Hemipogon trilobatus Bitencourt & Rapini, 2020

Bitencourt, Cássia, Santos, Amanda P. B., Snak, Cristiane & Rapini, Alessandro, 2020, Hemipogon trilobatus sp. nov. (Apocynaceae: Asclepiadoideae), a new microendemic from Chapada dos Veadeiros, Central Brazil, European Journal of Taxonomy 729, pp. 1-10 : 3-6

Hemipogon trilobatus Bitencourt & Rapini sp. nov.

urn:lsid:ipni.org:names:77213240-1

Figs 1–2

Diagnosis

Flowers with reduced, apically 3-lobed corona lobes. Similar to H. acerosus due to the acicular leaves, sessile cymes and urceolate corolla, internally bearded along the lobe basal half, but can be distinguished by the opposite leaves (vs verticillate in H. acerosus ) and presence of a corona (vs absence in H. acerosus ).

Etymology

The epithet ʻ trilobatus ʼ refers to the apically 3-lobed corona lobes.

Type material

BRAZIL • Goiás, Alto Paraíso de Goiás , Chapada dos Veadeiros , 9 km de Alto Paraíso para Vila S„o Jorge, Cachoeira S„o Bento ; 9 Sep. 1994; M. Aparecida da Silva, T.S. Filgueiras, R.C. Mendonça, M.L.F. Resende, F.C.A. Oliveira and E. Cardoso 2320; holotype: IBGE[33546] !; isotype: RB[496900] !.

Paratype

BRAZIL • Goiás, Alto Paraíso de Goiás , Chapada dos Veadeiros; 14 Aug. 1992; H.D. Ferreira 2579; UFG[14114] !.

Description

Herbs to subshrub erect, 20–30 cm tall; stems 2 or 3, diverging at base, cylindrical, glabrescent; latex white. Leaves opposite, obliquely erect, sessile, acicular to narrowly elliptic, 0.7–1 × 0.1–0.13 mm, apex acute, base cuneate, margins entire, coriaceous, glabrescent. Cymes alternate, 2- or 4-flowered, subaxillary; bracts lanceolate, ca 1.5 × 0.6 mm, glabrous, sessile. Flowers with pedicel 1–1.5 mm long; sepals ovate, 1.5–1.6 × 0.5–0.7 mm, apex acute, glabrescent, axillary colleters not seen; corolla urceolate, probably cream or white, abaxially glabrescent, adaxially bearded from base to centre of lobes, tube 0.5– 0.7 × 0.8–1.1 mm, lobes triangular, 1–1.2 × 0.8–1 mm, apex acute and recurved; corona staminal, lobes short, at base of anthers, oblate, 0.3–0.45 × 0.7–0.76 mm, apex 3-lobed; anthers 0.45–0.5 × 0.6–0.7 mm, triangular, wings triangular, 0.3–0.4 × 0.15–0.2 mm, connective appendage oblong, 0.3–0.4 mm long, over gynostegium; corpusculum ellipsoid, 0.17–0.25 × 0.08–0.1 mm; caudicles horizontal, ca 0.05 mm long, subapically attached to pollinia; pollinia ellipsoid, 0.16–0.2 × 0.06–0.08 mm; style-head apically mammillate, included within corolla tube. Follicles not seen.

Distribution, habitat and phenology

Hemipogon trilobatus sp. nov. is known from a small population nearby the S„o Bento waterfall, in Chapada dos Veadeiros, Goiás, Brazil ( Fig. 2 ). It grows in open savannah and wet grasslands locally known as “várzea” and was collected with flowers in August and September. The species has not been found since a fire burned the type locality (M.A. da Silva, pers. com., 2015).

Provisional conservation status

Hemipogon trilobatus sp. nov. is known from only two collections, both near the S„o Bento waterfall, in Chapada dos Veadeiros. Specimen labels provide no information about population density. However, the species is known to occur in a tourist location, surrounded by farms and cattle raising, has an area of occupancy (AOO) estimated at 8 km 2, probably under continuing decline in geographic range and habitat quality. During fieldwork in the type locality, we did not find any specimen of H. trilobatus sp. nov. and the new species has not been recollected since 1994. Based on criteria B2ab(i,ii,iii,iv) of the International Union for Conservation of Nature ( IUCN 2019) Red List assessment, we provisionally classify the species as Critically Endangered (CR).

Taxonomic note

Hemipogon trilobatus sp. nov. has narrow leaves, urceolate corolla with bearded lobes and was found in a savannah of Central Brazil. Together, these features support its classification in Hemipogon s. str. It most closely resembles H. acerosus based on the acicular leaves and sessile cymes, but differs from all other taxa in the genus by the opposite leaves and flowers with reduced corona lobes, as presented in the key below and Table 1 .

Figures

Fig. 1. Hemipogon trilobatus Bitencourt & Rapini sp. nov. A. Habitus. B. Cyme with two flowers and a bud. C. Flower. D. Flower with calyx and two corolla lobes removed to show the gynostegium. E. Corolla lobe, adaxial view. F. Anther with a staminal corona lobe basally attached. G. Corona lobe showing the 3-lobed apex, adaxial view. H. Gynostegium, viewed from above. I. Pollinarium. Drawn by Pétala Gomes Ribeiro from the holotype (IBGE[33546]).

Fig. 2. Habitat and distribution of Hemipogon trilobatus Bitencourt & Rapini sp. nov. A. Open savannah in Chapada dos Veadeiros, state of Goiás, Brazil. Photo by CB. B. Map showing the geographic distribution of H. trilobatus sp. nov. in the Cerrado domain (shaded area at reference map in A) and its occurrence (black star) nearby the Chapada dos Veadeiros National Park. Images and distribution maps were built and exported using ArcGIS online (https://www.arcgis.com). © Esri and its licensors, all rights reserved.