Mesanthophora rojasii ( Cabrera 1940: 133 ) Robinson (1999:76)

Soares, Gleison & Loeuille, Benoît, 2021, Notes in Brazilian Vernonieae (Asteraceae): two new combinations and a range expansion, Phytotaxa 522 (2), pp. 139-149 : 144-146

Mesanthophora rojasii ( Cabrera 1940: 133) Robinson (1999:76)

Perennial herbs, erect, 50–60 cm tall; branches cylindrical, glabrous. Leaves alternate, simple, sessile; blade lanceolate, 2–8 × 0.3–1.8 cm, concolorous, membranaceous, adaxially glandular-punctate, abaxially glabrous, margins entire to slightly sinuous, revolute, apex acute, base amplexicaul. Capitulescence seriate-cymose, terminal branches 14–28 cm long, leaf-like bracts sessile, 1.5–7 × 0.8–1.1 cm. Capitula 5–10, homogamous, discoid, short-pedunculate, inserted at the middle of internodes without subtending bracts; involucre 0.5–0.8 mm tall, widely campanulate, 5-seriate; phyllaries weakly imbricate, greenish, outer series ovate, 4–7 × 2–4 mm, inner series linear to lanceolate, 4–8 × 3–5 mm, glabrous, margins entire, apex acuminate or short-caudate; receptacle flat to slightly concave, naked. Florets 45–60, bisexual, fertile; corolla actinomorphic, 5-lobed, lilac, glabrous; corolla tube 2–4 mm long, corolla lobes 1.3–2 mm, papillose, apex acute; anthers brownish, 1.8–2.5 mm long, apical appendages acute, anther base sagittate; style shaft 5–7 mm long, lilac, glabrous throughout except for pubescent upper 0.4–0.6 mm beneath style arms, style arms 1–1.4 mm long, apex acute, pubescent outside, hairs acute, style base glabrous, lacking basal node. Cypsela turbinate to cylindrical, 1.8–2.3 × 0.8–1 mm, 10-ribbed, glabrous, brownish, carpopodium annular; pappus biseriate, unequal, outer series paleaceous, shorter than inner series, 0.9–1.2 mm long, persistent, inner series setose, 2.8–3.4 mm long, deciduous.

Specimen examined: — BRAZIL. Minas Gerais: Jaíba, Turno da Onça , 20 August 1984, M.C.B Teixeira & Carvalho s.n. ( MBM 145914 ) .

Additional specimen examined: — BRAZIL. Mato Grosso do Sul: Corumbá, Pantanal , 02 December 1987, A. Pott et al. 3630 ( CPAP) ; Fazenda Acurizal, Nabileque , 90 m, 19 December 1987, A. Pott et al. 3645 ( CPAP, MBM) ; Fazenda Bodoquena , 18 August 2004, G.A. Amador et al. 47 ( CGMS) ; Estação Carandazal , 19° 48’ 17” S, 57° 09’ 49” W, 102 m, 29 June 2011, D.S. Matos 17 ( CGMS) . Ladário , lote 42, 19 August 2011, P.P. Oliveira et al. 24 ( COR, SPF) .

Illustrations: — Cabrera (1940: 134, Fig. 1 ), Cabrera & Dematteis (2009: 238, Fig. 91).

Notes: — Mesanthophora Robinson (1992b: 172) is a small genus in the subtribe Mesantophorineae , comprising glabrous perennial herbs associated with limestone soils, with decurrent auriculate leaves and capitula emerging from the middle of internodes ( Robinson 2007). Two species are currently known: Mesanthophora brunneri Robinson (1992b: 172) and M. rojasii ( Cabrera & Dematteis 2009, Hind 2011). The former species is easily distinguished from the latter by its leaf shape (oblong-ovate vs. lanceolate) and leaf size (2–7 × 1–3 vs. 6–10 × 0.5–2 cm) ( Dematteis & Salgado 2001).

Mesanthophora rojasii occurs in the Chaco region in Bolivia (department of Santa Cruz), Paraguay (departments of Alto Paraguay, Concepción and Central), as well as in Brazil, in the Pantanal region of the state of Mato Grosso do Sul and now, for the first time, reported in the Caatinga domain, in northern Minas Gerais ( Fig. 4 ) ( Cabrera 1940, Cabrera & Dematteis 2009, Hind 2011, Roque et al. 2018). This species occurs over limestone outcrops in xerophytic vegetation (savannah, caatinga) or in carandazal (annually flooded vegetation composed of a native palm, Copernicia alba Morong in Morong & Britton (1893: 246)), the latter being closely associated with accumulation of sub-superficial carbonaceous concretions ( Silva et al. 2000). The notable new record in northern Minas Gerais (ca. 1,500 km from Mato Grosso do Sul) might be explained by the presence of similar limestone outcrops ( Oliveira et al. 2000) with xerophytic vegetation in both regions ( Rizzini 1997) and shows its likely adaptation to Seasonally Dry Forests in South America.

During our study of herbarium collections, we came across a single specimen from Minas Gerais, which makes the information provided on the voucher label doubtful, as it is an older collection (dated 1984) from a location with different environmental characteristics than those preferred by the species. To confirm its validity, we compared this voucher’s locality with other collections made by M.C.B. Teixeira & Carvalho on the same date and location. The voucher is one of many collections made by the collectors (especially M.C.B Teixeira) in the municipality of Jaíba between the years 1982 and 1984. The species identity remained undetermined at the time of collection. Based on this finding, we consider the location stated in the label to be correct and assume that the species was truly collected in Minas Gerais.

This is the third species of Mesanthophorinae recorded in the Caatinga domain, together with Acilepidopsis echitifolia (Mart. ex Candolle 1836: 60) Robinson (1989: 291) , in the state of Bahia, and Telmatophila scolymastrum Mart. ex Baker (1873: 170) , endemic to caatinga vegetation in the state of Piauí ( Nakajima 2020, Picanço et al. 2020). These monotypic genera differ mainly by characteristics of the leaves, capitulescence, position of the capitula and number of florets per capitulum ( Baker 1873, Robinson 1989, Robinson 1992b).

Figures

FIGURE 1. Holotype of Critoniopsis bradeana (RB00541935). Image: JSTOR Plants.

FIGURE 4. Geographic distribution of Mesanthophora rojasii, including the new record in the state of Minas Gerais.