Mimulopsis champluvierae Eb.Fisch., 2017

Fischer, Eberhard, 2017, Mimulopsis champluvierae, a new species of Acanthaceae from Rwanda and Burundi, Phytotaxa 299 (1), pp. 87-95 : 87-94

Mimulopsis champluvierae Eb.Fisch. sp. nov. ( Fig. 1–3 )

Type:— RWANDA. Western Province: Nyungwe National Park, km 22–23 of the road from Pindura to Bweyeye, 2°36’01’’S, 29°13’28’’E, 1840 m, 8 March 2013, Fischer 345/13 (holotype BR!, isotypes NHR!, K! KOBL!).

Diagnosis: —The new species is similar to Mimulopsis solmsii , but differs in the linear bracts with revolute margin, the long and violet glandular hairs in the whole inflorescence including bracts and calyx, the two bracteoles that are at least half as long as the sepals, the linear sepals, the yellow corolla with purplish patterning, the capitate stigma, and the ovary with only a few hairs at its apex.

Erect shrubby herb up to 2–2.5 m tall. Stems quadrangular, glabrous, up to 4(–8) mm in diameter. Leaves opposite; petiole 4–9.5 cm long or uppermost less than 2.5 cm long; lamina of lower ones ovate to broadly cordate, 9–15 × 6–8 cm, apex acuminate to cuspidate, base cordate with sinus to 1 cm deep, margins grossly crenate-dentate with teeth up to 1–1.5 cm long, dark green above, light green to whitish green below, sparsly sericeous-puberulent with distant eglandular hairs usually along midrib and main veins or glabrous to subglabrous; lamina of leaves ovate-lanceolate, 4.5 × 2 cm, apex acuminate, base cordate, margin coarsely dentate, sparse eglandular hairs along the veins on upper surface, and scattered to dense eglandular hairs on lower surface. Inflorescence an open branched panicle-like thyrse with long spreading branches; rachis covered with long violet glandular hairs; flowers in lax dichasia with up to 5 flowers. Bracts linear, green, persistent, margin revolute, 8–10 × 1 mm, densely covered with violet glandular hairs for up to 2.5–3 (–5) mm long. Branches and pedicels densely covered with long and short violet glandular hairs. Pedicels up to 4–10 (–12) mm long. Bracteoles 2, linear, 10–13 × 1.2 mm, (hairy or not). Calyx to 2.0 cm long, densely coverved with long violet glandular hairs for up to 3 (–5) mm long. Calyx 5-lobed to the base, lobes linear, apex obtuse, dorsal one 1.6–1.7 (–1.8) × 0.1 cm, ventral and lateral ones 1.5–1.6 × 0.1 mm. Corolla 2.3–2.5 cm long, yellow, with brownish-purplish reticulate patterning on upper and lower lip near the throat, covered with whitish hairs, basal cylindric part of tube 1.0– 1.2 cm long, 5-lobed, lobes all similar, broadly elliptic, 9–11 × 6–7 mm. Stamens 4, diadelphous; filaments free for ca. 5 mm then fused in pairs for ca. 1 mm, then adnate to corolla, glabrous; anthers 3.8–4.5 mm long, spur ca. 1.5 mm long. Ovary hairy in apical part, 4–5 × 2 mm; style ca. 1.5 cm long, slender, curved in apical part, with eglandular hairs in basal part; stigma ca. 0.2 mm long, small and capitate. Capsule lanceolate, 20 × 5 mm, glabrous. Seeds not developed.

Distribution: —The new species is distributed in Rwanda and Burundi and only known from four collections from Nyungwe National Park (2 localities) and adjacent Kibira National Park (1 locality) which represents the prolongation of Nyungwe National Park ( Fig. 4 ). Thus, It is another example of an Albertine Rift endemic restricted to a single montane forest on the Eastern Crest of the Rift.

Etymology: —The species is named after Dominique Champluvier, specialist in Acanthaceae at Meise (BR).

Notes: — Mimulopsis champluvierae is clearly similar to M. solmsii ( Fig. 5 ), which may require revision as varieties have been distinguished that may also merit specific status (see above). It is readily distinguished from the latter by the inflorescence completely covered with very long violet glandular hairs (not shorter purplish glandular hairs only in the upper part of the inflorescence axis and on the branches), bracts linear (not elliptic) with revolute (not flat) margins and densely covered with long violet glandular hairs (not shorter and colourless glandular hairs), bracteoles linear (not lanceolate) with revolute margins (not non-revolute margins), calyx lobes linear and straight (not linear-lanceolate and widest above the middle appearing slightly spathulate) and covered with long violet glandular hairs (not shorter glandular hairs), corolla yellow with purplish reticulate patterning on all five lobes near the throat (not with light brownish patterning near throat and yellow spot on lower lip, ovary with only a few hairs at its apex (not ovary and style densely hairy) and the stigma capitate (not stigma elongate, with dorsal lobe absent)

Mimulopsis champluvierae occurs at its type locality at 1840 m a.s.l. in pure stands and exhibits distinct mass flowering. On the other hand, M. solmsii is quite common in the montane forests of Western Rwanda (Volcano National Park, Gishwati-Mukura National Park, Nyungwe National Park) especially above 2000 m ascending to 2800 m, and single flowering individuals can be observed almost every year.

Habitat and Ecology: — Mimulopsis champluvierae occurs in montane rainforest along small streams and rivers between 1800 and 2100 m a.s.l. Like M. arborescens or Acanthopale conferta ( Lindau1894: 13) C.B. Clarke in Burkhill & Clarke (1899: 64), it exhibits a distinct plietesial life history, i.e. it represents a monocarpic plant with simultaneous mass flowering followed by mass death and typically simultaneous germination to start a new life cycle ( Daniel 2006). This type of life history is well observed in the genus Strobilanthes Blume (1826: 796) ( Deng et al. 2010, Kakishima et al. 2011, Tsukaya et al. 2011). This synchronous flowering and monocarpy is also observed in other Acanthaceae like Acanthopale confertiflora , Brachystephanus Nees von Esenbeck (1847: 511) ( Champluvier & Darbyshire 2009), Isoglossa Oersted (1854: 155) ( Darbyshire 2009, Darbyshire et al. 2011, Poriazis & Balkwill 2008, Balkwill et al. 2016) or other Mimulopsis species. Acanthopale confertiflora also showed mass flowering in March 2013 and was observed growing sympatrically with Mimulopsis champluvierae . The latter species always occurred in pure stands along the smaller tributary streams. The only other Mimulopsis species in this area was M. arborescens (Fig. 6), growing along a larger stream and also exhibiting mass flowering in March 2013. The last mass flowering of this latter species was observed at Gisakura in Nyungwe National Park in March 2005. During numerous visits to the area between Pindura and Bweyeye in 2006, 2007, 2009, 2010, 2011, and 2012, no flowering plants of Mimulopsis have been observed. Mimulopsis solmsii is also reported to exhibit mass flowering at intervals of seven years ( Vollesen 2008). However, the observations of this taxon in Rwanda and of the related M. excellens (Fig. 6) show that in most years, e.g. 2005, 2007, 2009, 2010, 2012, 2013, or 2016, single flowering specimens could be observed and that both taxa do not tend to show a pronounced synchronous flowering in contrast to their congeners M. arborescens and M. champluvierae . Unfortunately no data on pollination are available.

Conservation status.—With an area of occupancy of 27 km ², Mimulopsis champluvierae is considered to be endangered (EN, B1+2) according to criteria ( IUCN 2016). The whole population is located in two protected areas, i.e. Nyungwe National Park in Rwanda and Kibira National Park in Burundi, and the assessment should be EN B1a+2a.

Additional specimens examined (Paratypes):— RWANDA. Western Province Nyungwe National Park , environs de Rangiro, forêt de Bururi, 05 June 1981, Troupin 16275 ( BR, K) . BURUNDI. Bubanza: Mugomero , 3°13’S, 29°31’E, 2100 m, 12 June 1981, Reekmans 10608 ( BR, K) ; ibid., 01 May 1981, Reekmans 9999 ( BR, K) .

Figures

FIGURE 1.Mimulopsis champluvierae. A. Flower, lateral view; B. Flower, adaxial view; C. Calyx; D. Portion of dissected corolla; E. Stamens; F. Bract; G. Detail of bract margin showing glandular hairs; H. I. Details of calyx; K. Hairs on pedicel; L; Pistil, ovary with style and stigma.All drawn by Fischer from the type.

FIGURE 2.Mimulopsis champluvierae. A–B. Inflorescence; C–D. Habit. Photo by Fischer at Pindura, Bweyeye in March 2013.

FIGURE 3.Mimulopsis champluvierae. A–D. Various views of the flower. Photo by Fischer at Pindura, Bweyeye in March 2013.

FIGURE 4.Mimulopsis solmsii. A. Iinflorescence; B–D. Detail of inflorescence with flower. Photo by Fischer at Mt. Muzimu in March 2007.

FIGURE 5. Mimulopsis excellens., A. Inflorescence; B. Inflorescence with flower. Mimulopsis arborescens. C. Habit; D. Inflorescence. Photo by Fischer at Mt. Bigugu in March 2009 (A, B), C Pindura, Bweyeye in March 2013 (C) and Gisakura in March 2005 (D).