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| Viola guaxarensis M. Marrero, Docoito Díaz & Martín Esquivel
in Gómez, Esquivel, Díaz & Izquierdo, 2020.
DOI: 10.3372/wi.50.50102
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Abstract
Viola guaxarensis M. Marrero, Docoito Díaz & Martín Esquivel, sp. nov., belonging to V. sect. Melanium Ging. (Violaceae), is described and illustrated. It is a small chamaephyte currently known in only two localities within the high-mountain zone of Tenerife, Canary Islands. Data on aspects of its morphology, ecology, rarity and conservation status are provided, as well as the differences between this new taxon and the other two species from the Canary Island high-mountain habitats, V. cheiranthifolia Humb. & Bonpl. and V. palmensis Webb & Berthel., which are presumed to be the closest relatives.
KEYWORDS: Canary Islands, endemic, high mountain, new species, Teide National Park, Tenerife, Viola cheiranthifolia, Viola guaxarensis, Viola palmensis, Viola sect. Melanium, Violaceae
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| Fig. 2. Viola guaxarensis. – A: general aspect; B: upper leaf with stipules; C: ovary, style and stigma; D: anther; E: lower leaf; F: sepal; G: peduncle bracteoles; H: flower, lateral view; I: flower, frontal view; J: seed. – Drawn from TFC 53319 by M. V. Marrero Gómez. |
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| Fig. 4. Morphological characteristics of Viola guaxarensis. – A: flower; B: stipules; C: peduncle bracteole; D: upper leaves; E: lower leaf. |
Viola guaxarensis M. Marrero, Docoito Díaz & Martín Esquivel, sp. nov.
Diagnosis — The new species differs from Viola cheiranthifolia Humb. & Bonpl. mainly by its larger size, longer and wider leaves, 2- or 3-sect outer stipules with main lobe up to ¼ the length of the leaves, longer peduncles, violet and slightly hastate peduncle bracteoles, sinuatecrenate sepal appendices with purple tones, and glabrous spur. It differs from V. palmensis Webb & Berthel. by its shorter, wider and non-falcate leaves with petiole never reaching the lamina length, shorter stipules, slightly hastate peduncle bracteoles, and shorter, wider, glabrous spur (Table 1, Fig. 3, 4).
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| Fig. 5. Habitat of Viola guaxarensis (the blue-flowered plants). A: Spain, Canary Islands, Tenerife, Montaña Guajara, Jun 2019, photograph by M. Suárez Izquierdo. |
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| Fig. 5. Habitat of Viola guaxarensis (the blue-flowered plants). B: same locality, May 2019, photograph by J. R. Docoito Díaz. |
Distribution and ecology — Endemic to the high-mountain zone of Tenerife, Canary Islands, Spain, where it is known from only two localities (Fig. 1). Locally common near the summit of Montaña Guajara (..., 2600 m a.s.l.) with nearly 3000 individuals, but scarce (with only a few dozen individuals) at the second locality, Topo de la Grieta 3 km to the northeast (..., 2300 m a.s.l.). In general, the habitat is characterized by low or moderate slopes, with acid and rocky substrates sometimes mixed with pumice. These environments are subject to relatively strong winds (Wildpret & Martín 2005) and frequent winter frosts. Vegetation at the sites is dominated by a low mixed cushion-shrub community (Fig. 5) with Adenocarpus viscosus (Willd.) Webb & Berthel. subsp. viscosus (Fabaceae) one of the more common species. Other Canary Island endemics present are Erysimum scoparium (Brouss. ex Willd.) Wettst. (Brassicaceae), Nepeta teydea Webb & Berthel. (Lamiaceae), Sparto-cytisus supranubius (L. f.) Christ ex G. Kunkel (Fabaceae), and Tolpis webbii Sch. Bip. ex Webb & Berthel. (Asteraceae).
Habitat — The leaves and flowers of both Viola cheiranthifolia and V. guaxarensis are smaller than V. palmensis, possibly as an adaptation to a more xeric environment; the habitat of the two Tenerife taxa is much more arid (rainfall <500 mm/year) than that of the La Palma V. palmensis (rainfall c. 800 mm/year; Martín Osorio & al. 2007). The habitats of the Tenerife taxa also differ in temperature and precipitation, with V. cheiranthifolia occupying colder sites (annual average temperature 3.5–8.8°C) than V. guaxarensis (11.1°C). The pronounced reduction in some morphological structures in V. cheiranthifolia or even the disappearance of some of them (e.g. stipules) may indicate adaptations to a colder and harsher environment.
Etymology — The specific epithet refers to Montaña Guajara, the main location of the new species.
Manuel V. Marrero Gómez, José L. Martín Esquivel, José R. Docoito Díaz and Manuel Suárez Izquierdo. 2020. Viola guaxarensis (Violaceae): A New Viola from Tenerife, Canary Islands, Spain. Willdenowia. 50(1); 13-21. DOI: 10.3372/wi.50.50102
