[2.3] Viola sect. Chilenium W. Becker

Viola sect. ChileniumW. Becker in Nat. Pflanzenfam., ed. 2 [Engler & Prantl], 21: 376. 1925.

—Lectotype (designated here): Viola maculata Cav.—Note: Viola maculata is indicated as “Haupttypus” in the protologue (Becker 1925: 376).   ≡Viola [unranked] § I. Bicaules Reiche in Fl. Chile [Reiche] 1: 139. 1896—Lectotype (designated here): Viola maculata Cav. 

Description.—Perennial herbs. Axes not morphologically differentiated. Stem creeping, more or less densely noded, deeply seated. Stipules free, broad and glandular-laciniate, rarely entire. Lamina oblong, elliptical or rhombic-lanceolate to reniform, margin crenate, long-petiolate. Bracteoles broad, deeply glandular-laciniate. Corolla yellow, rarely white (V. commersonii). Bottom petal at least twice as broad as top petals, rarely only slightly broader than the top petals (V. rudolphii), with brown striation, rarely reddish-violet striation (V. commersonii). Spur shorter than tall, rarely much longer than tall (V. rudolphii and V. stuebelii). Style clavate or straight, concave, flattened or slightly acute apically with a continuous sharp dorsolateral rim, the rim truncate and hiding the stigma (V. stuebelii) or slightly prolonged on the upper side with an upcurved visible rostellum bearing the stigma (other species), usually beardless (white-hairy in V. rudolphii). Cleistogamous flowers produced; cleistogamy facultative. Allopolyploid.

Diagnostic characters.—All stems rhizomes AND corolla yellow with brown striation or white with reddish-violet striation AND facultative cleistogamy.

Ploidy and accepted chromosome counts.—≥4x; no chromosome counts.

Age.—Crown node age unknown, stem node age 7.4 (6.5–7.7) Ma [28].

Included species.—7. 

Viola commersonii DC. ex Ging., 

Viola germainii Sparre, 

Viola maculata Cav., 

Viola magellanica G. Forst., 

Viola reichei Skottsb. ex Macloskie, 

Viola rudolphii Sparre, 

Viola stuebelii Hieron. vedi aaa, bbb

Distribution.—Disjunct in southern (Argentina and Chile) and northern South America (Colombia, Ecuador, and Peru) 

Discussion.—Marcussen T 2022 modify Becker’s [1] original delimitation of sect. Chilenium by including V. stuebelii (=V. glandularis H. E. Ballard & P. Jørg.) based on shared diagnostic characters, and excluding V. huidobrii (=V. brachypetala Gay). Reiche [122,130] was the first to recognise this group, which he circumscribed under an invalid taxonomic rank (i.e., the unranked Bicaules within the invalid “Divisio” Sparsifoliae). Later, Sparre [62,63] revised the section and recognised eight southern South American species (some of them were later synonymised), which he distributed among three subsections, Maculatae (V. germainii, V. maculata, V. reichei), Magellanicae (V. commersonii, V. magellanica), and Lanatae (V. rudolphii), based on characteristics of the spur, style, and nectariferous appendages. We transfer the distinctive, violet-flowered V. huidobrii (Sparre as subsect. Coeruleae) to sect. Viola subsect. Rostratae. The new delimitation of sect. Chilenium renders the section geographically disjunct, with V. stuebelii in northern South America and the rest of the species in southern South America. Section Chilenium comprises only seven species, some closely related (e.g., V. maculata and V. reichei) and others known only from the type specimen (V. germainii and V. rudolphii), and in the absence of molecular data we choose not to keep Sparre’s subsections.

The South American sect. Chilenium is sister lineage of the Australian sect. Erpetion

References

1. Marcussen, T. et al. A Revised Phylogenetic Classification for Viola (Violaceae). Plants 11, 2224 (2022)p. 42-43 

2. Marcussen, T.; Heier, L.; Brysting, A.K.; Oxelman, B.; Jakobsen, K.S. From gene trees to a dated allopolyploid network: Insights from the angiosperm genus Viola (Violaceae). Syst. Biol. 2015, 64, 84–101