Paepalanthus myriothrixus Sauthier

Sauthier, Luana J., Tissot-Squalli, Mara L., Ramos, Renato & Sano, Paulo T., 2025, Taxonomic Revision of the Paepalanthus canastrensis Complex (Eriocaulaceae) with Descriptions of Four New Species from Serra da Canastra, Phytotaxa 708 (2), pp. 145-166 : 158-160

Paepalanthus myriothrixus Sauthier & Tissot-Sq., sp. nov. ( Figs. 10–11 )

Diagnosis: — Paepalanthus myriothrixus differs from other species of P. subg. Platycaulon in Serra da Canastra by the presence of a tuft of trichomes just below the hydathodes area at the leaf apex (× glabrous). From P. moedensis , it differs by the paler color on the leaf base (× castaneous color) and by the hyaline membranaceous spathe (× green, papery).

Type: — BRAZIL. Minas Gerais: São Roque de Minas: Parque Nacional da Serra da Canastra, Garagem de Pedras, 20 m atrás da garagem, 20º13’57.23’’S 46º37’32.47’’W, elev. 1384 m, 15 March 2020, L.J. Sauthier 172 et al. (Holotype SPF barcode SPF00253900!, Isotype HUIRB!).

Perennial herb, 16–29 cm high, habit in rosette, stem vertical, internodes shorter than 0.5 cm, remnants of vascular bundles deciduous or absent in straw fibers. Leaves 10.7–26.2 × 0.6–1.3 cm, spirallate, flat, narrow-triangular, leathering, without superficial wax, glabrous; apex cuspidate to acuminate with a tuft of trichomes just below the hydathodes area; margins ciliated with long deciduous cilia (more than three cells); leaf base with a paler color, membrane absent. Spathe membranaceous, almost transparent, very short and inconspicuous with 2.9–4.5 cm long, ciliated, truncate. Scapes 12–24 cm long, scarcely pilose, branched, grouping free capitula. External involucral bracts lanceolate to ovate, at least one third shorter than the internal involucral bracts, dorsally pilose with persistent indumentum, obtuse to acute, brown to dark brown. Internal involucral bracts ovate, dorsally pilose with persistent indumentum, obtuse to acute, dark brown. Flowers trimerous. Staminate flower 2.5–3.7 mm long; floral bracts 2.5–3.5 mm long, oblanceolate, dorsally glabrous but densely pilose towards the apex with subclavate trichomes, cuspidate to acuminate; sepals 2.5–3.5 mm long, oblanceolate to obovate, connate up the basal one third; obtuse to acute; floral tube not ciliated, hyaline. Pistillate flower 3–4.2 mm long, pedicellate; floral bracts 2.5–3.5 mm long, oblanceolate, dorsally glabrous but densely pilose towards the apex with subclavate trichomes, acuminate; sepals 2.3–3.5 mm long, oblanceolate to obovate, connate at the base, obtuse to acute; petals 1.9–2.9 mm long, obovate, obtuse to acute; gynoecium with nectariferous branches shorter than the stigmatic branches. Fruit loculicidal capsule. Seed ca. 1.5–1.6 mm long, dark brown, tegument forming white appendages after hydration.

Habitat, distribution and conservation: — Paepalanthus myriothrixus occurs in rocky fields of western Chapadão do Diamante, in dry sandy soil near the Garagem de Pedras ( Fig. 11 ). It has an AOO of 12 km 2, which indicates Endangered (EN) status, and an EOO of 2.36 km 2 ( Fig. 14 ), with Critically Endangered (CR) status. Due to the impact of fire in the area ( Fig. 15 ), an estimated number of less than 50 reproductively mature individuals should be indicated as CR using the B2ab(iii); D criteria.

Morphologic and taxonomic comments: —The most diagnostic feature of P. myriothrixus is the tuft of trichomes located just below the hydathodes area at the leaf apex ( Fig. 10c ), a rare trait in P. subg. Platycaulon reported only to P. moedensis Silveira (1928a: 234) , an endemic species from the Iron Quadrangle, Minas Gerais State ( Sauthier 2019). They differ in the shape of leaves, leaf base color, spathe length and texture, the indumentum of the involucral bracts, and in their allopatric distribution.

Trichomes have been reported as protective structures against ultraviolet rays by behaving as optical filters. Additionally, they can provide a superficial chemical barrier against biotic stress factors such as herbivores and pathogens through a mixture of phenolic compounds ( Karabourniotis et al. 2020; Wang et al. 2021). Their presence in species occurring in the campos rupestres is widespread and occurs in many unrelated families, but this agglomeration in tufts near the hydathodes without covering them deserves investigation.

Etymology: —This new species is named according to the presence of tufts of trichome right below the hydathode region. The name is composed of the Greek words myrios, meaning numberless or countless; and thrix, meaning hair ( Stearn 1983).

Additional specimens examined: — BRAZIL. Minas Gerais: São Roque de Minas. Parque Nacional da Serra da Canastra, Garagem de Pedra , 20º13’49’’S 46º37’29’’W, elev. 1392 m, 21 June 2001, M.N. Castro 02 et al. (SPF, HUFU image) ; Estrada para Sacramento, Garagem de Pedras , 20 March 1995, J.N. Nakajima 924 et al. (SPF, HUFU image) ; Caminho do Retiro de Pedra , 19 March 1998, P.T. Sano 945 et al. (SPF) ; Garagem de Pedras , 70 m atrás da garagem, 20º13’59.01’’S 46º37’32.77’’W, elev. 1380 m, 15 March 2020, L.J. Sauthier 173 et al. (SPF, HUIRB) ; 20º14’01.32’’S 46º37’33.01’’W, elev. 1380 m, 15 March 2020, L.J. Sauthier 174 et al. (SPF, HUIRB); Garagem de Pedras , 15 May 2007, M.L.O. Trovó 392 et al. (SPF) .

Figures

FIGURE 10. Paepalanthus myriothrixus, where: a) habit; b) leaf apex; c) tuft of trichomes just below the hydathodes area as indicated by the red arrow; d) spathe indicated by the red arrows; e) inflorescence; f) capitulum; g) external involucral bract; h) internal involucral bract; i) staminate flower; j) floral bract of the staminate flower; k) opened floral tube and sepals; l) pistillate flower; m) floral bract of the pistillate flower; n) sepals of the pistillate flower, adaxial face above and abaxial face bellow; o) fruit; p) petal of the pistillate flower with staminode indicated by the white arrow; q) gynoecium; r) seed. Photos a-b, e, o from L.J. Sauthier 173 et al.; d from L.J. Sauthier 174 et al.; c, f-n, p-r from L.J. Sauthier 172 et al. (SPF). Photos by L.J. Sauthier and M.L. Tissot-Squalli. Scale bars equal to 1 mm, except for the staminode and seed in p and r equal to 250 μm.

FIGURE 11. Geographical distribution of Paepalanthus myriothrixus in the Serra da Canastra region.

FIGURE 14. Fire recurrence historical series (1980-2020), Area of Occupation (AOO) and Extent of Occurrence (EOO) of Paepalanthus subg. Platycaulon species from the Serra da Canastra region.

FIGURE 15. Impact of the fire on the Paepalanthus subg. Platycaulon species in Serra da Canastra region, measured by recurrence of burned area.