}}
{|
|[[File:Viola canina 100.jpg|upright|thumb|130px|''[[Viola canina]]''|alt=Viola canina flower and leaves]]

======Section ''Andinium''======
With about 113 species, the South American section ''Andinium'' is the largest of the ''Viola'' sections. It is one of the four sections distributed primarily or exclusively in South America, and the basal group of Viola. New species continue to be identified.{{sfn|Gonzáles |Cano|2016}} Species include;{{sfn|Ballard|Iltis|2012}}
* ''[[Viola escarapela]]''{{sfn|Watson|Flores|2003}} 
* ''[[Viola lilliputana]]''{{sfn|Ballard|Iltis|2012}} 
{{clear}}
[[File:Viola biflora Kilpisjarvi 2012-07.jpg|upright|thumb|130px|''[[Viola biflora]]''|alt=Viola biflora flower and leaves]]

======Section ''Chamaemelanium''======
''Chamaemelanium'' was one of a number of sections originally classified on the basis of the shape of the stigma, in this case one that was facial shaped, had an absent beak and had lateral beards. But this section has subsequently been shown to be paraphyletic, requiring revision. It occurs at high altitudes (above 600&nbsp;m) in both N America and northeast Asia, including Siberia and Korea, and the species are perennial, caulous and herbaceous.{{sfn|Whang|2002}} With about 61 species including;
* ''[[Viola biflora]]'' – yellow wood violet, twoflower violet
* ''[[Viola glabella]]'' – stream violet
* ''[[Viola pedunculata]]'' – yellow pansy 
* ''[[Viola praemorsa]]'' – canary violet 
* ''[[Viola pubescens]]'' – downy yellow violet 
|} 
{{clear}}
{|
|[[File:Viola reichei.JPG|upright|thumb|130px|''[[Viola reichei]]''|alt=Viola reichei]]

======Section ''Chilenium''======
A small S American section with about 8 species, as sister group to ''Erpetion'', including;
* ''[[Viola reichei]]''
|} 
{{clear}}
Section ''Danxiaviola''
* ''[[Viola hybanthoides]]''

Section ''Delphiniopsis''
[[File:JDCANO Viola Cazorlensis.jpg|thumb|upright|''Viola Cazorlensis''|alt=Viola Cazorlensis]]
* ''[[Viola cazorlensis]]''
* ''[[Viola delphinantha]]''
* ''[[Viola kosaninii]]''

Section ''Erpetion''{{sfn|Thiele|Prober|2003}}
[[File:Viola banksii.jpg|thumb|upright|''Viola banksii''|alt=Viola banksii]]
* ''[[Viola banksii]]'' – Australian native violet, ivy-leaved violet
* ''[[Viola hederacea]]'' – Australian native violet, ivy-leaved violet

Section ''Leptidium''
[[File:Viola stipularis-La Soufrière-Guadeloupe 1.JPG|thumb|upright|''[[Viola stipularis]]''|alt=Viola stipularis]]
* ''[[Viola stipularis]]''

Section ''Melanium'' (pansies){{sfn|Yockteng et al|2003}}{{sfn|Chervin et al|2019}}
[[File:Common Violet.JPG|thumb|upright|''[[Viola tricolor]]''|alt=Flowers of Viola tricolor]]
* ''[[Viola arvensis]]'' – field pansy
* ''[[Viola bicolor]]''
* ''[[Viola pedunculata]]'' – yellow pansy, [[Pacific Ocean|Pacific]] coast.
* ''[[Viola bertolonii]]''
* ''[[Viola calcarata]]''
* ''[[Viola cheiranthifolia]]'' – Teide violet
* ''[[Viola cornuta]]''
* ''[[Viola lutea]]''
* ''[[Viola tricolor]]'' – wild pansy, heartsease

Section ''Nosphinium''
[[File:Viola pedata.jpg|thumb|upright|''[[Viola pedata]]''|alt=Flowers of Viola pedata]]
* ''[[Viola pedata]]''

Section A (''V. abyssinica'' group)
[[File:Viola abyssinica mt kenya 01.jpg|thumb|upright|''[[Viola abyssinica]]''|alt=Flower of Viola abyssinica]]
* ''[[Viola abyssinica]]''

Section B (''V. spathulata'' group)
* ''[[Viola spathulata]]''

Section ''Plagiostigma''
[[File:Viola epipsila 5999.jpg|thumb|upright|''[[Viola epipsila]]''|alt=Flower of Viola epipsila]]
* ''[[Viola epipsila]]''

Section ''Rubellium''
* ''[[Viola capillaris]]''{{sfn|V capillaris|2020}}
* ''[[Viola portalesia]]''{{sfn|Watson|Watson|2012}}
* ''[[Viola rubella]]''

Section ''Sclerosium'' 
* ''[[Viola cinerea]]''

Section ''Tridens''
[[File:Three-Toothed Violet (3279657452).jpg|thumb|upright|''[[Viola tridentata]]''|alt=Flowers of Viola tridentata]]
* ''[[Viola tridentata]]'' – mountain violet

Section ''Viola'' (violets)
[[File:Trip And Spring 005.jpg|thumb|upright| ''[[Viola sororia]]''|alt=Flowers of Viola sororia]]
* ''[[Viola canina]]'' – heath dog violet
* ''[[Viola hirta]]'' – hairy violet 
* ''[[Viola labradorica]]'' – alpine violet
* ''[[Viola odorata]]'' – sweet violet
* ''[[Viola persicifolia]]'' – fen violet
* ''[[Viola riviniana]]'' – common dog violet
* ''[[Viola rostrata]]'' – long-spurred violet
* ''[[Viola sororia]]'' – common blue violet, hooded violet

Section ''Xylinosium''
[[File:Viola decumbens Kogelberg.jpg|thumb|upright| ''[[Viola decumbens]]''|alt=Flower of Viola decumbens]]
* ''[[Viola decumbens]]''

===Evolution and biogeography===
One [[fossil]] seed of †'''''Viola rimosa''''' has been extracted from [[borehole]] samples of the [[Middle Miocene]] fresh water deposits in [[Nowy Sacz]] Basin, [[West Carpathians]], [[Poland]].{{sfn|Łańcucka-Środoniowa|1979}} The genus is thought to have arisen in S America, most likely the Andes.{{sfn|Yockteng et al|2003}}{{sfn|Ballard et al|1998}}

===Genetics===
[[Habitat fragmentation]] has been shown to have minimal effect on the genetic diversity and gene flow of the North American woodland violet ''Viola pubescens.''{{sfn|Culley et al|2007}} This may be partially attributed to the ability of ''Viola pubescens'' to continue to persist within a largely agricultural matrix.{{sfn|Culley|Grubb|2003}} This trend of unexpectedly high genetic diversity is also observed in ''Viola palmensis'', a Canary Island endemic known only from a 15 square kilometer range on La palma island.{{sfn|Batista|Sosa|2002}} High levels of genetic diversity within these species indicate that these plants are outcrossing, even though many violet species can produce many clonal offspring throughout the year via cleistogamous flowers. Plants that produce copious amounts of clonal seeds from cleistogamous flowers often experience increased levels of inbreeding.{{sfn|Culley|Klooster|2007}} These reportedly high rates of outcrossing and genetic diversity indicate that these violets are strong competitors for pollinators during the early spring when they are in bloom and that those pollinators can travel considerable distances between often fragmented populations.