Senecio moqueguensis Montesinos, 2014

Tubee, Daniel B. Montesinos, 2014, Three new caespitose species of Senecio (Asteraceae, Senecioneae) from South Peru, PhytoKeys 39, pp. 1-17 : 2-4

Senecio moqueguensis Montesinos sp. nov. Figs 1 , 4A , 5

Diagnosis.

The new species is morphologically similar to Senecio pucapampaensis but is clearly distinguished by the leaf lamina oblong-spathulate (vs. cuneiform), leaf surface covered by thin trichomes (vs. glabrous), corolla yellow (vs. white), calycular bracts linear-oblong, 6-9 mm long (vs. linear, 6-7 mm long), and phyllaries 9-12 (vs. 12-14).

Type.

PERU. Moquegua Region, General Sánchez Cerro Province, Ubinas District, NW of Tassa, terrestrial on clayey rocky soils on the plateau peaks near Lake Pacosani, elevation 4653 m, 16°06'43"S, 70°44'45"W, 3 April 2009, Montesinos 2400 (holotype USM!, isotypes MO 2383567, HUPCH 4185, CPUN, WAG 0246107).

Description.

Perennial herb, rhizomatous, creeping, low-growing, forming mats 2-4 cm tall and up to 60 cm in diam. Trichomes glandular, somewhat dense and irregularly distributed, multicellular, whitish transparent, 0.1-0.3 mm long and 0.05-0.1 mm wide and composed of 4-8 subrotund cells (each 30-50 µm long), apical cell rotund. Stems 1-3 cm long, often densely branched and leafy in the central part, rooting. Leaves cauline, lamina oblong-spathulate, 8-12 mm × 1-2.5 mm, sparsely covered by thin trichomes on the margins, lower and upper surfaces except at the base; base truncated, apex subpinnatifid; young leaves dark green with yellowish margins, turning light green-greyish with age. Synflorescences of solitary sessile or subsessile terminal capitula. Capitula homogamous, discoid. Involucres at first broadly cylindrical, gradually turning campanulate with age, ca. 7-10 mm long × 6-8.5 mm wide). Calycular bracts linear-oblong (6-9 mm × 1-2.5 mm), whitish green on the surface and whitish along the margins, with scarce trichomes near the midrib and margins, apex dark brown covered with short light-brown trichomes. Phyllaries 9-12, connate, 5-8 mm long × 0.7-1.2 mm wide, oblong-lanceolate, covered with thin trichomes sparsely on the surface and densely along the margins, apex greenish grey and dark brown with short white multicellular trichomes. Florets 24-28; corolla tubular, abruptly constricted near the base, 5-lobed, each lobe 0.5 mm long, bright yellow, tube 3-5 mm long × 0.8-1 mm wide; anthers linear-lanceolate, 1.5-2.5 mm long, 0.2-0.4 mm wide, ecalcarate, terminal appendages lanceolate, obtuse, margin whitish transparent and becoming yellow towards the centre; style dark yellow, truncate, papillae covering the whole surface of the apex. Achenes cylindrical, covered with trichomes, 1.8-2.5 mm long and 0.4-0.8 mm wide, light brown; carpopodium symmetrical in a small ring; pappus of smooth bristles, white, silky, 5-6 mm long, with fine single setulae.

Ecology and distribution.

Terrestrial plant on clayey rocky soils on the peaks of the highland summits and grasslands in the north of Moquegua Region, at elevations of ca. 4500 to 4800 m. Co-occurring species include Azorella compacta Phil., Calamagrostis vicunarum (Wedd.) Pilg., Pycnophyllum molle Remy, and Festuca spp. Flowers and fruits between March and April.

Etymology.

The specific epithet refers to Moquegua, where the only three collections are known from the north of the department.

Additional material examined

(paratypes). PERU. Moquegua Region, General Sánchez Cerro Province, Ubinas District, terrestrial on bare clayey soils in the verges of the road east Pillone town, elevation 4584 m, 16°10'02"S, 70°49'56"W, 24 March 2013, Montesinos 4022 (USM, HUSA). Moquegua Region, General Sánchez Cerro Province, Ubinas District, NW of Tassa, terrestrial on bare clayey soils in the verges of the road to Lake Cochapata, elevation 4687 m, 16°08'56"S, 70°43'0.30"W, 9 December 2013, Montesinos 4200 (CUZ).

Discussion.

A comparison of the material has shown that Senecio moqueguensis is most similar to Senecio pucapampaensis and Senecio tassaensis sp. nov. Together with Senecio evacoides , Senecio expansus , Senecio repens and Senecio humillimus , it forms a coherent morphological and geographical group within Senecio subser. Caespitosi which occurs from central Peru to northwest Argentina and is characterized by the presence of trichomes on stems, leaves and involucres. Senecio moqueguensis can be distinguished from Senecio pucapampaensis by the dense caespitose mat habit, leaves, calycular bracts, corolla color, involucres and achene morphology as summarised in Table 1 . Senecio moqueguensis can be distinguished from Senecio evacoides , Senecio expansus and Senecio repens by the habit, density of trichomes, leaf shape and length, as well as by the calycular bracts and phyllary length and form.

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 100 km² (ca. 50 km²) (B1); only three populations are known (B1b); habitat inferred to be continuing to decline (B1b(i-iii)); population estimated to number fewer than 300 individuals (D). The suitable habitats for Senecio moqueguensis on the mountain summits near the set of lakes in the Ubinas district are regarded as endangered because overgrazing of grasslands, changes in annual rainfall, volcanic activity, and exploitation of natural resources may all potentially reduce their extent.

Figures

Figure 1. Senecio moqueguensis Montesinos. A Leaf (upper side) B Leaf (underside) C Phyllary 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.