[2.5] Viola sect. Delphiniopsis 

Viola sect. Delphiniopsis W. Becker in Nat. Pflanzenfam., ed. 2 [Engler & Prantl], 21: 373. 1925

—Type (Shenzhen Code Art. 10.8): Viola delphinantha Boiss.

≡Viola [unranked] §.1. Delphinoideae Boiss., Fl. Orient. 1: 451. 1867.—Type: Viola delphinantha Boiss.

≡Viola [unranked] c. Lobulariae Nyman, Consp. Fl. Eur. 1: 79. 1878.—Type: Viola delphinantha Boiss.

Description.—Perennial herbs with a woody base. Axes not morphologically differentiated. All stems aerial, annual, growing in fascicles from a woody and sometimes thick rhizome (pleiocorm). Leaves sessile, consisting of 3–5 lanceolate, entire segments, lamina and stipule segments similar. Corolla pink to magenta. Spur 12–30 mm, down-curved. Style clavate, glabrous, unmargined, with a simple, wide stigmatic opening. Cleistogamous flowers not produced. Allotetraploid (CHAM + MELVIO). Secondary base chromosome number x’ = 10. ITS sequence of MELVIO type.

Diagnostic characters.—Corolla pink to magenta AND spur 12–30 mm, down-curved.

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

Age.—Crown node age unknown, stem node age 14.7 (6.3–18.6) Ma [1].

Included species.—3. 

Viola cazorlensis Gand., 

Viola delphinantha Boiss., 

Viola kosaninii (Degen) Hayek.

Distribution.—Disjunct in southern Europe: southern Spain (V. cazorlensis) and the Balkans (V. delphinantha, V. kosaninii) (Figure 1 and 2).

Discussion.—Section Delphiniopsis is highly distinct, phylogenetically, karyologically (x’ = 10), and morphologically. The species are specialised to be pollinated by a single species of day-flying hawk-moth (Macroglossum stellatarum, Sphingidae, Lepidoptera) [2,3]. The disjunct distribution of sect. Delphiniopsis, between V. delphinantha and V. kosaninii in the Balkans and V. cazorlensis in southern Spain, has been suggested to result from vicariance and to date from the Early Pliocene, 3.6–5.3 Ma [4]. The crown age of the section have so far not been phylogenetically dated, but the idea that the species are young is further supported by their morphological similarity and reports of their being able to hybridise in culture (plants of V. cazorlensis × V. delphinantha were displayed at the Midland AGS SHOW 2012). Phylogenetic analysis confirms that sect. Delphiniopsis is an isolated and highly specialised lineage on a rather long branch, indicating rapid evolution [1]. The characters once considered ”primitive” [4,5], such as woodiness, entire leaves and stipules, small and uniform chromosomes and rather common chromosome number, relict distribution, and lack of cleistogamy, should rather be interpreted as secondary specialisations, just like the highly specialised pollination. The low and apparently young diversity of the section may be explained by its high level of specialisation in both pollination syndrome and choice of habitat: the species inhabit limestone crevices, a rare habitat that minimises competition but at the same time limits the population size and dispersal, thereby increasing the risk of extinction. 

1. 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. [Google Scholar] [CrossRef]

2. Herrera, C.M. Selection on floral morphology and environmental determinants of fecundity in a hawk moth-pollinated violet. Ecol. Monogr. 1993, 63, 251–275. [Google Scholar] [CrossRef]

3.  McPavlis. Viola delphinantha and its sisters. Int. Rock Gard. 2010, 3, 11–12.

4. Melchior, H.; Cuatrecasas, J. La Viola cazorlensis, su distribución, sistemática y biología. Cavanillesia 1935, 7, 133–148. 

5.  Schmidt, A. Zur systematischen Stellung von Viola chelmea Boiss. et Heldr. ssp. chelmea und V. delphinantha. Boiss. Ber. Deutsch. Bot. Ges. 1964, 77, 256–261. 

6. Marcussen, T. et al. A Revised Phylogenetic Classification for Viola (Violaceae). Plants 11, 2224 (2022). p. 38

Further reading

1. Bianchi, C. N., Morri, C., Chiantore, M., Parravicini, V. & Rovere, A. Mediterranean Sea biodiversity between the legacy from the past and a future of change. in Life in the Mediterranean Sea: A Look at Habitat Changes (Nova Science Publishers, Inc., New York, 2012).

2. Rouchy, J. M., Orszag-Sperber, F., RivieÁre, M., Combourieu-Nebout, N. & Panayides, I. Paleoenvironmental changes at the Messinian-Pliocene boundary in the eastern Mediterranean (southern Cyprus basins): signi®cance of the Messinian Lago-Mare. Sediment. Geol. (2001).

3. Verdú, M. et al. Phylogenetic diversity in the Iberian flora through the Cenozoic. Environ. Exp. Bot. 170, 103888 (2020).

4. Cvetanoska, S. et al. First IUCN National Assessment for Thymus oehmianus Ronniger & Soška (Lamiaceae) and Viola kosaninii(Degen) Hayek (Violaceae) in the Republic of North Macedonia. Maced. J. Ecol. Environ. 25, 5–10 (2023).

5. Médail, F. et al. What is a tree in the Mediterranean Basin hotspot? A critical analysis. For. Ecosyst. 6, 17 (2019).

6. Mascle, G. & Mascle, J. The Messinian salinity legacy: 50 years later. Mediterr. Geosci. Rev. 1, 5–15 (2019).

7. Herrera, C. M. & Bazaga, P. Population‐genomic approach reveals adaptive floral divergence in discrete populations of a hawk moth‐pollinated violet. Mol. Ecol. 17, 5378–5390 (2008).

8. Cánovas, J. L., Jiménez, J. F., Mota, J. F. & Gómez, P. S. Genetic diversity of Viola cazorlensis Gand., an endemic species of Mediterranean dolomitic habitats: implications for conservation. Syst. Biodivers. 13, 571–580 (2015).

9. Stevanovič, V. & Tan, K. On the distribution of Viola kosaninii in the Balkan Peninsula. > for a background history of exploration and distribution

10. Herrera, C. M. The adaptedness of the floral phenotype in a relict endemic, hawkmoth-pollinated violet. 2. Patterns of variation among disjunct populations. Biol. J. Linn. Soc. 40, 275–291 (1990).

11. Harzhauser, M., Landau, B., Mandic, O. & Neubauer, T. A. The Central Paratethys Sea—rise and demise of a Miocene European marine biodiversity hotspot. Sci. Rep. 14, 16288 (2024)

12. Herrera, C. M., Castellanos-Martínez, J. & Medrano, M. Geographical context of floral evolution: towards an improved research programme in floral diversification. in Ecology and Evolution of Flowers 278-294. (Oxford University Press, Oxford, 2006).

13. Herrera, C. M. The adaptedness of the floral phenotype in a relict endemic, hawkmoth-pollinated violet. 1. Reproductive correlates of floral variation. Biol. J. Linn. Soc. 40, 263–274 (1990).

14. Herrera, C. M. Selection on Floral Morphology and Environmental Determinants of Fecundity in a Hawk Moth‐Pollinated Violet. Ecol. Monogr. 63, 251–275 (1993).