E D I N B U R G H J O U R N A L O F B O T A N Y 66 (3): 447–457 (2009)
447
Ó Trustees of the Royal Botanic Garden Edinburgh (2009)
doi:10.1017/S0960428609990059
SYSTEMATICS OF CLEMENSIELLA
(APOCYNACEAE – ASCLEPIADOIDEAE)
U . M E V E 1, O . L A U R E N T E 2, G . J . A L E J A N D R O 3 & T . L I V S H U L T Z 4
The genus Clemensiella (Apocynaceae – Asclepiadoideae) is reported to include two
species. Clemensiella mariae, a Philippine endemic, is redescribed, illustrated, and
lectotypified. Its chromosome number (2n 5 22) is reported for the first time. The recently
described Hoya viracensis is synonymised with Clemensiella mariae. Clemensiella omlori is
described as a new species from Borneo and Sumatra. The taxonomic relationship of
Clemensiella to other genera of tribe Marsdenieae is discussed.
Keywords. Borneo, chromosome number, Clemensiella, Hoya viracensis, lectotypification,
Marsdenieae, Philippines, Sumatra, taxonomy.
Introduction
Rudolf Schlechter (1915) described Clemensiella with a single validly published
species, Clemensiella mariae (Schltr.) Schltr. Clemensiella was considered one of three
genera of Apocynaceae – Asclepiadoideae endemic to the Philippines (Madulid, 1991).
The other two genera, Dolichostegia Schltr. and Quisumbingia Merr., have since been
put under synonymy of the genera Dischidia R.Br. (Livshultz, 2003) and Sarcolobus
R.Br. (Omlor, 1998), respectively. All of them belong to the tribe Marsdenieae
(Omlor, 1998). Clemensiella can no longer be considered a Philippine endemic either
since specimens unambiguously assignable to this genus have been collected in
Sumatra and Borneo. Omlor (1998) was the first to note that the specimen de Wilde &
de Wilde-Duyfjes 14377 (K) from Sumatra represents a species of Clemensiella,
although he was uncertain whether it should be considered as conspecific with
C. mariae. We have since identified two additional collections of this same species, one
from Sumatra, the other from Sarawak, Malaysian Borneo. These three specimens
represent a new species closely allied to Clemensiella mariae but clearly distinguishable by characters of the inflorescence and corolla. Recently, we also obtained living material of Clemensiella mariae; the plant flowered in the greenhouse at the
1
2
3
4
Department of Plant Systematics, University of Bayreuth, 95440 Bayreuth, Germany. E-mail:
ulrich.meve@uni-bayreuth.de
Faculty of Pharmacy, University of Santo Tomas, España, Manila 1008, Philippines.
College of Science and Research Center for the Natural Sciences, University of Santo Tomas, España,
Manila 1008, Philippines.
Academy of Natural Sciences, 1900 Benjamin Franklin Parkway, Philadelphia, PA 19103, USA. E-mail:
livshultz@ansp.org
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U. MEVE ET AL.
Department of Plant Systematics, Bayreuth, thereby offering an opportunity to
investigate this interesting and poorly known species in more detail. In the present
paper we (i) discuss the taxonomic affinities of Clemensiella, (ii) emend the
descriptions of Clemensiella and C. mariae, (iii) lectotypify C. mariae, and (iv)
describe a new species, C. omlori.
Taxonomic Relationships of CLEMENSIELLA
The placement of Clemensiella within the tribe Marsdenieae of Apocynaceae –
Asclepiadoideae was never in doubt – Schlechter (1915) originally placed it here,
and assumed that Marsdenia R.Br. and especially Telosma Coville were the most
closely related genera. Omlor (1998) in his generic revision of the tribe supposed, in
contrast, that Clemensiella is rather isolated within Marsdenieae without any direct
connection to any other genus. He nevertheless pointed out that the pollinaria are
most similar to those of Marsdenia, whereas the habit is very Hoya-like.
Clemensiella possesses a number of characters that are uncommon among genera
of Marsdenieae: epiphytic growth habit (occasionally reported in Clemensiella
mariae), adventitious roots (known only in C. mariae), persistent inflorescences,
and valvate corolla lobes. The combination of these four characters occurs in only
two other genera of the tribe: Hoya R.Br. and Dischidia. These four characters,
along with the robust dimensions of the plant, the fleshy, shallow corolla, and the
fleshy corona lobes, are the basis for the misinterpretation of Clemensiella mariae
as a species of Hoya (Kloppenburg & Siar, 2006). However, the corona and
gynostegium of the two genera are quite different. The corona lobes of Clemensiella
do not have the Hoya-characteristic fold on the underside of the corona lobes
(recently interpreted as a fusion of a basal process of the staminal corona lobe and
an ‘anther skirt’; Kunze & Wanntorp, 2008). The pollinia are clavate and not
elongatedly ellipsoid as is usual in Hoya, and they do not possess any sign of a sterile
pellucid germination crest typical for most species of Hoya (Figs 3, 4). In addition,
the corpuscles are small and narrowly oblong in Clemensiella, but massive and
rhomboid to broadly oblong in Hoya (Wanntorp, 2007). Caudicles are extremely
long, ribbon-shaped and geniculate in Clemensiella (Figs 3, 4), and not short and
broad as in Hoya.
Several characters of Clemensiella also link it to other genera of Marsdenieae. The
persistent inflorescences, present in Clemensiella, Hoya and Dischidia, are also shared
with several species of Marsdenia, including the type species, Marsdenia tinctoria
R.Br. The shape of the corona lobes of Clemensiella is very reminiscent of several
Marsdenia species, for example Marsdenia gonoloboides Schltr. (illustrated in
Forster, 1995), but their massive size relative to the anthers (Fig. 4) is unknown
among species of Marsdenia. The pollinarium structure and the depressed, umbonate
style-head of Clemensiella, along with the very short guide-rails, oriented at 45°, of
Clemensiella mariae, are reminiscent of the flowers of Sarcolobus, another genus of
Southeast Asian-Australasian distribution (see Forster, 1991). The surface of the
SYSTEMATICS OF CLEMENSIELLA
449
style-head umbo differs between the two genera: it is just a little uneven in
Clemensiella and not papillate as in Sarcolobus.
The seeds of Clemensiella, obovate with a small wing, and a long, apically attached
coma, are typical of most Marsdenieae except Dischidia and Hoya which have more
cylindrical seeds with wings highly reduced or absent (Omlor, 1998). A ciliate seed
margin, limited to rather scattered hairs in Clemensiella, is very unusual, otherwise
known only in a few species of Dischidia such as D. acutifolia Hook.f. (Livshultz,
pers. obs.). A ciliate seed margin has also been reported from Finlaysonia Wall.
(Forster, 1989) and Raphionacme namibiana Venter & Verh. of Apocynaceae –
Periplocoideae (Venter & Verhoeven, 1986). In the latter two taxa, however, there is
no apically attached, parachute-like coma, whereas in Clemensiella and Dischidia
acutifolia the marginal hairs co-occur with an apical coma.
Generic delimitation in Marsdenieae, particularly in drawing the boundaries of
Marsdenia, remains problematic (Forster, 1995; Omlor, 1998). However, Clemensiella possesses a unique combination of characters that places it outside the range
of morphological variation in Marsdenia. The presence of valvate corolla lobes is
a potential synapomorphy for Clemensiella, Dischidia and Hoya. A preliminary
phylogeny of chloroplast markers supports Clemensiella as sister to a Hoya–
Dischidia clade (Liede-Schumann & Meve, unpubl.). This indicates that the ecology,
physiology and anatomy of the occasionally epiphytic Clemensiella may hold
important clues as to how the epiphytic growth habit evolved in the common
ancestor of Dischidia and Hoya.
Taxonomy
Clemensiella Schltr., Repert. Spec. Nov. Regni Veg. 13: 566 (1915), substitute name
for Clemensia Schltr., Repert. Spec. Nov. Regni Veg. 13: 542 (1915), nom. illeg.
(non Clemensia Merr. 1908, Meliaceae). – Type: Clemensiella mariae (Schltr.)
Schltr. (Clemensia mariae Schltr.).
Large, herbaceous to slightly woody twiners with white latex. Leaves opposite,
blades thinly coriaceous to subsucculent, elliptic, basally rounded and slightly
peltate, apically acuminate, margins slightly revolute, with 1(–4) colleters adaxially
on the base of the midvein, discolorous, venation pinnate with 5–8 pairs of
secondaries diverging at 60–70° to the midvein, brochidodromous. Inflorescences
extra-axillary, solitary, much shorter than adjacent leaves, few-flowered, umbelliform, development bostrychoid; peduncles succulent, persistent. Flowers nectariferous; calyx with minute, axillary colleters; corolla rotate to campanulate, fused for
c.1/2–2/3 total length, succulent, adaxially papillose, glabrous; corolla lobes valvate
in bud, triangular; corolline corona absent; gynostegial corona of free staminal lobes
attached to the back of the anthers, longer than the gynostegium and connivent over
it, lobes succulent, laterally broadened and thickened, triangular to ovate, acuminate; pollinia acropetal to corpusculum in situ, clavate, without sterile pellucid
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U. MEVE ET AL.
regions, basally attached to the caudicles; caudicles geniculate, flattened, broadened
at the insertion of the corpusculum; corpusculum narrowly oblong, much smaller
than pollinia; style-head 5-angled, depressed, umbonate. Mericarps single, fusiform,
2-ribbed, light brown, smooth, glabrous. Seeds obovate, light brown, marginally
winged, sparsely ciliate; micropylar coma well-developed, white.
Distribution. Indonesia, Malaysia, Philippines (Fig. 1).
Key to the species
1a. Corolla rotate, gynostegium exserted for 1/3–1/2 of its length, bud apices
flattened-obtuse, peduncles 1–4 cm long _______________________________________ 1. C. mariae
1b. Corolla campanulate, gynostegium apex barely exserted from the corolla throat,
bud apices subobtuse to acute, peduncles 0.2–1 cm long _____________ 2. C. omlori
1. Clemensiella mariae (Schltr.) Schltr., Repert. Spec. Nov. Regni Veg. 13: 566
(1915), substitute name for Clemensia mariae Schltr., Repert. Spec. Nov. Regni
Veg. 13: 543 (1915). – Type: Philippines, [Lanao del Sur]: Mindanao, Lake Lanao,
Camp Keithley, iv 1906, Mary S. Clemens 512 (holo B, destroyed). Philippines,
Leyte: Dagami, viii 1912, Ramos 15307 (paratype, not traced). Philippines,
Laguna: Luzon, San Antonio, ix–x 1912, Ramos 15962 (lecto P!, designated here;
isolecto BM n.v., K n.v.). Figs 2, 3.
Clemensiella dischidioides Elmer in Merrill, Enum. Philipp. Fl. Pl. 3: 356 (1923);
Elmer, Leafl. Philipp. Bot. 10: 3549 (1938), nom. nud.
Hoya viracensis Kloppenb. & Siar, Fraterna 19(4): 5 (2006), syn. nov. – Type:
Philippines, Catanduanes: Virac, Brgy. Kalatagan, secondary forest, soil clay
loam, 2 xii 1991, Barbon, Garcia & Alvarez PPI 5658 (holo PNH n.v.; iso BISH
n.v., BRIT!, CAHUP n.v.).
Twiners up to 6 m tall, glabrous or nearly so. Taproots slender, occasionally with
unpaired adventitious roots on internodes when in contact with substrate. Stems
3–5[–10 basally] mm diameter, hollow, green, shiny. Leaf blades thinly coriaceous,
elliptic, basally rounded and slightly peltate, apically acuminate, 6–11 3 3–6 cm,
adaxially shiny, minutely ciliate, petioles 1–2 cm long, shiny. Inflorescences 3–7flowered, peduncles held perpendicular to the stems, 10–40 3 c.2 mm diameter,
slightly conical, rachis unbranched, up to 3 cm long. Flowers scentless; pedicels
c.5 mm long, conical, sepals broadly ovate, c.2 mm long, appressed to the corolla
tube; bud shape thickly lenticular with flattened apex; corolla rotate, 1.5–2 cm
diameter, sympetalous for c.1/2 of length, adaxially bright yellow to orange-brown,
occasionally spotted purplish, abaxially light green, occasionally spotted or tinged
purplish; corolla lobes ovoid-triangular, c.6 3 4 mm at base, with median depression, recurved, margins revolute; gynostegial corona with discoid outline,
concealed in corolla tube for 1/3–1/2 of its length, c.5 mm diameter, white, lobes
SYSTEMATICS OF CLEMENSIELLA
451
c.3 3 2 mm at base; anthers triangular, c.1 3 1.2 mm, guide-rails c.0.25 mm long,
spreading at an angle of 45°; anther connective appendages triangular-lanceolate,
hyaline, c.0.3 3 0.3 mm, covering style-head completely; pollinia positioned
horizontally on style-head in situ, c.0.6 3 0.25 mm, ovate in cross-section; caudicles
convexly recurved, c.0.5 mm long; corpusculum 0.15 3 0.05 mm, brown; style-head
c.2 mm diameter. Mericarps 6 pendent, c.5–8 3 0.5–0.7 cm, with small ridges along
dorsal and ventral sutures, broadening towards tip; seeds c.6.5 3 3 mm, wing up to
0.5 mm broad, with scattered white cilia, coma c.3 cm long, white.
Distribution. Philippines: Luzon (Laguna, Sorsogon), Catanduanes, Leyte, Mindanao (Lanao del Sur), Bohol (Fig. 1).
Ecology. Vigorous climber in forests (including secondary forests) and forest edges at
low to medium altitudes (c.0–800 m). Sometimes epiphytic on shrubs (Shorea sp.)
and small trees, or growing on rocks with little soil.
F I G . 1. Distribution of Clemensiella: C. mariae (m); C. omlori (d). Presence of Clemensiella
mariae in Leyte and Mindanao is based on specimens cited by Schlechter (1915) that are no
longer extant; occurrence on Bohol is based on a specimen cited by Omlor (1998), Ramos
43106 (BM n.v.). Map constructed using Online Map Creation (www.aquarius.geomar.de).
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F I G . 2. Clemensiella mariae Schltr. A, habit of plant, with adventitious roots; B, pedunculate
inflorescence; C, sepal; D, flower bud (scale as for E and F); E, top view of opening flower;
F, top view of open flower; G, top view of gynostegium with corona removed (including one
recurved staminal lobe); H, pollinarium; J, ripe follicle. (Drawn by B. Diego from Laurente
001, 002, 003 and 004 (University of Santo Tomas Herbarium, Manila, Philippines).)
SYSTEMATICS OF CLEMENSIELLA
453
F I G . 3. Clemensiella mariae Schltr. A, nectariferous flowers; B, corona in lateral view (SEM);
C, guide-rail in lateral view, corona lobes removed (SEM); D, pollinarium, attached to the
style-head (SEM). (All from ex hort. P. Gozon (UBT).)
Chromosomes. Root tips were pretreated in 0.002 M 8-hydroxychinoline solution
(Tjio & Levan, 1950), stained with carmine (Snow, 1963), and squashed. We counted
2n 5 22 chromosomes at the somatic metaphases (voucher: ex hort. P. Gozon
(UBT)). On average the chromosomes are 1.27 lm long (measurement based on the
analysis of four complete metaphase plates).
This count represents the first for Clemensiella. Because 94% of the investigated
taxa of Asclepiadoideae, and 100% of Marsdenieae, have been found to have 2n 5 22
chromosomes this result was expected. The average chromosome length of 1.27 lm
is also within the range of what has been reported for Marsdenieae (min. 0.91 – max.
1.44 lm), measured from 21 species in eight genera. However, it is above the range
of 0.91–1.06 lm documented for seven species of Hoya (Albers & Meve, 2001;
Meve, unpubl. data). As pointed out by Albers & Meve (2001), larger chromosomes
are ancestral in Asclepiadoideae.
Specimens examined. PHILIPPINES. Sorsogon: Luzon, Irosin, Mt. Balusan, vi 1916, Elmer 16374
(BISH, L, P, US) and vii 1916, Elmer 16801 (BISH, C, L, P, US); Luzon, Irosin, road going to
Lake Balusan, 9 ix 2005, Laurente 001 and 002, and 31 xii 2005, Laurente 003, and 30 iii 2006,
Laurente 004 (CAHUP, LBC, University of Santo Tomas Herbarium, Manila); Luzon, Irosin,
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SW of Balusan National Park, 11 vii 1996, Garcia & Fernando 25051 (PNH); s.c. and s.n. (ex
hort. P. Gozon) (UBT).
The holotype, which originated in Mindanao, was lost in the Berlin herbarium (B)
during World War II. Of the two paratypes from Leyte and Luzon (Ramos 15307 and
16592, respectively), we found a sheet of Ramos 16592 at P, here selected as the
lectotype. Omlor (1998) cited sheets of Ramos 16592 from BM and K, here designated
as isolectotypes. A second name under Clemensiella, C. dischidioides (see a specimen
under http://sciweb.nybg.org/science2/hcol/vasc/index.asp), circulated via herbarium
specimen exchange by Elmer, has never been validly published, because both Merrill
(1923) and Elmer (1938) realised early enough that it is a specimen of C. mariae.
Recently, Kloppenburg & Siar (2006) described a collection of Clemensiella mariae
from the island of Catanduanes as a new species of Hoya, H. viracensis Kloppenb. &
Siar. In citing the type specimen we have transcribed the collection number, locality,
and habitat data from the (newly spotted) isotype at BRIT; these differ somewhat
from the citation in the protologue. The date on the specimen is written as ‘02/12/91’
which is interpreted as 2 December 1991. In his report on Philippine Hoya, Gozon
(2006: 18, fig. 14) included a photograph of Clemensiella mariae of unknown
provenance labelled as ‘Dregea (?)’. The most recent collections were made by the
second author in Sorsogon Prov., Irosin, Balusan Lake for her MSc thesis on
Philippine Marsdenieae (Laurente, 2008). Altogether, Clemensiella mariae seems to
be rarely collected and documented, but it is not a narrow endemic, occurring
throughout the Philippine archipelago (Fig. 1).
2. Clemensiella omlori Livsh. & Meve, sp. nov.
Clemensiella mariae similaribus sed pedunculis brevioribus, corollis campanulatis,
alabastris cum apicem subobtusis ad acutis. – Type: Indonesia, Aceh: Gunung
Leuser Reserve, Camp Simpang and vicinity, 3–5 km upstream Lau [stream]
Ketambe, c.35 km NW of Kutatjane, 400–600 m, 19 viii 1972, de Wilde & de
Wilde-Duyfjes 14377 (holo L!; iso K, scan!). Fig. 4.
Twiners to 10 m tall (fide de Wilde & de Wilde-Duyfjes 14377). Roots unknown, no
evidence of adventitious roots. Stems 2–3.5 mm diameter, internodes 10–18 cm
long, pith solid. Leaf blades elliptic, basally rounded and slightly peltate, 8.1–11.1 3
3.5–6 cm, acumen 0.7–1.2 cm long, margins ciliate, petioles 2.2–5.9 cm long 3
1–1.6 mm diameter, with line of short adpressed hairs on adaxial side. Inflorescences
up to 12-flowered, peduncles 2–10 3 1.2–1.5 mm diameter, rachis unbranched.
Flowers with pedicels 3.3–3.8 3 1.3 mm diameter, sparsely puberulent, sepals ovate,
obtuse, c.1.5 3 1 mm, sparsely puberulent or ciliate; bud shape cylindrical with
(sub)obtuse to acute apex, with 5 sharp downward-pointed projections at bases of
corolla lobes; corolla campanulate, pale yellow to yellow-green (fide de Wilde & de
Wilde-Duyfjes 14377, Anderson & Bisset S20257), c.9–12 mm diameter, throat
c.3.5 mm diameter, tube with 5 rounded ribs opposite the lobes at base, tapering
SYSTEMATICS OF CLEMENSIELLA
455
F I G . 4. Clemensiella omlori Livsh. & Meve. A, bud; B, flower in lateral view, parts of the
corolla removed; C, anther with corona lobe, adaxial view; region of retinacle depicted with
diagonal cross-hatching; D, pollinarium. (A, B and D drawn from de Wilde & de WildeDuyfjes 14377 (K). C drawn from de Wilde & de Wilde-Duyfjes 14377 (L). A, B and D drawn
by R. Omlor; C drawn by Jennifer Prevatt; B and D from Omlor (1998), with permission.)
upwards, 3–5 3 4.5–5.5 mm diameter at base; corolla lobes 3.2–3.4 3 3.3–3.9 mm.
Gynostegial corona barely exserted from corolla throat, c.2 3 as tall as gynostegium,
2.9–4 3 2–2.8 mm; anthers 1.4–1.9 3 1–1.9 mm, guide-rails 0.4–0.7 mm long,
6 parallel to the vertical axis of the gynostegium; anther connective appendages
triangular, hyaline, c.1/3–1/2 total anther length, 0.6–0.8 3 0.3–0.6 mm, adpressed
to and covering the style-head apex; pollinia c.0.4 3 0.15 mm; caudicles 6 equal to
pollinia in length, pale yellow; corpusculum c.0.1–0.15 3 0.05 mm, brown; style-head
c.0.8 3 1.6 mm diameter. Fruit unknown.
Distribution. Known from two disjunct populations in North Sumatra and Aceh,
Indonesia, and Sarawak, Malaysian Borneo (Fig. 1).
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Ecology. A climber on trees in riparian rain forest (de Wilde & de Wilde-Duyfjes
14377) and a pendulous vine growing epilithically on damp limestone cliffs
(Anderson & Bisset S20257), at elevations from c.60–600 m.
Chromosomes. Unknown.
Paratypes. INDONESIA. North Sumatra: Sibaulangit [Sibolangit], Betimaesdal, 18 iv 1918,
Lörzing 5648 (L!). MALAYSIA. Sarawak: Seburan, Bau, 15 vii 1964, Anderson & Bisset S20257
(K, scan!, L!).
This species is very similar to the Philippine endemic Clemensiella mariae. The most
obvious distinguishing characters are to be found in the corolla, both in bud and at
anthesis. Clemensiella mariae has thickly lenticular (to slightly obovoid) buds with
flattened to obtuse apices. In Clemensiella omlori the bases of the corolla lobes form
sharp downward-pointed projections in bud that mark an abrupt transition zone
between the basally inflated, cylindrical tube and the lobes which form a subobtuse
to acute apex (Fig. 4). At anthesis, the corolla of Clemensiella mariae is rotate with
the gynostegium exserted from the corolla throat for 1/3–1/2 of its length while that
of C. omlori is campanulate with the tips of the corona lobes barely exserted from the
throat (compare Figs 2 and 4). The orientation of the corolla lobes is depicted as
somewhat erect in Fig. 4, but many flowers on herbarium specimens have rotate or
reflexed corolla lobes. The guide-rails of Clemensiella omlori are approximately
vertical (parallel to the long axis of the gynostegium) while those of C. mariae spread
at an angle of 45° (Fig. 3C). Clemensiella omlori also has shorter peduncles, typically
less than 1 cm long, while those of C. mariae are 1–4 cm long.
The cited specimens were first identified as ‘Hoya sp.’, ‘Secamone sp.’, and
‘Asclepiadaceae gen. et sp. indet.’. There are likely other collections of this species
in the world’s herbaria.
This species is named in honour of Dr Ralf Omlor (Mainz, Germany) who first
recognised it and discussed some of the differences between it and Clemensiella
mariae in his generic revision of Marsdenieae (Omlor, 1998).
Acknowledgements
We thank David Goyder for locating and imaging specimens of Clemensiella omlori
at K, the curators of BISH, BRIT, C, K, L, P, PNH and US for loan of specimens to
and/or hosting visits by the fourth author, T. Nyhuus for sending us living material
of Clemensiella mariae, Boy Diego for drawing C. mariae, and Ralf Omlor and
Jennifer Prevatt for drawing the figures of C. omlori.
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Received 24 November 2008; accepted for publication 8 June 2009