Pentacalia aedoi J.Calvo & Buira, 2018

Calvo, Joel & Buira, Antoni, 2018, Two new species of Pentacalia (Compositae, Senecioneae) from northern Andes, Phytotaxa 364 (2), pp. 193-201 : 194-197

1. Pentacalia aedoi J.Calvo & Buira , sp. nov. ( Fig. 2 )

Type: — COLOMBIA. Putumayo: Santiago, páramo del Bordoncillo , 01º07’37”N 77º04’49”W, 3025 m, 12 Dec 2017, A. Buira 3284 (holotype: MA 922466 ; isotypes: COL, MA 922467 , MO) .

Pentacalia aedoi differs from the other species with lateral, axillary synflorescences by its racemiform-thyrsoid synflorescences clearly longer than subtending leaves, composed of disciform capitula clustered in groups of 2–3(–4), subsessile or on short pedicels.

Scandent woody vines, indefinitely elongate. Stems terete, coarsely rugose, covered by tomentose-arachnoid indumentum and resinous exudate, usually becoming deciduous, not or narrowly fistulous. Leaves alternate, slightly fleshy on living plants, drying coriaceous, usually reflexed; lamina lanceolate-elliptic, 5–8 cm long, 3–4 cm wide, acute, mucronate, cuneate to obtuse, entire (sometimes with remote mucronate denticulations), slightly revolute, adaxial surface glabrous, lustrous with secondary venation conspicuous, abaxial surface weakly arachnoid (more abundant on the midrib) and somewhat protruding secondary venation; petiole 0.7–1.5 cm, arachnoid. Synflorescences lateral, axillary, narrowly racemiform-thyrsoid, longer than subtending leaves, 8–20 cm long, patent to reflexed, congested, with lanceolate bracts 1–1.5 cm long at the base of each synflorescence branch, slightly leafy the basal ones; synflorescence branches densely tomentose-arachnoid; capitula disciform (20–55 per synflorescence), clustered on groups of 2–3(–4), subsessile or on short pedicels 0.5–2 mm long arising from the apex of the synflorescence branches, rarely with tiny linear bracteoles. Involucre cylindrical, 7.5–8 mm long, 4.2–4.4 mm wide, with arachnoid indumentum at the base. Involucral bracts 6–8, 6–6.5 mm long, 1–2 mm wide, with scarce arachnoid indumentum, slightly fleshy (on living plants); supplementary bracts 2–3, 2.9–4.1 mm long, ca. 0.8 mm wide, ca. a half as long as the involucral bracts, with arachnoid indumentum. Female florets 5–6, tubular, 4.7–5.1 mm long, 4–5-lobed, pale yellowish; bisexual florets 15–17, 6–6.5 mm long, 5-lobed, pale yellowish.Anther’s base shortly sagittate, ca. a half as long as the filament collar. Style-branches truncate with a crown of sweeping-hairs. Achenes 1.6–2 mm long, 0.5 mm wide, cylindrical, blackish to yellowish, glabrous, 5–6-ribbed; pappus 6–6.5 mm long, barbellate, whitish. Chromosome number: unknown.

Distribution and habitat: —Known from the slopes of the Bordoncillo paramo between the Colombian departments of Putumayo and Nariño ( Fig. 3). It grows in humid subparamo, between 2900–3100 m.

Phenology: —Seen in bloom from October to December.

Etymology: —It is a pleasure to dedicate this species to the Spanish botanist Carlos Aedo, who unconditionally supported us in all our projects.

Additional specimens examined (paratypes): — COLOMBIA. Nariño: Pasto, corregimiento de El Encano, km 33 vía Sibundoy, 2900 m, 8 Oct 1985, B.R. Ramírez 371 (COL 341608). Putumayo: corregimiento San Antonio de Bellavista, páramo del Bordoncillo, 3100 m, 12 Nov 2016, G.A. Zambrano 7 (CAUP 045068).

Discussion: —This species is characterized by displaying only lateral, axillary synflorescences, and having disciform capitula with 5– 6 female florets. The narrowly racemiform-thyrsoid synflorescences are clearly longer than the subtending leaves, and the abaxial surface of the leaves are weakly arachnoid. The leaf margins are usually entire as the type material shows, however, plants with remote mucronate denticulation were also observed. It is interesting to note that the stem indumentum is composed of multicellular trichomes with the basal cells lageniform, somewhat rigid, and persistent, and the apical cells flageliform and quickly deciduous, which resemble arachnoid indumentum after being teased apart. As the plant ages, the stem surface usually becomes coarsely rugose because the basal cells of the trichomes mix with the resinous exudate generating a sort of protuberances.

The most morphologically similar species are P. retroflexa Díaz-Piedrahita in Díaz-Piedrahita & Méndez (1998: 188), P. uribei Cuatrecasas (1985: 171) from Colombia, and P. cazaletii Robinson & Cuatrecasas (1993: 286) , P. hurtadoi Robinson & Cuatrecasas (1993: 287) , P. moronensis Robinson & Cuatrecasas (1993: 288) , P. napoensis Robinson & Cuatrecasas (1993: 289) , and P. palaciosii Robinson & Cuatrecasas (1993: 289) from Ecuador.

The new species is readily distinguishable from P. retroflexa and P. uribei because of its disciform capitula; in the latter species are discoid, with all florets bisexual. From Pentacalia uribei , which is the morphologically closest species, it can furthermore be separated by the synflorescence length (8–20 cm long, clearly longer than subtending leaves vs. 3–6(–9) cm long, usually as long as subtending leaves in P. uribei ), number of capitula per synflorescence (20–55 vs. 10–20 in P. uribei ), shape and size of the synflorescence bracts (lanceolate, somewhat leafy the basal ones vs. linear, reduced in P. uribei ), and synflorescence type (capitula arrangement). The synflorescences are racemiform-thyrsoid in P. aedoi , composed of capitula clustered in groups of 2–3(–4), subsessile or on short pedicels, arising from the apex of the synflorescence branches. In contrast, the capitula of P. uribei are usually solitary and arise directly from the main axis, resulting in a strictly racemiform synflorescence. This latter species is known from northern Cauca Department to Risaralda Department along the Cordillera Central, plus a locality in the Cordillera Oriental (Monterredondo, Cundinamarca Department). The other similar species from Colombia is P. retroflexa , which is only known from the southern Cordillera Oriental, near Altamira in NE Huila Department. It has longer pedicels than P. aedoi (3–6 mm vs. 0.5–2 mm long, or almost subsessile) and the leaves are glabrous on both faces.

The Ecuadorian species P. hurtadoi , P. moronensis , and P. napoensis have also lateral, axillary synflorescences, but all of them display discoid capitula and glabrous stems and leaf laminas. In P. moronensis , with also racemiform-thyrsoid synflorescences longer than subtending leaves, the length of the pedicels is clearly longer than in P. aedoi . Pentacalia hurtadoi and P. napoensis (both from Napo Province and greatly similar) display mostly racemiform synflorescences, sometimes thyrsoid at the base, but not racemiform-thyrsoid as in P. aedoi . Another species found nearby is P. palaciosii . This species is very similar to the latter two species except for its disciform capitula. It can be differentiated from P. aedoi by the leaf length (10–15.5 vs. 5–8 cm in P. aedoi ), leaf indumentum (glabrous vs. weakly arachnoid beneath in P. aedoi ), and number of female florets (ca. 4 vs. 5–6 in P. aedoi ). Another species with lateral synflorescences and disciform capitula is P. cazaletii from the western side of the Andes (W Pichincha and Santo Domingo de los Tsáchilas provinces). However, any confusion with P. aedoi is unlikely because the synflorescences of P. cazaletii are notably laxer and with larger synflorescence bracts. Its plainly glabrous leaves with inconspicuous secondary venation, or almost so, is another character that also helps to easily differentiate each other.

Key to the Colombian Pentacalia species with lateral, axillary synflorescences (adjusted from Díaz Piedrahita & Cuatrecasas (1999) and Díaz-Piedrahita & Rodríguez-Cabeza (2011)).

1. Capitula radiate......................................................................................it continues to Díaz-Piedrahita & Rodríguez-Cabeza (2011)

- Capitula discoid or disciform.............................................................................................................................................................2

2. Capitula disciform; synflorescences racemiform-thyrsoid...................................................................................................... P. aedoi

- Capitula discoid; synflorescences racemiform or racemiform-thyrsoid............................................................................................3

3. Synflorescences racemiform-thyrsoid longer than subtending leaves ............................................................................. P. retroflexa

- Synflorescences racemiform as long as subtending leaves or almost so................................................................................ P. uribei

Figures

FIGURE 2. Pentacalia aedoi. A. Lateral, axillary synflorescences. B. Leaves. C. Detail of the capitula (arrows show some female florets of one capitulum). D. Habit.