Int. J. Curr. Res. Biosci. Plant Biol. 4(4), 61-74 (2017)
International Journal of Current Research in
Biosciences and Plant Biology
Volume 4 ● Number 4 (April-2017) ● ISSN: 2349-8080 (Online)
Journal homepage: www.ijcrbp.com
Original Research Article
doi: https://doi.org/10.20546/ijcrbp.2017.404.010
Two New Species of Loxogramme and Lepisorus (Polypodiaceae): Endemic
Ferns from Kivu-Ruwenzori Mountain System (Eastern D.R.Congo,
Albertine Rift)
Jean De Dieu Mangambu Mokoso1,2* and Ruurd van Diggelen2
1
Université Officielle de Bukavu, Département de Biologie, Laboratoire de Systématique Végétale et de Biodiversité, Bukavu,
D.R. Congo
2
Department of Biology, Vegetal Ecology Ecosystem Management Research Group, Antwerp University, Antwerp-Wilrijk, Belgium
*Corresponding author.
Abs tract
Article I nfo
This article mentions the presence of two new species or variation discovered and
described once in the Kivu-Ruwenzori mountain system in D. R. Congo. The used
methodology is related to taxonomy treatment of herbarium with macroscopic and
microscopic observations of spores. We have also established chronological and
ecological analysis. Loxogramme ntahobavukiana to simple fronds, pinnately lobed,
notched, oblanceolate the base and without sori exindusiate, elongated, oblique to costa.
While Lepisorus robbrechtiana was characterized by monomorphic fronds, with a
tendency to fronds monomorphic, with a tendency of dimorphism, lamina of two kinds,
assimilating holders of sori, long each lobed at the vein rib fork, and others are short
integers and simple vein.
Introduction
During our taxonomic research on ferns and allies ferns of
the mountains of the eastern Democratic Republic of
Congo (DRC), two new species of Polypodiaceae,
Loxogramme ntahobavukiana (Subfamily Polypodioideae,
tribus Loxogrammeae (Roux, 2001) and Lepisorus
robbrechtiana (Subfamily Polypodioideae, Tribus
Microsoreae (Roux, 2001) were collected and identified
as new. Both species are perennials, hemi-epiphytes of
shrubs or trees. The first species was found in the
Lemera and Kalehe areas middle plateau, in the
Tshivanga mountain area (Kahuzi-Biega National Park
“KBNP”) and in the Burhinyi escarpments at the
Accepted: 31 March 2017
Available Online: 06 April 2017
Keywords
Endemic Kivu-Ruwenzori
mountain system
Lepisorus robbrechtiana
Loxogramme ntahobavukiana
Polypodiaceae
Itombwe Natural Reserve (INR). As for the second
species, apart from the specimens collected from the
KBNP, its two samples were collected in the volcanic
rocks of the Virunga National Park (ViNP) in the
vicinity of Kilimanyoka.
The species named Loxogram ntahobavukiana has
affinity with Loxogramme abyssinica, which is an East
African Afromountain species, and Lepisorus
robbrechtiana also has similarities with Lepisorus
excavatus, an Afro-Madagascan species. A similar case,
the confusion between Lepisorus excavatus, and the new
species Lepisorus robbrechtiana, was reported by
Mangambu (2013). Several specimens of the KBNP and
M. Mangambu and R. Van Diggelen (2017) / Two New Species of Loxogramme and Lepisorus (Polypodiaceae): Endemic Ferns from
Kivu-Ruwenzori Mountain System (Eastern D.R.Congo, Albertine Rift)
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Int. J. Curr. Res. Biosci. Plant Biol. 4(4), 61-74 (2017)
a specimen of the ViNP, belonging to this new species,
have also been found in the undetermined material of the
genus. The two new species are dedicated to the two
professors (Robbrecht and Ntahobavuka) who have
carried out several researches in this region of the
Congo-Nile Ridge in eastern Congo. This is a way to
honor and immortalize them.
The two new species described belong to the family of
Polypodiaceae, which are leptosporangiated isospora
ferns characterized by Fronds mono-, hemi- or
dimorphic, articulated or not; stipe short or long, terete
or adaxially shallowly sulcate; lamina simple, unequally
lobed or pinnatifid, entire or shallowly crenate;
hypostomatic. Sori circular, oval, linear or in a soral
patch, superficial or slightly sunken, then embossed,
scattered or in a single row on either side of the primary
or secondary vein, positioned at the apex of the
acroscopic vein branch, at a vein plexus or on a soral
vein; sporangium stalk short or long, simple, 3-seriate
below the capsule;
capsule globose, with 12-21
indurated annulus cells and a well-defined stomium;
exindusiate; receptacle nude, with simple pluricellular
hairs, stellate hairs or with peltate clathrate paleae.
Spores ellipsoidal, monolete or trilete, smooth,
granulate, rugate, rugose or tuberculate.
Polypodiaceae has a near cosmopolitan distribution with
the greatest diversity in tropical areas, especially in
Asia. This order contains species that have relatively
young forms in full development and their systematic is
not yet definitively established (Autrey et al., 2008;
Roux, 2009; Crouch et al., 2011). The number of
families and genus are extremely variable. For this
paper, we used the classification of Roux (2009).
Indeed, the studies carried out by Fischer (1996) and
Mangambu et al. (2014) in KBNP and Plumptre et al.
(2007 and 2009) in the mountainous massifs (ViNP,
PNKB and INR) of eastern DRC, emphasize that the
Montana forests of this Kivu-Ruwenzori system are
among the most complex and important ecosystems
from the point of view of Floristic richness in ferns and
fern allies other vascular plants. For this reason, they are
considered to be of great importance for the
conservation of endemic and endangered species
(Plumptre et al., 2007; Mangambu et al., 2015). They
are characterized by an orophilous flora and have
exceptional and rich floras, with a singularity which is
the high endemism rate, with more or less 3000 endemic
species (Plumptre et al., 2007 and 2009).
Recent studies in pteridology (Pichi-Sermolli, 1983 and
1985; Lawalrée, 1990; Roux, 2009; Mangambu et al.,
2016) and other works of vascular plants (Fischer et al.,
2003; Detchuvi and Fischer, 2006; Cribb et al., 2010;
Lachenaud and Jongkind, 2010) showed the description
of several new species of the Congo-Nile Ridge where
these three conservation domains of the eastern DR
Congo are located.
In our collection and study site, apart from the work of
Pichi-Sermolli (1983 and 1985) and Lawalrée (1990),
apart from some fascicles from Central Africa, the thesis
of Mangambu (2013) and the publications of Mangambu
et al. (2012 and 2016), there is no work to strengthen the
systematic knowledge in deep pteridology. The overall
goal of this article is to describe these new species. The
specific objective is to indicate their ecological
conditions as well as their phytogeographical.
Materials and methods
Study area
The Kivu-Ruwenzori mountain system is located in the
Albertine Rift and consists of the mountain ranges of
which the Mount Mitumba (White, 1978) in the eastern
and western ridge of the Kivu (White 1978 and 1993);
the contiguous highlands from the northern end of Lake
Tanganyika to the Ruwenzori and also the western part
of Burundi as well as southeastern Rwanda and Uganda
(Roche, 1991; Linder, 2001). They are largely composed
of Precambrian rocks but also local islands of volcanic
deposits including the Virunga volcanoes (4507 m) still
active (Fig. 1).
Among the mountains constituting this mountain
range, some are vestiges of the uprising on the edge of
the great African plateau, while others, notably the
Ruwenzori (5119 m), have been raised under the
forces of compression linked to the formation of
Grabens. Others are weakly developed on very steep
slopes between 2200 and 3200 m (Kahuzi-Biega
National Park, Mangambu, 2016). The three
conservation areas of the eastern DRC, namely the
Kahuzi-Biega National Parks (created in 1970), the
Virunga National Parks (created in 1925) and the
Itombwe Natural Reserve (created in 2006) are found
in that system (Plumptre et al., . 2008 and 2009). In
Congolese conservation areas, they protect Eastern
lowland Gorillas (KBNP and INR) and the Mountain
Gorillas (ViNP).
M. Mangambu and R. Van Diggelen (2017) / Two New Species of Loxogramme and Lepisorus (Polypodiaceae): Endemic Ferns from
Kivu-Ruwenzori Mountain System (Eastern D.R.Congo, Albertine Rift)
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characteristics:
- qualitative characteristics (shape of rhizome, presence
or absence of scales, color of scales, general habit of
stem or stipe, type of fronds and veination, disposition,
costa, costules, sori, form of spores);
- quantitative characteristics (height of the plant, size of
frond, stipe, pinna, rhachis, ultimate segment, rachis,
spore dimension).
Laboratory analyzes
Spores observation
For morphological observation of spores, we proceeded
in two steps (Hu et al., 2010) to BR:
- The first operation which consists in dissecting
sporangia on a slide and under a four-step process.
The initial step consisted in placing the spores
inside 1.5 ml microtubes with 70% ethanol. This
initial treatment was followed by placing the
microtubes inside an ultrasonic wave bath (1510
BRANSON, 50-60Hz, 90W) for 10 min.
Fig. 1: Map of the Albertine Rift showing existing protected
areas or regions referred to in this study and the approximate
boundary of the Albertine Rift (portions of the Albertine Rift
showing the locations of the various protected areas (NP:
National Park; FR: Forest Reserve; WR: Wildlife Reserve).
The Latitude and longitude around the map are labeled in
degrees.
- This second step was followed by 4 min.
centrifugation (6000 rpm). This three steps protocol
was repeated three times, each washing step (70%
ethanol) required a re-suspension of the pellet of
spores. Subsequent to this treatment, the spores and
washing 70% ethanol solution were transferred to a
double sided adhesive tape with a micro-pipette.
Once the 70% ethanol solution vaporized the dried
spores were gold coated using standard electron
microscopy techniques. These samples were
subsequently observed and photographed under a
Hitachi
JSM-6360LV
Scanning
Electron
Microscope.
Collection and identification
The specimens that we use in this paper were
collected mainly between April 2004 and June 2015
in the Kahuzi Biega National Park (PNKB), and also
in the two neighboring conservation areas (ViNP and
RNI). They were deposited at the Herbarium of Lwiro
in the DRC (LWI), with duplicates in the herbarium
of the National Botanical Garden of Belgium (BR).In
order to identify it and to give distinctive features to
species with affinities, we have made macroscopic
and microscopic observations of the following
Encoding, taxonomic, chronological and ecological
treatment
The methodology used is the herbarium taxonomical
treatment. Phytochoria of White (1986 and 1993) were
followed. The ecological factors, i.e. habitat type,
altitude interval for collected specimens and adaptation
of the species were recorded in the field. In order to
enable encoding, we proceeded with data management
and treatment. The herbarium collections were encoded
using the BRAHMS 5.65 ® software.
M. Mangambu and R. Van Diggelen (2017) / Two New Species of Loxogramme and Lepisorus (Polypodiaceae): Endemic Ferns from
Kivu-Ruwenzori Mountain System (Eastern D.R.Congo, Albertine Rift)
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Results
Description of the two new species
Loxogramme ntahobavukiana Mangambu & van
Diggelen sp. nov.*
Typus: Mangambu 3711 (BR, LWI): South Kalehe
(208501, E2850881) 1612 m collected on 7july 2011
(holo-, BR!; iso-, LWI!).
sometimes on spontaneous trees, sometimes at 30 m
above ground in the undergrowth in secondary forests in
submontane level. In the montana level, present in the
covered and open areas, there are moist forest galleries
with Syzygium spp., Symphonia globilifera and / or
sometimes in the bottom of the ravines and in the
marshes; sometimes also in the dry zone along the
ravines. Altitude: 1390-2130 m. Endemic species of
Kahuzi-Biega National Park and Itombwe Natural
Reserve.
Description: Epiphytic, perennial, ascending Plant of
small size varying between 36.4-72.2 cm long, prostrate;
Rhizome slender, with masses of hairy roots and greysh
clathrate scales, widely creeping, branched, covered
with narrow, dense, peeled, foamed scales at the top,
pale brown to brown in color, margin with numerous
extensions along the whole length and provided with 2
ridge rows of short phyllopods pale or black, lanceolate,
acuminates. Fronds in tufts, monomorphic, articulated,
up to 16.2-38.22 cm in length; Stipe 3.78-4.6 cm long,
stramineous to purplish, distinct articulation, sometimes
distinct in a young, non-functional state; lamina 5-36 x
1-9 cm long, pinnately lobed, sometimes notched,
regularly sinuate, crenelated while still young, glabrous
on the upper side, scales on the lower side; veins
indistinct, obsolete glabrous on upper surface, midrib
and veins immersed; areoles oblique to the main vein;
presence of more or less inclined veins; staminated
rhachis, elevated on the underside, almost indistinct on
the upper surface. Indumentum composed of clavate,2celled hairs occurring abaxially on the lamina and
basifixed clathrate paleae ending in a small thin-walled
cell, often with shortunicellular trichomes along the
proximal margin of the paleae occurring on the rhizome
and stipe base. Sori subglobose linear, elongated, 6 to
11.6 cm long, exindusiate, oblique to the main vein, the
top of each sori slightly or does not exceed the base of
the upper sori; sporangia usually with cylindrical
glands, often deciduous in the adult state, with a thin,
short pedicel; Spores oblovoidal, monolete Gametophyte
mature thallus ribbon-shaped, often profusely branched,
rhizoids mostly in marginal clusters, glabrous,
gametangia borne on scattered superficial cushions
ventrally behind the meristematic region; archegonium
neck with 3 tiers of cells, nearly straight, neck canal cell
binucleate; vegetative reproduction by unicellular
marginal gemmae (Figs. 2 and 3).
Ecology, habitat and distribution: hemi-epiphytic plant,
often lithophyte of very covered environments, or
Fig. 2: Loxogramme ntahobavukiana: 1, full plant x1; 2,
scalped x 1/5 and 3, lamina portion in sore (x 3).
M. Mangambu and R. Van Diggelen (2017) / Two New Species of Loxogramme and Lepisorus (Polypodiaceae): Endemic Ferns from
Kivu-Ruwenzori Mountain System (Eastern D.R.Congo, Albertine Rift)
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Fig. 3: Loxogramme ntahobavukiana: original images of electronic scanning microscope showing the overall
view of mono oblovoidal spore (100μm) and magnification (10μm).
Other specimens examined : Ntamwira 222 (BR,
LWI) : Burhinyi (RNI, S309245, E2834265), 1659 m
alt. ; Mangambu 3338 (BR, LWI) : Lemera Nord
(S203973, E2842950), 1733 m alt.; Mangambu 3355
(BR, LWI) : Northern Lemera (S204.970, E2850.289),
1745 m alt.; Mangambu3912 (BR, LWI) : Tshivanga
(S217178, E2846349)1587 alt.; Mangambu 3827 (BR,
LWI) : Tshivanga(S213406, E2848992) 2012 m
alt.;Mangambu 3711 (BR, LWI) : South Kalehe
(208501, E2848229) 1612 m alt. ;Mangambu 3827 (BR,
LWI) : South Kalehe (208501, E2850881) 1612 m alt. ;
Mangambu 3912 (BR, LWI) : SouthKalehe (208501,
E2850881) 1612 m alt. ; Anataka 12 (LWI) : Tshivanga
(217178, E 2846349), 2050 m alt.
Notes: simple Fronds, notched lamina, pinnately lobed,
oblanceolated base; sori without indusia, elongated,
oblique in relation to the costa. The specimens
Mangambu 3338 and Mangambu 3355 except the
general characters, their pinna are long lobed.
Lepisorus robbrechtiana Mangambu & van Diggelen
sp. nov.*
Typus: Mangambu 2922(BR, LWI): Tshibati Nord
(S208.997, E2850.616): 1745 m, collected on 22 may
2010 (holo-, BR! ; iso-, LWI!).
Description: Perennial, hemi-epiphytic, ascending plant,
11.7 – 49.23 cm of length. Rhizome Creeping, with brown
clathrate lanceolate to narrowly ovate-acuminate
rhizome-scales up to (5.5-7.1 cm, covered with paperylaced scales, more or less pale, lanceolate, pale margin,
subentire to irregular. Fronds nonomorphic, in unequal
sizes, some long, others short, tender, spaced, erect; stipe
more or less short, hairy, stratified to brownish, 2-10.5 cm
long, 1.2-1.5 mm in diameter, scaly, gradually narrowed
at the base at the base and decurrent over most of the
length of stipe in a very fine wing, furnished with scales
scattered on the upper surface, more numerous on the
inferior side; tiny scales, peeled, appressed, ovatelanceolate, black in center, lacerated; lamina not identical
and unequal, one is long and lobed (30.7-41.9 cm)
dichotomous at the top (once to twice in forks), the others
wholly small (8.2-16.6 cm); margin reflected a little,
sometimes slightly undulating; rachis stramineous, raised
on both sides; dichotomous veinat the top (twice to three
times following the long lamina), according to the form of
a long penne fork, median vein not dichotomous,
prominent anastomosing, rounded in the abaxial part,
canaliculated in the adaxial part; areolas with several
veins included. Indumentum composed of 2–4-celled,
clavate hairs, apical cell appears glandular, the stalk
simple or with 1 (rarely 2) clavate, glandular trichomes
occurring adaxially and/or abaxially on the lamina and
with narrow basifixed or peltate clathrate paleae ending in
a small oblong thin-walled cell on the rhizome, axes and
abaxial lamina surface. Sori subglobose, exindusia in the
lower part of the lamina, protruding, up to 7.5 mm in
diameter, embedded in the pinna, in a row on either side
of the median vein; presence of peeled, pedicelled
paraphyses; spherical spores, monolites with a perispore
(Figs 3 and 4). Gametophyte mature thallus with a strapshaped posterior and a cordate anterior, midrib thin and
wings spreading, rhizoids restricted to the midrib,
dehiscence by the collapse of the cap cell.
M. Mangambu and R. Van Diggelen (2017) / Two New Species of Loxogramme and Lepisorus (Polypodiaceae): Endemic Ferns from
Kivu-Ruwenzori Mountain System (Eastern D.R.Congo, Albertine Rift)
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Endemic species of the mountain area of the PNKB,
INR and PNVi.
Fig. 4: Lepisorus robbrechtiana: 1, full plant x1/2; 2, scalped
x 1/4 and 3, lamina portion in sore (x 6).
Ecology, habitat and distribution: Frequent plant in
the middle plateau of Kalehe, Lemera. Also found in
the first 2 levels of mountain area of the PNKB.
Frequent in the forest at Newtonia buchanani at the
edge of streams and secondary forest in open places
and sunny areas, especially at roadside sometimes in
the shade on tree trunks and on high branches exposed
to light. Somewhat uncommon in rainforest, humid and
primary forests, but sometimes forming bushy and / or
shade on tree trunks and high branches exposed to
light. Small individuals of this species were observed
at 2352 m above sea level in the vicinity of mountain
crest. Bugulumiza at 2382. Altitude. 1500-2352 m.
Fig. 5: Lepisorus robbrechtiana, original M.E.B. images
showing the overall view of spore in mono-spherical shape
(100 μm) and magnification (10 μm).
Other Specimens examined: Mangambu 738 (BR,
LWI): Burhinyi (Itombwe; S323 582, E2845971),
1797 alt.; Mangambu 2206 (BR, LWI): Kilimanyoka
(PVi) 1402 alt.; Mangambu 2922 (BR, LWI): North
Tshibati (S216812/E2848040), 1745 m alt.;
Mangambu
3365(BR,
LWI): Tshibati Nord
(S208.997, E2850.616) 1745 m alt. ; Mangambu 3365
(BR, LWI): Tshibati Nord (S208.997, E2850.616)
1745 m alt.; Mangambu 3672 (BR, LWI): North
Tshibati
(S215473/
E2848682)
1745
m
alt.; Mangambu 3686 (BR, LWI): North Tshibati
M. Mangambu and R. Van Diggelen (2017) / Two New Species of Loxogramme and Lepisorus (Polypodiaceae): Endemic Ferns from
Kivu-Ruwenzori Mountain System (Eastern D.R.Congo, Albertine Rift)
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(S208.997, E2850.616) 1745 m alt.; Mangambu 3676
(BR, LWI): North Tshibati (S215473/ E2848682)
1842 m alt. ; Mangambu 3698 (BR, LWI): North
Tshibati (702803, 9761515) 1842 alt.; Mangambu
3698(BR, LWI): North Tshibati (S208.997,
E2850.616), 1745 m alt.; Mangambu 3912 (BR,
LWI): mount Bungulumisa (S17639, E2847269),
2350 m alt.; Mangambu 3913 (BR, LWI): mount
Bungulumisa (S17639, E2847269), 2382 m alt.
Note: Fronds tending towards dimorphism, all
assimilating to lamina entirely hairy mixed, scales
scattered on the upper face; lamina not identical,
some long in forks twice or sometimes thrice, the
other short and the protruding sori embedded in the
pinna.
Discussion
The two new species described have affinities with the
two other species that exist in eastern DRC. Their
connection is manifested in the similarity of the general
appearance, yet there are also other numbers of
characters and morphological traits which make the
difference between them. The tables and identification
keys below allow distinguishing them.
Table 1: Overview of the main features to distinguish between Loxogramme ntahobavukiana and Loxogramme abyssinica
(Fig. 6).
Features
Loxogramme ntahobavukiana
Loxogramme abyssinica
Rhizome
shortly creeping, not more than 15 cm long; short
phyllopodia, pale or black, lanceolate, acuminate;
narrowly scaled, dense, peeled, pale brown to
brown, acuminate.
long creeping up to 211 cm; long phyllopodia, black,
elliptical; dense scales, black brown, lanceolate,
acuminate.
Frondes
clump, up to 18.2- 46.22 cm long, oblanceolate base
spaced, 12-40 cm long with the base, elliptical base
stipe
6.78- 18.6 cm long, articulated, winged on two
sides up to the rhizome
short (pseudostipe), 1.7-6.9 cm long for long fronds, not
winged
Lamina
lanceolate, 5-36 x 1-9 cm pennatilobed, sometimes
wavy, crenelated when still young, glabrous on the
upper side, scales on the lower side.
elliptical, glabrous, 7-35×1-2 cm lamina, attenuated
shrunken and acute at the top, gradually reduced to the
base in one narrow wing almost to rhizome, entire margin.
Veins
obsolete veins only visible when still young, areolas
oblique to the main vein
indistinct, staminated, elevated on the lower side,
anastomosed, visible presence of veins included
Sori
mostly linear sori, 6 to 11.6 cm long, the top of each
sori little or not slightly exceed the base of the
upper sori.
linear, reaching 3.5 cm in length, very oblique to the spine,
the top of each exceeding the base of the upper.
The two neighboring species can be distinguished as follows
1. Simple, linear, elliptic, spaced frond, single pinna, elliptic, glabrous, attenuated, narrowed and
acute at the top, progressively reduced at the base in a narrow wing almost to the rhizome; not very
visible; linear sori, long, very slightly oblique in relation to the central vein; spores ellipsoidal,
monolete or trilete, papillate to rugate, 62–70 μm long ………..…………………..…….L. abyssinica
— Simple fronds, pinnatily-lobed or notched, crenated when still young, near glabrous on the upper
side, with hairs and scales on the lower side;lanceolated oblongs and dimidiated at the base,
thickenedvein, visible ;linear sores, oblique to the rhachis; spores oblovoidal, monolete
……………………………………………………………………………...……..…..L. ntahobavukiana
M. Mangambu and R. Van Diggelen (2017) / Two New Species of Loxogramme and Lepisorus (Polypodiaceae): Endemic Ferns from
Kivu-Ruwenzori Mountain System (Eastern D.R.Congo, Albertine Rift)
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Int. J. Curr. Res. Biosci. Plant Biol. 4(4), 61-74 (2017)
Fig. 6: Loxogramme ntahobavukiana on the left and Loxogramme abyssinica on the right (pictures taken by
Mangambu at KBNP).
Table 2. Overview of the main features to distinguish between Lepisorus excavates and Lepisorus robbrechtiana (Fig. 7).
Features
Lepisorus robbrechtiana
Lepisorus excavatus
Rhizome
papery scales, not concolored, more or less peeled,
concolored scales of the rhizome, covered with a white
lanceolate
iridescent substance
Frondes
two types, more or less with clumps
both equal and similar, monomorphes, spaced, erected
Stipe
hairy, stratified, 2-10.5 cm long, 1.2-1.5 mm in
diameter, scaly, gradually narrowed at the base and
sometimes winged
not identical and unequal, one is long and lobed (3041cm) dichotomous at the top (once to twice in
forks), the others are wholly small
2-6 cm long, 1 mm in diameter, with rare scale in
adulthood
vein
dichotomous at the top for lamina in forks and not
dichotomous for simple and short lamina
Simple, branched for all lamina
Sori
on the upper 4/5 of the lamina, globose, 4.3-7.76 mm
in diameter
circular, large, medial, in a single row parallel, on the
upper 2/3 of the lamina, round, 2.5-5 mm in diameter,
more rarely slightly elliptic
lamina
Identical lamina identical, 33 (-47) cm long and 0.6-2.7 (3) cm wide, simple with rare scales in the adulthood
M. Mangambu and R. Van Diggelen (2017) / Two New Species of Loxogramme and Lepisorus (Polypodiaceae): Endemic Ferns from
Kivu-Ruwenzori Mountain System (Eastern D.R.Congo, Albertine Rift)
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Int. J. Curr. Res. Biosci. Plant Biol. 4(4), 61-74 (2017)
The key feature distinguishing the two neighboring species is this
1. Fronds all equal and similar, tender, spaced, erect; Short stipe; similar lamina; simple with rare scales
at adulthood, pinna simple, hypostomatic venation anastomosing, Sori circular, large, medial, in a
single row parallel, circular, large, medial, in a single row parallel, on the upper 2/3 of the lamina,
spores ellipsoidal, monolete………………….........………………….........………………...L. excavates
— Fronds in unequal, ascending sizes; not similar pinna, some long and lobed (30-61cm) with
dichotomous main vein, others short (8-16) wholly small, wholly single gradually narrowed to single
ve; Sori subglobose, only in the upper part of the lamina (2/3), round with
elliptic….……………..……………………………………...............................………..L. robbrechtiana
Fig. 7: Lepisorus robbrechtiana on the left and Lepisorus excavatus on the right (photos taken by
Mangambu in Kahuzi-Biega National Park).
Taxonomic considerations
Prior to this study, the importance of this region in
Pteridophyta is confirmed by the inventory conducted by
Pichi-Sermolli (1983 and 1985). For example, these
inventories carried out in 1972 in the Kivu region (DRC)
and the mountainous areas of Rwanda and Burundi
resulted in the discovery of 9 new species of ferns and
allies ferns (Aleuritopteris vandervekenii (RDC), Pteris
auquieri (Rwanda, Burundi), P. microlepis (Rwanda)
Vandenboschia inopinata (DRC, Rwanda, Burundi and
various countries of tropical Africa, Madagascar and
M. Mangambu and R. Van Diggelen (2017) / Two New Species of Loxogramme and Lepisorus (Polypodiaceae): Endemic Ferns from
Kivu-Ruwenzori Mountain System (Eastern D.R.Congo, Albertine Rift)
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Int. J. Curr. Res. Biosci. Plant Biol. 4(4), 61-74 (2017)
Mascareignes) Blotiella bouxiniana(Rwanda Burundi),
Blotiella trichosora (Burundi), Maclethelypteris
rammelooi (Rwanda), Metathelypteris vandervekenii
(Rwanda), and Christella burundensis (Burundi). The
same inventories led Bizzarri (1981) to describe two
new species: Selaginella vanderystii“encountered in the
Congo Basin in the DRC”, and Selaginella kivuensis in
the Kivu Mountains in eastern DRC).
Specimens from Kivu in the DRC and the Rwanda
escarpment have led Lawalree (1990) to discover two
new species of the Tectariaceae family (Arthropteris
anniana and Arthropteris antungupffertiae). Apart from
these intense studies, other authors have described
species whose material comes from this region. For
example, the species: Lycopodium carolinum (endemic
to Mount Kahuzi in the PNKB), Asplenium ruthuruense
endemic to the escarpments of the Ruthuru area north of
Mount Nyamulagira and other species such as
Asplenium lambinonii and Selaginella auquieri.
Mangambu et al. (2013) reported the presence of 22 new
species for the Pteridological flora of the DRC,
discovered in the mountain forest of KBNP, the majority
of which were considered by Pichi -Sermolli (1983) as
endemic to Rwanda or Burundi, for example, Pteris
auquieri, Metathelypteris vandervekenii, Mangambu
et al. (2016) in their molecular investigations of the
genus Asplenium of the mountainous region of the Kivu,
described a new Asplenium kivuensis.
Paleoenvironmental and biogeographical considerations
Some authors (Barthlott et al., 1996; Plumptre et al.,
2009) consider that the mountain regions are rich in
plant diversity but with a systematic that is always
fragmentary and difficult due to multiple changes in
plants at different altitudes (Kapos et al., 2000). They
are areas rich in species of plants than the plains and
host the richest communities of plants on the planet
(White 1993; Barthlott et al., 1996). At present, the two
species described are all endemic to the Kivu-Ruwenzori
mountain range in eastern DRC, that is, their
chorological boundaries are in these three main
conservation reversals of Eastern DRC (KBNP, INR and
ViNP).
Fieldwork on the DRC pteridology has shown that the
majority of these species are located in the mountains of
the Kivu-Ruwenzori system (Bizzarri, 1981 and 1983;
Pichi-Sermolli, 1983; Aldasoro et al., 2004). The reason
for this diversity can be accounted for by the effects of
scenarios of paleoenvironmental variability (Meadows
and Linder 1993; Marchant and Hooghiemstra, 2004;
Runge, 2007). According to these authors, the
Congolese mountain system has a continually changing
vegetation cover in response to macroclimatic and
microclimatic variations due to the climatic stability of
past geological times (Fjeldsä and Lovett, 1997; Maley,
1980 and 1990).
That has allowed climatic conditions favorable to
vascular plants, which can retain spores and pollen
grains capable of germinating after several years
(Runge, 2007; Guillaumet, 2009). The same theory
asserts that there is a migration of species at lower
altitudes to high altitude after the latest glaciation
(Roche, 1991). Furthermore, several studies have
highlighted the importance of Pleistocene and Holocene
climatic fluctuations to explain the current distribution
of plants in this Congolese mountain system (Plumptre
et al., 2008).
The territory is marked, as regards the historical
chronology of the climatic events, by the alternation of
the cold and warm periods. These cyclic climatic
variations have had a major influence on plant diversity
and on the evolution of vegetation cover in eastern DRC
and Rwanda (Tchouto et al., 2008). In the eastern area of
the Kivu-Tanganyika region, during the period between
23000 and 3000 years BP, the vegetation reflects a
colder climate than the current one; (Faden, 1994; Mayr
and O'hara, 1986; Maley, 1987; Roche, 1991; Roche
and Ntaganda, 1999; Runge, 2007). We confirm that this
region of Kivu, like other African mountainous regions,
is also rich in ferns and allies ferns. The two species of
affinity with the two species described have a wide
distribution (Figs. 8 and 9).
Loxogramme abyssinica, is a multi-regional species of
Afro-Malagasy origin distributed in mountains or
hilltops of medium altitudes (Autrey et al, 2008; Roux,
2009) of seven mountain systems of White (1978 and
1983) in southern and eastern Africa, Madagascar,
Comoros, Mauritius and Reunion. While Lepisorus
excavatus, a mountain-dwelling Afro-Malagasy species
(Fig. 7), is distributed only in mountains and medium
altitude formations (Autrey et al., 2008; Roux, 2009) in
the Kivu-Ruwenzori system countries (Burundi, Rwanda
and Uganda), Ethiopian system (Ethiopia), ImatongsUsambara system (Kenya), Madagascar, UluguruMlanje (Tanzania)
M. Mangambu and R. Van Diggelen (2017) / Two New Species of Loxogramme and Lepisorus (Polypodiaceae): Endemic Ferns from
Kivu-Ruwenzori Mountain System (Eastern D.R.Congo, Albertine Rift)
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Int. J. Curr. Res. Biosci. Plant Biol. 4(4), 61-74 (2017)
Fig. 8: Distribution maps: Loxogramme abyssinica (in black points) and L. ntahovabukiana (in blue triangle).
Fig.9: Distribution maps: Lepisorus excavates (in black points) and L. robbrechtiana (in red rhombus).
M. Mangambu and R. Van Diggelen (2017) / Two New Species of Loxogramme and Lepisorus (Polypodiaceae): Endemic Ferns from
Kivu-Ruwenzori Mountain System (Eastern D.R.Congo, Albertine Rift)
71
Int. J. Curr. Res. Biosci. Plant Biol. 4(4), 61-74 (2017)
Conclusion
The field studies carried out have just shown that
knowledge of the flora of the DRC remains fragmentary
despite more than a century of multiple explorations and
plants gathering achieved. Thus, we suggest that local
researchers be supported financially, in order to realize
multiple crops of plants in general and of the ferns and
allies ferns in particular.
We believe that the discovery we have just made shows
that the bioclimatic conditions in the mountain ranges of
eastern DRC are conducive to the development and
diversity of the Pteridophytes following the habitats that
allow their implantation and development to
disseminations of the diaspores. Radiation, atmospheric
humidity, especially precipitation and mesothermal
shade species favor their development and abundance.
This is why we have a high rate of epiphytic plants in
comparison to terrestrial species.
Conflict of interest statement
Authors declare that they have no conflict of interest.
Acknowledgement
This work was carried out thanks to the material and
financial support granted by the Belgian Technical
Cooperation (BTC). We would also like to thank
UNESCO, through the Flemish government (Belgium)
for their contribution to the fieldwork and trips to the
herbaria (BR, LWI, ULB, GL, GENT, WAGENINGEN,
KEW ...) for the checking and observation of the
reference material. Thanks also to the anonymous peerreviewers of this paper.
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How to cite this article:
Mangambu, M., Van Diggelen, R., 2017. Two new species of Loxogramme and Lepisorus (Polypodiaceae): Endemic
ferns from Kivu-Ruwenzori Mountain System (Eastern D.R. Congo, Albertine Rift). Int. J. Curr. Res. Biosci. Plant
Biol. 4(4), 61-74. doi: https://doi.org/10.20546/ijcrbp.2017.404.010
M. Mangambu and R. Van Diggelen (2017) / Two New Species of Loxogramme and Lepisorus (Polypodiaceae): Endemic Ferns from
Kivu-Ruwenzori Mountain System (Eastern D.R.Congo, Albertine Rift)
74