Crepidorhopalon droseroides Eb.Fisch., Wursten & I.Darbysh., 2023

Fischer, Eberhard, Wursten, Bart & Darbyshire, Iain, 2023, A new and possibly carnivorous species of Crepidorhopalon (Linderniaceae) from Mozambique, Phytotaxa 603 (2), pp. 191-198 : 192-194

Crepidorhopalon droseroides Eb.Fisch., Wursten & I.Darbysh. sp. nov. ( Fig. 1 , 2 )

Holotype:— MOZAMBIQUE, Swanepoel Concession , Cheringoma, 18°33’14.72’’S 35°2’3.336’’E, 240 m, along path in dry dambo area on black cotton soil, 13 April 2017, B. Wursten 1765 (holotype LMA!, isotype BR0000027303641V!).

Diagnosis: —The new species differs from all known species of Crepidorhopalon in the dense and long sticky glandular hairs covering stems, leaves, pedicels and calyx. The morphologically closest species are Crepidorhopalon microcarpaeoides (Bonati) Fischer (1990: 413) ( Lindernia microcarpaeoides Bonati 1924: 101 ) from Madagascar and C. debilis (Skan) Fischer (1995: 8) ( Lindernia debilis Skan in Hemsley & Skan 1906: 344) from South Central Africa. They are also minute annuals not exceeding 2 cm of stem length and grow on rock outcrops or quartzitic white sands. Both differ in the yellow corolla, the only short and sparse glandular hairs and the ovate to lanceolate leaves (corolla white, leaves broadly ovate in C. droseroides ).

Description:— Annual herbs, up to 13–15 mm tall. Leaves, stems, pedicels and calyx densely covered with up to 0.34–0.4 mm long capitate sticky glandular hairs. Stems erect, quadrangular, up to 13 mm long, up to 0.32 mm in diameter. Leaves sessile, lamina broadly ovate, acuminate at apex, 3.7–4.56 × 2.9–3.55 mm, with entire margin, only midnerve visible. Inflorescence terminal, racemose, with 1–2 flowers borne in axils of leaf-like bracts. Bracts ovate, acute, 2.85–2.92 × 1.4–1.55 mm. Pedicel 2.93–5.16 mm long. Calyx 5-lobed, campanulate, glandular-pubescent, 1.85–2.1 mm long, lobes acute, 1.8–2.05 mm long, margins entire. Corolla up to 4 mm long, white with four bluish marks on lower lip at throat and yellow globose hairs of c. 0.05 mm length on a multicellular base, tube 2.9 mm long, inside with dense glandular hairs at base of staminal veins, upper lip with 2 acute lobes up to 0.15 mm long, 1.4 × 1.2 mm, inside with scattered glandular hairs, lower lip tripartite, up to 3.1 mm long, middle lobe 2.3–2.5 × 1.7–1.8 mm, rounded-obtuse, margin minutely fringed, lateral lobes 1.8–2 × 1–1.1 mm, rounded-obtuse. Stamens 4, filaments of the abaxial pair 1.5 mm long, with basal rounded deep yellow spur-like bosses up to 0.15 mm long covered by short glandular hairs, with 0.35–0.37 mm long rounded anthers, filaments of adaxial pair 0.7 mm long, with obtuse anthers 0.37 mm long. Ovary 1.2–1.5 × 0.7 mm, with straight to slightly curved, filiform style, 2.5 mm long, glabrous. Capsule and seeds not known.

Etymology:—The species name refers to the similarity of the plant with carnivorous Drosera species.

Distribution:—Only known from the type collection on the Cheringoma Plateau , Sofala Province in Mozambique.

Ecology:—Growing on open black cotton soil in a seasonally dry dambo area in miombo woodland dominated by Brachystegia spiciformis Bentham (1865: 312) at 240 m a.s.l.

Conservation status: —One population of this species has so far been found. A rough estimate would place the known population of mature individuals at less than 100, within the threshold to potentially qualify this species as Endangered under either criterion C or criterion D following the IUCN (2012, 2022) guidelines. However, no actual threats have been observed. The general area has formerly been used for selective logging but activities have ceased and the area currently falls under the protection of Gorongosa National Park as a Buffer Zone. With only a single collecting site, it is not possible to calculate an Extent of Occurrence (EOO) according to the IUCN criteria ( IUCN 2012, 2022) (e.g. Wagensommer et al. 2013, 2014). The area of occupancy (AOO) of 4 km 2 falls within the limits for the Critically Endangered category under criterion B2. However, as the species is minute and may have been overlooked elsewhere, it is best assessed as Data Deficient (DD).

The type locality for Crepidorhopalon droseroides , the Swanepoel Concession, is not currently included within the Important Plant Areas (IPA) network for Mozambique ( Darbyshire et al. 2023) but the site might qualify on the basis of the presence of this newly described species if it is considered to be globally threatened following full assessment. The Concession lies within the vast (over 23,000 km 2) Gorongosa-Marromeu Key Biodiversity Area (KBA; WCS et al. 2021), and this species should be incorporated into the KBA assessment under criterion B1 as a further point-endemic. Other endemic plant species are noted from the Cheringoma region, including the recently described Cola cheringoma Cheek ( Cheek et al. 2019: 9) which is restricted to the only known limestone forests of Mozambique, within the Cheringoma Limestone Gorges (Desfiladeiros de calcário de Cheringoma) IPA ca. 20 km to the WSW of the locality for C. droseroides ( Cheek et al. 2019; Darbyshire et al. 2023; Richards & Darbyshire 2023).

Figures

FIGURE 1. Crepidorhopalon droseroides. Eb.Fisch., Wursten & I.Darbysh. sp. nov.—A, B. Habit.—C. Detail of habit.—D. Flower. Photographs: B.Wursten, Cheringoma Plateau. Scale bars: A–D. 2 mm.

FIGURE 2. Crepidorhopalon droseroides. Eb.Fisch., Wursten & I.Darbysh. sp. nov..—Insects sticking to the viscid glands.—A, B. Phoridae, Diptera.—C. Culicidae, Diptera.—D. Unidentified spider. Photographs: E.Fischer, from the holo- and isotype. Scale bars: A. 1 mm, B–D. 0.5 mm.