Lindernia barthlottii (Linderniaceae), a new species from inselbergs in Madagascar Author Fischer, Eberhard Institute for Integrated Natural Sciences-Biology, University of Koblenz, Universitätsstrasse 1, 56070 Koblenz, Germany. Author Andriantiana, Jacky Lucien Parc Botanique et Zoologique de Tsimbazaza (PBZT), Rue Fernand Kasanga, Tsimbazaza, 101, Antananarivo, Madagascar. jacky. andry @ yahoo. fr Author Sieder, Anton Botanischer Garten der Universität Wien, Rennweg 14, 1030 Wien, Austria. Anton. text Phytotaxa 2023 2023-11-23 626 3 191 198 https://phytotaxa.mapress.com/pt/article/download/phytotaxa.626.3.5/51310 journal article 278756 10.11646/phytotaxa.626.3.5 141d1773-71e6-4946-a05a-3fa8a0ab8c29 1179-3163 10200280 Lindernia barthlottii Eb.Fisch., Andriant. & Sieder , sp. nov . ( Figs. 1–2 ). Type :— MADAGASCAR . Mahajanga , Sofia , inselberg near RN 32 between Ankobakobaka und Ampombilava , humid rocks fully exposed in the sun, 15°06’24.0`` S 48°15’52.5``E , 280 m a.s.l. , 8 February 2020 , A. & C . Sieder & J. Andriantiana, 8174 ( holotype WU0134599 ! , isotype TAN ) . Diagnosis: — Lindernia barthlottiii differs from all Madagascan species of Lindernia in the small rosulate habit with condensed stems, the broad obtuse sepals (2.8–2.9 × 0.5–0.7 mm ), and the large and except for the palate entirely blue corolla. FIGURE 1. Lindernia barthlottti Eb.Fisch., Andriant. & Sieder sp. nov . —A. Habit.—B. Corolla with upper lip removed.—C. Detail of corolla showing adaxial stamens (scale bar as in C).—D, E. Staminodes.—F, G. Stamens.—H. Calyx with pistil, style and stigma. Drawn by E.Fischer from A. & C. Sieder & J. Andriantiana, 8174. Description: —Erect annual rosulate herbs. Roots at base of stem white, dense, up to 6 × 0.5 mm . Stems, leaves and pedicels glabrous. Stems condensed, not exceeding 7–10 mm of length. Leaves opposite, rosulate, rounded-orbicular, veins hardly visible, 4.3–7 × 2.5–5 mm , apex obtuse, margin entire. Inflorescences frondose, condensed, with leaflike bracts, flowers axillary and solitary, each node of bracts with just one fertile bract bearing a flower; flowers ebracteolate; pedicels 3–4.6 mm long. Calyx dull green with purple margin at the lobes, 2.4–2.9 mm long, 5-lobed with obtuse lobes 2–2.2 mm long, glabrous. Corolla entirely blue with dark purple-blue veins and white palate, bilabiate; tube held erect, cylindrical, 4–4.2 mm long, c. 1–1.7 mm in diameter; upper lip hooded, 2.4–2.6 mm long, triangular from broad base, 4–5 mm , distinctly bifid; lower lip with three rounded obtuse lobes 2.3–2.6 mm long and 1.6–2.1 mm wide, palate white, minutely puberulous with minute clavate hairs centrally and extending into throat. Stamens two, adaxial, attached at base of upper lip, filaments 1.3–1.4 mm long, glabrous, convergent, the divergent anther thecae forming a cross-shape, thecae 0.5 × 0.05 mm , obtuse at apex; abaxial staminode s attached in tube, lower part connate with tube, 1.3–1.6 mm long, densely covered with yellow glands, free part clavate, slightly curved at apex, 0.3–0.4 mm wide, densely covered with yellow glands. Pistil glabrous; ovary oblong, 1.1–1.3 mm long; style slender, 1.8–2 mm long; stigma of two broad membranous lobes, 0.7–0.8 mm in diameter. Mature fruit not known. Immature seeds not alveolated, with shallow longitudinal ribs. FIGURE 2. Lindernia barthlottti Eb.Fisch., Andriant. & Sieder sp. nov . —A,. Detail of habitat.—B. Habit. Photographs: A.Sieder, 8 February 2020. Scale bars: A. 5 mm – B. 2 mm. Distribution :— Madagascar , Mahajanga , Mandritsara region, only known from the type locality ( Fig. 3 , 4 ). Habitat :—Granitic inselberg, in seasonally humid ephemeral flush vegetation ( Fig. 4 ). Etymology :—Named after Wilhelm Barthlott who first defined the vegetation of inselbergs. Conservation status :— Lindernia barthlottii has at present only been observed at the type locality. There is no observation of an actual threat at this locality. From the AOO and EOO it could qualify for the Critically Endangered category (CR), according to criterion B of IUCN (2022) .Although in similar cases plant species of different genera and families on various continents have often been attributed to this threat category ( Wagensommer & Venanzoni 2021 , Ngoc et al. 2022 , Zhigila & Muasya 2022 ), there are no observations on population size and possible decline of L. barthlottii . Moreover, the species may prove to be more abundant in adjacent areas. Thus, it is provisionally assessed as DD (Data Deficient).