Giuliettia minima (Silveira) Andrino, L. H. Rocha & Gonella, 2024

Andrino, Caroline Oliveira, Rocha, Luiz Henrique & Gonella, Paulo Minatel, 2024, A tiny rediscovery in the Land of Giants: a new combination in Giuliettia (Eriocaulaceae, Poales) and other implications of finding Paepalanthus minimus again, Willdenowia 54 (1), pp. 81-93 : 83-89

Giuliettia minima (Silveira) Andrino, L. H. Rocha & Gonella , comb. nov.

≡ Paepalanthus minimus Silveira, Floral. Mont. 1: 107, t. 66. 1928.

– Holotype: Brazil, Minas Gerais, in campis et sub rupibus prope Barauna [in fields and under rocks near Barauna – former name of the current Barão de Guaicuí, district of the municipality of Gouveia], Apr 1918, A. Silveira 697 ( R [barcode R000181868 ]!; isotype: UB!) . – Fig. 1–6 .

Description — Herbs annual, rupicolous, 1–12.5 cm tall. Roots capillary. Stem unbranched, restricted to rosette or etiolated, elongated, decumbent, thin, 0.1–8.8 mm long. Leaves rosulate or spiralled, green, linear-lanceolate, flat, 0.5–3 × 0.1–0.3 cm, membranous, pilose with short trichomes on both surfaces c. 1 mm long, central nerve visible up to ⅔ of length, margin ciliate, apex acute. Spathes 0.1–0.6 mm long, abaxial surface pilose, base with a tuft of long trichomes, margin ciliate, aperture oblique, apex acuminate. Scapes free, fasciculate, 1–35 per plant, green, 0.6–4.5 cm long, pilose with trichomes 0.2–0.5 mm long. Capitula cream-coloured, 2–6 mm in diam.; involucral bracts in 2 series; bracts of external series green, linear-lanceolate to narrowly ovate, 1.2–3 × 0.2–0.8 mm, surpassing length of flowers by 0.7–2 mm, pilose along central nerve abaxially, margin ciliate, apex acute to obtuse; bracts of internal series ovate, 1–1.2 × 0.7–1.4 mm, hyaline, surfaces glabrous, margin ciliate, apex obtuse to rounded. Floral bracts narrowly ovate, c. 1 mm long, hyaline, surfaces glabrous, margin ciliate, apex obtuse. Flowers 3-merous, diclinous, with pistillate flowers in periphery of capitula and staminate flowers in centre. Staminate flowers c. 1.5 mm long; pedicel c. 0.5 mm long, with trichomes c. 2 mm long; sepals 3, free, narrowly oblong, c. 0.5 mm long, hyaline, surfaces glabrous, margin ciliate, apex obtuse; androphore plus petals c. 1 mm long; petals 3, fused except free at apex, c. 0.3 mm long, hyaline, glabrous, margin entire; anthers dorsifixed; pistillodes filiform. Pistillate flowers 1.5–2 mm long; pedicel c. 0.5 mm long, pilose, trichomes equalling those of staminate flowers; sepals 3, oblongoblanceolate, c. 1 mm long, hyaline, enlarging and becoming hygroscopic in fruit, margin ciliate; petals 3, free, narrowly obovate, c. 0.5 mm long, hyaline, glabrous, apex fimbriate; staminodes absent; gynoecium with nectariferous and stigmatic branches inserted in column at same height; stigmatic branches 3, bifid, c. 0.8 mm long; nectariferous branches 3, c. ½ as long as stigmatic branches, papillose; ovary c. 0.5 mm long. Fruit a loculicidal capsule, dispersed as an entire unit by calyx (autochorous). Seeds reddish brown, ovoid, 390–500 × 230–290 µm; seed coat formed by irregular isodiametric cells, without appendages.

Phenology — Collected with flowers and fruits in February, March, April, May and June; not observed during the dry season, when only dried and dead plants of the previous rainy season could be found (usually from July to October).

Distribution, habitat and ecology — The exact location where Álvaro da Silveira collected the specimens he used to describe Paepalanthus minimus is unknown, because the specimen label states it was collected around Barauna, a district now named Barão de Guaicuí, in the municipality of Gouveia (located at around 1200 m a.s.l.), but the protologue ( Silveira 1928) indicates it was collected in the Pico do Itambé, at around 2000 m a.s.l. ( Fig. 1 ). Both the specimen label and the protologue indicate that the species was found under rocks in a shaded place. Both areas are located in quartzitic campo rupestre, in the Diamantina plateau, part of the Espinhaço range in central Minas Gerais ( Fig. 1 ).

The new specimens were collected over 200 km to the southeast of the possible type locality ( Fig. 1 ), in quartzitic campo rupestre areas of Serra do Padre Ângelo, municipality of Conselheiro Pena, Minas Gerais. In this Serra, the species was found in two localities c. 3 km distant from each other, in the Pico da Bela Adormecida (also known as Pico do Padre Ângelo; Fig. 4A ) and in the contiguous Serra da Palha Branca (locally known as Mirante da Bela; Fig. 4B ) to the southeast ( Fig. 1C , 5 ). At both places, Giuliettia minima grows on north-facing, vertical rock walls with seasonal seepages. The species is found mainly in rock crevices protected from direct sunlight ( Fig. 3A–C ), agreeing with the type specimen label, which indicates that the species was found under rocks. Only a few individuals were also observed on more exposed seepages, also facing north ( Fig. 3D ). The species is found at elevations from 1080 to 1400 m.

Like other species of Giuliettia , G. minima is an annual species (therophyte), which means it has a generation time of a few months, with seeds germinating in the early rainy season and individuals dying by the early dry season after setting seeds for the next generation ( Andrino & al. 2023a). A second, even shorter-lived generation may also occur, as implied by the small flowering specimens attached to the capitula of larger individuals, suggesting vivipary (e.g. the specimen P. M. Gonella & al. 3588; Fig. 3A ). The durability of the seed bank in the soil is unknown for this species, although it has been estimated to last for at least two years in other Eriocaulaceae species ( Garcia & al. 2014).

Preliminary conservation status — Critically Endangered: CR B1ab(iii)+B2ab(iii). Giuliettia minima was first collected in 1918, either near Barão de Guaiçuí (district of Gouveia) or in the Pico do Itambé, but was never found again in this region, even though both localities were visited by many botanists over the last century, including the authors of this paper and several Eriocaulaceae specialists. Although the lack of new specimens from this region could be due to the diminutive size and specific habitat of the plants, which could have hindered their being refound, it is also possible that the species could have gone locally extinct as a result of habitat alterations in the past century. Because of the lack of precise information on the collection site of the type specimen, it is not possible to assess the current situation of the habitat where it was first collected, nor include it in the calculations of AOO and EOO. Pico do Itambé is located in a state-level protected area, the Pico do Itambé State Park.

The situation of the known population is alarming, however, with continuing threats and an observed decline in habitat quality ( Fig. 4 , 5 ). The region of Serra do Padre Ângelo was once surrounded by a matrix of semideciduous seasonal forest, now largely degraded and converted into pastures or agricultural land ( Fig. 4G , 5B ; MapBiomas Project 2023). The removal of the forest buffer around the campos rupestres areas in addition to the common use of fire for pasture renovation has favoured the invasion by alien species, especially molasses grass, Melinis minutiflora P. Beauv. ( Poaceae ; Fig. 4E ), and bracken fern, Pteridium aquilinum (L.) Kuhn ( Dennstaedtiaceae ; Fig. 4F ), representing a severe threat to the quality of the habitat, especially for the micro-endemic species, which have very specific and restricted habitats ( Gonella & al. 2015; Andrino & Gonella 2021; Couto & al. 2023). At both sites where the species was found at Serra do Padre Ângelo (AOO of 8 km 2; EOO polygon cannot be calculated given the reduced number of sites), the habitat is altered by human activities (e.g. fire, deforestation; Fig. 4 ) and severely invaded by the aforementioned invasive species. Furthermore, both areas are still subject to constant, uncontrolled wildfires originating from farming activities ( Fig. 5C ), such as the one that affected the Bela Adormecida population in late 2020 ( Fig. 4D , 5D ). The population of Serra da Palha Branca already shows signs of decline due to the history of fire and the presence of invasive species, because it is extremely localized even though the area presents several similar habitats that are not occupied by the species. Given the annual growing cycle (which means yearly fluctuation of the number of individuals), the complex topography of the habitat, the likely existence of a seed bank and the capacity of the species to flower at a small size, estimation of population size is very difficult. Considering the fragile habitat and the annual life cycle of the species, its generation time is very short in a way that a stochastic event, such as an intense fire or an extreme climatic event like a drought, could cause local extinction or a dramatic reduction of population size within a year.

Considering the reduced known population, restricted occurrence, a narrow habitat preference that is susceptible to several threats to its quality and the fact that none of its known subpopulations are within a protected area, we recommend that Giuliettia minima should be categorized as Critically Endangered based on the aforementioned IUCN (2012) criteria.

Proposed vernacular name — “sempre-viva-mínima” (Portuguese). Following the suggestion of Marinho & Scatigna (2022), we propose a vernacular name for this species as a way to promote knowledge about it to the local communities and to address the urgency of promoting conservation actions to protect the species and its habitat. The proposed name considers the common name of many Eriocaulaceae species in Brazil (“sempre-viva” – Portuguese for “everlasting”) plus the specific epithet, which is easily relatable in Portuguese, meaning “minimal” or “very small”.

Taxonomic remarks — The morphologically most similar species to Giuliettia minima is G. bifida (Schrad.) Andrino & Sano , both species sharing the small, delicate habit and green involucral bracts surpassing the height of the flowers in the capitula. However, G. bifida presents a cylindric, erect, stiff, often brownish stem (vs acaulescent, or rarely with a filiform, slender, green stem in G. minima ; Fig. 2A–C , 3 ), leaves chartaceous with long trichomes and multiple parallel nerves (vs membranous, with short trichomes and a single central nerve) and the involucral bracts lanceolate to linear-lanceolate, both internal and exterior series with an acute apex, the external series green and the internal series bronze-coloured with hyaline margins (vs involucral bracts linear-lanceolate to narrowly ovate with an acute to obtuse apex in the exterior series [ Fig. 2E ] and ovate with an obtuse apex in the interior series [ Fig. 2F ], the external series green and the interior series hyaline [ Fig. 3F–G ]).

When describing Paepalanthus minimus, Silveira (1928) compared it with P. pullus Körn. , which was kept in the genus Paepalanthus in the classification of Andrino & al. (2023a). Paepalanthus pullus is distinct in having a dense rosette of glabrous leaves, scapes glabrous, involucral and floral bracts dark castaneous and stigmatic branches simple ( Andrino & al. 2023b).

Additional specimens examined — BRAZIL, MINAS GERAIS: Conselheiro Pena, Serra do Padre Ângelo, Pico da Bela Adormecida , 19°19'0.07"S, 41°34'46.67"W, 1400 m, 15 Mar 2021 (fl./fr.), P. M. Gonella & al. 2303 ( UB); ibid., 23 Feb 2022 (fl.), L. H. Rocha & al. 46 ( UB); ibid., 11 May 2022 (fl./fr.), P. M. Gonella & al. 3474 ( MBML, UB); ibid., 9 Oct 2022 (fr.), P. M. Gonella & al. 3588 ( UB); Serra da Palha Branca , 19°20'19.5"S, 41°33'26.3"W, 1080 m, 9 Jun 2020 (fl./fr.), P. M. Gonella & al. 1286 ( UB).

Figures

Fig. 1. Distribution map of Giuliettia minima. – A: reference map of South America highlighting Brazil and Minas Gerais; B: approximate occurrence of type collection of G. minima and new records reported here; C: main regions of João Pinto formation.

Fig. 2. Giuliettia minima. – A–C: habit showing variation in size, stem and number of scapes per plant; D: capitulum, side view; E: involucral bracts of external series; F: involucral bracts of internal series; G: staminate flower, one sepal removed for observation; H: staminate flower with corolla sectioned for observation of pistillodes and stamens; I: pistillate flower; J: petal of pistillate flower; K: gynoecium; L: seed. – Based on P. M. Gonella 3474. – Drawn by Joelcio Freitas.

Fig. 3. Giuliettia minima. – A: habitat on shaded rock crevices, with some capitula presenting apparent vivipary; B: habitat under rocks in shade with mosses; C: close-up of plants in habitat; D: plants in a humid rock crevice with organic matter in more exposed site; E: collected specimen, P. M. Gonella 3474; F, G: capitula; F: posterior view, showing involucral bracts; G: front view. – Photographs: A: Serra da Palha Branca, March 2023, by Júlio César Ribeiro; B, C: Serra da Palha Branca, June 2020, by Gabriele A. da Silva; D–G: Pico da Bela Adormecida, May 2022, by Paulo Minatel Gonella.

Fig. 4. Habitat of Giuliettia minima and conservation threats. – A: Pico da Bela Adormecida, one of the highest peaks of Serra do Padre Ângelo and habitat of G. minima, May 2022; B: Serra da Palha Branca, part of Serra do Padre Ângelo, August 2022; C: habitat of Pico da BelaAdormecida population in June 2020, before the fire; D: same area as C in October 2020, immediately after the fire; E: invasion of molasses grass, Melinis minutiflora, in Pico da Bela Adormecida, with individuals of Vellozia gigantea in background, July 2017; F: area of Serra da Palha Branca invaded by bracken fern, Pteridium aquilinum, February 2021; G: pastures and degraded areas surrounding Pico da Bela Adormecida, April 2023. – All photographs by Paulo Minatel Gonella.

Fig. 5. Distribution of Giuliettia minima at Serra do Padre Ângelo and conservation threats. – A: occurrence map of G. minima at Serra do PadreÂngelo; B: land use of region; C: fire record in region between 1985 and 2020; D: fire record in region in 2020, when a wildfire affected Pico da Bela Adormecida. – Data on land use and fire from MapBiomas Project (2023).

Fig. 6. Scanning electron micrographs of seeds of Giuliettia minima. – A: from specimen P. M. Gonella 3588 (UB); B: from specimen A. Silveira 697 (UB isotype).