A Revised Phylogenetic Classification for Viola (Violaceae)

Abstract

The genus Viola (Violaceae) is among the 40-50 largest genera among angiosperms, yet its taxonomy has not been revised for nearly a century. In the most recent revision, by Wilhelm Becker in 1925, the then-known 400 species were distributed among 14 sections and numerous unranked groups. Here, we provide an updated, comprehensive classification of the genus, based on data from phylogeny, morphology, chromosome counts, and ploidy, and based on modern principles of monophyly. The revision is presented as an annotated global checklist of accepted species of Viola, an updated multigene phylogenetic network and an ITS phylogeny with denser taxon sampling, a brief summary of the taxonomic changes from Becker's classification and their justification, a morphological binary key to the accepted subgenera, sections and subsections, and an account of each infrageneric subdivision with justifications for delimitation and rank including a description, a list of apomorphies, molecular phylogenies where possible or relevant, a distribution map, and a list of included species. We distribute the 664 species accepted by us into 2 subgenera, 31 sections, and 20 subsections. We erect one new subgenus of Viola (subg. Neoandinium, a replacement name for the illegitimate subg. Andinium), six new sections (sect. Abyssinium, sect. Himalayum, sect. Melvio, sect. Nematocaulon, sect. Spathulidium, sect. Xanthidium), and seven new subsections (subsect. Australasiaticae, subsect. Bulbosae, subsect. Clausenianae, subsect. Cleistogamae, subsect. Dispares, subsect. Formosanae, subsect. Pseudorupestres). Evolution within the genus is discussed in light of biogeography, the fossil record, morphology, and particular traits. Viola is among very few temperate and widespread genera that originated in South America. The biggest identified knowledge gaps for Viola concern the South American taxa, for which basic knowledge from phylogeny, chromosome counts, and fossil data is virtually absent. Viola has also never been subject to comprehensive anatomical study. Studies into seed anatomy and morphology are required to understand the fossil record of the genus.

Keywords: Viola; Violaceae; fossils; monophyletic; morphology; nomenclature; phylogeny; polyploidy; taxonomic revision.

Figure 1

Illustration of Viola odorata in the herbal of Matthiolus, printed in 1562 [8]. At least partly, the foliage appears to represent the common hybrid V. hirta × odorata. In the accompanying text (fol. CCCLIIII) the rooting stolons of V. odorata are described and compared to those of Fragaria and Pilosella officinarum.

Figure 2

Global distribution of Viola L. (Violaceae), showing the predominantly temperate distribution of the genus.

Figure 3

Photos of representative members of the sections and subsections of Viola.—(a–l) Subg. Neoandinium.—(m–av) Subg. Viola.—(a) Sect. Confertae: V. nassauvioides.—(b) Sect. Ericoidium: V. fluehmannii (photo © John M. Watson).—(c) Sect. Grandiflos: V. cheeseana (photo © John M. Watson).—(d) Sect. Inconspicuiflos: V. weibelii (photo © John M. Watson).—(e) Sect. Inconspicuiflos: V. lilliputana (photo © Harvey E. Ballard).—(f) Sect. Relictium: V. dandoisiorum (photo © John M. Watson).—(g) Sect. Rhizomandinium: V. escondidaensis (photo © John M. Watson).—(h) Sect. Rosulatae: V. volcanica (photo © Ana R. Flores).—(i) Sect. Sempervivum: V. atropurpurea (photo © John M. Watson).—(j) Sect. Subandinium: V. subandina (photo © Ana R. Flores).—(k) Sect. Triflabellium: V. triflabellata (photo © Ana R. Flores).—(l) Sect. Xylobasis: V. beati (photo © Ana R. Flores).—(m) Sect. Abyssinium: V. abyssinica (photo © Robert v. Blittersdorff).—(n) Sect. Chamaemelanium: V. pubescens (photo © Kim Blaxland).—(o) Sect. Chilenium: V. maculata (photo © Instituto de Botánica Darwinion).—(p) Sect. Danxiaviola: V. hybanthoides (photo © Qiang Fan).—(q) Sect. Delphiniopsis: V. cazorlensis (photo © Santiago Martín-Bravo).—(r) Sect. Erpetion: V. banksii (photo © Dewald du Plessis).—(s) Sect. Himalayum: V. kunawurensis (photo © Vladimir Epiktetov).—(t) Sect. Leptidium: V. boliviana (photo © Sam Wilson).—(u) Sect. Melanium, subsect. Bracteolatae: V. tricolor and V. arvensis (photo © Thomas Marcussen).—(v) Sect. Melanium, subsect. Cleistogamae: V. rafinesquei (photo © Mary Ann Yaich).—(w) Sect. Melanium, subsect. Dispares: V. dyris (photo © Alan Keohane).—(x) Sect. Melanium, subsect. Ebracteatae: V. parvula (photo © Albert Keshet).—(y) Sect. Melanium, subsect. Pseudorupestres: V. nummulariifolia (photo © Sylvain Piry).—(z) Sect. Melvio: V. decumbens (photo © Magriet Brink).—(aa) Sect. Nematocaulon: V. filicaulis (photo © Andrew Townsend).—(ab)Sect. Nosphinium, subsect. Borealiamericanae: V. fimbriatula (photo © Kim Blaxland).—(ac) Sect. Nosphinium, subsect. Clausenianae: V. clauseniana (photo © Thomas Marcussen).—(ad) Sect. Nosphinium, subsect. Langsdorffianae: V. langsdorffii (photo © Jonathan Goff).—(ae) Sect. Nosphinium, subsect. Mexicanae: V. nannei (photo © Neptalí Ramírez Marcial).—(af) Sect. Nosphinium, subsect. Nosphinium: V. maviensis (photo © Karl Magnacca).—(ag) Sect. Nosphinium, subsect. Pedatae: V. pedata (photo © Kim Blaxland).—(ah) Sect. Plagiostigma, subsect. Australasiaticae: V. sumatrana (photo © Mário Duchoň).—(ai) Sect. Plagiostigma, subsect. Bilobatae: V. hamiltoniana (photo © Toshihiro Nagata).—(aj) Sect. Plagiostigma, subsect. Bulbosae: V. tuberifera (photo © Masashi Igari).—(ak) Sect. Plagiostigma, subsect. Diffusae: V. huizhouensis (photo © Yanshuang Huang).—(al) Sect. Plagiostigma, subsect. Formosanae: V. formosana (photo © Kuan-Chieh (Chuck) Hung).—(am) Sect. Plagiostigma, subsect. Patellares: V. tokubuchiana (photo © Masashi Igari).—(an) Sect. Plagiostigma, subsect. Stolonosae: V. pluviae (photo © Kim Blaxland).—(ao) Sect. Rubellium: V. rubella (photo © Pablo Silva).—(ap) Sect. Sclerosium: V. cinerea (photo © Jerome Viard).—(aq) Sect. Spathulidium: V. pachyrrhiza (photo © Dieter Zschummel).—(ar) Sect. Tridens: V. tridentata (photo © larsonek).—(as) Sect. Viola, subsect. Rostratae: V. canina (photo © Thomas Marcussen).—(at) Sect. Viola, subsect. Viola: V. collina (photo © Thomas Marcussen).—(au) Sect. Xanthidium: V. flavicans (photo © Instituto de Botánica Darwinion).—(av) Sect. Xylinosium: V. arborescens (photo © Abdelmonaim Homrani Bakali).—All images used in this figure were cropped and gamma-corrected.—Links to the online sources for the images used in this figure under a creative commons (CC) licence: V. abyssinica, http://www.westafricanplants.senckenberg.de/root/index.php?page_id=47&id=2203#image=22051, (accessed on 5 May 2022) © Robert v. Blittersdorff; V. arborescens, https://www.teline.fr/en/photos/violaceae/viola-arborescens#photo-7 (accessed on 11 May 2022), © Abdelmonaim Homrani Bakali, CC BY-NC 4.0; V. nummulariifolia, https://www.inaturalist.org/observations/89240299 (accessed on 5 May 2022), © Sylvain Piry, CC BY-NC 4.0; V. banksii, https://inaturalist.nz/observations/25048808 (accessed on 12 May 2022), © Dewald du Plessis, CC BY-NC 4.0; V. boliviana, https://ecuador.inaturalist.org/photos/57308380 (accessed on 5 May 2022), © Sam Wilson, CC BY-NC; V. cazorlensis, https://www.inaturalist.org/observations/109331467 (accessed on 5 May 2022), © Santiago Martín-Bravo, CC BY-NC 4.0; V. cinerea, https://www.inaturalist.org/observations/65108391 (accessed on 5 May 2022), © Jerome Viard, CC BY-NC 4.0; V. decumbens, https://www.inaturalist.org/observations/10807224 (accessed on 5 May 2022), © Magriet Brink, CC BY-NC 4.0; V. filicaulis, https://www.inaturalist.org/observations/67950856 (accessed on 5 May 2022), © Andrew Townsend, CC BY-NC; V. formosana, https://www.inaturalist.org/observations/25305342 (accessed on 5 May 2022), © Kuan-Chieh (Chuck) Hung, CC BY-NC 4.0; V. hamiltoniana, https://www.inaturalist.org/observations/74528783 (accessed on 5 May 2022), © Toshihiro Nagata, CC BY-NC 4.0; V. langsdorffii, https://www.inaturalist.org/observations/73470330 (accessed on 5 May 2022), © Jonathan Goff, CC BY-NC-SA 4.0; V. maviensis, https://www.inaturalist.org/observations/39272209 (accessed on 7 May 2022), © Karl Magnacca, CC BY-NC 4.0; V. nannei, https://www.inaturalist.org/observations/6527547 (accessed on 5 May 2022), © Neptalí Ramírez Marcial, CC BY-NC; V. rafinesquei, https://www.inaturalist.org/observations/111043498 (accessed on 5 May 2022), © Mary Ann Yaich, CC BY-NC 4.0; V. rubella, https://www.inaturalist.org/observations/93725094 (accessed on 5 May 2022), © Pablo Silva, CC BY-NC 4.0; and V. tridentata, https://www.inaturalist.org/observations/103467450 (accessed on 5 May 2022), © larsonek, CC BY-NC 4.0.—Links to the relevant CC licences: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/; accessed on 5 May 2022), CC-BY-NC and CC BY-NC 4.0 (https://creativecommons.org/licenses/by-nc/4.0/; accessed on 5 May 2022), CC BY-NC-SA 4.0 (https://creativecommons.org/licenses/by-nc-sa/4.0/; accessed on 5 May 2022).

Figure 3

Photos of representative members of the sections and subsections of Viola.—(a–l) Subg. Neoandinium.—(m–av) Subg. Viola.—(a) Sect. Confertae: V. nassauvioides.—(b) Sect. Ericoidium: V. fluehmannii (photo © John M. Watson).—(c) Sect. Grandiflos: V. cheeseana (photo © John M. Watson).—(d) Sect. Inconspicuiflos: V. weibelii (photo © John M. Watson).—(e) Sect. Inconspicuiflos: V. lilliputana (photo © Harvey E. Ballard).—(f) Sect. Relictium: V. dandoisiorum (photo © John M. Watson).—(g) Sect. Rhizomandinium: V. escondidaensis (photo © John M. Watson).—(h) Sect. Rosulatae: V. volcanica (photo © Ana R. Flores).—(i) Sect. Sempervivum: V. atropurpurea (photo © John M. Watson).—(j) Sect. Subandinium: V. subandina (photo © Ana R. Flores).—(k) Sect. Triflabellium: V. triflabellata (photo © Ana R. Flores).—(l) Sect. Xylobasis: V. beati (photo © Ana R. Flores).—(m) Sect. Abyssinium: V. abyssinica (photo © Robert v. Blittersdorff).—(n) Sect. Chamaemelanium: V. pubescens (photo © Kim Blaxland).—(o) Sect. Chilenium: V. maculata (photo © Instituto de Botánica Darwinion).—(p) Sect. Danxiaviola: V. hybanthoides (photo © Qiang Fan).—(q) Sect. Delphiniopsis: V. cazorlensis (photo © Santiago Martín-Bravo).—(r) Sect. Erpetion: V. banksii (photo © Dewald du Plessis).—(s) Sect. Himalayum: V. kunawurensis (photo © Vladimir Epiktetov).—(t) Sect. Leptidium: V. boliviana (photo © Sam Wilson).—(u) Sect. Melanium, subsect. Bracteolatae: V. tricolor and V. arvensis (photo © Thomas Marcussen).—(v) Sect. Melanium, subsect. Cleistogamae: V. rafinesquei (photo © Mary Ann Yaich).—(w) Sect. Melanium, subsect. Dispares: V. dyris (photo © Alan Keohane).—(x) Sect. Melanium, subsect. Ebracteatae: V. parvula (photo © Albert Keshet).—(y) Sect. Melanium, subsect. Pseudorupestres: V. nummulariifolia (photo © Sylvain Piry).—(z) Sect. Melvio: V. decumbens (photo © Magriet Brink).—(aa) Sect. Nematocaulon: V. filicaulis (photo © Andrew Townsend).—(ab)Sect. Nosphinium, subsect. Borealiamericanae: V. fimbriatula (photo © Kim Blaxland).—(ac) Sect. Nosphinium, subsect. Clausenianae: V. clauseniana (photo © Thomas Marcussen).—(ad) Sect. Nosphinium, subsect. Langsdorffianae: V. langsdorffii (photo © Jonathan Goff).—(ae) Sect. Nosphinium, subsect. Mexicanae: V. nannei (photo © Neptalí Ramírez Marcial).—(af) Sect. Nosphinium, subsect. Nosphinium: V. maviensis (photo © Karl Magnacca).—(ag) Sect. Nosphinium, subsect. Pedatae: V. pedata (photo © Kim Blaxland).—(ah) Sect. Plagiostigma, subsect. Australasiaticae: V. sumatrana (photo © Mário Duchoň).—(ai) Sect. Plagiostigma, subsect. Bilobatae: V. hamiltoniana (photo © Toshihiro Nagata).—(aj) Sect. Plagiostigma, subsect. Bulbosae: V. tuberifera (photo © Masashi Igari).—(ak) Sect. Plagiostigma, subsect. Diffusae: V. huizhouensis (photo © Yanshuang Huang).—(al) Sect. Plagiostigma, subsect. Formosanae: V. formosana (photo © Kuan-Chieh (Chuck) Hung).—(am) Sect. Plagiostigma, subsect. Patellares: V. tokubuchiana (photo © Masashi Igari).—(an) Sect. Plagiostigma, subsect. Stolonosae: V. pluviae (photo © Kim Blaxland).—(ao) Sect. Rubellium: V. rubella (photo © Pablo Silva).—(ap) Sect. Sclerosium: V. cinerea (photo © Jerome Viard).—(aq) Sect. Spathulidium: V. pachyrrhiza (photo © Dieter Zschummel).—(ar) Sect. Tridens: V. tridentata (photo © larsonek).—(as) Sect. Viola, subsect. Rostratae: V. canina (photo © Thomas Marcussen).—(at) Sect. Viola, subsect. Viola: V. collina (photo © Thomas Marcussen).—(au) Sect. Xanthidium: V. flavicans (photo © Instituto de Botánica Darwinion).—(av) Sect. Xylinosium: V. arborescens (photo © Abdelmonaim Homrani Bakali).—All images used in this figure were cropped and gamma-corrected.—Links to the online sources for the images used in this figure under a creative commons (CC) licence: V. abyssinica, http://www.westafricanplants.senckenberg.de/root/index.php?page_id=47&id=2203#image=22051, (accessed on 5 May 2022) © Robert v. Blittersdorff; V. arborescens, https://www.teline.fr/en/photos/violaceae/viola-arborescens#photo-7 (accessed on 11 May 2022), © Abdelmonaim Homrani Bakali, CC BY-NC 4.0; V. nummulariifolia, https://www.inaturalist.org/observations/89240299 (accessed on 5 May 2022), © Sylvain Piry, CC BY-NC 4.0; V. banksii, https://inaturalist.nz/observations/25048808 (accessed on 12 May 2022), © Dewald du Plessis, CC BY-NC 4.0; V. boliviana, https://ecuador.inaturalist.org/photos/57308380 (accessed on 5 May 2022), © Sam Wilson, CC BY-NC; V. cazorlensis, https://www.inaturalist.org/observations/109331467 (accessed on 5 May 2022), © Santiago Martín-Bravo, CC BY-NC 4.0; V. cinerea, https://www.inaturalist.org/observations/65108391 (accessed on 5 May 2022), © Jerome Viard, CC BY-NC 4.0; V. decumbens, https://www.inaturalist.org/observations/10807224 (accessed on 5 May 2022), © Magriet Brink, CC BY-NC 4.0; V. filicaulis, https://www.inaturalist.org/observations/67950856 (accessed on 5 May 2022), © Andrew Townsend, CC BY-NC; V. formosana, https://www.inaturalist.org/observations/25305342 (accessed on 5 May 2022), © Kuan-Chieh (Chuck) Hung, CC BY-NC 4.0; V. hamiltoniana, https://www.inaturalist.org/observations/74528783 (accessed on 5 May 2022), © Toshihiro Nagata, CC BY-NC 4.0; V. langsdorffii, https://www.inaturalist.org/observations/73470330 (accessed on 5 May 2022), © Jonathan Goff, CC BY-NC-SA 4.0; V. maviensis, https://www.inaturalist.org/observations/39272209 (accessed on 7 May 2022), © Karl Magnacca, CC BY-NC 4.0; V. nannei, https://www.inaturalist.org/observations/6527547 (accessed on 5 May 2022), © Neptalí Ramírez Marcial, CC BY-NC; V. rafinesquei, https://www.inaturalist.org/observations/111043498 (accessed on 5 May 2022), © Mary Ann Yaich, CC BY-NC 4.0; V. rubella, https://www.inaturalist.org/observations/93725094 (accessed on 5 May 2022), © Pablo Silva, CC BY-NC 4.0; and V. tridentata, https://www.inaturalist.org/observations/103467450 (accessed on 5 May 2022), © larsonek, CC BY-NC 4.0.—Links to the relevant CC licences: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/; accessed on 5 May 2022), CC-BY-NC and CC BY-NC 4.0 (https://creativecommons.org/licenses/by-nc/4.0/; accessed on 5 May 2022), CC BY-NC-SA 4.0 (https://creativecommons.org/licenses/by-nc-sa/4.0/; accessed on 5 May 2022).

Figure 3

Photos of representative members of the sections and subsections of Viola.—(a–l) Subg. Neoandinium.—(m–av) Subg. Viola.—(a) Sect. Confertae: V. nassauvioides.—(b) Sect. Ericoidium: V. fluehmannii (photo © John M. Watson).—(c) Sect. Grandiflos: V. cheeseana (photo © John M. Watson).—(d) Sect. Inconspicuiflos: V. weibelii (photo © John M. Watson).—(e) Sect. Inconspicuiflos: V. lilliputana (photo © Harvey E. Ballard).—(f) Sect. Relictium: V. dandoisiorum (photo © John M. Watson).—(g) Sect. Rhizomandinium: V. escondidaensis (photo © John M. Watson).—(h) Sect. Rosulatae: V. volcanica (photo © Ana R. Flores).—(i) Sect. Sempervivum: V. atropurpurea (photo © John M. Watson).—(j) Sect. Subandinium: V. subandina (photo © Ana R. Flores).—(k) Sect. Triflabellium: V. triflabellata (photo © Ana R. Flores).—(l) Sect. Xylobasis: V. beati (photo © Ana R. Flores).—(m) Sect. Abyssinium: V. abyssinica (photo © Robert v. Blittersdorff).—(n) Sect. Chamaemelanium: V. pubescens (photo © Kim Blaxland).—(o) Sect. Chilenium: V. maculata (photo © Instituto de Botánica Darwinion).—(p) Sect. Danxiaviola: V. hybanthoides (photo © Qiang Fan).—(q) Sect. Delphiniopsis: V. cazorlensis (photo © Santiago Martín-Bravo).—(r) Sect. Erpetion: V. banksii (photo © Dewald du Plessis).—(s) Sect. Himalayum: V. kunawurensis (photo © Vladimir Epiktetov).—(t) Sect. Leptidium: V. boliviana (photo © Sam Wilson).—(u) Sect. Melanium, subsect. Bracteolatae: V. tricolor and V. arvensis (photo © Thomas Marcussen).—(v) Sect. Melanium, subsect. Cleistogamae: V. rafinesquei (photo © Mary Ann Yaich).—(w) Sect. Melanium, subsect. Dispares: V. dyris (photo © Alan Keohane).—(x) Sect. Melanium, subsect. Ebracteatae: V. parvula (photo © Albert Keshet).—(y) Sect. Melanium, subsect. Pseudorupestres: V. nummulariifolia (photo © Sylvain Piry).—(z) Sect. Melvio: V. decumbens (photo © Magriet Brink).—(aa) Sect. Nematocaulon: V. filicaulis (photo © Andrew Townsend).—(ab)Sect. Nosphinium, subsect. Borealiamericanae: V. fimbriatula (photo © Kim Blaxland).—(ac) Sect. Nosphinium, subsect. Clausenianae: V. clauseniana (photo © Thomas Marcussen).—(ad) Sect. Nosphinium, subsect. Langsdorffianae: V. langsdorffii (photo © Jonathan Goff).—(ae) Sect. Nosphinium, subsect. Mexicanae: V. nannei (photo © Neptalí Ramírez Marcial).—(af) Sect. Nosphinium, subsect. Nosphinium: V. maviensis (photo © Karl Magnacca).—(ag) Sect. Nosphinium, subsect. Pedatae: V. pedata (photo © Kim Blaxland).—(ah) Sect. Plagiostigma, subsect. Australasiaticae: V. sumatrana (photo © Mário Duchoň).—(ai) Sect. Plagiostigma, subsect. Bilobatae: V. hamiltoniana (photo © Toshihiro Nagata).—(aj) Sect. Plagiostigma, subsect. Bulbosae: V. tuberifera (photo © Masashi Igari).—(ak) Sect. Plagiostigma, subsect. Diffusae: V. huizhouensis (photo © Yanshuang Huang).—(al) Sect. Plagiostigma, subsect. Formosanae: V. formosana (photo © Kuan-Chieh (Chuck) Hung).—(am) Sect. Plagiostigma, subsect. Patellares: V. tokubuchiana (photo © Masashi Igari).—(an) Sect. Plagiostigma, subsect. Stolonosae: V. pluviae (photo © Kim Blaxland).—(ao) Sect. Rubellium: V. rubella (photo © Pablo Silva).—(ap) Sect. Sclerosium: V. cinerea (photo © Jerome Viard).—(aq) Sect. Spathulidium: V. pachyrrhiza (photo © Dieter Zschummel).—(ar) Sect. Tridens: V. tridentata (photo © larsonek).—(as) Sect. Viola, subsect. Rostratae: V. canina (photo © Thomas Marcussen).—(at) Sect. Viola, subsect. Viola: V. collina (photo © Thomas Marcussen).—(au) Sect. Xanthidium: V. flavicans (photo © Instituto de Botánica Darwinion).—(av) Sect. Xylinosium: V. arborescens (photo © Abdelmonaim Homrani Bakali).—All images used in this figure were cropped and gamma-corrected.—Links to the online sources for the images used in this figure under a creative commons (CC) licence: V. abyssinica, http://www.westafricanplants.senckenberg.de/root/index.php?page_id=47&id=2203#image=22051, (accessed on 5 May 2022) © Robert v. Blittersdorff; V. arborescens, https://www.teline.fr/en/photos/violaceae/viola-arborescens#photo-7 (accessed on 11 May 2022), © Abdelmonaim Homrani Bakali, CC BY-NC 4.0; V. nummulariifolia, https://www.inaturalist.org/observations/89240299 (accessed on 5 May 2022), © Sylvain Piry, CC BY-NC 4.0; V. banksii, https://inaturalist.nz/observations/25048808 (accessed on 12 May 2022), © Dewald du Plessis, CC BY-NC 4.0; V. boliviana, https://ecuador.inaturalist.org/photos/57308380 (accessed on 5 May 2022), © Sam Wilson, CC BY-NC; V. cazorlensis, https://www.inaturalist.org/observations/109331467 (accessed on 5 May 2022), © Santiago Martín-Bravo, CC BY-NC 4.0; V. cinerea, https://www.inaturalist.org/observations/65108391 (accessed on 5 May 2022), © Jerome Viard, CC BY-NC 4.0; V. decumbens, https://www.inaturalist.org/observations/10807224 (accessed on 5 May 2022), © Magriet Brink, CC BY-NC 4.0; V. filicaulis, https://www.inaturalist.org/observations/67950856 (accessed on 5 May 2022), © Andrew Townsend, CC BY-NC; V. formosana, https://www.inaturalist.org/observations/25305342 (accessed on 5 May 2022), © Kuan-Chieh (Chuck) Hung, CC BY-NC 4.0; V. hamiltoniana, https://www.inaturalist.org/observations/74528783 (accessed on 5 May 2022), © Toshihiro Nagata, CC BY-NC 4.0; V. langsdorffii, https://www.inaturalist.org/observations/73470330 (accessed on 5 May 2022), © Jonathan Goff, CC BY-NC-SA 4.0; V. maviensis, https://www.inaturalist.org/observations/39272209 (accessed on 7 May 2022), © Karl Magnacca, CC BY-NC 4.0; V. nannei, https://www.inaturalist.org/observations/6527547 (accessed on 5 May 2022), © Neptalí Ramírez Marcial, CC BY-NC; V. rafinesquei, https://www.inaturalist.org/observations/111043498 (accessed on 5 May 2022), © Mary Ann Yaich, CC BY-NC 4.0; V. rubella, https://www.inaturalist.org/observations/93725094 (accessed on 5 May 2022), © Pablo Silva, CC BY-NC 4.0; and V. tridentata, https://www.inaturalist.org/observations/103467450 (accessed on 5 May 2022), © larsonek, CC BY-NC 4.0.—Links to the relevant CC licences: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/; accessed on 5 May 2022), CC-BY-NC and CC BY-NC 4.0 (https://creativecommons.org/licenses/by-nc/4.0/; accessed on 5 May 2022), CC BY-NC-SA 4.0 (https://creativecommons.org/licenses/by-nc-sa/4.0/; accessed on 5 May 2022).

Figure 3

Photos of representative members of the sections and subsections of Viola.—(a–l) Subg. Neoandinium.—(m–av) Subg. Viola.—(a) Sect. Confertae: V. nassauvioides.—(b) Sect. Ericoidium: V. fluehmannii (photo © John M. Watson).—(c) Sect. Grandiflos: V. cheeseana (photo © John M. Watson).—(d) Sect. Inconspicuiflos: V. weibelii (photo © John M. Watson).—(e) Sect. Inconspicuiflos: V. lilliputana (photo © Harvey E. Ballard).—(f) Sect. Relictium: V. dandoisiorum (photo © John M. Watson).—(g) Sect. Rhizomandinium: V. escondidaensis (photo © John M. Watson).—(h) Sect. Rosulatae: V. volcanica (photo © Ana R. Flores).—(i) Sect. Sempervivum: V. atropurpurea (photo © John M. Watson).—(j) Sect. Subandinium: V. subandina (photo © Ana R. Flores).—(k) Sect. Triflabellium: V. triflabellata (photo © Ana R. Flores).—(l) Sect. Xylobasis: V. beati (photo © Ana R. Flores).—(m) Sect. Abyssinium: V. abyssinica (photo © Robert v. Blittersdorff).—(n) Sect. Chamaemelanium: V. pubescens (photo © Kim Blaxland).—(o) Sect. Chilenium: V. maculata (photo © Instituto de Botánica Darwinion).—(p) Sect. Danxiaviola: V. hybanthoides (photo © Qiang Fan).—(q) Sect. Delphiniopsis: V. cazorlensis (photo © Santiago Martín-Bravo).—(r) Sect. Erpetion: V. banksii (photo © Dewald du Plessis).—(s) Sect. Himalayum: V. kunawurensis (photo © Vladimir Epiktetov).—(t) Sect. Leptidium: V. boliviana (photo © Sam Wilson).—(u) Sect. Melanium, subsect. Bracteolatae: V. tricolor and V. arvensis (photo © Thomas Marcussen).—(v) Sect. Melanium, subsect. Cleistogamae: V. rafinesquei (photo © Mary Ann Yaich).—(w) Sect. Melanium, subsect. Dispares: V. dyris (photo © Alan Keohane).—(x) Sect. Melanium, subsect. Ebracteatae: V. parvula (photo © Albert Keshet).—(y) Sect. Melanium, subsect. Pseudorupestres: V. nummulariifolia (photo © Sylvain Piry).—(z) Sect. Melvio: V. decumbens (photo © Magriet Brink).—(aa) Sect. Nematocaulon: V. filicaulis (photo © Andrew Townsend).—(ab)Sect. Nosphinium, subsect. Borealiamericanae: V. fimbriatula (photo © Kim Blaxland).—(ac) Sect. Nosphinium, subsect. Clausenianae: V. clauseniana (photo © Thomas Marcussen).—(ad) Sect. Nosphinium, subsect. Langsdorffianae: V. langsdorffii (photo © Jonathan Goff).—(ae) Sect. Nosphinium, subsect. Mexicanae: V. nannei (photo © Neptalí Ramírez Marcial).—(af) Sect. Nosphinium, subsect. Nosphinium: V. maviensis (photo © Karl Magnacca).—(ag) Sect. Nosphinium, subsect. Pedatae: V. pedata (photo © Kim Blaxland).—(ah) Sect. Plagiostigma, subsect. Australasiaticae: V. sumatrana (photo © Mário Duchoň).—(ai) Sect. Plagiostigma, subsect. Bilobatae: V. hamiltoniana (photo © Toshihiro Nagata).—(aj) Sect. Plagiostigma, subsect. Bulbosae: V. tuberifera (photo © Masashi Igari).—(ak) Sect. Plagiostigma, subsect. Diffusae: V. huizhouensis (photo © Yanshuang Huang).—(al) Sect. Plagiostigma, subsect. Formosanae: V. formosana (photo © Kuan-Chieh (Chuck) Hung).—(am) Sect. Plagiostigma, subsect. Patellares: V. tokubuchiana (photo © Masashi Igari).—(an) Sect. Plagiostigma, subsect. Stolonosae: V. pluviae (photo © Kim Blaxland).—(ao) Sect. Rubellium: V. rubella (photo © Pablo Silva).—(ap) Sect. Sclerosium: V. cinerea (photo © Jerome Viard).—(aq) Sect. Spathulidium: V. pachyrrhiza (photo © Dieter Zschummel).—(ar) Sect. Tridens: V. tridentata (photo © larsonek).—(as) Sect. Viola, subsect. Rostratae: V. canina (photo © Thomas Marcussen).—(at) Sect. Viola, subsect. Viola: V. collina (photo © Thomas Marcussen).—(au) Sect. Xanthidium: V. flavicans (photo © Instituto de Botánica Darwinion).—(av) Sect. Xylinosium: V. arborescens (photo © Abdelmonaim Homrani Bakali).—All images used in this figure were cropped and gamma-corrected.—Links to the online sources for the images used in this figure under a creative commons (CC) licence: V. abyssinica, http://www.westafricanplants.senckenberg.de/root/index.php?page_id=47&id=2203#image=22051, (accessed on 5 May 2022) © Robert v. Blittersdorff; V. arborescens, https://www.teline.fr/en/photos/violaceae/viola-arborescens#photo-7 (accessed on 11 May 2022), © Abdelmonaim Homrani Bakali, CC BY-NC 4.0; V. nummulariifolia, https://www.inaturalist.org/observations/89240299 (accessed on 5 May 2022), © Sylvain Piry, CC BY-NC 4.0; V. banksii, https://inaturalist.nz/observations/25048808 (accessed on 12 May 2022), © Dewald du Plessis, CC BY-NC 4.0; V. boliviana, https://ecuador.inaturalist.org/photos/57308380 (accessed on 5 May 2022), © Sam Wilson, CC BY-NC; V. cazorlensis, https://www.inaturalist.org/observations/109331467 (accessed on 5 May 2022), © Santiago Martín-Bravo, CC BY-NC 4.0; V. cinerea, https://www.inaturalist.org/observations/65108391 (accessed on 5 May 2022), © Jerome Viard, CC BY-NC 4.0; V. decumbens, https://www.inaturalist.org/observations/10807224 (accessed on 5 May 2022), © Magriet Brink, CC BY-NC 4.0; V. filicaulis, https://www.inaturalist.org/observations/67950856 (accessed on 5 May 2022), © Andrew Townsend, CC BY-NC; V. formosana, https://www.inaturalist.org/observations/25305342 (accessed on 5 May 2022), © Kuan-Chieh (Chuck) Hung, CC BY-NC 4.0; V. hamiltoniana, https://www.inaturalist.org/observations/74528783 (accessed on 5 May 2022), © Toshihiro Nagata, CC BY-NC 4.0; V. langsdorffii, https://www.inaturalist.org/observations/73470330 (accessed on 5 May 2022), © Jonathan Goff, CC BY-NC-SA 4.0; V. maviensis, https://www.inaturalist.org/observations/39272209 (accessed on 7 May 2022), © Karl Magnacca, CC BY-NC 4.0; V. nannei, https://www.inaturalist.org/observations/6527547 (accessed on 5 May 2022), © Neptalí Ramírez Marcial, CC BY-NC; V. rafinesquei, https://www.inaturalist.org/observations/111043498 (accessed on 5 May 2022), © Mary Ann Yaich, CC BY-NC 4.0; V. rubella, https://www.inaturalist.org/observations/93725094 (accessed on 5 May 2022), © Pablo Silva, CC BY-NC 4.0; and V. tridentata, https://www.inaturalist.org/observations/103467450 (accessed on 5 May 2022), © larsonek, CC BY-NC 4.0.—Links to the relevant CC licences: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/; accessed on 5 May 2022), CC-BY-NC and CC BY-NC 4.0 (https://creativecommons.org/licenses/by-nc/4.0/; accessed on 5 May 2022), CC BY-NC-SA 4.0 (https://creativecommons.org/licenses/by-nc-sa/4.0/; accessed on 5 May 2022).

Figure 4

Stacked bar plot showing species richness among the 31 sections of Viola. Species counts are indicated above each bar. Sections containing subsections are indicated as stacked bars with the distribution of species among subsections indicated in different colours. For details on each subsection, see Table 1.

Figure 5

Dated phylogeny for monophyletic sections of Viola, updated from Marcussen et al. [28]. Estimated base ploidy is indicated after the name of each Viola section. Curved lines indicate parental lineages of an allopolyploid lineage and filled diamonds indicate the estimated time of allopolyploidisation [28]. Daggers denote parental lineages that are extinct or unsampled and extant only as a subgenome of an allopolyploid lineage. Horizontal black triangles indicate the estimated crown node of a section (and is prone to increase as more taxa are added). No phylogenetic data exist for sect. Nematocaulon and sect. Xanthidium of subg. Viola and for another seven sections of subg. Neoandinium.

Figure 6

Dated BEAST phylogeny of the Internal Transcribed Spacers (ITS) 1 and 2 in selected taxa of Viola and secondary age calibration of five internal nodes. Tip names are shown as section, subsection (if available), and species. Node bars indicate the posterior 95% credibility interval for node height; nodes with bars indicated in brown were used for age calibration. Mean ages are indicated on nodes. The outgroup (Melicytus) was pruned.

Figure 7

Wire diagram illustrating the major taxonomic differences between the phylogenetic classification of Viola proposed here (“Marcussen et al. 2022”) compared to the morphological classification proposed by Becker (1925 [1]). Merging lines denote lumping of two or more of Becker’s infrageneric groups into one taxon, while splitting lines denote segregation into two or more taxa. Taxa placed on the same line and interlinked with a horizontal line are synonymous, but may differ in delimitation, rank, or name (for reasons of priority). Taxa indicated with a dagger have been reduced to synonymy under another taxon. Taxa indicated with an asterisk are new infrageneric segregates described here. We do not show infrasectional taxa for sect. Chamaemelanium, which are not accepted here, or for sect. Melanium and the sect. Andinium/subg. Neoandinium pair, for which our treatments differ substantially from that by Becker.

Figure 8

Discrete historical biogeography of Viola sections, showing the South American origin of the genus and independent dispersal into the northern hemisphere by the CHAM and MELVIO lineages. Ancestral states were inferred by stochastic character mapping [103] using a 1-rate model and 1000 replicates, given the monoploid multilabelled timetree with 50 leaves that results from unfolding the network in Figure 5 to a tree. Sections Nematocaulon (New Zealand) and Xanthidium (South America), for which data are lacking, are not included.

Figure 9

Style shapes in Viola. (a–ae) Subg. Neoandinium. (af–fe) Subg. Viola.—Sect. Confertae: (a) V. nassauvioides [1].—Sect. Ericoidium: (b) V. fluehmannii [80].—Sect. Grandiflos: (c) V. acanthophylla [122].—Sect. Inconspicuiflos: (d) V. lilliputana, (e) V. membranacea [1].—Sect. Relictium: (f) V. ovalleana [48].—Sect. Rhizomandinium: (g) V. escondidaensis [80].—Sect. Rosulatae: (h) V. aurantiaca [1], (i) V. kermesina, (j) V. niederleinii [1], (k) V. replicata [1], (l) V. rugosa [1], (m) V. volcanica [1].—Sect. Sempervivum: (n) V. atropurpurea [80], (o) V. auricolor [80], (p) V. bangii, (q) V. coronifera [80], (r) V. cotyledon [1], (s) V. dasyphylla [80], (t) V. hieronymi [80], (u) V. micranthella, (v) V. pygmaea, (w) V. sacculus [80], (x) V. sempervivum.—Sect. Subandinium: (y) V. araucaniae [1], (z) V. polypoda, (aa) V. pusilla, (ab) V. subandina [80], (ac) V. weberbaueri.—Sect. Triflabellium: (ad) V. triflabellata [80].—Sect. Xylobasis: (ae) V. beati, tip of style [123].—Sect. Abyssinium: (af) V. abyssinica.—Sect. Chamaemelanium: (ag) V. beckwithii, (ah) V. biflora, (ai) V. canadensis, (aj) V. charlestonensis, (ak) V. cuneata, (al) V. douglasii, (am) V. flettii, (an) V. frank-smithii, (ao) V. guadalupensis, (ap) V. hallii, (aq) V. lithion, (ar) V. lobata, (as) V. nuttallii, (at) V. ocellata, (au) V. orientalis (redrawn from [78]), (av) V. scopulorum, (aw) V. sheltonii, (ax) V. trinervata, (ay) V. wallichiana (redrawn from [78]).—Sect. Chilenium: (az) V. commersonii [80], (ba) V. maculata, (bb) V. reichei, (bc) V. stuebelii.—Sect. Danxiaviola: (bd) V. hybanthoides (redrawn from [90]).—Sect. Delphiniopsis: (be) V. cazorlensis [1], (bf) V. delphinantha.—Sect. Erpetion: (bg) V. banksii.—Sect. Himalayum: (bh) V. kunawurensis (redrawn from [124]).—Sect. Leptidium: (bi) V. stipularis [1].—Sect. Melanium, subsect. Bracteolatae: (bj) V. cornuta [29], (bk) V. tricolor (redrawn from [125]).—Sect. Melanium, subsect. Cleistogamae: (bl) V. rafinesquei.—Sect. Melanium, subsect. Ebracteolatae: (bm) V. dirimliensis.—Sect. Melvio: (bn) V. decumbens.—Sect. Nematocaulon: (bo) V. filicaulis.—Sect. Nosphinium, subsect. Borealiamericanae: (bp) V. brittoniana, (bq) V. cucullata, (br) V. palmata, (bs) V. pedatifida, (bt) V. pratincola, (bu) V. sagittata, (bv) V. septemloba, (bw) V. sororia, (bx) V. viarum, (by) V. villosa.—Sect. Nosphinium, subsect. Clausenianae: (bz) V. clauseniana.—Sect. Nosphinium, subsect. Langsdorffianae: (ca) V. howellii, (cb) V. langsdorffii.—Sect. Nosphinium, subsect. Mexicanae: (cc) V. grahamii, (cd) V. guatemalensis, (ce) V. hookeriana, (cf) V. humilis, (cg) V. nannei, (ch) V. nubicola, (ci) V. oxyodontis.—Sect. Nosphinium, subsect. Nosphinium: (cj) V. kauaensis, (ck) V. maviensis [1].—Sect. Nosphinium, subsect. Pedatae: (cl) V. pedata.—Sect. Plagiostigma, subsect. Australasiaticae: (cm) V. austrosinensis (redrawn from [126]), (cn) V. annamensis, (co) V. kwangtungensis (redrawn from [78]), (cp) V. sumatrana (redrawn from [74]).—Sect. Plagiostigma, subsect. Bilobatae: (cq) V. arcuata (redrawn from [75]), (cs) V. merrilliana (redrawn from [74]), (ct) V. triangulifolia (redrawn from [78]), (cr) V. hamiltoniana [29].—Sect. Plagiostigma, subsect. Bulbosae: (cu) V. bulbosa (redrawn from [76]), (cv) V. tuberifera (redrawn from [76]).—Sect. Plagiostigma, subsect. Diffusae: (cw) V. diffusa [29], (cx) V. huizhouensis (redrawn from [127]), (cy) V. jinggangshanensis (redrawn from [128]), (cz) V. nagasawae (redrawn from [75]).—Sect. Plagiostigma, subsect. Formosanae: (da) V. formosana (redrawn from [75]), (db) V. stolonifolora (redrawn from [97]).—Sect. Plagiostigma, subsect. Patellares: (dc) V. dactyloides [1], (dd) V. japonica [29], (de) V. macroceras [1], (df) V. patrinii [1], (dg) V. pinnata [29], (dh) V. selkirkii.—Sect. Plagiostigma, subsect. Stolonosae: (di) V. suecica, (dj) V. blanda, (dk) V. brevipes, (dl) V. davidii (redrawn from [78]), (dm) V. fargesii (redrawn from [78]), (dn) V. grandisepala (redrawn from [78]), (do) V. jalapaensis, (dp) V. lanceolata, (dq) V. macloskeyi, (dr) V. minuscula, (ds) V. occidentalis, (dt) V. palustris, (du) V. pluviae, (dv) V. primulifolia, (dw) V. renifolia, (dx) V. rossii (redrawn from [76]).—Sect. Rubellium: (dy) V. capillaris [1], (dz) V. portalesia [1], (ea) V. rubella.—Sect. Sclerosium: (eb) V. stocksii, (ec) V. etbaica [1], (ed) V. somalensis [1].—Sect. Spathulidium: (ee) V. spathulata.—Sect. Tridens: (ef) V. tridentata [1].—Sect. Viola, subsect. Rostratae: (eg) V. acuminata (redrawn from [76]), (eh) V. adunca, (ei) V. appalachiensis, (ej) V. canina, (ek) V. elatior [29], (el) V. huidobrii [80], (em) V. jordanii, (en) V. labradorica, (eo) V. papuana (redrawn from [74]), (ep) V. rostrata, (eq) V. rupestris [29], (er) V. stagnina [29], (es) V. striata, (et) V. uliginosa [29], (eu) V. umbraticola, (ev) V. walteri.—Sect. Viola, subsect. Viola: (ew) V. barhalensis (redrawn from [129]), (ex) V. chelmea [1], (ey) V. hirta [29], (ez) V. odorata, (fa) V. pilosa [1].—Sect. Xanthidium: (fb) V. flavicans, (fc) V. pallascaensis.—Sect. Xylinosium: (fd) V. arborescens [1], (fe) V. scorpiuroides.—All drawings by Kim Blaxland, H.E.B, and T.M. except where indicated.

Figure 9

Style shapes in Viola. (a–ae) Subg. Neoandinium. (af–fe) Subg. Viola.—Sect. Confertae: (a) V. nassauvioides [1].—Sect. Ericoidium: (b) V. fluehmannii [80].—Sect. Grandiflos: (c) V. acanthophylla [122].—Sect. Inconspicuiflos: (d) V. lilliputana, (e) V. membranacea [1].—Sect. Relictium: (f) V. ovalleana [48].—Sect. Rhizomandinium: (g) V. escondidaensis [80].—Sect. Rosulatae: (h) V. aurantiaca [1], (i) V. kermesina, (j) V. niederleinii [1], (k) V. replicata [1], (l) V. rugosa [1], (m) V. volcanica [1].—Sect. Sempervivum: (n) V. atropurpurea [80], (o) V. auricolor [80], (p) V. bangii, (q) V. coronifera [80], (r) V. cotyledon [1], (s) V. dasyphylla [80], (t) V. hieronymi [80], (u) V. micranthella, (v) V. pygmaea, (w) V. sacculus [80], (x) V. sempervivum.—Sect. Subandinium: (y) V. araucaniae [1], (z) V. polypoda, (aa) V. pusilla, (ab) V. subandina [80], (ac) V. weberbaueri.—Sect. Triflabellium: (ad) V. triflabellata [80].—Sect. Xylobasis: (ae) V. beati, tip of style [123].—Sect. Abyssinium: (af) V. abyssinica.—Sect. Chamaemelanium: (ag) V. beckwithii, (ah) V. biflora, (ai) V. canadensis, (aj) V. charlestonensis, (ak) V. cuneata, (al) V. douglasii, (am) V. flettii, (an) V. frank-smithii, (ao) V. guadalupensis, (ap) V. hallii, (aq) V. lithion, (ar) V. lobata, (as) V. nuttallii, (at) V. ocellata, (au) V. orientalis (redrawn from [78]), (av) V. scopulorum, (aw) V. sheltonii, (ax) V. trinervata, (ay) V. wallichiana (redrawn from [78]).—Sect. Chilenium: (az) V. commersonii [80], (ba) V. maculata, (bb) V. reichei, (bc) V. stuebelii.—Sect. Danxiaviola: (bd) V. hybanthoides (redrawn from [90]).—Sect. Delphiniopsis: (be) V. cazorlensis [1], (bf) V. delphinantha.—Sect. Erpetion: (bg) V. banksii.—Sect. Himalayum: (bh) V. kunawurensis (redrawn from [124]).—Sect. Leptidium: (bi) V. stipularis [1].—Sect. Melanium, subsect. Bracteolatae: (bj) V. cornuta [29], (bk) V. tricolor (redrawn from [125]).—Sect. Melanium, subsect. Cleistogamae: (bl) V. rafinesquei.—Sect. Melanium, subsect. Ebracteolatae: (bm) V. dirimliensis.—Sect. Melvio: (bn) V. decumbens.—Sect. Nematocaulon: (bo) V. filicaulis.—Sect. Nosphinium, subsect. Borealiamericanae: (bp) V. brittoniana, (bq) V. cucullata, (br) V. palmata, (bs) V. pedatifida, (bt) V. pratincola, (bu) V. sagittata, (bv) V. septemloba, (bw) V. sororia, (bx) V. viarum, (by) V. villosa.—Sect. Nosphinium, subsect. Clausenianae: (bz) V. clauseniana.—Sect. Nosphinium, subsect. Langsdorffianae: (ca) V. howellii, (cb) V. langsdorffii.—Sect. Nosphinium, subsect. Mexicanae: (cc) V. grahamii, (cd) V. guatemalensis, (ce) V. hookeriana, (cf) V. humilis, (cg) V. nannei, (ch) V. nubicola, (ci) V. oxyodontis.—Sect. Nosphinium, subsect. Nosphinium: (cj) V. kauaensis, (ck) V. maviensis [1].—Sect. Nosphinium, subsect. Pedatae: (cl) V. pedata.—Sect. Plagiostigma, subsect. Australasiaticae: (cm) V. austrosinensis (redrawn from [126]), (cn) V. annamensis, (co) V. kwangtungensis (redrawn from [78]), (cp) V. sumatrana (redrawn from [74]).—Sect. Plagiostigma, subsect. Bilobatae: (cq) V. arcuata (redrawn from [75]), (cs) V. merrilliana (redrawn from [74]), (ct) V. triangulifolia (redrawn from [78]), (cr) V. hamiltoniana [29].—Sect. Plagiostigma, subsect. Bulbosae: (cu) V. bulbosa (redrawn from [76]), (cv) V. tuberifera (redrawn from [76]).—Sect. Plagiostigma, subsect. Diffusae: (cw) V. diffusa [29], (cx) V. huizhouensis (redrawn from [127]), (cy) V. jinggangshanensis (redrawn from [128]), (cz) V. nagasawae (redrawn from [75]).—Sect. Plagiostigma, subsect. Formosanae: (da) V. formosana (redrawn from [75]), (db) V. stolonifolora (redrawn from [97]).—Sect. Plagiostigma, subsect. Patellares: (dc) V. dactyloides [1], (dd) V. japonica [29], (de) V. macroceras [1], (df) V. patrinii [1], (dg) V. pinnata [29], (dh) V. selkirkii.—Sect. Plagiostigma, subsect. Stolonosae: (di) V. suecica, (dj) V. blanda, (dk) V. brevipes, (dl) V. davidii (redrawn from [78]), (dm) V. fargesii (redrawn from [78]), (dn) V. grandisepala (redrawn from [78]), (do) V. jalapaensis, (dp) V. lanceolata, (dq) V. macloskeyi, (dr) V. minuscula, (ds) V. occidentalis, (dt) V. palustris, (du) V. pluviae, (dv) V. primulifolia, (dw) V. renifolia, (dx) V. rossii (redrawn from [76]).—Sect. Rubellium: (dy) V. capillaris [1], (dz) V. portalesia [1], (ea) V. rubella.—Sect. Sclerosium: (eb) V. stocksii, (ec) V. etbaica [1], (ed) V. somalensis [1].—Sect. Spathulidium: (ee) V. spathulata.—Sect. Tridens: (ef) V. tridentata [1].—Sect. Viola, subsect. Rostratae: (eg) V. acuminata (redrawn from [76]), (eh) V. adunca, (ei) V. appalachiensis, (ej) V. canina, (ek) V. elatior [29], (el) V. huidobrii [80], (em) V. jordanii, (en) V. labradorica, (eo) V. papuana (redrawn from [74]), (ep) V. rostrata, (eq) V. rupestris [29], (er) V. stagnina [29], (es) V. striata, (et) V. uliginosa [29], (eu) V. umbraticola, (ev) V. walteri.—Sect. Viola, subsect. Viola: (ew) V. barhalensis (redrawn from [129]), (ex) V. chelmea [1], (ey) V. hirta [29], (ez) V. odorata, (fa) V. pilosa [1].—Sect. Xanthidium: (fb) V. flavicans, (fc) V. pallascaensis.—Sect. Xylinosium: (fd) V. arborescens [1], (fe) V. scorpiuroides.—All drawings by Kim Blaxland, H.E.B, and T.M. except where indicated.

Figure 9

Style shapes in Viola. (a–ae) Subg. Neoandinium. (af–fe) Subg. Viola.—Sect. Confertae: (a) V. nassauvioides [1].—Sect. Ericoidium: (b) V. fluehmannii [80].—Sect. Grandiflos: (c) V. acanthophylla [122].—Sect. Inconspicuiflos: (d) V. lilliputana, (e) V. membranacea [1].—Sect. Relictium: (f) V. ovalleana [48].—Sect. Rhizomandinium: (g) V. escondidaensis [80].—Sect. Rosulatae: (h) V. aurantiaca [1], (i) V. kermesina, (j) V. niederleinii [1], (k) V. replicata [1], (l) V. rugosa [1], (m) V. volcanica [1].—Sect. Sempervivum: (n) V. atropurpurea [80], (o) V. auricolor [80], (p) V. bangii, (q) V. coronifera [80], (r) V. cotyledon [1], (s) V. dasyphylla [80], (t) V. hieronymi [80], (u) V. micranthella, (v) V. pygmaea, (w) V. sacculus [80], (x) V. sempervivum.—Sect. Subandinium: (y) V. araucaniae [1], (z) V. polypoda, (aa) V. pusilla, (ab) V. subandina [80], (ac) V. weberbaueri.—Sect. Triflabellium: (ad) V. triflabellata [80].—Sect. Xylobasis: (ae) V. beati, tip of style [123].—Sect. Abyssinium: (af) V. abyssinica.—Sect. Chamaemelanium: (ag) V. beckwithii, (ah) V. biflora, (ai) V. canadensis, (aj) V. charlestonensis, (ak) V. cuneata, (al) V. douglasii, (am) V. flettii, (an) V. frank-smithii, (ao) V. guadalupensis, (ap) V. hallii, (aq) V. lithion, (ar) V. lobata, (as) V. nuttallii, (at) V. ocellata, (au) V. orientalis (redrawn from [78]), (av) V. scopulorum, (aw) V. sheltonii, (ax) V. trinervata, (ay) V. wallichiana (redrawn from [78]).—Sect. Chilenium: (az) V. commersonii [80], (ba) V. maculata, (bb) V. reichei, (bc) V. stuebelii.—Sect. Danxiaviola: (bd) V. hybanthoides (redrawn from [90]).—Sect. Delphiniopsis: (be) V. cazorlensis [1], (bf) V. delphinantha.—Sect. Erpetion: (bg) V. banksii.—Sect. Himalayum: (bh) V. kunawurensis (redrawn from [124]).—Sect. Leptidium: (bi) V. stipularis [1].—Sect. Melanium, subsect. Bracteolatae: (bj) V. cornuta [29], (bk) V. tricolor (redrawn from [125]).—Sect. Melanium, subsect. Cleistogamae: (bl) V. rafinesquei.—Sect. Melanium, subsect. Ebracteolatae: (bm) V. dirimliensis.—Sect. Melvio: (bn) V. decumbens.—Sect. Nematocaulon: (bo) V. filicaulis.—Sect. Nosphinium, subsect. Borealiamericanae: (bp) V. brittoniana, (bq) V. cucullata, (br) V. palmata, (bs) V. pedatifida, (bt) V. pratincola, (bu) V. sagittata, (bv) V. septemloba, (bw) V. sororia, (bx) V. viarum, (by) V. villosa.—Sect. Nosphinium, subsect. Clausenianae: (bz) V. clauseniana.—Sect. Nosphinium, subsect. Langsdorffianae: (ca) V. howellii, (cb) V. langsdorffii.—Sect. Nosphinium, subsect. Mexicanae: (cc) V. grahamii, (cd) V. guatemalensis, (ce) V. hookeriana, (cf) V. humilis, (cg) V. nannei, (ch) V. nubicola, (ci) V. oxyodontis.—Sect. Nosphinium, subsect. Nosphinium: (cj) V. kauaensis, (ck) V. maviensis [1].—Sect. Nosphinium, subsect. Pedatae: (cl) V. pedata.—Sect. Plagiostigma, subsect. Australasiaticae: (cm) V. austrosinensis (redrawn from [126]), (cn) V. annamensis, (co) V. kwangtungensis (redrawn from [78]), (cp) V. sumatrana (redrawn from [74]).—Sect. Plagiostigma, subsect. Bilobatae: (cq) V. arcuata (redrawn from [75]), (cs) V. merrilliana (redrawn from [74]), (ct) V. triangulifolia (redrawn from [78]), (cr) V. hamiltoniana [29].—Sect. Plagiostigma, subsect. Bulbosae: (cu) V. bulbosa (redrawn from [76]), (cv) V. tuberifera (redrawn from [76]).—Sect. Plagiostigma, subsect. Diffusae: (cw) V. diffusa [29], (cx) V. huizhouensis (redrawn from [127]), (cy) V. jinggangshanensis (redrawn from [128]), (cz) V. nagasawae (redrawn from [75]).—Sect. Plagiostigma, subsect. Formosanae: (da) V. formosana (redrawn from [75]), (db) V. stolonifolora (redrawn from [97]).—Sect. Plagiostigma, subsect. Patellares: (dc) V. dactyloides [1], (dd) V. japonica [29], (de) V. macroceras [1], (df) V. patrinii [1], (dg) V. pinnata [29], (dh) V. selkirkii.—Sect. Plagiostigma, subsect. Stolonosae: (di) V. suecica, (dj) V. blanda, (dk) V. brevipes, (dl) V. davidii (redrawn from [78]), (dm) V. fargesii (redrawn from [78]), (dn) V. grandisepala (redrawn from [78]), (do) V. jalapaensis, (dp) V. lanceolata, (dq) V. macloskeyi, (dr) V. minuscula, (ds) V. occidentalis, (dt) V. palustris, (du) V. pluviae, (dv) V. primulifolia, (dw) V. renifolia, (dx) V. rossii (redrawn from [76]).—Sect. Rubellium: (dy) V. capillaris [1], (dz) V. portalesia [1], (ea) V. rubella.—Sect. Sclerosium: (eb) V. stocksii, (ec) V. etbaica [1], (ed) V. somalensis [1].—Sect. Spathulidium: (ee) V. spathulata.—Sect. Tridens: (ef) V. tridentata [1].—Sect. Viola, subsect. Rostratae: (eg) V. acuminata (redrawn from [76]), (eh) V. adunca, (ei) V. appalachiensis, (ej) V. canina, (ek) V. elatior [29], (el) V. huidobrii [80], (em) V. jordanii, (en) V. labradorica, (eo) V. papuana (redrawn from [74]), (ep) V. rostrata, (eq) V. rupestris [29], (er) V. stagnina [29], (es) V. striata, (et) V. uliginosa [29], (eu) V. umbraticola, (ev) V. walteri.—Sect. Viola, subsect. Viola: (ew) V. barhalensis (redrawn from [129]), (ex) V. chelmea [1], (ey) V. hirta [29], (ez) V. odorata, (fa) V. pilosa [1].—Sect. Xanthidium: (fb) V. flavicans, (fc) V. pallascaensis.—Sect. Xylinosium: (fd) V. arborescens [1], (fe) V. scorpiuroides.—All drawings by Kim Blaxland, H.E.B, and T.M. except where indicated.

Figure 10

Global distribution of Viola subg. Neoandinium.

Figure 11

Global distribution of Viola sect. Abyssinium.

Figure 12

Global distribution of Viola sect. Chamaemelanium.

Figure 13

Ultrametric phylogeny of diploid taxa of Viola sect. Chamaemelanium, showing the basal irresolution among otherwise well-supported infrasectional lineages and the non-monophyly of Becker’s greges at both the diploid and allopolyploid level. Outgroups have been trimmed. The analysis was performed on a concatenated matrix of four loci (GPI, ITS, NRPD2a, trnL-trnF). The squares indicated on branches show the approximate phylogenetic placement of homoeologs of five North American allopolyploids [60], V. bakeri (8x), V. douglasii (8x), V. glabella (4x), and V. guadalupensis (4x). Branch support is given as posterior probabilities. * Viola biflora has a circumboreal distribution.

Figure 14

Global distribution of Viola sect. Chilenium.

Figure 15

Global distribution of Viola sect. Danxiaviola.

Figure 16

Global distribution of Viola sect. Delphiniopsis.

Figure 17

Global distribution of Viola sect. Erpetion.

Figure 18

Global distribution of Viola sect. Himalayum.

Figure 19

Global distribution of Viola sect. Leptidium.

Figure 20

Global distribution of Viola sect. Melanium.

Figure 21

Global distribution of Viola sect. Melvio.

Figure 22

Global distribution of Viola sect. Nematocaulon.

Figure 23

Global distribution of Viola sect. Nosphinium.

Figure 24

Reticulate allopolyploid phylogeny of Viola sect. Nosphinium, simplified from Marcussen et al. [45]. Allopolyploidisations are indicated by curved lines. Ploidy (x) is indicated.

Figure 25

Historical biogeography of the Hawaiian violets, Viola subsect. Nosphinium, based on ITS sequences and simultaneous estimation of phylogeny and discrete biogeography using BEAST. Kauai is indicated as the most likely island of colonisation, based both on age, which excludes all the other islands, and on receiving the highest posterior probability (pp) by ancestral state reconstruction. The 95% credibility interval for node age is shown as a node bar on the crown node. Ancestral states are colour-coded according to island and indicated on each node along with the pp. Each island is shown as a silhouette and its age is indicated by a vertical line. Outgroups have been trimmed.

Figure 26

Global distribution of Viola sect. Plagiostigma.

Figure 27

Phylogeny of Viola sect. Plagiostigma showing the delimitation of subsections (4x) with known allopolyploids (8x) superimposed, based on concatenated sequences of eight nuclear gene loci (GPI-C, GPI-M, ITS-C, ITS-M, NRPD2a-C, NRPD2a-M, SDH-C, and SDH-M). Outgroups have been pruned. The relative ages for polyploids are not to scale. Branch support is given as posterior probabilities. Abbreviations: bla, inc = V. blanda and V. incognita; pal = V. palustris; plu = V. pluviae.

Figure 28

Global distribution of Viola sect. Rubellium.

Figure 29

Global distribution of Viola sect. Sclerosium.

Figure 30

Global distribution of Viola sect. Spathulidium.

Figure 31

Global distribution of Viola sect. Tridens.

Figure 32

Global distribution of Viola sect. Viola.

Figure 33

Phylogeny of Viola sect. Viola showing the delimitation of subsections (4x) with known allopolyploids (8x) superimposed, based on concatenated sequences of eight nuclear gene loci (GPI-C, GPI-M, ITS-C, ITS-M, NRPD2a-C, NRPD2a-M, SDH-C, and SDH-M). Outgroups have been pruned. The ages and placements for polyploids are not to scale. Branch support is given as posterior probabilities. Abbreviations: amb = V. ambigua; can, lac, pum = V. canina, V. lactea, and V. pumila; pse, wil = V. pseudomirabilis and V. willkommii.

Figure 34

Global distribution of Viola sect. Xanthidium.

Figure 35

Global distribution of Viola sect. Xylinosium.