Micronesica 41(1): 131–164, 2009
Plant Endemism, Rarity, and Threat in Palau, Micronesia: A
Geographical Checklist and Preliminary Red List Assessment
CRAIG M. COSTION
1
Department of Ecology and Evolutionary Biology,
School of Earth and Environmental Sciences,
University of Adelaide, Adelaide SA 5001
ccostion@googlemail.com
ANN HILLMANN KITALONG
The Environment, Inc., P.O. Box 1696, Koror, Palau 96940
TARITA HOLM
Palau Conservation Society/PALARIS, P.O. Box 1811, Koror, Palau, 96940
Abstract—An official checklist of the endemic plant species of Palau
has been long awaited, and is presented here for the first time. For each
species a substrate limitation, growth form, and relative abundance is
listed. In addition an IUCN red list assessment was conducted using all
available data. For over half of the endemic species there is insufficient
data to provide a red listing status however an expected minimum
number of threatened plants out of the total is inferred. Approximately
15% of Palau’s endemic plants are believed to be only known from the
type collection and many more only known from a few collections.
These taxa however may now be prioritized and targeted for future
inventory and research. The taxonomic robustness of several of these
taxa is questionable and it is expected that more endemic species will be
lost to synonymy in the future. Previous estimations have significantly
over-estimated the rate of plant endemism in Palau (e.g., 194). Here,
130 plants are recognized for Palau, making its level of plant endemism comparable to some of its neighboring Micronesian islands to the
east, notably Guam and Pohnpei. Several species are known to be restricted to isolated disjunct populations however the causes for their
rarity are poorly known and have never been intensively studied. Palau
although notable for its high percentage of remaining primary forest
compared to other oceanic islands faces increasing threat from development making these small populations highly vulnerable. Nothing is
known about how these rare species will respond to the imminent threat
of climate change. There is no current legislation protecting specific
plant species as their rarity has never been systematically quantified.
This paper represents a step towards plant conservation in Micronesia
and it aims to stimulate further studies to address the data deficiencies
documented here.
1
Author to whom correspondence should be addressed
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Micronesica 41(1), 2009
Introduction
The islands of Palau, lying roughly north of Papua New Guinea and East of
the Philippines, contain a unique and rich flora that is shared with it’s
neighboring islands to the east, the Caroline Islands, and the Marianna Islands to
the northeast. This geographic region, known as Micronesia, comprises the
northwestern part one of the 34 recognized biodiversity hotspots on earth (Myers
et al. 2000). The Polynesia-Micronesia hotspot has been quoted as the
“epicenter” of the current global extinction crisis. Palau at the western most
boundary of this region is at a pivotal location. This tiny island nation, which is
one of the newest countries in the world, as well as one of the smallest, has been
noted for years by various authors in environmental evaluation reports for
containing the highest rates of plant endemism out of all its neighboring island
states in Micronesia.
This should be expected considering Palau by far contains the highest
number of native plant species in Micronesia. Palau with a native vascular plant
species count of approximately 724 species, rivals its neighboring islands
significantly. The numbers drop by over half traveling to the first island east with
376 in Yap (Fosberg et. al. 1979, 1982, 1987), then 328 in Guam (Stone 1970)
and 357 in Pohnpei (Balick unpubl.). The numbers continue to drop rapidly
traveling east to the Marshall islands before reaching a vast blue expanse of
ocean that stretches eastward to Hawaii. The flora of Micronesia is an attenuated
flora deriving largely from the Indo-Malesian region to the west. Conservation
International (2007) declares a total of 3,074 endemic plant species in the region
from western Micronesia across to southeastern Polynesia. The Office of
Environmental Response and Coordination in Palau (2002) reported a total of
194 of these to be endemic to Palau, emphasizing that experts believe there to be
more than this.
Where these statistics have been taken from and how they have been
calculated has been one of the questions that has driven the author for the past
several years. There has never been a checklist of endemic plants published for
Micronesia. Throughout the course of the research presented in this paper, not
only has the expected number of endemic species significantly dropped, but the
original assumption that Palau takes the limelight for plant endemism rates in
Micronesia has been critically re-evaluated. The results presented here suggest
that Palau may actually have the second highest rate of plant endemism in
Micronesia, Guam being the first and that the neighboring islands have
comparable rates to that of Palau.
Although the endemic statistics have remained obscure over time, the flora
of the region is very well known in comparison to many other parts of the tropics.
The prospect of finding new species, though clearly present, is relatively low
compared to places such as Southeast Asia and the Neotropics. Progress on the
flora of Micronesia began during the Japanese occupation of the region. Notable
collectors included Hosokawa, Kanehirae, and Tuyama. Many of the current
Costion et al.: Endemic Palau plants
133
names accepted for Palau’s endemic plants were described by these pioneer
botanists. Another early notable collector was Schlecter, a German botanist and
orchidologist, who named many of Palau’s recognized orchid species. During the
American occupation, work was continued mostly by Raymond Fosberg and his
collaborators who described several new taxa, new combinations, and most of
Palau’s endemic varieties. Although their geographical checklists (Fosberg et al.
1979, 1982, 1987) have proved to be an indispensable resource, it has also been a
source of some confusion regarding which plants are endemic. In the Flora of
Micronesia (Fosberg & Sachet 1975a, 1975b, 1977, 1980b; Fosberg et al. 1993),
and other occasional publications on the flora of the region, endemic status is
usually established. However these accounts are nowhere near a complete
representation of the flora.
What the geographical checklists lacked was a clear indication of which
plants were actually endemic to the region. In the abstracts it is clearly stated
how many of the plants listed are endemic to the Carolines, the Marianas, and
endemic to the entire region but there is no further mention of endemism outside
the abstract. The taxa presented in the checklist are not distinguished by these
categories. The users have been left to determine this for themselves. This has
lead to a great degree of error in calculating figures of plant endemism for some
of the respective island states. For example, if a plant’s distribution within
Micronesia is restricted to Palau, its distribution is listed as only occurring in
Palau. This naturally has lead to assumptions that the taxa in question is endemic,
when more often than not, its native distribution extends further west into
Malesia. Many of these plants are at the eastern most limits of their native range
in Palau.
An additional significant factor has contributed to this problem. Over time, a
significant number of the names published during the Japanese era and even
recent times have become basionyms or synonyms for species with a wider
geographical range. This trend continues today and demonstrates how the
determination of species as endemic to the region has been obscured by the slow
simultaneous progress on the flora of Malesiana where as noted above, the vast
majority of Micronesia’s plants are derived. In addition to this, there is even
slower progress towards published monographs of families and genera from the
region.
These floristic problems came to the attention of the authors while
inventorying collections from Palau at overseas herbaria and revising the
checklist of vascular plants for the country, and stimulated the beginning of an
effort extended over several years, amidst other projects, to compile an accurate
list of endemic plants for Palau. Simultaneous work has been carried out by other
Pacific researchers for the islands of Pohnpei and Kosrae and plans are underway
to update the checklist of plants for the entire Micronesia region. The discussion
here is limited to the islands of the Republic of Palau, geographically defined as
the western Caroline islands, excluding the island state of Yap of the Federated
States of Micronesia.
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In addition to contributing to the taxonomic progress of the endemic plants
it has been decided to do so within the context of conservation. The link between
biodiversity conservation and endemism is indeed, as stated previously, at the
“epicenter” of current discussion in the field of biology. This is especially so for
small island nations where the threat of losing an endemic species is much
greater due to very small population sizes and vulnerable ecosystems with
unoccupied niches. These uneven island biotas, often without predators, can be
easily exploited by invasive species. The link is put even more into the context of
taxonomy when it is considered how limited funds and resources could be
misspent on taxa believed to be endemic that are actually widespread.
For these reasons a preliminary assessment for the taxa represented here has
been done using the IUCN Red List criteria (IUCN 2001). For the majority, data
has not been sufficient for establishing even preliminary status. It is hoped that
this will not detract from the value of this checklist but instead stimulate effort
and funding for a complete and thorough study to produce a complete red list
assessment of Palau’s endemic plants.
Lastly, it is expected that as new taxonomic treatments are published, this
list, and naturally the statistics of endemic species for Palau, will continue to
change. Many of Palau’s endemic plants are poorly known and in some cases
only by the type specimens or a few additional collections. Critiques on the
taxonomy and endemic status of taxa listed here are welcomed and encouraged.
Methods
Primary sources of information utilized include the working database in
Palau referred to as the Palau Vascular Plants Database (PVPD 2006), the
Provisional Checklist of the Plants of Palau (Kitalong et al. 2008), and Fosberg et
al.’s checklists (1979, 1982, 1987). All species previously listed as endemic in
any of the above checklists were critically assessed to verify their status. In
addition, Fosberg et al.’s lists were reviewed systematically to check for any
possible endemic taxa excluded from the former lists. The task of assessing
endemic status began during herbarium inventories at the Bishop Museum. Any
taxa listed as endemic with specimen records found in other countries were
simply crossed off the list. This effort was later continued with a thorough
literature review and inventory of digital herbaria and taxonomic databases
world-wide.
The following databases were consulted for distribution records and the
most up to date taxonomy:
GBIF: Global Biodiversity Information Facility website: http://data.gbif.org/
welcome.htm (accessed August 2007)
Kew World Checklist of Selected Plant Families. Royal Botanic Gardens
Kew, online resource http://www.kew.org/wcsp/home.do (accessed August 2007)
ILDIS: International Legume Database Information Service. School of Plant
Sciences, University of Reading. Website http://www.ildis.org/ (accessed August
2007)
Costion et al.: Endemic Palau plants
135
IPNI: International Plant Names Index website: http://www.ipni.org/
index.html (accessed August 2007)
HUH: Harvard University Herbaria website: http://www.huh.harvard.edu/
(accessed August 2007)
If the name and its distribution information were not found in one of these
databases, often by conducting an online search, publications or articles that
mentioned the taxa were found, from which distribution records were often
obtained. If the plant occurred in other countries, then usually several links were
identified by the search engine. For most of Palau’s confirmed endemics, there
were very few if any links found. In addition, for each family and genus that
occurs in Palau, a search was done for any published monographs using the
library resources at the Royal Botanic Gardens Edinburgh. The Flora of
Malesiana was also thoroughly reviewed which was relevant to many of Palau’s
taxa. In most cases, if a taxa recognized by Fosberg et al. (1979, 1982, 1987) was
reduced to synonymy in the Flora Malesiana, the Flora Malesiana was followed.
In some cases however, Fosberg et. al’s treatment (1979, 1982, 1987) was
retained.
Only species found to be endemic to Palau are listed. Anything not listed
here has been found to have distributional records outside Palau. Geographic data
within the Palau archipelago was obtained from two primary sources; Fosberg et
al.’s (1979, 1982, 1987) checklists and the author’s database of over 14,000 plant
collection records from Palau. This database was compiled from all databased
herbarium specimens collected in Palau that are held at the Smithsonian
herbarium (US), the Bishop Museum herbarium (BISH), and the Belau National
Musuem, in addition to presence/absence records obtained from the Babeldaob
Forest Survey in 2005 (Costion & Kitalong 2006). Several cases proved that this
supplementary data was worthwhile by extending the distributional ranges
presented in Fosberg et al. (1979, 1982, 1987).
SYMBOLS
(*) A “*” is applied following the name to indicate the particular taxon was
either insufficiently represented or not represented at all in the author’s database
and its substrate restriction data (volcanic, limestone, generalist) was determined
solely from the literature. A complete list of the literature consulted for
distribution data is as follows: Hartley (2001); Hassler et al. (unpublished world
checklist of Orchidaceae); Holttum (1977); Huynh (1999); Fosberg & Raulerson
(1990); Fosberg & Sachet (1979, 1980, 1981, 1987, 1991); Fosberg et al. (1979,
1982, 1987, 1993). The lack of specimens from inventoried herbaria suggests that
these taxa are relatively poorly known, although it is known that un-databased
material exists at the Smithsonian and the University of Guam, but was not seen
by the authors. Until these records are databased, they remain unavailable for
analysis.
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Micronesica 41(1), 2009
(+) A “+” is listed after the name to indicate that the taxon is only known by
the author from the type specimen or otherwise a single collection, or even in
some cases where no specimen at all could be located. This serves to highlight
taxa very poorly known and in need of further collections. Distributions of these
taxa were determined from the checklists of Fosberg et al. (1979, 1982, 1987)
and/or from the protologues or type specimen labels.
IUCN RED LIST STATUS
All species listed have been assessed using the IUCN Red List categories
and criteria (IUCN 2001). Taxa recognized as endemic only to the varietal rank,
have not been assessed. Abbreviations used for the categories are as follows:
CR: Critically Endangered
EN: Endangered
VU: Vulnerable
NT: Near Threatened
LC: Least Concern
DD: Data Deficient
Categories that classify as threatened are highlighted in bold. If a taxa meets
the criteria for one of the threatened categories, then the specific criteria that it
qualifies under is listed in parenthesis following the IUCN red listing format
(IUCN 2001). For example, Cycas silvestris K.D. Hill,VU(D2) is an Australian
cycad that qualifies as vulnerable under criteria D2 which states that the area of
occupancy must be less than 20 km² or the number of locations is less than or
equal to five. This species is restricted to the Cape York peninsula, Queensland
and only known from a few small stands that lack adequate protection (Hill,
1992). The specifications of the categories criteria are easily obtained from the
IUCN website (www.iucnredlist.org) and will not be repeated here.
FORMS
Eight growth forms were abbreviated as shown below. Some species have
more than one form.
T = Tree
T(u) = understory tree
T(c) = canopy tree
S = shrub
L = liana
HP = hemi-parasite
H= herb
E = epiphyte
RELATIVE ABUNDANCE CODES
Costion et al.: Endemic Palau plants
137
This category was determined roughly from overall knowledge of the
authors’ field experience, data records, and review of the literature. It is included
to help distinguish between different types of rarity. Plants that are uncommon to
rare but across the island, plants that are locally abundant but restricted to small
localities, and plants that are widespread. Code abbreviations are as follows:
R = Rare, very uncommon or very poorly known
RR = Range restricted, only known to specific localities
U = Uncommon, but found throughout the substrate type
C = Common, widespread in occurrence
A = Abundant, grows in abundance where found
D = Dominant, forms a dominant layer in the forest structure
DD = Data deficient, insufficiently known
Results
A total of 130 vascular plant species are listed here as restricted to Palau
with an additional 23 endemic varieties. Well over 100 plants that were
considered potentially endemic in the PVPD were found to have wider
distributions outside Palau. Most of these had ranges extending into Malesia and
some shared their distributions with other Micronesian island states. Plant
distributions within the archipelago can be divided into three main categories.
Plants restricted to volcanic islands, plants restricted to limestone islands, and
generalist plants occurring on both substrates. A few taxa are restricted to
specific islands within these categories. A total of 75 species were found to be
restricted to volcanic islands including one restricted to the island of Malakal in
Koror; 31 species are restricted to Limestone islands including one restricted to
Peleliu and one restricted to Angaur; 24 species are considered generalists
occurring on both volcanic and limestone islands.
SPECIES ENDEMIC TO VOLCANIC ISLANDS
It is believed that the volcanic islands of Palau were formed beneath the
ocean’s surface and were subsequently uplifted during the Miocene and Pliocene
(Fig.1). Clay was formed from the erosion of upper exposed parts of the Island
down into the swamps and coastal areas (Goldich et al. 1948). Today parts of the
originally exposed basalt rock can be found scattered on the high ridges and hill
tops of Babeldaob. Below these small areas it is mostly volcanic clay. Though
the soils are acidic and nutrient poor, the total land mass of Babeldaob has
produced high rates of plant diversity and endemism in comparison to other
islands of Micronesia. Babeldaob is 331 km², making it the second largest island
in Micronesia. The volcanic islands of Koror, Malakal, and Ngarekebesang
although mostly urbanized, contain remnant patches of a similar flora to that of
Babeldaob. The volcanic sections of Koror are virtually entirely deforested,
though Malakal has some patches remaining. The island of Ngarekebesang
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Micronesica 41(1), 2009
Figure 1. Volcanic islands, Palau
contains the largest area that has not been developed on the volcanic parts of
Koror and has not been intensively surveyed.
A total of 75 vascular plant species and 12 endemic varieties are listed here
as endemic to Palau’s volcanic islands. The majority of these are expected to be
found only on Babeldaob, however many do have ranges that extend to the
volcanic islands of Koror state. Since it is difficult to presume exactly how
similar the original vegetation of the Koror islands was to Babeldaob, prior to
human habitation, it is most logical to treat all the volcanic islands as one floristic
unit. There are a total of four endemic fern species, three Sellaginella species,
and 68 endemic angiosperm species. Families most strongly represented are the
Orchidaceae with a total of 21 species, Rubiaceae with eleven, and Pandanaceae
with five.
Only one plant is known with a range restricted to a volcanic island in
Koror. Timonius salsedoi is only known from the island of Malakal (Fig.2).
Costion et al.: Endemic Palau plants
139
Described by Fosberg
& Sachet (1987) this
plant is only known
from
the
type
specimens
and
is
poorly known. No
information has been
recorded regarding the
population size or
ecology. However, the
amount of suitable
habitat on this island
qualifies this species
under the class of
Critically Endangered,
under the IUCN red list
guidelines. Malakal is
a very small island
with less than half of
Figure 2. Malakal Island
its land area providing
suitable habitat for
native vegetation. This small area is restricted to patches on top of the island’s
hill and fragmented from subsistence farming. The island is heavily developed
along the coast at the bottom of the hill and the vegetation at the urban boundary
is occupied by introduced and invasive species. Currently there is no known
legislation to protect the remaining areas of vegetation on the hill. The
occurrence of this threatened species warrants protection of all remaining forest
on the island until further studies can be undertaken. Collection of population
data on the island of Malakal for this species is highly recommended. A
phylogenetic study of the genus Timonius in Palau would be beneficial to
confirm it is a distinct species and not merely a regional variant of another more
widespread species. To date, no other species have been described as restricted to
any islands as small as this one in Palau.
SPECIES RESTRICTED TO LIMESTONE FOREST
The limestone islands are derived from lime-secreting organisms that
flourished in tropical seas that became shallow from the volcanic eruptions
forming Babeldaob and Koror. These deposits have likely been continuous since
the Miocene. Parts of southern Babeldaob are actually limestone formed from
these deposits (Fig. 3). The high limestone islands known today as the Rock
Islands are older, formed from the Miocene to the Pleistocene and were also
subject to significant uplift (Goldich et al. 1948). There are between 250 and 300
islands with a total area of 47 km². They are composed of karst limestone which
is jagged and sharp making it dangerous to traverse. Early Palauan settlers were
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Micronesica 41(1), 2009
known to inhabit these
islands but they have long
since been abandoned and are
now virtually all undisturbed
virgin forest. The vegetation
here is distinct with virtually
no topsoil. The plants often
literally cling to shear rock.
Some of the endemic plants
are restricted to the karst
Rock islands, but many also
occur on the low platform
islands to the south. The low
platform islands and reef
atolls such as Peleliu,
Angaur, and Kayangel, are
younger, believed to be
formed from deposits from
the Pleistocene to recent
times (Goldich et al. 1948).
Peleliu and Angaur are lower
and generally flat islands that
have undergone heavy disturbance particularly in the
Figure 3. Limestone Islands
20th century, and are currently
inhabited.
A total of 31 endemic species and seven endemic varieties were found to be
restricted to the limestone islands of Palau including four ferns, two palms, three
orchids, and four members of the Rubiaceae family. The remaining families are
represented by only one to two species. Families that occur here, but are not
represented on the volcanic islands by any endemic species, include
Lomariopsidaceae, Arecaceae, Caparidaceae, Cucurbitaceae, Elaeocarpaceae,
and Vitaceae.
Due to its inaccessibility the Rock Islands are relatively undisturbed,
however they are also poorly studied. It is expected that most of the taxa listed
here are distributed throughout the limestone islands though with some restricted
to the Rock Islands. Further studies are needed to determine the degree of
abundance or rarity and assess the degree of threat proposed to many of these
plants. One endemic palm, Ponapea palauensis is considered critically
threatened as it is restricted to a few Rock islands and of the three areas where it
has been found only one has a healthy stand of trees (Lewis 2008). A second
endemic palm species, Hydriastele palauensis, is more common than the former,
though only occurring in scattered patches throughout the Rock Islands. Both
palms are considered threatened by two species of introduced parrots (Mueller-
Costion et al.: Endemic Palau plants
141
Dombois & Fosberg 1998). Manner and Raulerson (1989) documented the
continued plight of Hydriastele in the Seventy Islands reserve, which was once
believed to provide a refuge for the palm, emphasizing its continuing decline.
Follow up studies have been limited.
SPECIES RESTRICTED TO PELELIU
Peleliu is one of the largest limestone islands in Palau, with a total land area
of 13 km², and is the most populated with approximately 700 inhabitants (Fig.3).
The island is most notable for being the site of a major WWII battle, the Battle of
Peleliu. From what is currently known, there were not many endemic plants on
the island to begin with. Local lore asserts that after the battle, only one coconut
tree was left standing. Today the untrained eye would never be able to tell, as it is
quite heavily forested. However the majority of the vegetation is secondary regrowth and has become dominated by the non-native Timonius timon. One
endemic species, Pandanus peliliuensis Kaneh., is recognized as being restricted
to Peleliu (Fosberg & Sachet 1987). This taxa is only known from isotype
specimens (HUH, NY), and these are only fragments. Further collections are
needed to verify to what extent it occurs on the island and quantify its population
size.
SPECIES RESTRICTED TO ANGAUR
Angaur is positioned further south from Peleliu and across an ocean channel
(Fig. 3). Unlike the rest of the archipelago discussed here, which occurs within a
sheltered coral lagoon, Angaur is surrounded by open ocean. It has a land area of
8 km² and a small population of less than 200. The island was also a WWII battle
site, and was mined for phosphate from 1909 to 1954. It is likely to have
experienced much disturbance in the past century but today is mostly forest. One
endemic plant is currently recognized as being restricted to Angaur; Maesa
canfieldiae. The authors of this species (Fosberg & Sachet 1979) however note
that the plant has only been known to the local inhabitants after WWII and could
have possibly been introduced from elsewhere. They further document that the
plant is closely related to Maesa tetrandra (Roxb.) A. DC. and Maesa papuana
Warb., which occur in Papua New Guinea and the Malesian region, though it
doesn’t match either of them exactly. It has tetramerous flowers like the latter
two, unlike all the other Micronesian species which have pentamerous flowers.
The Myrsinaceae family has to date not been treated in the Flora Malesiana. Until
this has been done, or other studies indicate otherwise, the name M. canfieldiae
will be retained.
GENERALIST ENDEMICS
The following 24 endemic species occur on both volcanic and limestone islands
of Palau. They are all angiosperms. Families not represented by species in the
volcanic and limestone restricted categories include; Anacardiaceae,
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Micronesica 41(1), 2009
Celastraceae, Flacourtiaceae, Myristicaceae, Myrtaceae, Olacaceae, Piperaceae,
and Putranjivaceae, suggesting that the taxa represented by these families may
have better dispersal capabilities and/or less habitat specificity within the
archipelago. Most of them are widespread, common species and unlike the
former categories, few are poorly known.
CANDIDATE ENDEMICS
Two species are listed as candidate endemics due to considerable doubt over
their taxonomic status as separate species. A brief summary of the known
information regarding them is provided.
Limnophila palauensis T. Yamaz.
Possibly same as L. indica var. raymundii which also occurs on Guam. The
author of the former did not view the type of the latter when describing the new
taxon (Yamazaki 1993), and some of the characters used to distinguish them are
questionable. If it is distinct however, then it is endemic to Palau. Further study is
required.
Decaspermum raymundii Diels
Both Fosberg et al. (1979) and Stone (1970) doubted that this was distinct
enough from D. parviflorum (Lamarck) A. J. Scott to validate the application of a
separate species name. However, Scott (1979) accepts the name and lists it as
endemic to Babeldaob. The former authors were the most experienced in the
flora of the region, however the later author specialized in this genus. Further
study will enable its delimitation with confidence.
ENDEMIC VARIETIES
A total of 23 endemic varieties are recognized here from 12 different
angiosperm families. In all families except the Rubiaceae, there are only one to
two endemic varieties. The Rubiaceae has nine recognized endemic varieties
with four represented by the genus Psychotria and four represented by the genus
Timonius. A total of 17 of the 23 varieties were described by Fosberg and Sachet.
All the names presented here are recognized in the current literature. However, it
is reasonable to expect that some will become synonyms after monographs of the
respective genera are completed. The regional variation that Fosberg and his
colleagues often used as a basis for splitting taxa is sometimes viewed differently
by authors of monographs that study genera across a larger distribution.
RATE OF ENDEMISM
Figure 4 shows three different trends. Each data point represents one of the
families represented in the checklist of endemic species. The vast majority of
families are low in both numbers of native species and endemic species, with no
obvious reciprocal relationship between the number of species and number of
Costion et al.: Endemic Palau plants
143
Figure 4. Number of endemic species in proportion to number of native species
endemics (Fig.4). These families often have high rates of endemism at the family
level (see Table 1). This is likely the result of few representative species being
dispersed to Palau in addition to relatively low rates of species radiation. The
Orchidaceae, Rubiaceae, and Euphorbiaceae (sensu lato) however demonstrate a
trend of endemism being directly proportionate to an increase in the number of
native species. These families are notable worldwide for high rates of species
diversity (Judd et al. 2002). The percentage endemism for these families in Palau
(Table 1) is significantly lower than families such as Annonaceae and
Myrsinaceae, the high relative endemic species richness in these later three
families is likely a combination of higher rates of successful dispersion of native
taxa to the islands and high rates of insular speciation.
Wind dispersed taxa, including the Poaceae and Cyperaceae, although high
in species richness, have the lowest rates of endemism. The same is true for
Asteraceae, which has no endemic species in Palau. Wind dispersal, allowing
propagule movement between Pacific islands, is likely a significant factor
contributing to this. There is also palaeoenvironmental evidence to suggest that
the abundance of these groups, particularly the Poaceae and Cyperaceae, is a
recent occurrence in Palau. Athens & Ward (2002) showed from sediment core
analysis that savannas and pollen from savanna indicator plants either do not
appear in the sediment record at all or are very limited prior to the colonization of
humans and forest clearing. The sudden appearance of Graminoid pollen
suggests that many or some Graminoid and even Asteraceae taxa may have
dispersed to the islands more recently after the expansion of suitable habitat
following human disturbance.
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Micronesica 41(1), 2009
Figure 4 appears to provide
some support for the recent theory
of “diversity begets diversity”
Epiphytes
(Emerson & Kolm 2005a, b), which
12%
suggests high rates of species
Trees
diversity foster higher rates of
38%
speciation and endemism, particularly on islands. However, clearly
Shrubs
for wind-dispersed taxa this model
16%
does not apply. There are also
additional outliers evident in Figure
4, notably the Myrsinaceae, Pandanaceae, and Fabaceae that don’t
Herbs
strongly support this model. The
28%
skewness of biodiversity has been
Figure 5: Growth forms of all endemic
well documented for both taxonspecies
omic groups and geographical locations (Pimm et al. 1995; Purvis et al.
2000; Sechrest et al. 2002). The data presented here seems to support the
“diversity begets diversity” theory primarily for taxonomically skewed families,
i.e. those prone to high rates of speciation. The remaining families do not appear
to follow any obvious trends on the whole.
The majority of endemic plants in Palau are trees, comprising 38% of the
total, followed by herbaceous terrestrial plants with 28%. Shrubs and lianas
together comprise 22% and epiphytes total to 12% (Fig. 5). These figures were
compared to all native plants using the growth form categories from the
Provisional Checklist of the Plants of Palau (Kitalong et al. 2008) in Table 2.
Trees and shrubs have higher representation in the endemic species count
compared to native plant tallies. This demonstrates a stronger trend towards
endemism with arborous habit. However, epiphytes were not distinguished from
herbs in the Provisional Checklist, thus they could not be compared. Due to the
high rate of endemism in the orchids, epiphytes are also expected to have a high
tendency towards endemism whereas terrestrial herbs, abundant with graminoid
species, are likely to have a lower percentage.
Plant endemism on limestone islands, when calculated per square kilometer
(34%), is significantly higher than on the volcanic islands (21%), where the
majority of endemics occur (Table 3). To explore the reasons for this thoroughly
and adequately, requires further investigation and comparison with other islands
across the region which shall be left for subsequent publications. This data may
however suggest support for the general dynamic theory and speciation pulse
model for island biogeography of Whittaker et al. (2007, 2008). This model
considers island age to have primary importance in species diversity and
endemism on islands. New islands increase in diversity and endemism with time
but only to a certain point at which opportunities and niches for evolution and
Lianas
6%
145
Costion et al.: Endemic Palau plants
radiation diminish through time. The karst limestone islands are notably younger
than the volcanic islands.
Table 1: Percent Endemism of Selected Families
Family
Annonaceae
Gesnariaceae
Myrsinaceae
Pandanaceae
Melastomataceae
Sapotaceae
Orchidaceae
Euphorbiaceae
Fabaceae
Cyperaceae
Poaceae
Native
Species
2
2
6
10
3
3
73
27
24
52
60
Endemic
Species
2
2
5
7
2
2
29
9
3
2
1
Percent
Endemism
100%
100%
83%
70%
67%
67%
40%
33%
13%
4%
2%
Table 2: Comparison of the distribution of different growth forms for native and
endemic angiosperm species.
Flowering
Plants
Native
Endemic
Trees
177
49
Shrubs
29%
41%
71
21
12%
18%
Lianas/
Vines
56
9%
8
7%
Herbs &
Epiphytes
301
50%
41
34%
Table 3: Percent endemism (E/km²) for each island type (km² data for
substrate types provided by USDA Natural Resources Conservation
Service).
Restricted to
Volcanic
Restricted to
Limestone
Generalists
Total for Palau
Endemic
Species (E)
75
Total Area
(km²)
363
% Endemism
(E/km²)
21%
31
90
34%
24
130
453
453
5%
29%
IUCN RED LIST
There is insufficient data for 61% of Palau’s endemic species thus these
species cannot be adequately assessed under the IUCN criteria (Fig. 7). These
will remain as data deficient, “DD,” until further studies are done. There is
sufficient data for the remaining 39%, of which 30% of these, or 39 species, were
of “Least Concern” because they were either common or widespread. Five
endemic species (4%) are considered near threatened, three species (2%) are
146
Micronesica 41(1), 2009
considered vulnerable, and the last two categories, critically endangered and
endangered
are
each
represented by two species
(1.5%). If this 39% is
considered a representative
sample of all Palaun species,
we can make an estimate of
the IUCN categories for the
61% of data deficient taxa and
the entire endemic flora.
The percentages of the
species with sufficient data
are shown in Figure 6. If we
assume that the data deficient
taxa
follow
a
similar
proportion of rareness then it
can be estimated that there
would be approximately 99
species of least concern, 13
Figure 6: Percentages of all plants assessed for
species of near threatened,
each IUCN red list category
eight vulnerable species, five
endangered, and five critically
endangered endemic species for Palau. This is a very conservative estimate, as
many of the species considered of least concern are taxa that are well known. It is
more likely that there will be a higher proportion of threatened species
represented from the Data Deficient category listed here. Many of Palau’s poorly
known taxa may be rare or have restricted ranges. Indeed a total of 19 (15%) are
only known from the type collections. An estimated minimum number of
endemic plants expected to be threatened in Palau is inferred as shown in Figure
7. This was calculated by excluding the data deficient taxa then recalculating
percentages for all known taxa. The 39 (30%) LC taxa becomes 76% which is
then multiplied by 130, the total number of endemic species equaling 99. The
minimum expectation is the sum of 8, 5 and 5 (VU + EN + CE in Figure 7), 18
species (14%). An additional 1% is added to give the greater benefit of doubt
considering this is a conservative estimate. This produces an estimation of 20
(15%) out of the total of Palau’s endemic plants. It is stressed that this is the
estimated minimum that may be considered threatened following more thorough
studies. By the time these studies are done, there may very likely be additional or
increased threats.
Previous results produced by the author (Costion 2007) demonstrate that this
may be a relatively accurate expectation. Turnover, or β diversity, for the island
of Babeldaob was calculated using DIVA-GIS. The results clearly suggested that
most of Palau’s endemics are widely distributed across the island, with a small
percentage that have small restricted ranges or disjunct distributions.
Costion et al.: Endemic Palau plants
147
Figure 7: Percentages inferred from the total of assessed taxa with sufficient data. The
lower pie is the same as that in Figure 6.
The results showed a significant difference in β diversity for all native
species compared to the β diversity for endemic species only. Clearly, the
endemic species formed a more consistent component of the vegetation across
the island as a whole, with a small turnover rate, whereas the same analysis for
native species showed a higher turnover rate.
Six endemic trees are known to have rare and restricted populations including Ponapea palauensis, mentioned above. Parkia parvifoliola is only known
from one healthy population with two scattered individuals adjacent to this area
and three disjunct individuals recorded further south. Terminalia crassipes is a
riparian tree only known to occur along two of Babeldaob’s river systems.
Rauvolfia insularis occurs in very small numbers with a scattered distribution.
Goniothalmus carolinensis is a poorly known species that has only been recorded
from a few collections on Babeldoab. Kitalong (2008) documented the occurrence of G. carolinensis on the limestone islands. This data however could not be
sourced or verified so it remains listed as restricted to the volcanic islands.
Manilkara udoido is abundant and can form a dominant understory canopy where
it occurs, but its range is restricted to the southern portion of Babeldaob with the
exception of a few disjunct individuals. The causes of population disjunctions for
all of these trees are unknown.
148
Micronesica 41(1), 2009
BIOGEOGRAPHIC COMPARISON
A total of 724 plants are listed as native or endemic in Palau’s latest
checklist (Kitalong et al. 2008). If the total number of endemic species, 130, are
divided by this figure then Palau has a rate of endemism calculated by no. of
endemic spp. (E/N), of 18%. Calculated per sq. km for the total land area, 458
km², the rate is 29%. These new figures are important in that is has been
traditionally assumed that Palau has the highest plant endemism rates in
Micronesia. Based on the revised data presented here Palau appears to not be
significantly different from other Micronesian islands. Guam has a plant
endemism rate of 21% (calculated by E/N) based on statistics from the Flora of
Guam (Stone, 1970). This percentage exceeds that of Palau’s. The list of endemic
species for Guam however, may need to be updated as recent work in the
Caroline Islands has clearly demonstrated. The number of accepted native and
endemic species has significantly changed since 1970. Recent estimates for the
eastern Caroline Islands (Balick unpubl.) indicate that Pohnpei’s flora is only 1%
lower than Palau (calculated by E/N) and Kosrae’s flora is also only 1% lower
(calculated by E/km²) showing comparable rates of endemism to that of Palau’s.
Distance from continental sources have clearly effected the richness of plant
species in the islands of Micronesia, but does not appear to have affected equally
the rates of plant endemism. Similar results are shown by (Keppel 2008, Keppel
et al. 2009) where isolation is highlighted as a more significant factor contributing to plant endemism rates on oceanic islands in the Southwest Pacifc.
What factors then, are most significant in determining rates of plant endemism in
the region; distance from source, island size, elevation gradients, or island age? A
comprehensive biogeographical analysis and comparison of floristic data for each
of the respective islands in the Micronesian region is now needed to explore
these questions further. This should include updated checklists for native and
endemic species for each island. Palau, Pohnpei, and Kosrae have all been
recently updated and checklists are currently being finalized for publication.
Updates are needed for Guam, Yap, and Chuuk.
THREATS
Palau boasts 70% of its land mass covered by intact forest. On Babeldaob, it
is difficult to discern areas that are actually pristine primary forest from forests
regenerated from early Palauan disturbance however the limestone Rock Islands
are the least impacted and contain areas virtually untouched. Their inaccessibility
renders a comforting protection to them and they are one of the only areas
remaining as such in all of Micronesia (Mueller-Dombois & Fosberg 1998). As a
whole, Palau may be considered a “good news area” for Micronesia (Myers et al.
2000), with its high percentage of intact forest. For this to remain true prompt
action must be taken as the island of Babeldaob, approximately 70 % of the total
land mass of the archipelago, faces increasing imminent threat from
development.
Costion et al.: Endemic Palau plants
149
Islands have historically been exceptionally vulnerable to extinctions. The
IUCN determined that of all recorded extinctions for mammals, birds, amphibians, reptiles, and molluscs; 72% were island species (Baillie et al. 2004). This
has been especially true for birds. Ricketts et al. (2005) document 245 extinctions
from mammals, birds, selected reptiles, amphibians, and conifers that have
occurred since 1500. Of these, 80% occurred on islands and more than one half
were from tropical moist forests. The current percentage is now more balanced,
but not due to a reduced threat on islands, rather an increased threat in
continental areas (Ricketts et al. 2005; Baillie et al. 2004). Islands are still
arguably at greatest risk. Of all the recorded extinctions that occurred after 1983,
over half were from islands, the bulk of which were from Hawaii and Guam
(Baillie et al. 2004). These extinctions render the Pacific as having more recorded
extinctions over the last 25 years than any other biogeographic realm. This
suggests that the Pacific islands may be one of the most threatened of all of
Myers et al. (2000) biodiversity hotspot regions, or at least the most vulnerable to
extinction.
Of the recent extinctions, 85% of species had restricted ranges. Commonly
cited causes of extinction are habitat loss, invasive alien species, and overexploitation. Of the recent extinctions post-1983, the most commonly recorded
cause was habitat loss, followed by introduced species. Over-exploitation was not
a significant factor in these recent extinctions (Baillie et al. 2004). This trend is
similar historically and highly relevant in Palau.
The primary threat to native vegetation historically in Palau has been forest
degradation as a result of human activities. Palaeoenvironmental investigations
conducted in Palau (Athens & Ward, 2002, 2005) provide convincing evidence
that the island of Babeldaob was entirely forested prior to human colonization.
After the first evidence of humans occurs in the pollen records, charcoal deposits
as well as pollen from savanna indicator species; Poaceae, Pandanaceae, and
Cyperaceae, rise significantly. These pollen types are absent or minimal prior to
this. In addition, several unknown pollen types recorded from pre-human times
rapidly decrease after human settlement. Some of them completely disappear and
are no longer present in contemporary pollen profiles.
Similar results have been shown for other Pacific islands. On the island of
Kosrae, the entire lowland vegetation was replaced by agroforest within 500
years of human colonization (Athens et al. 1996). On the island of O’ahu, Hawaii
a similar scenario has been shown although the causes are less likely to be due to
direct clearing for agriculture and possibly related to the introduction of the
pacific rat or other causes (Athens 1997, Athens et al. 2002). On the island of
Guam, indicators of disturbance arise around the same time as Palau at 4500 to
4300 cal. BP. Ample evidence from additional islands throughout the Pacific
support a similar scenario occurring at different times, all independent of climate
change (Athens & Ward 2005).
This implies that not only has the extent of native forest been significantly
reduced, but many current areas of seemingly “pristine” forest may actually be
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Micronesica 41(1), 2009
re-growth. Studies in Palau have shown (Endress & Chinea 2001) that the edges
of forest do expand back into savanna areas if the savannas are left alone and not
burnt. Further more, the evidence of “unknown” pollen types suggests the
likelihood that some species may have either been significantly reduced in their
area of occurrence or even gone extinct. This evidence raises many questions
regarding the rare and disjunct distribution patterns of several of Babeldaob’s
endemic species discussed above.
Endemic plants that are rare or with very small restricted natural ranges,
often restricted only to one hilltop or valley, are not uncommon in the tropics
(Myers 1988, 1990). These localized endemics with very small ranges are well
documented in the Neotropics and on islands (Gentry 1986; Cody 1986). These
can be neoendemics that have evolved more recently such as the case in
Amazonia with the result of Andean uplift creating many new isolated habitats
(Gentry 1982), or relict or palaeo-endemics which are often rare due to the loss
of a former more widespread habitat such as has been suggested for many
monotypic genera in the Australian wet tropics of Queensland (Bowman 2000,
Kershaw et al. 2005, Greenwood & D. C. Christophel 2005). Alternatively they
may be localized as a result of human activities and habitat loss.
The neoendemic model proposed by Gentry (1982) implies habitat
specialization. Although Ponapea palauensis is only found near depressions that
are damp or near lakes in the Rock Islands and Terminalia crassipes is restricted
to streams and rivers, their distributions are disjunct and restricted. Although not
a complete explanation, as not all of the known rare endemics occur in specialized habitats, recent molecular work strongly supports the notion that much of
the Pacific biota has evolved recently (Price & Clague 2002; Keast 1996; Keppel
et al. 2008a, 2009, unpubl.).
The palaeo-endemic model is unlikely due to the relatively young age of the
islands. In any case, there is insufficient palaeoenvironmental data but the studies
that have been done (Athens 1997; Athens & Ward 2002, 2005; Athens et al.
2002) do not indicate significant vegetation turnover prior to human settlement in
the Pacific.
The relationship between the increase in charcoal and savanna indicators, as
well as the loss of “unknown” pollen types at the time of human colonization, is
suggestive of an anthropogenic cause of rarity. However, the mystery is far from
solved. More data and studies are needed to support any of the above hypotheses
for Palau. The causes of rarity in the tropics are a poorly understood and are an
understudied topic. In any case it is indisputable that these plants are significantly
threatened. Their habitats need only be destabilized or disturbed to put them at
risk of “summary extinction” or secondary causes of extinction (MacArther &
Wilson 1967, Myers 1988, MacKinnon 2005).
Historically fire has clearly been the most effective method of forest
clearing for Palauans, but this has become an increasingly pertinent issue today.
Traditional systems of government that regulated the use of fire have eroded.
Every year careless fires are lit and occasionally some get out of control and
Costion et al.: Endemic Palau plants
151
destroy patches of forest. Today however, fire is not the only threat to
Babeldaob’s remaining forest. The construction of the 53 mile Compact Road,
which encircles the island, has opened Babeldaob up for development. Building
the road was part of the Compact Free Association Agreement with the US,
which granted Palau independence. In return for allowing the US military access
to the island at anytime in the future Palau was granted the funding for the
Compact Road, additional funding, and other benefits. There has been much
written about this elsewhere. It is mentioned here only to highlight a potentially
significant future threat. The construction of a US military base on Babeldaob
would undoubtedly result in massive forest clearance and pose a serious threat to
some of Palau’s rare trees among other environmental problems. This has
certainly been the case in Guam.
A national highway, which has very much been needed and appreciated by
the island’s inhabitants, has now for the first time made development on the
island of Babeldaob possible. The majority of the country’s population resides on
the island of Koror but many have plans to build and resettle on Babeldaob after
the road is completed. Others have plans to lease land to foreign developers for
building vacation homes for Asian tourists, building resorts and some even
propose building golf courses. The impact of such development on such a tiny
island ecosystem will be severe.
Invasive species are playing an increasingly significant role in Palau though
this has not to date been as extreme as has happened on other Pacific islands such
as Hawaii. Much on this topic has been treated elsewhere. Notable invasive
plants include the interestingly native but invasive vine Merremia peltata,
Clidemia hirta in the understory, and Falcataria moluccana which towers over
the native canopy layer out-competing native trees. On a whole however,
invasive species appear to be a secondary or lesser threat to that of habitat loss.
Areas of Babeldaob harboring major invasions of non-native plants tend to be
previously disturbed areas. The primary forest remains very much intact and
native. From the pollen record, Athens & Ward (2002) documented that Palau’s
native forests displayed a resilience to introduced species brought by early
Palauans giving the island a “non-insular” character. This curious documentation
is worthy of further investigation.
Climate change has been documented as a significant threat to existing rare
plant populations across the globe (Harte et al. 2004; Thomas et al. 2004; Hannah
et al. 2005;). Modeling techniques have been developed that can predict the
amount of change that particular ecosystems are expected to undergo given
current global warming trends (Li & Hilbert 2008; Beaumont et al. 2005, 2008;
Hijmans & Graham 2006). Whilst modeling methods are still developing, it is
well established that native ranges of many plant species are expected to change
significantly as global temperatures rise and rainfall patterns change (Bartlein et
al. 1997; Matsui et al. 2008; Tylianakis et al. 2008; Wirth et al. 2008). This can,
and is likely to, lead to many extinctions where species’ ranges are restricted.
Habitat fragmentation, which is occurring everywhere on earth at alarming rates,
152
Micronesica 41(1), 2009
has been acknowledged as a serious exacerbant of the problem presenting
additional barriers to plant and animal migration corridors. As a whole,
knowledge on this topic is very limited for the tropics (Stork et al. 2007; Colwell
et al. 2008). However analyses have been conducted for the Queensland Wet
Tropics (Hilbert et al. 2001; Williams et al. 2003), and in other montane areas of
the tropics (Colwell et al. 2008; Raxworthy et al. 2008), which stress a significant
proportion of species that will be pushed to extinction as their habitable ranges
shrink, or even vanish completely leaving them with nowhere to migrate to.
Virtually no comparable studies have been conducted for tropical Pacific
Islands. However, both the Queensland wet tropics and the montane tropics are
comparable to that of Micronesia. Both mountain tops and islands serve to isolate
gene pools which can promote speciation events, but are particularly vulnerable
to extinction. The Queensland Wet Tropics region has also been regarded as
having an insular character, being a rainforest pocket within an arid continent. It
also shares many genera with Palau. Given this, it is reasonable to expect similar
future climate change induced species extinctions on islands of the Pacific.
Further information and study on this issue is urgently needed, as vegetation
turnover in response to past climate change in the Pacific palaeoenvironmental
record is a hotly debated topic.
This evidence presented above justifies the application of IUCN red list
criteria B (b(iii)) for several of Palau’s endemic plants. This criterion refers to a
continuing decline in area/extent or quality of habitat. Clearly Palau’s forests as a
whole have been in decline since early human occupation. There has likely been
some regeneration at particular intervals, but the current trend with the opening
of Babeldaob for development is certainly continuing decline. Since very few
population-based studies have been conducted in Palau, this criterion, in addition
to cases where species qualify as fragmented and very small in population size,
have been the primary criteria used for establishing threatened status in this
report. It is hoped that a comprehensive study can be funded and conducted to
assess all of Palau’s endemic plants. This will not only improve the data
presented here by conducting population studies but also fill the huge data
deficiency gap for Palau’s poorly known taxa.
Although the rate of data deficiency for Palau is exceptionally high, this is
not surprising. In one of their recent global assessments, the IUCN (Baillie et al.
2004) determined that only 4% of the worlds described plant species have been
evaluated under the IUCN Red List Criteria (IUCN 2001). Since 3% of these are
listed as threatened it is evident that assessments have been biased towards
selected taxa that are known to be threatened. Considering the known threats, and
the vulnerability of island endemics to extinction, it is imperative that Palau’s
61% data deficient endemic plants be assessed. If a threatened species does not
have formal recognition of its rarity, it is very difficult to justify its protection
and prevent the loss of crucial habitat. In 2001, the Conservation International
established a goal to increase the number of plants on the IUCN Red List to meet
the 2010 CBD target of obtaining preliminary assessments of all the world’s
Costion et al.: Endemic Palau plants
153
described plant species (Baillie et al. 2004). Since Palau is a member of the CBD
this need is even more relevant. Focusing efforts of the assessment first on the
endemics is an obvious priority. This has been successfully achieved in much
larger tropical regions including the island of Socotra, Ecuador (Baillie et al.
2004) and is a realistic goal for Palau.
Conclusion
A total of 130 endemic plants are listed here as endemic to the Palau
archipelago, 75 restricted to volcanic islands, 31 restricted to limestone, and 24
occurring widespread. Several of these are known to have small, restricted ranges
and a total of 7 qualify for threatened status under the IUCN red list criteria.
Although there is a considerable paucity of data for over half of Palau’s endemic
plants it can be expected that at least 15% are threatened. It is clear that the plants
with restricted ranges on the volcanic islands are the most threatened due to
human activities, primarily forest clearance. Evidence suggests that this is not a
recent trend but has continued from the very first early Palauan settlers. Recent
development however has accelerated this trend significantly making the need for
a complete understanding of the distribution of Palau’s endemic plants more
pertinent then ever. A full scale IUCN red list assessment for all of Palau’s
endemic plants, especially those listed as data deficient in this paper, is urgently
needed along with studies investigating the degree of threat posed by climate
change.
The results presented here are by no means a final product. It is expected
that the number of endemic species cited here will actually decrease as further
taxonomic studies are conducted, not increase as has been previously suggested.
The discovery of a few new species is also likely. However the likelihood of
several species listed here as endemic being reduced to synonymy in the future is
much higher. Furthermore, as additional collections are made and studies are
conducted, current understandings of plant distributions may change.
Acknowledgements
This paper was many years in the making and would not have been possible
without the help and support of innumerable people and several institutions
which cannot all be listed here. We thank the Republic of Palau, the Belau
National Museum, UNESCO, The Nature Conservancy, Peace Corps, The Royal
Botanic Gardens Edinburgh, the University of Adelaide, Kew Gardens, the
Bishop Museum, USDA Natural Resources Conservation Service, and the
National Tropical Botanic Garden, and the Smithsonian Institution. Our personal
gratitude also extends in no particular order to Tarita Holm, Naito Soaladaob,
Julian Dendy, Andy Lowe, Louise Ronse de Craene, David Lorence, Michael
Balick, Tony Miller, Robert Gavenda, Agnes Rinehart and Gunnar Keppel.
154
Micronesica 41(1), 2009
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Micronesica 41(1), 2009
Checklist of Endemic Species
Taxon Name
Lycophyta
SELLAGINELLACEAE
Selaginella dorsicola Hosok.
Selaginella palauensis Hosok.
Selaginella pseudo-volkensii Hosok.
Pteridophyta
LOMARIOPSIDACEAE
Cyclopeltis kingii (Hance) Hosok.
PTERIDACEAE
Adiantum palaoense C. Chr. *
Pteris tapeinidiifolia H. Itô *
POLYPODIACEAE
Grammitis palauensis Hosok. +
Prosaptia palauensis Hosok.
THELYPTERIDACEAE
Thelypteris carolinensis (Hosok.) Fosberg +
Thelypteris pseudarfakiana (Hosok.) C.F. Reed
*
Thelypteris rupi-insularis Fosberg +
Basal Angiosperms
ANNONACEAE
Goniothalamus carolinensis Kaneh.
Polyalthia merrillii Kaneh. *
MYRISTICACEAE
Horsfieldia palauensis Kaneh.
PIPERACEAE
Peperomia kraemeri C.DC.
Peperomia palauensis C.DC.
Piper hosokawae Fosberg
Monocots
ARECACEAE
Ponapea palauensis Kaneh.
Hydriastele palauensis (Becc.) W.J.Baker &
Loo
CYPERACEAE
Hypolytrum flavinux (T.Koyama) D.A.
Simpson *
Fimbristylis palauensis Ohwi *
ORCHIDACEAE
Bulbophyllum desmanthum Tuyama *
Bulbophyllum hatusimanum Tuyama
Chiloschista loheri Schltr.
Cleisostoma porrigens (Fukuy.) Garay
Crepidium calcarea (Schltr.) D. L. Szlachetko
Crepidium kerstingiana (Schltr.) D.L.
Szlachetko *
Substrate
Form
Abundance
Status
V
V
V
H
H
H
U
U
U
DD
DD
DD
L
H-E
DD
DD
V
L
H
H-E
DD
DD
DD
DD
V
V
E
H
DD
DD
DD
DD
L
H
DD
DD
V
H
DD
DD
L
H
DD
DD
V
L
T
T
U-R
DD
NT
DD
G
T
C
LC
G
G
G
H
H
L
DD
C
C
LC
LC
LC
L
T
U-R
CE (B2abc)
L
T
U-R
NT
V
H
DD
DD
V
H
DD
DD
V
V
G
V
L
E
E
E
E
H
DD
DD
C
U
DD
DD
DD
LC
DD
DD
G
H
U
DD
161
Costion et al.: Endemic Palau plants
Taxon Name
Substrate
Crepidium palawensis (Schltr.) D. L.
V
Szlachetko
Crepidium setipes (Schltr.) D. L. Szlachetko
V
Cystorchis ogurae (Tuyama) Ormerod &
V
P.J.Cribb
Dendrobium brachyanthum Schltr.
V
Dendrobium implicatum Fukuy.
V
Dendrobium kerstingianum Schltr. *
V
Dendrobium palawense Schltr. *
L
Dendrobium patentifiliforme Hosok. +
V
Dipodium freycinetioides Fukuy.
V
Liparis dolichostachya Fukuy. +
V
Liparis palawensis Tuyama *
V
Liparis yamadae (Tuyama) Fosberg & Sachet *
V
Micropera draco (Tuyama) P.J. Cribb & P.
V
Ormerod +
Moerenhoutia laxa Schltr.
V
Nervilia trichophylla Fukuy. +
V
Oberonia palawensis Schltr.
G
Peristylus palawensis (Tuyama) Tuyama
V
Phreatia kanehirae Fukuy.
V
Phreatia palawensis (Schltr.) Tuayama
L
Robiquetia palawensis Tuyama
G
Taeniophyllum palawense Schltr.
V
Zeuxine palawensis Tuyama
V
PANDANACEAE
Freycinetia villalobosii Martelli
V
Pandanus aimiriikensis Martelli
V
Pandanus kanehirae Martelli
V
Pandanus lorencei Huynh +
L
Pandanus macrojeanneretia Martelli
V
Pandanus palawensis Martelli
V
Pandanus peliliuensis Kaneh. +
L
POACEAE
Panicum palauense Ohwi *
V
Eudicots
ACANTHACEAE
Hemigraphis palauana Hosok. +
Pseuderanthemum inclusum Hosok.
ANACARDIACEAE
Buchanania palawensis Lauterb.
APOCYNACEAE
Melodinus insularis (Markgr.) Fosberg *
Rauvolfia insularis Markgr.
ARALIACEAE
Osmoxylon oliveri Fosberg & Sachet
Osmoxylon pachyphyllum (Kaneh.) Fosberg &
Sachet
Form
Abundance
Status
H
U
LC
H
A
LC
H
DD
DD
E
E
E
E
E
E
H-E
H-E
H-E
C
DD
DD
DD
DD
C
DD
DD
DD
LC
DD
DD
DD
DD
DD
DD
DD
DD
E
DD
DD
H
H
E-H
H
E
E
E
E
H
U
R
DD
R
DD
DD
DD
U
C
DD
NT
LC
NT
DD
DD
DD
DD
LC
L
T(u)
T
T
T
T
T-S
C-A
C-A
U
DD
U
DD
DD
LC
LC
NT
DD
DD
DD
VU (D2)
H
DD
DD
V
V
H
H
DD
DD
DD
DD
G
T
C
LC
V
V
L
T
DD
U,RR
DD
VU (D1,2)
G
T(u)
A
LC
G
T(u)
U
LC
162
Micronesica 41(1), 2009
Taxon Name
Osmoxylon truncatum (Kaneh.) Fosberg &
Sachet +
BORAGINACEAE
Cordia micronesica Kaneh. & Hatus.
CAPARIDACEAE
Capparis carolinensis Kaneh. *
CELASTRACEAE
Maytenus palauica (Loes.) Fosberg
CLUSIACEAE
Calophyllum pelewense P.F. Stevens
Garcinia matsudai Kaneh.
Kayea pacifica Hosok.
COMBRETACEAE
Terminalia crassipes Kaneh. & Hatus.
CUCURBITACEAE
Trichosanthes hosokawae Fosberg *
ELAEOCARPACEAE
Elaeocarpus rubidus Kaneh. +
EUPHORBIACEAE
Claoxylon longiracemosum Hosok.
Cleidion sessile Kaneh. & Hatus.
FABACEAE
Crudia cynometroides Hosok.
Dalbergia palauensis Hosok.
Parkia parvifoliola Hosok.
GENTIANACEAE
Fagraea ksid Gilg & Benedict
GESNARIACEAE
Cyrtandra palawensis Schltr.
Cyrtandra todaiensis Kaneh.
MALVACEAE
Sterculia palauensis Kaneh.
Trichospermum ledermannii Burret
MELESTOMATACEAE
Astronidium palauense (Kanehira) Markgr.
Medinilla blumeana Mansf.
MYRSINACEAE
Discocalyx mezii Hosok. *
Discocalyx palauensis Hosok. +
Maesa palauensis Mez *
Myrsine palauensis (Mez) Fosberg & Sachet
MYRTACEAE
Syzygium palauensis (Kaneh.) Hosok. *
OLACACEAE
Anacolosa glochidiiformis Kaneh. & Hatus.
PHYLLANTHACEAE
Cleistanthus carolinianus Jabl.
Cleistanthus insularis Kaneh. *
Substrate
Form
Abundance
Status
V
T(u)
DD
DD
V
T
U-R
DD
L
S
DD
DD
G
S
C
LC
V
V
V
T(c)
T
T
U
C-A
U, DD
DD
LC
DD
V
T(c)
A, RR
EN (B1ab(iii)
+2a,b(iii))
L
L
DD
LC
L
T
DD
DD
V
L
T
T
U
DD
DD
DD
V
V
T
L
U
DD
V
T(c)
R, RR
DD
DD
EN (B1ab(iii)
+2ab(iii))
V
T
C
LC
V
L
L
S
U-C
DD
LC
LC
L
V
T(c)
S
DD
A
DD
LC
V
V
T(u)
L
C
DD
LC
DD
G
L
L
V
T(u)
T
S
T(u)
U, DD
DD
DD
C
DD
DD
LC
LC
G
T
G
T
U
DD
G
V
T
T
U
U
LC
DD
DD
163
Costion et al.: Endemic Palau plants
Taxon Name
Glochidion macrosepalum Hosok.
Glochidion palauense Hosok. *
Phyllanthus palauensis Hosok.
Phyllanthus rupi-insularis Hosok.
PUTRANJIVACEAE
Drypetes nitida Kaneh.
RHAMNACEAE
Ventilago nisidai Kaneh.
RUBIACEAE
Badusa palauensis Valeton
Bikkia palauensis Valeton
Hedyotis aimiriikensis Kaneh. *
Hedyotis cornifolia Kaneh.
Hedyotis korrorensis (Valeton) Hosok
Hedyotis sachetiana Fosberg *
Hedyotis suborthogona Hosok. +
Hedyotis tomentosa (Valeton) Hosok.
Hedyotis tuyamae Hosok.
Maesa canfieldiae Fosberg & Sachet *
Morinda latibractea Valeton
Morinda pedunculata Valeton
Ophiorrhiza palauensis Valeton
Psychotria cheathamiana Kaneh. *
Psychotria diospyrifolia Kaneh.
Psychotria mycetoides Valeton +
Timonius corymbosus Valeton
Timonius korrensis Kaneh. +
Timonius mollis Valeton
Timonius subauritus Valeton
Substrate
G
G
V
L
Form
S
T
S
S
Abundance
DD
C
C-A
DD
Status
LC
LC
LC
LC
G
T
C
LC
V
L-S
DD
DD
G
L
V
V
V
V
V
G
V
L
L
V
G
L
V
V
G
L
V
V
T
S
S
H
S
S
H
H
S
T-S
T(u)
S-T
H
T(u)
L-S
S
T-S
T
T(u)
S
C
C
DD
DD
C-A
DD
DD
C
DD
DD
U
C
U
DD
U
DD
DD
DD
DD
C
Timonius salsedoi Fosberg & Sachet +
V
T(u)
DD
LC
LC
DD
DD
LC
DD
DD
DD
DD
VU (D2)
DD
LC
DD
DD
DD
DD
DD
DD
DD
LC
CE (B1ab(iii)
+2,ab(iii))
L
V
S
S-T
C
DD
LC
DD
L
T
DD
DD
V
L
T
T
C-D,RR
DD
LC
DD
G
T
C
LC
V
L
H
S
DD
DD
DD
DD
L
L
DD
DD
RUTACEAE
Melicope palawensis (Lauterb.) T.G.Hartley
Melicope trichantha (Lauterb.) T.G.Hartley *
SAPINDACEAE
Elattostachys palauensis Hosok. +
SAPOTACEAE
Manilkara udoido Kaneh.
Planchonella calcarea (Hosok.) P. Royen
SALICACEAE
Casearia hirtella Hosok.
URTICACEAE
Elatostema stoloniforme Kaneh. *
Pipturus micronesicus Kaneh. *
VITACEAE
Cayratia palauana (Hosok.) Suesseng. +
164
Micronesica 41(1), 2009
Checklist of Endemic Varieties
Taxon Name
ARECACEAE
Heterospathe elata Scheff. var. palauensis (Becc.)
Becc.
CLUSIACEAE
Calophyllum inophyllum var. wakamatsui (Kaneh.)
Fosberg & Sachet
Garcinia rumiyo var. calcicola Fosberg
EBENACEAE
Diospyros ferrea (Willd.) Bakh. var. palauensis
(Kanehira) Fosberg
EUPHORBIACEAE
Acalypha amentacea Roxb. var. heterotricha Fosberg
*
Acalypha amentacea Roxb. var. palauensis Fosberg +
FABACEAE
Serianthes kanehirae var. kanehirae Fosberg
GENTIANACEAE
Fagraea berteroana var. galilai (Gilg & Benedict)
Fosberg
ORCHIDACEAE
Zeuxine palawensis var. variegata Tuyama *
PIPERACEAE
Peperomia palauensis C.DC. var. occidentalis
Fosberg
POACEAE
Pschaemum polystachyum Presl var. chordatum
(Trin.) Fosberg &Sachet
Paspalum orbiculare G. Forst. var. otobedii Fosberg
& Sachet
RUBIACEAE
Hedyotis divaricata (Valeton) Hosok. var. divaricata
Psychotria hombroniana var. canfieldiae Fosberg
Psychotria hombroniana var. peliliuensis Fosberg +
Psychotria rotensis var. palauensis (Hosok.) Fosberg
Timonius corymbosus Valeton var. takamatsui
Fosberg & Sachet
Timonius mollis Valeton var. submollis Fosberg &
Sachet
Timonius mollis var. villosissimus (Kaneh.) Fosberg &
Sachet
Timonius subauritus var. strigosus Fosberg & Sachet
Uncaria lanosa var. korrensis (Kaneh.) Ridsdale
SCROPHULARIACEAE
Limnophila fragrans (G. Forst) Seem var. brevis
Schltr.
SYMPLOCACEAE
Symplocos racemosa Roxb. var. palauensis (Koidz.)
Nooteb.
Substrate
Form
Abundance
G
T
C-D
V
T
A
L
T
C
G
T(u)
C
V
S
C
L
S
R
G
T
U-C
V
HP
U
V
H
U
L
H
U-C
V
H
DD
V
H
DD
V
L
L
L
H
T(u)
T(u)
T(u)
R
C
DD
C
L
S
DD
V
T(u)
DD
V
S
DD
V
V
S
S
DD
C
?
H
DD
V
T
A