Roquea multiserialis Loeuille & Antar, 2024

Loeuille, Benoît, Almeida, Roberto Baptista Pereira, Siniscalchi, Carolina M., Lusa, Makeli G. & Antar, Guilherme Medeiros, 2024, Roquea, a new genus of Lychnophorinae (Vernonieae, Asteraceae) from Brazil and its phylogenetic placement, Phytotaxa 675 (2), pp. 97-114 : 103-107

Roquea multiserialis Loeuille & Antar sp. nov., adhuc unica.

Type: — BRASIL. Minas Gerais: Monte Azul, Pico da Serra da Formosa, 15º14ʹ17.66ʹʹS, 42º49ʹ15.47ʹʹW, 1070–1805 m, 3 Mar 2023, R. B. Almeida et al. 1070 (holotype SPF!, isotypes K!, SAMES!) ( Figs. 5 , 6 ).

Treelet or shrub up to 2 m tall. Stems moderately branched, greyish, blackish towards base, pubescent, indumentum composed of long-stalked stellate trichomes, sometimes with forked arms or geminate or short-stalked and swollen stellate trichomes. Leaves shortly petiolate, 3–5 mm long, leaf sheath semi-amplexicaul, 2.2–4.1 × 2.9–5 mm, adaxially densely white pilose (unbranched long trichomes); blade rhombic, wide obovate, rarely wide elliptic, 2.6– 4.9 × 1.4–2.7 cm, venation eucamptodromous, midrib thick and flattened, furrowed, prominent abaxially, sunken adaxially, including secondary veins, chartaceous to subcoriaceous, conspicuously discoloured, adaxial surface green, dark green or nearly black in sicco, glabrescent with sparse short-stalked swollen stellate trichomes, tomentose in the midrib, especially near the base, glandular-punctate, abaxial surface greyish lanate, older leaves dark greyish, lanate, indumentum composed of dense short-stalked swollen stellate trichomes along midrib and venation and sparse darker long-stalked stellate trichomes in stomatal crypts, sometimes with forked arms or geminate, margin slightly thickened, entire or sinuate to crenate, especially near apex, apex obtuse or acute, sometimes retuse or acuminate, base attenuate or cuneate. Inflorescence axillary, capitula organised in a dense corymb; flowering branch 7.7–20.5 cm long, cylindrical or slightly flattened and four-angled, mostly near base of capitula, greyish, sometimes blackish, pubescent, indumentum composed of stellate trichomes with long- or short-stalked trichomes, leaf-like bracts 0.9–2.9 × 0.5–1.4 cm. Capitula 3–6 per corymb, pedunculate, associated to 1–2 leafy spatulate tomentose subinvolucral bract erect or slightly conduplicate towards apex, peduncle 1.4–3.2 cm long, flattened, costate, greyish, sometimes blackish, with similar indumentum as branches; involucre 9.5–13.1 mm tall, 12–18.5 mm in diam., campanulate; phyllaries imbricate, 7–9-seriate, densely light greyish to ochraceous, indumentum of short-stalked stellate and unbranched trichomes, apex dark brown and sparsely tomentose, outer phyllaries ovate to elliptic, 3.4–4.3 × 1.6–2.1 mm, apex acute and recurved, inner phyllaries elliptic to narrowly oblanceolate, 4.8–6.7 × 1.1–1.9 mm long, acute to acuminate and straight to slightly recurved; receptacle fimbrillate, fimbria up to 0.5 mm. Florets 130–150 per capitulum; corolla lilac to pale pink, usually actinomorphic but sometimes asymmetric due to a higher number of lobes and size variation of sinuses, corolla tube 4.5–5.8 × 0.3–0.6 mm, glabrous, sparsely glandular-punctate, corolla lobes 5(–8), 3.2–4.1 × 0.3–0.5 mm, glabrous or sparsely pubescent, apex acute, densely villous; anthers 5(–8), purple, apical anther appendage triangular, anther base calcarate and tailed; style lacking a basal node, style shaft 8.1– 8.9 mm long, whitish to lilac, glabrous throughout except for pubescence upper ca. 1.5–2 mm beneath style-arms, style-arms 1.9–2.5 mm long. Cypsela prismatic, 3.2–4.1 × 0.7–1.1 mm, 10-ribbed, brownish usually with darker extremities, glabrous; carpopodium inconspicuous; pappus setae biseriate, light stramineous, paleaceous, outer series setae 0.9–1.1 mm long, of unequal sizes, slightly fused at base or free, serrulate, sometimes twisted, persistent, apex erose, inner series setae 3.5–4.4 mm, free, slightly serrulate, twisted, deciduous, apex acute.

Etymology: —The specific epithet refers to the high number of series of phyllaries. The Lychnophorinae taxa typically have fewer than the 7–9 series as in Roquea multiserialis .

Distribution, habitat, and phenology: — Roquea multiserialis is currently considered endemic to the locality of Serra da Formosa, in the municipality of Monte Azul, in the northern portion of the Espinhaço Range, Minas Gerais, Brazil ( Fig. 7 ). The species is only found in elevations above 1700 m, in campo rupestre vegetation, where it can be dominant amongst other species, e.g. Baccharis platypoda Candolle (1836: 409) , Begonia grisea Candolle (1859: 138) , Clusia burle-marxii Bittrich (1996: 76) , Declieuxia cacuminis Müller Argoviensis (1876: 438) , Lippia hederifolia Martius & Schauer in Schauer (1847: 593), Miconia sclerophylla Triana (1872: 119) , Mimosa aurivillus Martius (1838: 52) , and Symphyopappus cuneatus ( Candolle 1836: 149) Sch.Bip. ex Baker (1876: 367) . It grows between rocks in rocky-sandy soils. The species was found flowering in March and April and with old capitula and fruits in October.

Preliminary conservation status: — Roquea multiserialis is currently known from just four collections, although it is described as dominant in the higher part of Pico da Formosa. Both EOO and AOO are 4 km ². The species has a very limited distribution, probably restricted to this single mountain, a general pattern seen with microendemic species in the campos rupestres ( Vasconcelos et al. 2020). Roquea multiserialis does not occur in protected areas. Serra da Formosa has been under human-induced threats, including fires, quartzite mining, and road construction for the installation of wind turbine generators. If these threats continue to advance within its potential range, it could negatively impact the species, leading to habitat degradation and decline. Considering the species restricted distribution, potential threats, and AOO value ( IUCN 2012, 2019), Roquea multiserialis could be assessed as Critically Endangered CRB2a,b[iii].

Additional specimens examined (paratypes): — BRAZIL. Minas Gerais: Monte Azul, Pico da Formosa , 15º14ʹ20ʹʹS, 42º49ʹ16ʹʹW, 1800 m, 23 Oct 2018, G. Martinelli et al. 20471 ( HUFU, RB!, SPF!) ; ibid., 15º14ʹ11ʹʹS, 42º49ʹ16ʹʹW, 1713 m, 08 Apr 2022, M. Verdi et al. 9096 ( HUEFS, RB!, SPF!) ; ibid., 1802 m, 08 April 2022, M. Verdi et al. 9110 ( HUEFS, RB!, SPF!) .

Comments: —The position of Roquea in Lychnophorinae is strongly supported by our phylogenetic analysis ( Fig. 4 ) and fits into the concept of the subtribe by its woody habit, the presence of apical anther appendages with conspicuous wall thickenings ( Fig. 2B ), style without a basal node, presence of leaf sheath and paleaceous, deciduous pappus ( Loeuille et al. 2019). Roquea can be distinguished from the other genera in Lychnophorinae by the following combination of characters: shrub or treelet, indumentum composed of stellate trichomes, capitulum with 130–150 florets, involucre with 7–9 series of phyllaries and tailed anthers. Tailed anthers are rare in Lychnophorinae and found only in Minasia , Hololepis and Roquea ( Robinson 1992, 1999); the ones in Roquea are unsclerified like in Minasia ( Fig. 2C ). The dense indumentum is composed of several types of tector trichomes, mostly stellate, but unbranched trichomes were found in the adaxial surface of the leaf sheath. Stellate trichomes are more frequent in early-diverging lineages, being replaced by 3- to 5-armed trichomes in the derived Lychnophorinae ( Wagner et al. 2014, Loeuille et al. 2015). The short-stalked swollen trichomes of Roquea are uncommon, found in Chronopappus bifrons (DC. ex Persoon 1807: 391) Candolle (1836: 84) and Eremanthus crotonoides , but also sporadically in more derived genera. Two types of trichomes were thought to occur exclusively in a single genus but also occur in Roquea : the geminate long-stalked trichomes of Chronopappus bifrons ( Wagner et al. 2014) and the long-stalked trichomes with forked arms of Blanchetia ( Loeuille et al. 2014) . The glandular trichomes of the adaxial surface of leaf are similar to those found in Gorceixia decurrens , also in the adaxial surface. The ones found in Eremanthus crotonoides are larger (higher number of secretory cells), not sunken, and occur in the abaxial surface (Lusa, ined.). Some glandular trichomes were also found in the upper callus region of the cypsela (Fig. F, G, H). Unlike the glandular trichomes previously found in cypselae of Lychnophorinae ( Lychnophora semirii D.Marques & J.N.Nakaj. in Marques et al. 2018: 1051; Piptolepis spp. ) ( Marques et al. 2018, 2022), they are caducous.

The high number of florets and phyllary series is rare in the subtribe, found only in Proteopsis Mart. & Zucc. ex Schultz-Bipontinus (1864: 378) , which has 80–140 florets and 5–10-seriate phyllaries. Proteopsis differs from Roquea mostly by the caulirosulate habit, indumentum composed of unbranched trichomes, and untailed anthers. Minasia Robinson (1992: 648) also shares some characteristics with Roquea : a high number of phyllary series (5–8) and tailed anthers; however it differs by its caulirosulate habit and indumentum composed of T-shaped swollen trichomes ( Loeuille et al. 2019).

The presence of stellate trichomes links Roquea to some of the early-diverging lineages like Gorceixia , Blanchetia and Eremanthus crotonoides . Only Blanchetia and Roquea share the stellate trichomes with forked arms, but the former differs from Roquea by its smaller shrubby habit (never a treelet), sheathless leaves (vs. semi-amplexicaul leaf sheath), ovoid capitula (vs. campanulate), phyllaries 3–4-seriate (vs. 7–9-seriate) and 5–10 florets (130–150) ( Loeuille et al. 2014). Roquea has long-stalked stellate, sometimes geminate trichomes like Eremanthus crotonoides , which is placed as incertae sedis in Loeuille et al. (2019), and Gorceixia . Eremanthus crotonoides and Gorceixia are trees or treelets (1–4 m tall and 5–7 m tall, respectively), whereas Roquea hardly reaches 2 m, they have sheathless leaves (vs. semi-amplexicaul leaves), smaller capitula (3–5 vs. 130–150 florets) and lower number of phyllary series (3 for Gorceixia , 5–6 for E. crotonoides vs. 7–9) ( Hind et al. 2006, Loeuille et al. 2019) ( Table 1).

Roquea shares the habit, the presence of semi-amplexicaul leaf sheath and biseriate pappus with Anteremanthus and Paralychnophora . However, the latter differs from Roquea by the capitula organised into a syncephalium (vs. absence of syncephalium), the indumentum composed of 3- to 5-armed trichomes, swollen or not, and unbranched trichomes (vs. stellate and unbranched trichomes). Anteremanthus shares with Roquea the absence of syncephalium, but its indument is composed of T-shaped trichomes and the carpopodium is prominent (vs. inconspicuous). Anteremanthus and Paralychnophora have capitula with a smaller number of phyllary series (3–6 vs. 7–9) and a smaller number of florets (2–26 vs. 130–150) ( Loeuille et al. 2019) ( Table 1).

Geographically, Roquea occurs in sympatry with Paralychnophora glaziouana Loeuille in Loeuille et al. (2012: 290) and Maschalostachys mellosilvae Loeuille & Roque (2017: 42) ; the latter is easily distinguishable from Roquea by the habit (monopodial treelet) and capitula organised in axillary loose spikes of syncephalia or rarely a cyme of syncephalia ( Loeuille & Roque 2017).

It is worth noting that abnormal florets were found in some capitula of Roquea multiserialis , with six to eight corolla lobes and stamens ( Fig. 5H, I ). While tetramerous florets are relatively widespread in the family and have been identified in more than 80 taxa from disparate lineages (initially listed for disc florets by Gardner 1977), the increase in the number of corolla lobes and stamens is extremely rare. To our knowledge, only cases of up to hexamerous florets have been found in wild species as Aster prainii ( Drummond 1907: 91) Chen (1981: 1314) ( Small 1927), Flaveria trinervia Sprengel (1800: 63) Mohr (1901: 810) ( Misra 1957), and some Barnadesioideae ( Svoma et al. 2020) . Fusion of florets has been reported in Flaveria trinervia (nine corolla lobes, nine stamens, two styles or eight corolla lobes, eight abortive stamens and two abortive styles) ( Misra 1957) and Helianthus annuus ( Linnaeus 1753: 904) ( Joshi 1934) . The abnormal florets of Roquea multiserialis have a single style and normal stamens, but the high number of florets densely compacted in the capitulum may eventually lead to some kind of fusion, a hypothesis that should be tested with developmental studies.

Figures

FIGURE 2. Anthers of Roquea multiserialis. A. Anther. B. Apical appendage with sclerified cells (black arrowhead). C. Tails.

FIGURE 4. Phylogenetic relationships among Roquea multiserialis (bold and purple) and members of Lychnophorinae (green) from multispecies coalescent phylogenetic reconstruction of Lychnophorinae. Support values are local posterior probabilities, values below 0.75 not shown.

FIGURE 5. Roquea multiserialis Loeuille & Antar. A. Flowering branch. B. Detail of abaxial leaf midrib indumentum composed of stellate trichomes (some indument removed). C. Detail of adaxial leaf midrib indumentum composed of stellate trichomes. D. Capitulum. E. Longitudinal section of capitulum. F. Outer phyllary. G. Inner phyllary. H. Abnormal corolla with 8 lobes. I. Abnormal corolla opened and showing 8 anthers. J. Apex of corolla lobe. K. Anther. L. Style. M. Cypsela with a pappus. A.–I. Illustration by Margaret Tebbs based on R.B. Almeida et al. 1070 (K).

FIGURE 6. Roquea multiserialis Loeuille & Antar. A. Habitat. B. Habitat and habit. C. Habit. D, E. Branch in flower. F. Capitula detail. A–F. Photos by R.B. Almeida.

FIGURE 7. Distribution map of Roquea multiserialis Loeuille & Antar. Upper left corner inset highlights Brazilian phytogeographic domains (Cerrado, pink; Mata Atlântica, green; Caatinga, yellow).