Research Article |
Corresponding author: Miguel Leal ( mleal@wcs.org ) Academic editor: Hugo de Boer
© 2014 Miguel Leal.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Leal M (2014) Dorstenia luamensis (Moraceae), a new species from eastern Democratic Republic of Congo. PhytoKeys 42: 49-55. https://doi.org/10.3897/phytokeys.42.7604
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A new species of Dorstenia L. (Moraceae), D. luamensis M.E.Leal, is described from the Luama Wildlife Reserve, west of Lake Tanganyika and north of the town of Kalemie in the eastern part of the Democratic Republic of Congo (DRC). This species is endemic to the region and differs from any of the other species by its fernlike lithophytic habit and lack of latex. A description and illustration of this species is presented here. Dorstenia luamensis M.E.Leal inhabits moist and shady vertical rock faces close to small waterfalls in the forest; the species is distributed in small populations within the type locality, and merits the conservation status of endangered (EN).
Dorstenia , Albertine Rift, endemic, lithophytic
In 2012, a specimen of Dorstenia L. was collected from the Luama Wildlife Reserve in eastern DRC (M.E. Leal 2551) hanging from vertical cliffs and rock faces close to a waterfall on the shear zone of two figaus. These plants have a typical Dorstenia L. inflorescence but their hanging habit and lack of latex is unusual. The only other hanging Dorstenia species (hemi-epiphyte) is D. astyanactis Aké Assi first described from Ivory Coast (
The specimens collected in the Luama Wildlife Reserve keyed out to the section of Kosaria using
Therefore in this study, I compared the specimens collected from the Luama Wildlife Reserve with D. benguellensis Welw. to determine: 1) whether differences are insignificant and the existing description of D. benguellensis Welw. should be broadened to incorporate these specimens, or 2) whether differences are significant and these specimens should be described as a separate species. I argue that differences beyond habit are significant and that they merit their own status as a new species from the Luama Wildlife Reserve, D. luamensis M.E.Leal.
The collected specimens from the Luama Wildlife Reserve were compared to D. benguellensis Welw. following terminology and description format of
Table
D. benguellensis | D. luamensis | |
---|---|---|
Plant | Succulent herb | Herbaceous Herb |
length | Up to 50(-60) cm | 10–17 cm |
Root system | Tuber | Tuber |
posture | Erect | Hanging |
Leaves arrangement | Spiral | horizontal |
lamina | Oblong, sub(ob)ovate, linear, elliptic, ovate | Subfalcate |
dimensions | 1–15×0.2–4.5 cm | 5–7×1.1.4 cm |
apex | acute to subacuminate or obtuse | Acute and micrunate |
base | cuneate, sometimes obtuse to rounded | asymetrical cunate and rounded |
margin | finely to rather coarsely dendate (to subcrenate) or sometimes serrulate | Entire to coarsely dendate |
surfaces | puberulous to hirstellous or to hispidulous | Glabrous, subspiculate, bicolorous |
lateral veins | 4–12, up to 25 pairs, often (fainly) loop connected, reticulum rather narrow | 5–7 |
petiole | (0-)0.1–0.2(-0.5) cm long | 1–2 mm long |
stipules | persistent, triangular to oblong, up to 5 mm long, sometimes foliaceous, puberulous | Not observed |
Inflorescences | solitary or sometimes in pairs | solitary |
Peduncle | (0.3-)0.5–2.5(-7) cm long, ca. 1–1.5 mm thick | 0.1 cm long |
minutely puberulous to hirstellous or to hispulous | glabrous | |
receptacle | discoid to broadly turbinate, sometimes, shallowly cup-shaped, suborbicular 0.5–2(2.5) cm in diameter | elliptic to round, 3–4 mm in diameter, patelliform |
outside sparsely, to densely minutely puberulous to hirtellous to hispidulous | glabrous | |
flowering face | (sub)orbicular, sometimes to subangular or almost elliptic, fringe up to 1 mm broad or absent | elliptic to round |
appendages | inner (=marginal) row numerous, triangular to subulate or filiform, up to 1–5(-7) mm long, forming a (sub)crenate rim, or indistinct and the rim entire to faintly repand, | triangular lobes, 1 mm |
outer (=submarginal) row, usually ca. 5–12 mm, less commonly more than 12, up to 23, or less than 5, down to 2, or even 0, (broadly) ligulate to filiform or sometimes subspatulate or oblong, (0.1)0.2–3.5(-8) cm long, up to 2.5 mm broad | subspathulate, 2–3 mm long, 0.5 mm broad | |
staminate flowers | ±crowed, tepals 2, puberulous with white, red-brown or almost black hairs, stamen 2, filaments ca. 0.3–0.5 mm long, slender | few, glabrous, stamen 2, filaments ca.0.1 mm |
pistillate flowers | several to many, free part of the perianth shortly tubular, puberulous with white, red-brown or almost black hairs, stigmas 2, filiform, ca. 0.2–0.3 mm long, equal or unequal in length, sometimes one of the stigmas strongly reduced or a single stigma | few, glabrous, stigmas 2, filiform, ca. 0.1 mm long, |
Endocarp | body tetrahedral to subglobose, ca. 2 mm long, tuberculate, pale brown | Not observed |
D. benguellensis Welw. and the specimens collected from the Luama Wildlife Reserve are most conspicuously different in vegetative morphology, both in size and shapes. Key differences mentioned in the key to “succulent and semi-succulent species of the Old world” (
D. benguellensis has been characterized as highly variable, which might raise the question whether the specimens from the Luama Wildlife Reserve are an adaptation to growing on vertical rock faces. Are there two types of D. benguellensis Welw.? The most common one is erect and grows in between rocks and the hanging one is rare and only grows on vertical rock faces. If this were the case, than I would have expected to find the erect type at the same location of the hanging type. This was however, not the case.
Based on the differences in vegetative morphology, the specimens from the Luama Wildlife Reserve can easily be keyed out from the sister species in the same section of Kosaria (see the key provided under “distinct from other species”. These plants from the Luama Wildlife Reserve resemble ferns hanging from rocks. This has not been observed elsewhere for the genus. Therefore, I conclude that the specimens from the Luama Wildlife Reserve merit their own separate status as new species, Dorstenia luamensis M.E.Leal, sp. nov.
Haec species notabilis ab omnibus Dorstenia speciebus differt ob filicinu lithophitu habitu novu familae
The Democratic Republic of Congo, Katanga Province, Tumbwe Sector, Luama Wildlife Reserve, M.E. Leal 2551 (holo LWI, iso BR), S5°14,526', E 28° 52,215', 1176m, 31 October 2012.
Lithophytes 10–17 cm long with a tuber 0.5 cm; stems aerial, hanging, glabrous; internodes 2.5–3 cm long; no white latex or translucent exudate. Stipules absent or deciduous without scars. Leaves distichous; blade narrowly subfalcate 5–7 × 1–1.4 cm, membranaceous, apex micrunate, base cunate, adaxial side glabrous and subspiculate, abaxial side white and glabrous; margins entire; petiole 1–2 mm long; venation brochidodromous; 5–7 pairs of secondary veins; tertiary veins scalariform. Receptacle elliptic to round, 3–4 mm in diameter, patelliform; margin greenish with triangular lobes (1 mm) and subspathulate appendages, 2–3 mm long; peduncle 1 mm long, glabrous. Staminate and pistilate flowers (7 to 8) tightly packed in receptacle: perianth short lobed, whit apex minutely 2–3 lobed, glabrous; stigma 0.1 mm long. Drupes and seeds are unknown.
This new species can be distinguished from any other Dorstenia species by its fernlike habit, hanging from vertical rock faces and the absence of latex.
The new species is added to the existing key of
1 | Stems succulent and thick, internodes short; leaves subrosulate | section Acauloma |
1’ | Stems (semi-)succulent, or herbaceous, internodes long; leaves spaced, sometimes crowded at stem apices | section Kosaria, 2 |
2 | Plants stem hanging | |
3 | Plant lithophyte, multiple appendages | D. luamensis |
3’ | Plant epiphyte, one appendage | D. astyanactis |
2’ | Plants stem erect to ascending | |
4 | Plants annual, without a rhizome or a tuber | D. annua |
4’ | Plants perennial, with rhizome or a tuber | |
5 | Petiole relatively short, (0-)0.1–0.2(-0.5) cm long | D. benguellensis |
5’ | Petiole relatively long (0.2-)0.5–2.5(-3) cm long | other species of section Kosaria |
The specimens were collected in late October.
D. luamensis M.E.Leal inhabits moist and shady vertical rock faces close to small waterfalls in forest within a riverine forest-open woodland-savanna mosaic.
The species is distributed in small populations within the type locality, and according to these demographic characteristics it merits the conservation status of endangered (EN).
The epithet luamensis refers the Luama Wildlife Reserve which is drained by the Luama River.
This study was financially supported by the Mac Arthur Foundation. The author is grateful to the Centre de Recherche en Sciences Naturelles (CRSN/Lwiro) for administrative support and to Phytokeys secretary for providing the essential references and the reviewers for their valuable comments.