Hysterionica chamomilloides Deble, 2021

Deble, Leonardo Paz, 2021, Hysterionica chamomilloides (Asteraceae: Astereae) a new species from the grassland ecosystem of Río de La Plata, Phytotaxa 482 (1), pp. 36-44 : 37-41

Hysterionica chamomilloides Deble , sp. nov. ( Figs. 1 and 2 )

Type:— BRAZIL. Rio Grande do Sul: Quaraí, Palmar do Coatepe , em afloramento rochoso, encosta do cerro, 4 November 2013, L.P. Deble et al. 13588 (holotype CTES!, isotype PACA!) .

Diagnosis: — Hysterionica chamomilloides is morphologically related to H. filiformis by its woody habit, linear-filiform leaves, and longer and whitish trichomes, which cover the stems, leaves, peduncles and heads. Nevertheless, the new species differs by its smaller heads, smaller and white colored ray flowers, with 4–6 mm long (vs. yellow, 8–15 mm long), size of disk flowers (1.8–3 vs. 3.5–5 mm), cypselae slightly compressed, few ribbed and smaller, and outer pappus composed by a crown of scales (vs. few barbellate bristles, which do not form a crown).

Description: —Perennial subshrubs, densely ramified at base, 15–60 cm high; stems several, ascendant or erectascendant, not ramified or 2–3-branched in distal third, 12–45 cm long, with abundant longer and whitish filiform trichomes. Leaves chartaceous, sessile, alternate, internodes 0.1–1.5 cm long, shorter towards base; leaf-blades linearfiliform, 15–55 × 0.4–1 mm, apex obtuse or acute, apiculate, margin entire, revolute, base truncate, both slides with longer filiform trichomes 800–2.400 µm. Heads radiate, ca. 10–16 mm diameter, pedunculate, peduncles 2.8–14 cm long; involucres hemispheric, resinous, 4–5 × 7–10 mm; phyllaries in 3 series, subequal, at apex subulate glutinous; outer phyllaries linear-lanceolate, 2.5–3.3 × 0.3–0.4 mm, dorsally densely covered by longer whitish filiform trichomes 200–1.100 µm; middle phyllaries lanceolate or elliptic, 3–4 × 0.4–0.8 mm, dorsally with scattered whitish filiform trichomes; inner phyllaries elliptic or lanceolate-elliptic, 2.5–3.5 × 0.5–0.8 mm. Clinanthium slightly convex, alveolate. Ray flowers 1–2-seriate, pistillate, white; corolla 4–6 mm long, apically ligulate; tube hairy, 0.9–1.6 mm long; ligule linear-elliptic, 3–4.4 × 0.3–0.7 mm; style filiform, 0.5–1.8 mm long, branches filiform, ca. 0.5 mm. Disk flowers ca. 100–140, perfect, corolla 1.8–3 mm, with an ampliated throat, 5-dentate at apex, teeth 0.3–0.4 mm; style filiform, 1.5– 2 mm long, style-branches 0.3–0.4 mm, truncate at apex, covered by sweeping trichomes. Cypsela obovate, slightly compressed, 4–5-ribbed, 0.8–1.4 × 0.4–0.5 mm, densely covered by sericeous trichomes 350–700 µm long. Pappus 2-seriate; outer series composed by ca. 10 scales, 0.5–1 mm long; inner series composed by 9–18 bristles, 1.6–2.5 mm long.

Etymology:—The epithet chamomilloides refers to the general vegetative aspect of the plant and its heads, with white ray flowers and yellow disk flowers, which superficially resemble Matricaria chamomilla Linnaeus (1753: 891) .

Material Examined:— BRAZIL. Rio Grande do Sul: Santana do Livramento, Serra do Caverá, Cerros verdes, na encosta rochosa, 31 March 2018 , L.P. Deble & B.P. Moreira 18021 (CTES!); Cerro dos Munhoz , no topo do cerro, 11 November 2012 , L.P. Deble et al. 11404 (HDCF!); Quaraí, Palmar de Coatepe , entre rochas, 11 November 2019 , L.P.

Deble & B.P. Moreira (CTES!); estrada municipal da associação rural, afloramento rochoso de origem basáltica 6km após a entrada, 12 October 2018, L.P. Deble & B.P. Moreira 18294 (CTES!). URUGUAY. Rivera: Tranqueras, ruta 30, subida de Peña, 2 November 2019, L.P. Deble & B.P. Moreira 18411 (MVFA! CTES!). Artigas: Mazoller, af. basáltico, 10 November 2018, L.P. Deble & B.P. Moreira 17856 (MVFA!, CTES!) .

Phenology:—Flowering and fruiting period from October to December and February to March. Flowers and fruits sporadically registered during other months of the year.

Distribution and habitat:— Hysterionica chamomilloides was found on mountainous places in Rivera and Artigas Departments, northern Uruguay, and Quaraí and Santana do Livramento municipalities, southwestern Rio Grande do Sul State, Brazil. The plants grow on cliffs of rocks of different origin, mainly volcanic and silicified sandstones, which comprise the principal geological formation of the region.

Conservation:—The populations of Hysterionica chamomilloides have a geographical distribution of less than 20,000 km ² and an area of occupancy of less than 2,000 km ². The new species have less than 10 populations known, which generally contain 5–20 individuals. Based on the area of occurrence, threats observed and others criteria of IUCN (2017), it is reasonable to assess this species as Vulnerable VU: B1 + B2 a, b(i, ii, iii, iv) + D.

Discussion:— Hysterionica chamomilloides by its woody habit, filiform leaves covered by longer and hispid and whitish filiform trichomes, and general aspect resembles H. filiformis ; however, H. chamomilloides can be easily distinguished by its smaller heads (6–8 × 10–16 mm vs. 8–10 × 16–24 mm), smaller and white ray flowers 4–6 mm long (vs. yellow, 8–15 mm long), and size of disk flowers (1.8–3 vs. 3.5–5 mm). From Hysterionica pinifolia the new species differs by its linear-filiform leaves, 0.4–1 mm wide, densely covered by longer and whitish trichomes (vs. linear-oblong or linear-lanceolate, 1–2 mm wide, glabrous or with scarce trichomes), smaller heads (6–8 × 10–16 mm vs. 9–12 × 16–26 mm), shorter and white ray flowers, 4–6 mm long (vs. yellow or golden-yellow, 9–17 mm long), and size of disk flowers (1.8–3 vs. 5–7.5 mm). Furthermore, H. chamomilloides can be segregated from H. filiformis and H. pinifolia by the outer pappus which is composed by a crown of scales (in the others two species mentioned the outer pappus is composed by few barbellate bristles, which do not form a crown), and cypselae with 4–5 ribs, obovate and slightly compressed (vs. 7–10 ribs, obovate-fusiform, not compressed).

Nesom (1994a), when rehabilitating the genus Neja , recognized the woody habit and the fusiform cypselae with 7–11 ribs of this genus to distinguish it from Hysterionica , which was characterized by its herbaceous or weakly woody habit and strongly compressed cypselae with only 2 lateral ribs.Additionally, the type of Neja , N. filiformis [ N. gracilis ], and other related species possess the outer pappus composed by few barbellate bristles, which do not form a complete crown. Hysterionica jasionoides , the type of the genus, also has this type of pappus, while several other species of Hysterionica show the outer pappus composed by scales forming a crown. Hysterionica pinnatiloba Matzenbacher & Sobral (1996: 17) , H. pinnatisecta Matzenbacher & Sobral (1996: 16) , and H. nebularis , all these species described after of the work of Nesom, have the woody habit (as Neja ), and cypselae strongly compressed, with the outer pappus composed by scales that form a crown (as the remaining species of Hysterionica ). Hysterionica chamomilloides is also quite interesting, by its pappus and cypselae similar to those found in Hysterionica , and contrasts by the woody habit and the vegetative morphological similarity with the species currently recognized in Neja .

New discoveries made in this group, namely the new species with intermediate morphologic characters, make it difficult to separate Hysterionica from Neja , and we adopt a broader concept firstly stablished by Bentham & Hooker (1873) and followed in recent works (e.g., Sancho & Vitali 2014), which considered Neja a synonym of Hysterionica . With the description of this new species, Hysterionica now comprises 17 species: Hysterionica aberrans , H. bakeri Hicken (1924: 149) , H. chamomilloides , H. cabrerae , H. dianthifolia ( Grisebach 1879: 174) Cabrera (1946: 352) , H. filiformis , H. glaucifolia , H. jasionoides , H. marginata ( Grisebach 1866: 149) Gomez de la Maza (1890: 272) , H. matzenbacheri , H. nebularis , H. pinifolia , H. pinnatiloba , H. pinnatisecta , H. pulchella Cabrera (1931: 323) , H. pulvinata , and H. resinosa . Except for H. marginata , endemic to the island of Cuba (see Nesom 1993), the remaining species are distributed in southern Brazil, Argentina, Uruguay and Paraguay.

Figures

FIGURE 1. Hysterionica chamomilloides. A. Habit. B. Capitulum. C. Ray flower. D. Disk flower. E. Cypsela. F. Phyllaries. G. Leaf and detail of stem. H. Trichomes (from L.P. Deble et al. 13588).

FIGURE 2. Hysterionica chamomilloides. A. Habit. B. Detail of the plant. C. Capitulum, upper view. D. Capitulum, lateral view (A–B from L.P. Deble et al. 13588, C–D from L.P. Deble & B.P. Moreira 18411).