Paepalanthus leucocephalus Ruhland, 1903

Andrade, Maria José Gomes De, Trovó, Marcelo, Rocha, Lamarck & Giulietti, Ana Maria, 2022, Paepalanthus (Eriocaulaceae) without scapes and spathes, a survey with the description of a new species, Phytotaxa 560 (2), pp. 135-152 : 146-147

3. Paepalanthus leucocephalus Ruhland in Engler, Pflanzenr. IV.30 (Heft 13): 200. 1903.

Lectotype, first-step (designated by Moldenke 1975): at B. Lectotype, second-step (here designated): BRAZIL. Minas Gerais: Serra dos Cristaes , 4 April 1892, C.A.W. Schwacke 8503 ( B [10_0243944]! , isolectotypes B [10_0243943]!, K [000640071]!). ( Figures 2A–B , 3 , 4N –P, 6A–H )

Ruhland (1903) described Paepalanthus leucocephalus based on the collection Schwacke 8503, gathered in Minas Gerais. We found three specimens related to this collection, two deposited at B, where Willy Ruhland mostly worked, and one housed at K. It is also a situation with no holotype being clearly indicated, requiring a lectotype selection ( McNeill 2014, Turland et al. 2018). Moldenke (1975) indicated that the type of this species is deposited at B with the indication “ Thelxinoë leucocephala ”. The two specimens at B contain the same annotation, therefore we consider Moldenke’s (1975) statement as a first-step lectotype indication according to the article 9.17 of the ICN ( Turland et al. 2018). One of the specimens housed at B contains Ruhland’s original handwritings and drawings attached, also perfectly matching the description. We designate this specimen [B barcode 10_0243944] as the second-step lectotype.

Paepalanthus leucocephalus is sister of P. scleranthus and they are the only species in Paepalanthus subg. Thelxinoë according to Ruhland (1903). They also share the annual caulescent habit of small plants, with the absence of scapes and spathes, capitulum sessile, involucral bracts not differentiated from the apical leaves, floral bracts acuminate, and dimerous flowers. They are sympatric in the Espinhaço Range in some mountains in Minas Gerais, and also in Rio de Contas, Bahia. There is also a population occurring in sandy soils further north in Morro do Chapéu in Bahia ( Figure 3 ). P. leucocephalus is morphologically similar to P. scleranthus ( Figures 6 I-N), sharing also the loss of the nectariferous branches ( Silva et al. 2016), a condition observed in P. paganuccii and P. sessiliflorus as well ( Figures 4–5 ). The whitish capitula are a visible character to distinguish P. leucocephalus from P. scleranthus , along with the convex leaves clearly distinguished into sheath and blade, and the morphology of the flowers, illustrated for the first time in this paper. However, the segregation of these species is weak and deserve further investigations as previously stated by Moldenke “The species is extremely close to P. scleranthus and I am not at all certain that the two are distinct” ( Moldenke 1975).

As expected of a widespread species, Paepalanthus leucocephalus encompasses a relevant morphological variation and the relationship with P. scleranthus is complex ( Figures 2 , 4 , 6 ). Some populations, as the one represented by the specimen Andrade 625 from Rio de Contas in Bahia, are composed of individuals noteworthy for being smaller than specimens from other populations, especially from those occurring in the Southern Espinhaço Range. The populations from Minas Gerais, occurring mostly in the Diamantina Plateau , also have more hairy floral structures and a shinier white capitulum. The inclusion of specimens from the whole morphological and geographical range of P. leucocephalus and P. scleranthus in future studies at the population level is crucial to circumscribe these species more accurately.

Additional selected material examined:— BRAZIL. Bahia: Morro do Chapéu, Tabuleiro dos Tigres , 11°36’09”S, 41°09’44”W, 20 July 2005, M. J. G . Andrade et al. 589 ( HUEFS); Rio de Contas, Serra Marsalina , campo cerrado, 16 August 2006, M. J. G . Andrade et al. 620 ( HUEFS); Idem, M. J. G . Andrade et al. 625 ( HUEFS) . Minas Gerais: Datas, 04 km da estrada Datas-Milho Verde , 07 April 2004, M. J. G . Andrade et al. 549 ( HUEFS); Diamantina , 05 May 2010, C . Munhoz et al. 7283 ( UB); Grão Mogol, Trilha do Barão , 02 April 2004, M. J. G . Andrade et al. 481 ( HUEFS); Mariana, Parque Estadual do Itacolomi , 06 April 2018, D. Rodrigues et al. 27 ( OUPR) .

Figures

FIGURE 2. Life-forms and inflorescences in Paepalanthus species without scape. A–B. Paepalanthus leucocephalus growing in the Chapada Diamantina, BA. C–E. P. paganuccii. C. Population growing in Tocantins (Harley 56669) on sandy soil. D. Rupiculous individual growing on sandstone. E. Detail of the capitulum. F. P. scleranthus, growing in Diamantina, MG, showing the black capitula. G. P. sessiliflorus growing in campo rupestre in Pico das Almas, BA. Scale bar: 5 mm. (photo credits: A–B. C.N. Fraga, C–E, G. R.M. Harley, F. M. Trovó).

FIGURE 3. Geographical distribution of Paepalanthus species without scape. Red-orange symbols = Paepalanthus ser. Leptocephali; Blue-green symbols = P. subg. Thelxinoë.

FIGURE 6. SEM micrographs. A–H: Paepalanthus leucocephalus. A. leaf with two types of trichomes: filamentous and malpighiaceous (2 armed) trichomes. B. staminate flower showing bract, calyx, anthophore, corolla and anther. C. pistillate flower showing bract, calyx with two concave sepals and one petal and part of ovary. D. pistillate flower showing one sepal, one petal and gynoecium with style with stigmate branch, lacking nectariferous branch. E. pistillate flower showing detail of the petal and gynoecium.F. detail of the external ovary surface. G. mature seed, seed coat with a reticulate pattern. H. detail of the seed coat showing the cells 4-5 walled. I–N: Paepalanthus scleranthus. I. leaf with two types of trichomes: filamentous and malpighiaceous (2 armed) trichomes. J. adaxial leaf surface showing detail of the filamentous and malpighiaceous trichomes. K. pistillate flower showing bract, one sepal, one petal and gynoecium. L. staminate flower showing calyx, anthophore, corolla and anther. M. pistillate open flower showing two sepals bigger than the two petals and gynoecium with stigmatic branch, lacking nectariferous branches. N. pistillate closed flower showing two concave sepals involving the corolla. (A–C. Andrade 589, D–F. Andrade 625, G–H: Andrade 620, I–J, M. Harley 55538a, K–L, N. Harley 55538b).

FIGURE4.MorphologyofplantandflowersinPaepalanthuswithoutscape.A–K:Paepalanthuspaganuccii.A.habit.B.leaf.C.capitulum. D. involucral bract of the outer series. E. involucral bract of the inner series. F. open staminate flower showing calyx, anthophore, corolla, androecium and floral bract. G. closed staminate flower showing pedicel, calyx and corolla trichomes. H. open pistillate flower showing calyx, corolla, gynoecium and floral bract. I. sepal. J. petal. K. developing fruit with two petals. L–M: Paepalanthus sessiliflorus var. sessiliflorus. L. open staminate flower showing calyx, anthophore, corolla, androecium and floral bract. M. open pistillate flower showing calyx, corolla, gynoecium and floral bract. N–P: Paepalanthus leucocephalus. N. open staminate flower showing calyx, anthophore, corolla, androecium and floral bract. O. closed pistillate flower showing calyx, corolla and floral bract apex. P. open pistillate flower showing calyx, corolla and gynoecium. Q–S: Paepalanthus scleranthus. Q. open staminate flower showing calyx, anthophore, corolla, androecium and floral bract. R. closed pistillate flower showing calyx, corolla and floral bract apex. S. open pistillate flower showing calyx, corolla and gynoecium [A–K. Queiroz 10917, holotype of P. paganuccii (HUEFS), L–M. Andrade 623 (HUEFS), N–P. Andrade 549 (HUEFS), Q–S. Alves 4015 (RB), drawings by AMG inked in by Carla Lima].