[2.16] Viola sect. Spathulidium 

Viola sect. Spathulidium Marcussen, sect. nov.

—Type: Viola spathulata Willd.

Description.—Perennial herbs. Axes not morphologically differentiated. All stems rhizomatous, forming cushions. Stipules ¾ adnate to petiole. Lamina spathulate to lanceolate, subentire, tapering into short and indistinct petiole. Corolla pale violet, pink or whitish. Spur 1.5–4 mm, longer than tall. Style clavate, geniculate at base, at apex 2-lobed, with a distinct dorsolateral margin and ventral rostrum. Cleistogamous flowers not produced. Allo-octoploid (CHAM + MELVIO). ITS sequence of MELVIO type.

Diagnostic characters.—Lamina spathulate to lanceolate, subentire, tapering into short and indistinct petiole AND style clavate, at apex 2-lobed, with a distinct dorsolateral margin AND cleistogamous flowers not produced.

Ploidy and accepted chromosome counts.—[Section by origin 8x], 16x (V. spathulata). Chromosome number unknown.

Age.—Crown node c. 1 Ma; stem node 5.0 (4.2–5.3) Ma [28].

Included species.—3. Violamaymanica Grey-Wilson, V. pachyrrhiza Boiss. & Hohen., V. spathulata Willd. ex Schult.

Distribution.—Disjunctly distributed in the high mountains of southwestern Asia (Figure 30): Viola pachyrrhiza in northeastern Iraq and southern Iran; V. spathulata in northern Iran (Elburs mountains); and V. maymanica in northwestern Afghanistan.

Etymology.—The name Spathulidium refers to the distinctive spathulate leaves.

Discussion.—Section Spathulidium is an allooctoploid CHAM + MELVIO lineage and has retained the MELVIO homoeolog for ITS (Figure 2). The lineage is morphologically recognisable on being cushion plants, inhabiting rock fissures, with spathulate short-petiolate leaves, a somewhat bilobed style, and the absence of cleistogamous flowers. The Spathulidium lineage is inferred to be the alloploid of two unknown tetraploid lineages; further allopolyploidy based on 8x may have happened in V. spathulata (16x) [28]. The three species of sect. Spathulidium have traditionally been grouped within sect. Plagiostigma subsect. Patellares based on being violet-flowered rosette plants with narrow leaves and adnate stipules [1,248]. However, sect. Spathulidium differs from subsect. Patellares in being cushion plants, having leaves with entire or subcrenate margins, in lacking cleistogamy, and in ploidy. Section Spathulidium differs from sect. Himalayum in being cushion plants, in having a margined style apex and a much longer spur, and in lacking cleistogamous flowers. Both sections are 8x but have different allopolyploid origins.

Section Spathulidium is most closely related to the African sect. Abyssinium (see note under the latter).