Aptosimum lineare Marloth & Engl.

Kolberg H., van Salgeren M. 2016. A synopsis of Aptosimum and Peliostomum (Scrophulariaceae) in Namibia, including the description of a new species, Aptosimum radiatum, and keys to all accepted species. Kew Bulletin 71:16. DOI 10.1007/S12225-016-9628-7

Type

Type: Namibia, Erongo Region, Hereroland, Usakos, Marloth 1241 (lectotype PRE-590785!, selected here; isolectotype PRE-158545). — see Notes.

Morphology General Habit

Shrub or caespitose, to 25 cm tall, sparsely short hairy all over, spinescent

Morphology Stem

Stems erect to ascending, densely leafy, 2 – 15 (– 40) cm long, base woody, slightly to pronounced corky, tips densely bristly, sometimes rufous villous, short glandular or very minutely puberulous

Morphology Leaves

Leaves alternate to fascicled, narrowly linear, linear-oblanceolate, narrowly elliptic to lanceolate, 30 – 120 × 1.5 – 6 mm, glabrous, hispidulous, appressed hairy or sparingly glandular-hairy, pubescence sometimes ferruginous; apex acute to obtuse, shortly mucronate; base attenuate, subsessile or sessile, sometimes papillose above; midrib stout, whitish, sparsely hispid beneath, spinescent; margins glabrous, sparsely ciliate only at base to ciliate on lower half

Morphology Reproductive morphology Flowers

Flowers solitary or in 3 – 5-flowered dichasia, axillary, sessile to subsessile; pedicel short; bracteoles narrowly linear, 3 – 10 × 1 mm, overtopping calyx, villous, apex attenuate

Morphology Reproductive morphology Flowers Calyx

Calyx lobed to near base, green; tube 2 – 3 mm long; lobes linear to narrowly linear-lanceolate, broadest at base, 5 – 10 mm long, villous or rarely glandular outside, glabrous, scabrid or glandular-pubescent inside, apex acuminate to acute, margins or sinuses long ciliate

Morphology Reproductive morphology Flowers Corolla

Corolla 20 – 25 mm long, sparsely and shortly bristly, glandular-pilose to villous outside; tube basally 5 – 12 mm long, 1 mm diam., gradually widened towards mouth, wide part 6 – 12 mm long, 5 – 6 mm diam., whitish to pale purple with dark venation outside, white inside; lobes broadly ovate to obovate, subequal, 3 – 7 mm long and wide, inside bright blue to purple, very dark purple patch at base

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens four, filaments of longer pair 9 – 12 mm long, shorter pair 4 – 8 mm; anthers of longer pair 2 – 3.5 mm in diam., pilose, those of shorter pair much smaller, mostly sterile

Morphology Reproductive morphology Flowers Gynoecium Ovary

Ovary ovoid, glabrous, 2 mm long; style filiform, c. 20 mm long, exserted from corolla tube, base hairy; stigma capitellate

Morphology Reproductive morphology Fruits

Capsule compressed-obovoid, c. 7 × 5 mm, sparsely short pilose with conical papillae, reticulate; apex emarginate

Morphology Reproductive morphology Seeds

Seeds subcylindrical, black, minutely rugose or scrobiculate

Ecology

Occurs on a diversity of soil types and topographical features in all vegetation types of Mendelsohn et al. (2010) except those in the extreme north-east and south-west of Namibia. Found in all phytogeographical regions of Craven (2009), except the Namib Dune group. Altitude: 730 – 1800 m.

Conservation

This is the most widespread species of Aptosimum in Namibia and populations can be quite large. The EOO and AOO are well above the threshold for threatened categories under criterion B and no threats could be identified, making the evaluation here LC (IUCN 2012, 2013). In South Africa the status was also evaluated as LC (SANBI 2014).

Phenology

Flowering and fruiting throughout the year. Peak flowering: Feb. – April. Peak fruiting: March – April.

Vernacular

Hereroveilchen (German, Namibia); ximahlomahlwane (Tsonga, South Africa).

Note

Merxmüller & Roessler (1967: 17) were of the opinion that the varieties of Aptosimum lineare described by Weber (1907: 37) could not be upheld because they are not clearly distinguishable morphologically nor are their distributions geographically separate. The overlap in morphological features between varieties was confirmed in this study and the varieties are thus sunk.

Aptosimum lineare may be confused with A. glandulosum, but is distinguished on calyx morphology; see Notes under the latter species. A. transvaalense Emil Weber is similar to A. pumilum and A. lineare in the leaf shape and ciliate leaf bases, but the calyx of A. transvaalense is lobed only to the middle, whereas that of the latter two species is lobed nearly to the base. The characters as described for A. lineare and A. pumilum overlap, in particular that of the now synonymised A. lineare var. acaule and var. ciliatum. There are a few Namibian specimens that more closely resemble the type of A. pumilum than the type of A. lineare or any of its synonyms. On the other hand, the distribution of these specimens does not overlap with that of A. lineare in Namibia, which would suggest a different species. The distribution of the specimens cited under A. pumilum is quite disjunct from the known distribution for that species, but this could be due to the scarcity of specimens from countries between Tanzania (the southern-most country of the main distribution area of A. pumilum) and Namibia, in particular from Angola, or misidentification of specimens. Philcox in his treatment of Aptosimum for Flora Zambesiaca (1990) recorded A. lineare for Zimbabwe and a doubtful locality in Zambia. These specimens, however, do not resemble the Namibian specimens placed under A. pumilum in this study but rather A. lineare. Since the known distribution of A. pumilum is in drier parts of Africa, it is not expected to occur in the FZ area, but the Namibian specimens cited are closer to the FZ area than to the drier parts of both Angola and Namibia. A more detailed investigation is needed to clarify the identity of the Namibian specimens placed provisionally here under A. pumilum and if A. lineare should be synonymous with A. pumilum, the latter then being the older name.

One of the specimens of Marloth 1241 reported to be at PRE (PRE-590785) is selected here as lectotype because it is a complete specimen. The second specimen (PRE-158545) that is housed at PRE according to their online database (http://sibis.sanbi.org/faces/SearchSpecimen/SpecimenResults.jsp?1=1) was not seen and according to herbarium staff has been mislaid. Schinz 515, the type of Aptosimum lineare var. acaule, is represented as “2 Bogen” [2 sheets] in Z, of which the more copious one (Z-28251) is chosen here as the (lecto)type in view of Art. 9.1 of the ICN (McNeill et al. 2012). Lüderitz 104 at Z is selected as the lectotype for A. lineare var. ciliatum because it is a good quality, complete specimen. Dinter 1113, another syntype, could not be traced and was most likely lost at B during World War II, while Fleck 584 could not be found in the herbaria where it is considered most likely to be housed. For A. nelsii, Nels 253 at Z is selected as lectotype because the other syntype, Rautanen 426 could not be found, including in Z where most Rautanen specimens are housed.

Extinction risk predictions for the world's flowering plants to support their conservation (2024). Bachman, S.P., Brown, M.J.M., Leão, T.C.C., Lughadha, E.N., Walker, B.E. https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.19592

Conservation

Predicted extinction risk: not threatened. Confidence: confident