Thismia petasiformis D. F. Silva & J. M. A. Braga 2022, sp. nov.
Creators: name: Silva, Diego Ferreira Da
name: Braga, João Marcelo Alvarenga
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Liliopsida
Dioscoreales
Burmanniaceae
Thismia
Thismia petasiformis

description: Thismia petasiformis D.F.Silva & J.M.A.Braga, sp. nov. (Figures 1–3)   
 Type:— BRAZIL. Mato Grosso: Nova Bandeirantes, Fazenda Marúpa, próximo à rodovia MT-208, 09º59’40”S, 57º49’18”W, 6 March 2021, fl. and fr., D. F. Silva et al. 198 (holotype RB 830081 [barcode RB01461462]!; isotype RB2735 [barcode RBspirit01461469]!).   
 Diagnosis:— Similar to Thismia fungiformis and T. melanomitra, but differs from both in having perianth tube apparently trigonous with slightly curved sides, narrowing of the medial portion up to an apical circular opening, annulus inconspicuous; inner perianth lobes triangular, connate over the tube opening and forming a hat-shaped mitre, brownish, umbilicate with base of the lobes free and forming a tripod.   
 Description:—Herbs 2.5–9 cm tall, terrestrial, mycoheterotrophic, achlorophyllous. Roots 5–21 × 0.1–0.2 cm, vermiform, sometimes branched, creeping, tan-colored to yellowish-orange. Stem 2–4 cm × ca. 0.2 cm, elongating up to ca. 8.3 cm long when in fruit, erect, terete, unbranched, glabrous, white. Leaves 1–5, 1–5 × 1–2 mm, alternate, scattered along the stem, scale-like, conduplicate, concave, reticulate, lanceolate, apex acute, margin entire or sparsely serrate, glabrous, translucent white. Bracts 3, 2–7 × 1–2 mm, surrounding the ovary base, spirally-alternate, scale-like, conduplicate, concave, reticulate, lanceolate, apex acute, margin entire or sparsely serrate, glabrous, translucent white. Flowers 13–14 × 7–8 mm, solitary, actinomorphic; pedicel 1–4 × 1–2 mm, elongating up to 4–38 × 2–3 mm when in fruit, white; perianth tube 7–8 × 4–5 mm, apparently trigonous with slightly curved sides, narrowing at middle into an apical, circular, darkened opening, ca. 2 mm in diameter, annulus inconspicuous, white, outer surface smooth, with 2 vertical darkened lines, inner surface with lobed and striated laminar projections, with 6 prominent vertical lines; perianth lobes in two whorls (3+3); outer perianth lobes 9–12 × ca. 2 mm, near the base of the tube, pointing up, lanceolate, twisted, curved surface, apex truncate, tumescent, glabrous, tan-colored, sometimes with irregular darkened macules at base; inner perianth lobes ca. 5 × 8 mm, triangular, connate over the tube opening and forming a hat-shaped mitre, tan-colored, umbilicate, lobes base free forming a tripod supporting the mitre, slightly curved sides, margin slightly involute, almost imperceptibly white-ciliolate, externally smooth, internally with horizontal striations and very tiny papillose trichomes on the entire surface of the mitre. Stamens 6, ca. 3 × 0.5 mm, spathulate, glabrous, white, pendulous, attached to the inner wall of perianth tube, inserted ca. 0.5 mm below the annulus, interstaminal lobes absent; filaments ca. 1.3 mm long, free; connectives inconspicuous; anthers ca. 1.7 × 0.5 mm long, elliptic, apex obtuse, surrounded by a thin and clear membranous projection. Ovary ca. 3 × 4 mm, unilocular, obconical, smooth, white, glabrous, multi-ovulate placentation parietal; style ca. 0.5 mm long, inconspicuous, white; stigma 1.9–2 × ca. 2 mm, trilobed, pyramidal, central orifice surrounded by auriculate lobes, densely covered with very tiny papillose trichomes, white. Fruits 3–7 × 5–8 mm, cup-shaped, inner surface with circular striations, margin irregular, with 6 symmetrical lobes 1.7–3 × 0.1–0.3 mm, rounded, glabrous, white. Seeds 0.5–0.6 × ca. 0.2 mm, obovoid to ellipsoid, reticulate, tan-colored, seminiferous nucleus brown; funiculus filiform, persistent, white.   
 Additional specimens examined (Paratype): — BRAZIL. Mato Grosso: Nova Bandeirantes, Fazenda Marúpa, próximo à rodovia MT-208, 09º59’42”S, 57º49’23”W, 7 March 2021, fl. and fr., D. F. Silva et al. 199 (RB 830083 [barcode RB01461464]!).   
 Etymology:— The specific epithet (Latin: pĕtăsus: i, m) refers to its hat-shaped mitre.   
 Phenology:— Flowering and fruiting was observed in March. A notable phenological characteristic of this species is that its stem elongates when fruiting, increasing up to almost ten times in length than when flowering.   
 Distribution:— This species is known only from the type locality, in the municipality of Nova Bandeirantes, State of Mato Grosso, Brazil (Figure 4).   
 Habitat and Ecology:— Thismia petasiformis is known from a few sparse individuals found in a Dense Ombrophilous Forest remnant in the southern region of the Brazilian Amazon Forest, around 300 m a.s.l. The individuals were observed growing on the forest litter in humid and shady places in areas of preserved forests.   
 Conservation status: — Thismia petasiformis is only known by about 20 individuals found growing amongst leaf litter, under shade in an isolated fragment of the Brazilian Amazon Forest with approximately 800 ha, located on private property in the extreme north region of the State of Mato Grosso. In the same fragment were also found individuals of T. melanomitra and T. ribeiroi Engels, D.F.Silva & Soares-Lopes (in Silva et al. 2020: 268).Although the native vegetation is still preserved, the site is not an environmental protection area, with recent activities of logging and expansion of pasture areas being observed, in addition to traces of fires. This fragment is located in the deforestation arc of Brazil’s Legal Amazon, a region globally known for large-scale deforestation for logging, extensive monoculture and ranching expansion, and fires (Fearnside 2005; Carvalho et al. 2019; Silva Junior et al. 2022). Despite studies indicating that the preserved native forests of the Brazilian Amazon can be profitable and economically sustainable (Nobre et al. 2021), deforestation has been accelerating and drastically destroying the ecosystems and natural landscapes (Garrett et al. 2021). To make this chaotic scenario worse, in recent years, deforestation has increased dramatically at rates never before documented (Silva Junior et al. 2021). These factors place T. petasiformis in high danger of extinction. Due to the low number of known mature individuals, the extent of occurrence (EOO) cannot be measured. The occupancy area (AOO) is estimated at less than 4 km 2. Therefore, we suggested the preliminary status of Critically Endangered (CR) by meeting the criteria B2ab(ii, iii), according to the IUCN (2012, 2019).   
 Notes: — Thismia petasiformis belongs to T. subg. Ophiomeris sect. Pyramidalis due to its horizontal cylindrical roots, terete stem with scattered leaves along the stem, pyramidal stigma, stamens with inconspicuous connective, interstaminal lobes absent, and parietal placentation extending from the base to the top of the ovary. Recently, Shepeleva et al. (2020) showed that Thismia is polyphyletic, with T. subg. Ophiomeris being distantly related to the T. subg. Thismia, but related to the Neotropical monotypic genus Tiputinia P.E.Berry & C.L.Woodw. (in Woodward et al. 2007: 158). This preliminary resulted already proves the need for further molecular and genomic research about the Neotropical species of Thismia, so that doubts about the phylogenetic position of these subgenera may be put to rest.   
 Thismia petasiformis is similar to T. fungiformis, which is a species endemic to the Atlantic Forest of the State of Rio de Janeiro. However, it differs by its perianth tube 7–8 × 4–5 mm, apparently trigonous with slightly curved sides, external surface smooth (vs. 6–9 × 6–9 mm, urceolate, external surface somewhat wrinkled in T. fungiformis), outer perianth lobes pointing up, lanceolate, twisted, with apex truncate (vs. outer perianth lobes reflexed, plane, apex acute), and inner perianth lobes united over the tube opening and forming a hat-shaped mitre (vs. inner perianth lobes inserted below the annulus, each lobe forming a bowl-shaped structure at apex, mitre absent). It also shares the presence of a mitre with T. melanomitra, another species from the Amazon Forest, from which it differs mainly by the perianth tube 7–8 mm long, apparently trigonous with slightly curved sides (vs. ca. 14 mm long, oblanceoloid-hexagonal in T. melanomitra), outer perianth lobes 9–12 × ca. 2 mm, lanceolate, twisted, apex truncate (vs. 5–6 × 4–5 mm, ovate, plane, apex rounded to obtuse), and annulus inconspicuous (vs. prominent). The complete comparison of the morphological characters of these three species is shown in Table 1.
description: Published as part of Silva, Diego Ferreira Da & Braga, João Marcelo Alvarenga, 2022, Thismia petasiformis (Thismiaceae), a new fairy lantern species from the Brazilian Amazon Forest, pp. 221-229 in Phytotaxa 564 (2) on pages 222-227, DOI: 10.11646/phytotaxa.564.2.5, http://zenodo.org/record/7087262