Phyllanthus allemii G.L. Webster (2002: 24

Mendes, Jone Clebson Ribeiro, Figueira, Maurício, Schindler, Bianca, Noronha, Sérgio E., Simon, Marcelo Fragomeni, Sales, Margareth Ferreira De & Athiê-Souza, Sarah Maria, 2022, Novelties in Phyllanthus (Phyllanthaceae) from the Brazilian Cerrado: new records of the rare species P. allemii, Phytotaxa 538 (2), pp. 149-156 : 151-152

Phyllanthus allemii G.L. Webster (2002: 24 , Figures 1 , 2 , 3 ).

Type:— BRAZIL. Goiás [Tocantins]: Mun. Taguatinga , 7 km a nordeste de Taguatinga, BR - 242, rumo a Barreiras , 12°20’S / 46°25’W, 850 m, 19 November 1984, A. C . Allem , G. L . Webster & W. E . Werneck 3041 (holotype CEN8729 !; isotypes DAV153082 !, DAV153085 !; MICH1259636 !; SP 315080 !) .

Subshrub, 0.2‒1 m tall, erect, monoecious. Stem terete, glabrous, smooth, grayish, small lenticels. Non-phyllanthoid branching. Cataphylls absent. Branchlet axes terete, glabrous, sparsely ramifying, pinatiform, 2.2‒5.5 cm long, with (9‒)10‒17(‒20) leaves; stipules intrapetiolar persistent, 0.5‒0.7 mm long, 0.3‒0.6 mm wide, triangular, glabrous, with irregular margin, reddish brown, persistent. Petioles 0.6‒1 mm long, subcylindric, glabrous. Leaf blades 3.8‒7.1 × 2.6‒6.4 mm, orbicular, suborbicular, broad-obovate, discolorous when dry; base truncate or obtuse, apex rounded, emarginated or with short acumen 0.1mm long, symmetrical, glabrous in both surfaces, margin entire, coriaceous,adaxial surface with hifodromous venation, main vein flattened, abaxial surface with venation simple brochidodromous or hifodromous, secondary veins (3‒)4–5 pairs, flattened, tertiary veins absent. Inflorescence axillary, cymules unisexual, pistillate flowers solitary on distal axils of branchlets, staminate flowers 1 or 2 on proximal axils of branchlets. Bracts ca. 1 mm long, triangular, glabrous. Staminate flowers with pedicels 1‒1.5 mm long, sepals 5, 1‒1.3 × 0.5‒1 mm, obovate, disk segments 5, glandular, elliptic, 0.25‒0.3 mm in diam., stamens 2, completely connate into a column, 0.6 mm high, anthers sessile on the column, dehiscing obliquely, 0.25‒0.3 mm wide. Pistillate flowers with pedicels 3‒5 mm long, 0.5‒0.7 mm in diam., sepals 5, the outer 1.1‒1.2 mm long, the inner 1.4‒1.6 mm long, ca 1 mm wide, elliptic; glandular disk entire, patelliform, pitted; ovary 1.3 mm long, 3-locular, globose, style 3, appressed, bifid until half, stigma rounded. Capsule ca. 4 mm diam., mericarps 6, oblate, calyx and stigma persistent, fruiting pedicels 5‒7 mm long, columella ca. 1.5 mm long. Seeds 1.8‒2 mm long, trigonous, cream or brownish, vernicose; seed surface longitudinally finely verrucose-striate, with coarse strigose cross-striae; hilum obtriangular, terminal.

Material examined: — BRAZIL. Tocantins: Ponte Alta , ESEC Serra Geral do Tocantins, 85 km SE de Ponte Alta , 15 N km do Acampamento Brejo do Leite, Serra da Muriçoca , 10°37’33”S, 46°59’06”W, 450 m, 01 March 2021, fl., fr., M. F . Simon et al. 4168 ( CEN 118047 , PEUFR); Mateiros, ESEC Serra Geral de Tocantins. Morro à esquerda da estrada em direção a Mateiros , 10°40’06”S, 46°15’29”W, 674 m, 17 June 2021, fl., B . Schindler et al. 197 ( CEN 119070 , PEUFR, UB 217420 ) .

Taxonomic Considerations: —Original description of P. allemii was based on the A. C. Allem et al. 3041 collection made in 1984 in the municipality of Taguatinga, which formerly belonged to Goiás state, but nowadays is located within Tocantins. The species was assigned to Phyllanthus subgen. Phyllanthus sect. Phyllanthus subsect. Clausseniani by the presence of free stamens, with connective deeply emarginated or with stipitate thecae ( Webster 2002). The species was named in honour of Dr. Antonio Costa Allem, a renowned Brazilian expert in Euphorbiaceae , who collected the type material. Comparisons of the vegetative and reproductive structures of the recently collected specimens with those of the type collections ( Fig. 2 ) allowed an accurate identification of these specimens as P. allemii . According to Webster (2002), diagnostic characteristics that distinguish P. allemii from closely related species are the staminate flowers with two stamens, filaments united in a column, clavate fruiting pedicels, and larger and ornamented seeds. All these features are present in the recently collected material, confirming their usefulness in species delimitation.

Phenology: —The species has an apparently asynchronous phenology with flowering observed along the year and fruiting individuals collected in November and March.

Habitat: — Phyllanthus allemii was found growing in shrubby vegetation on the rocky slopes ( cerrado rupestre ) of flat plateaus (Serra Geral), as well as on the residual flat-topped mountains widespread in the region ( Fig. 3 ). These formations, which belong to the geological group Urucuia, are derived from the erosion of sandstone rocks ( Villela & Nogueira 2011). Rupicolous species that are conspicuous in these habitats include Cheilanthes pohliana Mettenius (1859: 23) ( Pteridaceae ), Encholirium disjunctum Forzza (2005: 15–16 , 19, 39), and Pitcairnia ensifolia Mez (1894: 436) ( Bromeliaceae ). Our new collections, together with label information on the type specimen, suggest that P. allemii is restricted to rocky soils between 450 and 850 m altitude associated with sandstone formations of the Urucuia group.

Distribution and preliminary conservation status: —So far, the species is endemic to Tocantins state. Its known geographic range extends from the slopes of Serra Geral in the Tocantins / Bahia border (town of Taguatinga) to the north on rocky slopes of remnant mountains in eastern Tocantins, ca. 180 km northwest of the original collection ( Fig. 1 ).

Phyllanthus allemii was previously classified by Santana (2021) as data deficient (DD) since it was only known from the type collection. With the new records obtained here, however, we were able to calculate an EOO of 7,531 km 2 and an AOO of 12 km 2. Native vegetation covered 82% of the species EOO in 2020. We observed an annual rate of habitat loss of 0.5% from 1985 to 2020. Decline in natural vegetation occurred mainly on the flat landscapes (plateaus) that are more suitable for large-scale agriculture.

Considering IUCN’s criterion A (population reduction), the inferred decline in the extent of EOO observed over the last ten years (2.2%; 168 km 2) does not qualify P. allemii as threatened. Considering IUCN’s criterion B (geographic range), an AOO <500 km 2, in association with a number of locations ≤ 5 and a continuing decline in EOO (observed habitat loss of 18% from 1985 to 2020; 1243 km 2), would qualify P. allemii as Endangered B2ab(i) based on IUCN criteria. However, we preferred to classify P. allemii as Near Threatened, which is applied to taxa that do not qualify as threatened now, but may be nearing that status. We justify this choice because we believe that the restricted AOO (12 km 2) and number of locations (three) reported here, both critical parameters in assessing a species under criterion B, have been clearly underestimated because of the poor sampling effort in the region. We expect that the species occurs all over the slopes of the Serra Geral, stretching for more than 300 km along the border between south-eastern Tocantins and western Bahia, as well as on rocky slopes associated with mesetas to the west. More intensive field surveys in the region would probably reveal a higher AOO and number of locations.

Field observations in two populations, both located inside a protected area, indicate that local abundance is relatively high, despite the sparse occurrence in the landscape. A recent survey in the study region ( Antar & Sano 2019) was not able to find P. allemii , suggesting that it may be relatively rare. However, these authors did not sample vegetation on rocky substrates, the preferred habitat of P. allemii .

The geographic range of P. allemii coincides with that of the Matopiba, a region comprised of parts of the states of Maranhão, Tocantins, Piauí and Bahia. These combined areas have been experiencing accelerated habitat loss caused by agricultural expansion in recent decades ( Araújo et al. 2019). Such loss of native vegetation within the range of P. allemii may result in population reduction. However, it is likely that the ecological preference of P. allemii for rocky habitats that are less suitable for large scale agriculture makes it less threatened than plants that occur on flat deep soils.

Despite its high floristic richness, which includes a large number of undescribed, rare and threatened species (e.g. Barbosa-Silva & Antar 2020), the Matopiba region still lacks detailed floristic studies since most of its territory remains under-sampled ( Antar & Sano 2019, Santana 2021). We expect that greater collection efforts in the region will reveal additional populations of P. allemii , in addition to other species rare or new to science, highlighting that the Matopiba remains a major biodiversity repository within the Cerrado region.

Figures

FIGURE 1. Location of the type collection of Phyllanthus allemii made in 1984 (circle) and two additional records in the Estação Ecológica Serra Geral do Tocantins (EESGT) collected in 2021 (triangles). Brazilian states: BA (Bahia), MA (Maranhão), PI (Piauí), TO (Tocantins). Map produced with QGIS version 3.10 (QGIS Development Team 2019).

FIGURE 2. Details of morphological structures of Phyllanthus allemii, comparing recently collected material and type specimens. A. reproductive branch, B. flowering branchlets, C. fruiting branchlets, D. stipule, E. leaf, adaxial surface, F. leaf, abaxial surface, G. leaf, adaxial surface (holotype), H. leaf, abaxial surface (holotype), I. columella of pistillate flower (holotype), J. flower, lateral view, K. staminate flower, L. pistillate flower, M. pistillate flower (holotype), N-O. fruit, P. seed, lateral and dorsal view, Q. seed, lateral and dorsal view (isotype), R. seed, ventral view; S. seed, ventral view (isotype). A-F, J-L, N-P, R from Simon et al. 4168; G-I, M from Allem et al. 3041 (holotype, CEN8729); Q, S from Allem et al. 3041 (isotype, MICH1259636). Photos: Q and S by Deise Gonçalves and Paul Berry.

FIGURE 3. Vegetation and habit of Phyllanthus allemii. A. General view of the flat topped mountain and rocky slopes of the Estação Ecológica Serra Geral do Tocantins (EESGT), B. Rocky slope of EESGT where a population of P. allemii was found (Schindler 197), C. habit, D. detail of flowering branch. C-D from Schindler et al. 197. Photos: A-B by Sérgio Noronha; C-D by Maurício Figueira.