Pamphalea tenuissima Trujillo, Bonifacino & Pasini, 2019

Trujillo, Cristina, Bonifacino, José M. & Pasini, Eduardo, 2019, Pamphalea tenuissima (Nassauvieae, Asteraceae), a new species from southern Brazil, Phytotaxa 392 (1), pp. 61-66 : 62-65

Pamphalea tenuissima Trujillo, Bonifacino & Pasini , sp. nov. ( Figs. 1–3 )

Type:— BRAZIL. Rio Grande do Sul: São José dos Ausentes, distrito Silveira, RS-020, calle asfaltada, camino a Silveira, lado izquierdo, borde alambrado, sitio encharcado, con Sphagnum sp. , Lat. 28˚42’28.9” S, Long. 50˚0’2.6” W, 10 December 2015, Pasini et al. 1078 (holotype MVFA).

Rosulate herbs 15.5–60 cm high; stems decumbent, forming secondary rosettes and adventitious roots on basal nodes, sometimes main stems erect and secondary decumbent, internodes 0.3–8.5 cm long, glandular trichomes sparse to absent. Leaves alternate, arranged in a rosette, sessile, 8–20.6 × 1–2 cm, pseudopetiole 2–14 cm long, flat, sheathing, lamina narrowly elliptic to obovate, margin lyrate-pinnatisect, attenuate at the base, apex acute, apical lobe 0.25–1.5 × 0.1–1.4 cm, ovate to elliptical, 3–5-lobed, deeply incised, lateral lobes (5–)6–12 pairs, 0.2–1.2 × 0.05–0.4 cm, very thin, herbaceous, entire to 2 lobed due to a deep incision, 1 pair sometimes 1-dentate, glabrous. Cauline leaves alternate, sessile, 0.2–13.2 × 0.05–2.1 cm, similar in shape to basal leaves, semi-amplexicaul, apex acute, margin dentate only at base, with very deep incisions, glabrous, thin and herbaceous. Capitulescences paniculiform with peduncles attached on one side of rachis, heads 2 to 25, peduncles 2–6.4 cm long, glandular trichomes very sparse; bracts 2, 0.8–1.5 × 0.5–1 mm, ovate, scarious. Involucres 2.5–3.5 × 2–3.5 mm, cylindrical; phyllaries 8(–10), arranged in one series, imbricate, 2.2–3.4 × 0.8–1.5 mm, elliptic to narrowly ovate, sometimes obovate or oblong, apex mucronate, margin scarious, glandular trichomes present towards the apex. Receptacles convex, glandular trichomes sparse. Florets 12– 20, isomorphic, bisexual, corollas bilabiate, tube 1.3–1.6 mm long, glandular trichomes present mainly in the ventral and lateral areas, abaxial lip 2–3.2 × 1.2–2 mm, ovate to elliptical, limb 3-toothed, white, adaxial lip 1.3–2 × 0.8–1 mm, ovate, white, sometimes yellow at base. Anthers 1.1–2 mm long, dorsifixed, base sagittate, apical appendages 0.5–0.7 × 0.2–0.25 mm, narrowly elliptic to ovate, collar 0.25–0.4 × 0.1–0.2 mm. Style 1.5–2.6 mm long, style branches 0.4–0.7 mm long, apex truncate, penicillate, sterile appendages ca. 0.1 mm long, nectariferous disk ca. 0.1 mm high. Achene 1.9–2 mm long, obovoid, with a short carpopodium, sparsely covered by twin trichomes.

Note 1:—Throughout the history, the generic name was spelled two ways: “ Panphalea ” with “n” or “ Pamphalea ” with “m”. Katinas (1995) and Katinas et al. (2008) proposed to use the original form “ Panphalea ” as originally published by Lagasca (1811), while Platt et al. (2016) proposed to maintain the spelling correction made by Candolle (1812). The spelling correction is in accordance with Art. 60.1 of the International Code of Nomenclature for algae, fungi and plants ( Turland et al. 2018). “ Pamphalea ” is a compound word formed by the junction of the Greek roots “pan” and “phalos”, where the dental consonant “n” in juxtaposition becomes the labial “m” ( Platt et al. 2016). In the present work, the spelling “ Pamphalea ” is followed.

Note 2:—The glandular trichomes present in Pamphalea tenuissima are of biseriate vesicular beta subtype ( Ramayya 1962).

Note 3:— Pamphalea tenuissima is morphologically most similar to P. cardaminifolia , from which it differs by more finely dissected leaves with a softer texture ( Fig. 2 ) and all or most of its stems being decumbent. Pamphalea cardaminifolia has an erect stem and coarsely dissected, chartaceous leaves. Plants of Pamphalea tenuissima seem to support themselves in surrounding vegetation, developing adventitious roots on nodes; they are generally associated with Sphagnum sp. on flooded soils. Both Pamphalea tenuissima and P. cardaminifolia occur in Rio Grande do Sul in waterlogged habitats, but P. cardaminifolia has not been observed growing with Sphagnum sp.

Distribution and habitat:—Southern Brazil; so far considered endemic to the South Brazilian highland grasslands in the state of Rio Grande do Sul. It occurs on waterlogged soils associated with Sphagnum , or sometimes on marshes dominated by Eriocaulaceae ( Figs. 3–4 ).

Phenology:—Flowering from November to December, fruiting from December.

Additional specimens examined (paratypes):— BRASIL. Rio Grande do Sul: São José Dos Ausentes, [28˚42’32.7” S, 50˚11’9.7” W], 9 December 2015, Pasini et al. 1076 ( MVFA) ; from São José dos Ausentes to Silveira, left side, in humid low to 500 m of registered coordinates, [28˚39’23.17” S, 49˚57’9.71” W], 10 December 2015, Pasini et al. 1079 ( MVFA) ; [28˚35’17.53” S, 49˚50’38.65” W], 10 December 2015, Pasini et al. 1085 ( MVFA) ; São José dos Ausentes, 21 November 2007, Schneider 1547 ( ICN 152230 !) .

Figures

FIGURE 1. Illustration of Pamphalea tenuissima. A. Habit. B. Leaf from basal rosette, al: apical lobe, ll: lateral lobe. C. Bract. D. Phyllary. E. Floret (achene removed); note glandular trichomes at the base of corolla. F. Stamen (note anther collar and dorsal insertion of filament). G. Style, nd: nectariferous disk. H. Achene. Drawn by Trujillo, based on the holotype (Pasini et al. 1078; MVFA).

FIGURE 2. Compared leaf morphology of Pamphalea cardaminifolia and Pamphalea tenuissima A. Rosette leaf of P. cardaminifolia. B. Rosette leaf of P. tenuissima. C. Cauline leaf of P. cardaminifolia. D. Cauline leaf of P. tenuissima.

FIGURE 3. Pamphalea tenuissima. A. Habit. B, C. Cauline leaves. D. Rosette leaf. E, F. Habit, the main rosette not shown in picture. G. Head, lateral view. H. Head, superior view. Photographs: Bonifacino.