[2.4] Viola sect Danxiaviola

Viola sect. Danxiaviola W. B. Liao & Q. Fan in Phytotaxa 197: 19. 2015

—Type: Viola hybanthoides W. B. Liao & Q. Fan

Description.—Subshrub. Axes not morphologically differentiated. All stems erect or ascending. Stipules free, conspicuous, oblong-lanceolate, remotely long-fimbriate. Lamina elliptic or ovate-lanceolate, margin serrate, short-petiolate. Corolla whitish to pale violet. Bottom petal clawed, much larger than the other, reduced petals, whitish to pale violet with a yellowish green blotch at base. Spur short and saccate. Style capitate, at apex slightly bilobate, beardless, not beaked and with a stigmatic opening in front and with a lamellar processus below the opening. Cleistogamous flowers not produced. Chromosome number x = 10. ITS sequence of CHAM type.

Diagnostic characters.—Bottom petal clawed, much larger than the other petals.

Ploidy and accepted chromosome counts.—Probably 4x; 2n = 20.

Age.—Crown node age not applicable (monotypic section), stem node age probably 17.8–19.3 Ma.

Included species.—1. 

Viola hybanthoides W. B. Liao & Q. Fan

Distribution.—Southeastern China (northern Guangdong). Known only from two sites on Mt. Danxia (Figure 1)

Discussion.—The single species in the section, V. hybanthoides, is phylogenetically isolated within the north hemisphere allopolyploid tangle, based on both ITS and chloroplast sequences [1]. The combined features of the larger bottom petal and much smaller lateral and upper petals is unique in Viola but found recurrently in most bilaterally symmetrical genera of the Violaceae, such as genera currently being segregated from the former polyphyletic Hybanthus, and sisters to Viola, Noisettia and Schweiggeria [2]. We infer that V. hybanthoides is probably a CHAM + MELVIO meso-allotetraploid, judging from its chromosome number (2n = 20) which in sect. Viola and sect. Delphiniopsis reflects 4x, the small size of its chromosomes and tricolporate pollen which both reflect a certain time since the polyploidisation, and its phylogenetic placement nested within a tetraploid clade [1] .

1. Fan, Q.; Chen, S.; Wang, L.; Chen, Z.; Liao, W. A new species and new section of Viola (Violaceae) from Guangdong, China. Phytotaxa 2015, 197, 15–26.

2. Wahlert, G.A.; Marcussen, T.; de Paula-Souza, J.; Feng, M.; Ballard, H.E. A phylogeny of the Violaceae (Malpighiales) inferred from plastid DNA sequences: Implications for generic diversity and intrafamilial taxonomy. Syst. Bot. 2014, 39, 239–252.