Senecio tassaensis Montesinos, 2014

Tubee, Daniel B. Montesinos, 2014, Three new caespitose species of Senecio (Asteraceae, Senecioneae) from South Peru, PhytoKeys 39, pp. 1-17 : 6-7

Senecio tassaensis Montesinos sp. nov. Figs 3 , 4C , 5

Diagnosis.

Similar to Senecio moqueguensis but clearly distinguished by the leaf lamina obovate-spathulate (vs. oblong-spathulate), leaf length 6-9 mm (vs. 8-12 mm), leaf surface densely covered by trichomes (vs. sparsely covered), trichomes 0.3-1.2 mm long (vs. 0.1-0.3 mm long), corolla white (vs. yellow), calycular bracts 4-6 mm long (vs. 6-9 mm), phyllaries 12-16 (vs. 9-12), involucre length 6-8 mm (vs. 7-10 mm), and achene length 1-1.2 mm (vs. 1.8-2.5 mm).

Type.

PERU. Moquegua Region, General Sánchez Cerro Province, Ubinas District, NW of Tassa, terrestrial on clayey rocky soils on the summits of Pirhuani peak, elevation 4657 m, 16°09'58"S, 70°43'49"W, 07 April 2011, Montesinos 3103 (holotype HUSA!, isotypes MOL, USM).

Description.

Perennial herb, tufted, up to 2-4 cm high and up to 4 cm in diam. Trichomes glandular, densely covering the plant, multicellular, whitish transparent, 0.3-1.2 mm long × 0.1-0.2 mm wide, composed of 6-10 ovate or elongate cells (each 60-80 µm long), apical cell rotund. Stems thick, <1 cm long, often densely branched and leafy in the central portion. Leaves arranged in irregular rosettes, lamina obovate-spathulate, 6-9 mm × 1-2.5 mm, densely covered by thin trichomes on the margins; base truncated and apex pinnatifid; lower and upper surface of the leaves gradually becoming shorter towards the tip; margin incised with 5-7 obtuse lobes or rarely acuminate; mature leaves with involute margins; young leaves green yellow turning greenish grey with age. Synflorescences of solitary sessile or subsessile terminal capitula. Capitula homogamous, discoid. Involucres at first cylindrical, turning campanulate with age (ca. 6-8 mm long × 5-7 mm wide). Calycular bracts ovate-oblong (4-6 mm × 1 mm), greyish green on the surface and covered with trichomes on the margins, dark brown apex covered apically with short brown multicellular trichomes. Phyllaries 12-16, connate, 5-8 mm long × 0.8-1.2 mm wide, linear-lanceolate, covered with thin trichomes scarcely on the surface and densely along the margins, apex dark brown and covered with short multicellular trichomes. Florets 18-21, corolla tubular, abruptly constricted near the base, 5-lobed, each lobe 0.2-0.4 mm long, purple pink gradually becoming pale white towards the tip, tube 2-2.5 mm long × 1 mm wide; anthers linear-lanceolate, 1.5-2 × 0.3-0.4 mm, terminal appendages lanceolate, acute to somewhat protuberant, bases ecalcarate; anthers margin white becoming dark yellow towards the centre; style dark purple, truncate, papillae covering the whole surface of the apex. Achenes ovate, striate, covered with trichomes, 1-1.2 mm long and 0.6-0.8 mm wide, pale yellow; carpopodium symmetrical in a shallow ring; pappus of smooth bristles, white, silky, 3.5-5 mm long, with fine single setulae.

Ecology and distribution.

Terrestrial plant on clayey rocky soils on the peaks of the highland summits of the Pirhuani peak, near Tassa town, Moquegua Region, at elevations of 4650-4700 m. It occurs with Azorella , Calamagrostis , Pycnophyllum , Mniodes , Senecio , and Xenophyllum . Flowers and fruits between March and April.

Etymology.

This Senecio is named after the town of Tassa (Moquegua Region), downslope of Pirhuani peak where the species was found.

Discussion.

Senecio tassaensis appears to be closely related to Senecio moqueguensis which grows at the same elevational range but approaches the known range of Senecio tassaensis within a few hundred metres. Senecio moqueguensis is generally distinctive in the series for its larger size, attaining dense ground mats, and for its yellow corolla. Senecio tassaensis has 12-16 phyllaries (vs. 9-12), an involucre length of 6-8 mm and achene length of 1-1.2 mm, being much shorter than in Senecio moqueguensis . Senecio tassaensis is relatively a very rare species with an estimated 100 individuals known. It is less similar to Senecio pucapampaensis , Senecio evacoides , Senecio expansus and Senecio repens , and can be distinguished on the basis of the habit, trichomes, leaf shape and length, calycular bracts and phyllaries length and shape as summarized in Table 1 .

Conservation status.

Following the criteria and categories of IUCN (2001), a preliminary status of Critically Endangered (CR) is assigned. The new species deserves protection because its total area of occupancy is less than 10 km² (ca. 5 km²) (B2); only one population is known (B2b); habitat inferred to be continuing to decline(B2b(i-iii)); population estimated to number fewer than 100 individuals (D). The suitable habitats for Senecio tassaensis on the mountain summits of Pirhuani peak in the Ubinas district are indicated as endangered, because changes in the annual rainfall, volcanic activity and exploitation of natural resources, may all reduce their extent.

Figures

Figure 3. Senecio tassaensis Montesinos. A Leaf (upper side) B Leaf (underside) C Phyllaries trichomes D Leaf trichomes E Capitulum F Calycular bracts G Phyllary H Stamens arrangement in a floret I Floret J Pappus bristles K Stamens L Style M Papillose stigma N Achene.

Figure 4. Habit photographs of: A Senecio moqueguensis B Senecio sykorae C Senecio tassaensis.

Figure 5. Distribution map showing collection and recorded sites for Senecio moqueguensis (red circles), Senecio sykorae (yellow squares) and Senecio tassaensis (green triangles). Inset: Photograph of the highland plains of Tassa, Moquegua, where populations of Senecio moqueguensis occur.