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Vaccinium exiguum (Ericaceae, Vaccinieae),
a new species from the ultramafic summit of
Mt. Victoria, Palawan Island, Philippines
Maverick N. Tamayo1,2, Rene Alfred Anton Bustamante2, Peter W. Fritsch3
1Department of Biology, College of Science, University of the Philippines Baguio, 2600, Baguio City, Philip-
pines 2Philippine Taxonomic Initiative Inc., Botanica Building, El Nido, 5313, Palawan, Philippines 3Bo-
tanical Research Institute of Texas, 1700 University Drive, Fort Worth, 76107, Texas, USA
Corresponding author: Maverick N. Tamayo (mntamayo@up.edu.ph)
Academic editor: Pieter Pelser | Received 5 May 2021 | Accepted 22 June 2021 | Published 21 July 2021
Citation: Tamayo MN, Bustamante RAA, Fritsch PW (2021) Vaccinium exiguum (Ericaceae, Vaccinieae), a new
species from the ultramac summit of Mt. Victoria, Palawan Island, Philippines. PhytoKeys 179: 145–154. https://doi.
org/10.3897/phytokeys.179.68323
Abstract
Vaccinium exiguum from the ultramac summit of Mt. Victoria, Palawan Island, Philippines is here de-
scribed as a new species of Ericaceae. It closely resembles V. hamiguitanense but is distinct by having much
shorter petioles and leaves, longer and glabrous calyx lobes with serrate lobe margins, a larger corolla with
deeper sulcations, and longer stamens with spurs oriented laterally. Vaccinium exiguum represents the third
Vaccinium species found on the Island of Palawan and 36th in the Philippines.
Keywords
Ericales, endemic species, Malesia, sect. Bracteata, Vaccinioideae
Introduction
e Island of Palawan is situated on the south-western side of the Philippine Archi-
pelago and is bordered by the West Philippine Sea in the north and the Sulu Sea in the
south. Palawan is a biodiverse area, regarded both biogeographically and geologically as
Copyright Maverick N. Tamayo et al. 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.
PhytoKeys 179: 145–154 (2021)
doi: 10.3897/phytokeys.179.68323
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Maverick N. Tamayo et al. / PhytoKeys 179: 145–154 (2021)
146
a portion of the Sunda Shelf, with many of its species shared with Borneo (Dickerson
1928; Heaney 1986; Voris 2000; Esselstyn et al. 2004). e long and complex geohis-
tory of the island which started during the mid-Oligocene, as well as its highly variable
elevation and climate, has promoted high rates of speciation and endemism (Anacker
2011; Galey et al. 2017). In particular, the extensive areas of ultramac substrates have
resulted in the evolution of many endemic plant species in Palawan (e.g. Robinson et
al. 2009, 2016; Malabrigo 2020; Quakenbush et al. 2020; Tandang et al. 2020) and it
is to be expected that more species await discovery in these ultramac regions as they
are further explored and studied.
e tropical species of Vaccinium L. are predominantly montane inhabitants with
a high degree of endemicity (Argent 2018). e genus is the most species-rich of the
Philippine genera of the family and is currently represented by 35 species, 32 of which
are endemic to the country (Argent 2008; Pelser et al. 2011 onwards). e highly
regarded taxonomic treatments by Copeland (1930) and Sleumer (1966–1967) are
the most comprehensive, thus far, for Philippine Vaccinium. However, gaps in our
knowledge of Philippine Vaccinium remain, especially in various species complexes
(e.g. V.caudatum Warb./V. benguetense S.Vidal) and many character ambiguities used
for the treatments require clarication and resolution. After Sleumer’s work (1966–
1967), three species have been added to the list, viz. V. cebuense Salares and Pelser,
V. hamiguitanense P.W.Fritsch, and V. oscarlopezianum Co (Co et al. 2002; Salares et
al. 2018; Fritsch et al. 2020).
During eldwork on Mt. Victoria, Palawan Island in February 2021, author Bus-
tamante documented a species of Vaccinium that grows at the ultramac summit of
the mountain (Fig. 1A) and closely resembles the recently described V. hamiguitanense
from Mt. Hamiguitan, Mindanao Island. However, the inorescence of this species
diers from that of V. hamiguitanense in shape. After detailed morphological examina-
tion, it was conrmed that the specimen possesses distinguishing characters demon-
strating its status as a species new to science, which we describe here under a biological
species concept (Mayr 2000). Our discovery increases the number of species of Vac -
cinium in the Philippines to 36 and increases the number of known Vaccinium species
from Palawan Island to three. Photographs and an illustration of the new species are
also provided.
Materials and methods
e description was based on in-situ observations, herbarium specimens, and spirit
samples preserved in Copenhagen solution. Microscopic details were described with
the aid of a Swift SM100 stereo zoom microscope (30× magnication). Relevant lit-
erature and taxonomic keys (i.e. Copeland 1930; Sleumer 1966–1967; Argent 2018)
were also consulted.
Vaccinium exiguum, a new species of Ericaceae from the Philippines 147
Taxonomy
Vaccinium exiguum M.N.Tamayo, R.Bustam. & P.W.Fritsch, sp. nov.
urn:lsid:ipni.org:names:77218415-1
Figs 1B, 2, 3
Type. Philippines, Palawan Island (= Palawan Province), Municipality of Narra, Mt.
Victoria, 9°21'56"N, 118°20'02"E, exposed ultramac summit, ca. 1700 m elevation,
27 February 2021, PTI-8 by R. Bustamante (holotype: PNH!; isotypes: PPC!; BRIT!).
Diagnosis. Vaccinium exiguum closely resembles V. hamiguitanense, but is distinct
by having shorter petioles (0.5–1.0 mm vs. 1.2–1.8 mm), shorter leaves (4.9–9.3 mm
vs. 8.8–16.0 mm), longer calyx lobes (1.8–2.0 mm vs. 1.1–1.3 mm) that are glabrous
(vs. merely ciliate) with serrate calyx lobe margins (vs. entire), a larger corolla (6.0–7.0
× 4.0–5.0 mm vs. 4.6–5.0 × ca. 2.6 mm) with deeper (vs. shallow) sulcations, and
longer stamens (3.5–4.0 mm vs. 2.8–3.5 mm) with spurs oriented laterally (vs. slightly
upcurved and oriented ± apically). e calyx lobes of V. exiguum are unique amongst
Philippine species in that they are nearly as long as or longer than the hypanthium.
Unlike V. hamiguitanense, V. exiguum has a corolla that appears distinctly star-shaped
in cross section because of its deep sulcations.
Description. Habit shrubs, terrestrial, evergreen, 0.3–1.5 m tall, densely branched.
Branchlets when young with nely translucent erect, straight trichomes ca. 0.2 mm
long, at maturity brown, slightly compressed and often ridged, 0.5–1.5 mm wide, not
lenticellate, outer surface brownish; perennating buds compressed-ovoid, 0.5–0.8 mm
long, with several obscurely overlapping scales. Leaves persistent on older branchlets,
densely crowded, spirally and evenly arranged; petiole green with a tinge of red, 0.5–
1.0 × 0.4–0.8 mm, nearly as long as wide, with translucent, erect, straight trichomes
ca. 0.1 mm long, in cross section abaxially rounded, adaxially nearly at; leaf blade
elliptic or oblong, larger leaves on each branchlet 4.9–9.3 × 3.0–6.0 mm, coriaceous,
both surfaces greenish red when young, glabrous, except occasionally puberulent at
base, smooth, abaxial surface without punctae, green and glossy, light brown in sicco,
adaxial surface green and nitid, dark brown in sicco, base cuneate, margin with 4 or 5
impressed ± evenly distributed crenations per side with occasional minute translucent
lanceolate glands on crenations, thinly recurved, apex obtuse to rounded, the very tip
with a gland, marginal glands 3 or 4 per side, scattered along length of margin, ca.
0.1mm diameter, midvein slightly raised abaxially, attened adaxially or nearly so,
secondary veins 2 to 4 on each side of midvein with rst pair arising from base and
remainder along midvein, arc-ascending, slightly raised or obscure abaxially, obscure
adaxially, tertiary veins faintly evident or obscure. Inorescences pseudo-terminal or
terminal, racemose, ca. 1.5 cm long at anthesis, developing beyond connes of per-
ennating bud, densely owered, 3 to 8 per axil, (3 to)5 or 6-owered; rachis green,
puberulent, slightly ridged with translucent trichomes ca. 0.1 mm long; bracts sub-
Maverick N. Tamayo et al. / PhytoKeys 179: 145–154 (2021)
148
Figure 1. Vaccinium exiguum A ultramac summit of Mt. Victoria B owering branchlets in situ. Photo
A by Alastair Robinson. Photo B by Rene Alfred Anton Bustamante.
tending pedicels, foliaceous, greenish, brown in sicco, ovate to elliptic, planar or oc-
casionally cucullate, 3.0–8.0 × 4.0–7.5 mm, coriaceous, glabrous, margin crenulate
or serrulate with 4 or 5 (or 6) impressed crenations per side, with minute translu-
cent lanceolate glands on crenations, apex obtuse or rounded. Flowers articulated at
junction with pedicel, 6.0–7.0 mm long. Pedicel nodding, 2.0–5.0 × 0.8–0.9 mm at
anthesis, white-puberulent; bracteoles persistent, 2, borne at base of pedicel, margin
with minute translucent lanceolate glands on crenations, linear-lanceolate to oblong
or nearly so, 1.0–1.2 × 0.3–0.5 mm long, glabrous, margin serrate, apex sharply acute.
Hypanthium green, glossy, cupuliform, 1.4–1.8 × 0.9–1.0 mm, glabrous; calyx limb
Vaccinium exiguum, a new species of Ericaceae from the Philippines 149
Figure 2. Vaccinium exiguum A owering branchlet B leaf, abaxial view C lateral view of ower show-
ing ribbed corolla D distal portion of pedicel, as well as hypanthium, calyx lobes and style E stamen in
oblique-lateral view showing spurs F stamen in ventral view G cross section of ovary showing seven loc-
ules. Illustrated by Maverick N. Tamayo.
Maverick N. Tamayo et al. / PhytoKeys 179: 145–154 (2021)
150
0.7–1.0mm long, glabrous; calyx lobes broadly triangular, 1.8–2.0 mm long, glabrous
both sides, margin serrate, with minute translucent lanceolate glands on crenations,
apex acute, without sessile and terminal gland. Corolla in bud closed, broadly ur-
ceolate and strongly 5- to 7-ribbed (sulcations) along the petal midveins, pale green,
at anthesis strongly 5- to 7- ribbed, white with tinge of pale red or pink near and on
lobes, 6.0–7.0 × 4.0–5.0 mm, glabrous inside and outside; corolla lobes 5 to 7, ca.
1.0 × 1.0 mm, apex acute or obtuse. Stamens 8 to 10, monomorphic, free from each
other, 3.5–4.0 mm long; laments straight, 1.9–2.0 mm long, white-pubescent mainly
at base, trichomes ca. 0.1 mm long (shorter distally); anthers 1.5–2.1 mm long, cells
1.2–1.3 mm long, echinulate, tubules parallel, broadly cylindrical, 0.8–1.0 mm long,
slightly narrower than cells, opening by oblique ventrally oriented apical pores, pore
apex rounded, spurs present, minute, borne ± midway along anther, laterally oriented,
0.15–0.20 mm long. Ovary 5 or 6 (or 7)-locular, but appearing pseudo-10- to 12- (to
14-) locular with false partitions extending 0.20–0.25 mm from inner wall; ovules in
two columns per locule, each column separated by false partitions; disk circular with
prominent ridges on margin, ca. 2.0 mm in diameter, glabrous; style not exserted from
corolla, 4.0–5.0 mm long, glabrous. Fruit not observed.
Etymology. e epithet “exiguum” refers to the overall small stature and leaf mor-
phology of the new species.
Distribution and habitat. Vaccinium exiguum is currently known from a single in-
dividual from a single location at the exposed ultramac forest summit of Mt. Victoria,
Palawan Island, Philippines at ca. 1700 m elevation.
Conservation status. Only a single owering plant was documented from a single
location at the summit of Mt. Victoria, Palawan. Other summits within the mountain
range are similar to the type locality in elevation, but these have yet to be explored. As
such, we propose the conservation threat status Data Decient (DD) (IUCN Stand-
ards and Petitions Committee 2019) due to the scarcity of data with which to con-
dently assess the species against the IUCN guidelines.
Many species are endemic to Mt. Victoria (Robinson et al. 2009, 2016). ough
harboring high biodiversity, Mt. Victoria is unfortunately not legislated as a protected
Figure 3. Translucent glands of Vaccinium exiguum A leaf margin B calyx lobe C bract. Photos by
Maverick N. Tamayo.
Vaccinium exiguum, a new species of Ericaceae from the Philippines 151
area (PA). Mining activities within the area are considered a signicant threat that
poses the risk of habitat and forest degradation. us, the lack of legal protection is the
greatest threat to this species and to the biodiversity of the area.
Phenology. e new species was observed owering during the month of February.
Discussion
Vaccinium exiguum belongs to section Bracteata Nakai (Nakai and Koidzumi 1927)
sensu Sleumer (Sleumer 1966–1967) as exhibited by its well-developed and often
many-owered racemes, corolla consisting of a single homogenous layer, and the ab-
sence of a membranaceous wing at the sinuses and anthers that open by short introrse
slits or terminal pores (Co et al. 2002; Salares et al. 2018; Fritsch et al. 2020).
In the key of Sleumer (1996–1967) of the Malesian Vaccinium section Bracteata,
V. exiguum best keys to V. gitingense Elmer (endemic to the Philippines). However, the
new species diers from V. gitingense by having shorter petioles (0.5–1.0 mm vs. ca.
2.0 mm), smaller leaf blades (4.9–9.3 × 3.0–6.0 mm vs. 15–35 × 8–15 mm), glabrous
calyx lobes (vs. nely ciliate), a non-glaucous and glabrous corolla (vs. glaucous and oc-
casionally bears few hairs), and longer laments (1.9–2.0 mm vs. ca. 1.5 mm) (Elmer
1912). In the key to the Bornean species of Vaccinium (Argent 2018), the species best
keys to V. coriaceum var. stapanum (Sleumer) Argent (restricted to Mt. Kinabalu, Ma-
laysia); however, Vaccinium exiguum diers by having shorter leaf blades (4.9–9.3 mm
vs. 6.0–13.0 mm), a crenate leaf margin (vs. entire), longer calyx lobes (1.8–2.0 mm
vs. ca. 1.3 mm) that are triangular (vs. ovate), and a corolla with deep sulcations (vs. no
sulcations). Likewise, the presence of translucent lanceolate glands on the crenations
along the margins of the leaves, bracts, bracteoles, and calyx lobes of V. exiguum (Fig.
3) is a character shared by the three species.
Although the species exhibits morphological similarities with V. hamiguitanense,
the owers of V. exiguum are unique amongst all other Philippine Vaccinium in having
a broadly urceolate and strongly 5- to 7-ribbed corolla and calyx lobe margins that are
serrate. Vaccinium exiguum also possesses the smallest leaves amongst the Philippine
Vaccinium species with a size range near V. hamiguitanense and V. microphyllum Reinw.
e latter species is easily distinguished from V. exiguum by its axillary solitary owers
(vs. terminal multi-owered inorescences). In addition to the characters distinguish-
ing V. exiguum from V. hamiguitanense as specied in the diagnosis, the two species
have distinct geographical ranges.
Currently, two species of Vaccinium are recorded in Palawan: V. brachytrichum Sle-
umer and V. palawanense Merr. e new species can be easily dierentiated from V.
brachytrichum by bearing fewer owers per inorescence [(3 to)5 or 6 vs. 5 to 8)],
longer anthers (1.5–2.1 mm vs. ca. 1 mm), and a glabrous (vs. pubescent) hypanthi-
um. It diers from V. palawanense in the short and densely owered inorescences that
are much shorter than the leaves (vs. owers in racemes about as long as the leaves),
a shorter pedicel (2.0–5.0 mm vs. 5.0–7.0 mm), and a 5- or 6-(or 7-) locular ovary
(vs. 5) (Merrill 1908; Sleumer 1961). Moreover, the strongly ribbed corolla and the
Maverick N. Tamayo et al. / PhytoKeys 179: 145–154 (2021)
152
small leaves with crenate margins are also remarkable characters of the new species that
easily distinguish it from the two Palawan species. At its type locality, V. exiguum was
observed to be sympatric with V. palawanense.
Due to the paucity of collections and relative lack of study, intraspecic morphologi-
cal variation within the species of Philippine Vaccinium (Salares et al. 2018), as well as
sectional boundaries and composition, are imprecisely known (Vander Kloet and Dickin-
son 2009; Fritsch et al. 2020). A detailed monographic study of this group is warranted.
Acknowledgements
We thank Mr. Crispin O. Lumba Jr., acting Municipal Mayor of Narra, Mr. Ronico
Masbang, Chief of the Tagbanua Tribe, and the Palawan Council for Sustainable De-
velopment (PCSD) for issuing the gratuitous permit no. 2018-28, transport permit no.
PPC-LTP-AO12-2021-316 and certicate of inspection no. 1614239583882; Prof.
Lea Camangeg, Jehson Cervancia, William Cabanillas, and Prof. Marjorie delos An-
geles for their invaluable help and support; Mr. Jonah van Beijnen and Ms. Kyra Ho-
evenaars of Fins & Leaves for their generous sponsorship of the research eldwork; Dr.
Alastair Robinson for the use of his photograph of the Mt. Victoria summit; and John
Charles Altomonte (PTI), Yu Pin Ang (PTI) and reviewers Dr. Jasper Obico, Mr. Val
Salares, and Dr. Wendy Mustaqim for helpful comments and suggestions that greatly
improved the manuscript. We gratefully acknowledge the support of Palawan State
University (PSU), especially Dr. Ramon M. Docto (President), Dr. Muriel Toquero
(Vice President for Research and Extension), Prof. Imelda R. Lactuan (Dean, College of
Sciences), and the U.S.-National Science Foundation (grant DEB-1754697 to PWF).
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