Embedded Files
Viola subsect. Mexicanae (W. Becker) Marcussen & H. E. Ballard, stat. nov.
≡ Basionym: Viola [sect. Nomimium; unranked] Mexicanae W. Becker in Repert. Spec. Nov. Regni Veg. 19: 396. 1923
≡ Viola sect. Mexicanae (W. Becker) Espeut in Botanica Pacifica 9(1): 35. 2020.
Lectotype (designated here): Viola humilis Kunth
Description.—Perennial herbs. Axes usually morphologically differentiated into a perennial rhizome terminating in an apical rosette and lateral stolons which are often absent. Stipules narrow, free or basally to mostly adnate, glandular-lacerate. Laminas undivided. Calycine appendages mostly short and rounded. Petals violet or whitish, lateral glabrous or sparsely bearded (sometimes densely bearded in V. grahamii, V. nubicola, and V. oxyodontis). Style clavate with a sharp-edged or sometimes weakly thickened apically oriented or slightly incurved dorsolateral rim (somewhat prolonged on the upper side in V. hookeriana) continuing partly or fully to the ventrally oriented rostellum. Cleistogamous flowers produced, simultaneous. Allo-14-ploid (10x with an additional 4x genome from sect. Plagiostigma). Secondary base chromosome number x’ = 40.
Diagnostic characters.—Habit rosulate or stoloniferous AND stipules free or adnate AND petals violet or whitish AND lateral petals glabrous or sparsely (rarely densely) bearded AND style with weakly thickened apically oriented (rarely prolonged) dorsolateral rim and ventrally oriented rostellum AND cleistogamy present.
Ploidy and accepted chromosome counts.—14x; 2n = 80 (Viola nannei).
Age.—Crown node 5.1 (2.6–7.8) Ma (Figure 6), stem node age 3.2–8.8 Ma [45].
Included species.—10.
Viola beamanii Calderón, >iNat
Viola cuicochensis Hieron.,
Viola guatemalensis W. Becker, >iNat
Viola hemsleyana Calderón, >iNat
Viola hookeriana Kunth, >iNat
Viola humilis Kunth, >iNat
Viola nubicola H. E. Ballard, ined. [J. H. Beaman 2976],
Viola oxyodontis H. E. Ballard>iNat
Distribution.—Mexico to Ecuador.
Discussion.—This subsection currently comprises 10 species expressing diverse morphologies but which appear to belong to a single lineage (an unpublished ITS phylogeny by HEB including most species was monophyletic with strong support among other lineages of the genus). It arose from a secondary allopolyploidisation event from the ancestor of the Nosphinium lineage and an early sister lineage to the North American sublineage of Stolonosae [45]. Slightly more than half produce above-ground stolons, two non-stoloniferous species often produce adventitious shoots on roots (V. beamanii and V. hookeriana), a few species have white flowers (V. grahamii, V. oxyodontis, and central Mexican populations of V. hookeriana), and most species have lateral petals beardless or with sparse beards. One species has strongly adnate outer stipules (V. humilis) while two others have basally adnate stipules (V. grahamii, V. oxyodontis). The style apex has the thin short dorsolateral rim erect (rather than spreading as in the Borealiamericanae). Most species are restricted to Mexico, a few extend into Central America, and two are found in northern South America.
Google Sites
Report abuse