Endangered Plant Species in the Bonin (Ogasawara) Islands

Transcription

Endangered Plant Species in the Bonin (Ogasawara)
Islands: Causal Factors and Present Situation
Yoshikazu
SHIMIZU
The Bonin (Ogasawara) Islands are typical oceanic islands in Japan. Among 309
indigenous plant species, 124 species (nJ%) are endemic to the Bonins. The
Japanese Red Data Book ofPlants listed 4 extinct, 20 endangered, 38 vulnerable, and
I unknown species from the Bonins. Present situations of these endangered species
were described with possible causal factors of endangerment and related ecological
features of each species. Ten factors which caused the Bonin plants to become
endangered were as follows: (l) deterioration of habitats by a long-tenn environmental fluctuation, (2) logging of particular tree species, (3) destruction and
decline of habitats, (4) ilegal collection by man, (5) unusual climate (drought,
typhoon), (6) attack of insects or pests, (7) damage by introduced animals (feral
goats, giant African snails), (8) competition with introduced plants' (9) loss of
pollinators, (10) hybridization with introduced relatives. Plural causal factors often
affect one endangered species. Propagation and planting of endangered species are
being carried out, but the reasons that made the species become endangered are
themselves the neck of restoration in the Islands. Especially, the loss of original
habitats and environmental conditions is the largest problem. To protect endangered
species, the concerned organizations in the Bonin Islands must be more active than the
present.
necessary.
I. Introduction
1.
General setting
The Bonin (Ogasawara) Islands are located
about
1000
27" 45'N)
base
km to the south of Tokyo (26" 4O'N-
in the north-west Pacific Ocean. The
of the Islands originated from the early Ter-
Each island of the Bonins is very small compared with that of the Galapagos and the Hawaiian Islands. The largest island: Chichijima is only
241<rf in area and 317 m in altitude, and the
second largest island: Hahajima is 2l km2 and 462
m. The annual mean temperature is 22.9" C with
the maximum and the minimum monthly mean
temperatures of 27.6"C in August and t7.6" C in
February, respectively. The recent annual precipi-
is
mm at Chichijima
tiary volcanic activities in the Izu-OgasawaraMariana Arc, and the present islands emerged
tation ( 1969-1988)
above sea level at least up to one million years ago
(Kaizuka 1981). The Bonins are typical oceanic
islands in Japan, known as "the Orient Galapagos." They consist of 10 islands with an area of
more than 100 ha and about 20 small islets, which
are divided into 3 groups, Mukojima-retto, Chichi-
ry ( 1907-1939) was
jima-retto, and Hahajima-retto ("retto"
maximum population was about 7000 before
means
island group in Japanese). Kazan-retto of the
Quaternary origin, located about 200 km to the
south of Hahajima-retto, is included in the Bonin
Islands in a broad sense, but in this paper, plants
of Kazan-retto will be considered only when it is
t< Department
1255
(Honm a 1992) while that of the early z0th centu1609
mm (Asami 1970).
The first settlers, five westerners with 15 Polynesians, came to the Bonins in 1830. Since the
Islands belonged to Japan in I 87 6, many Japanese
settled and developed the Islands ( 10 major islands) changing forests into cultivated fields. The
World War II. Villagers were evacuated from the
Islands to the mainland of Japan in lg$ to avoid
the battle of World War II. The Japanese Army
with about 20,000 soldiers was stationed on the
Islands until the end of the War. After the War
of Natural Sciences, Komazawa University.
-r45-
Endangered Plant Species in the Bonin (ogasaw ara) (Shimizu)
the Bonins were controlled by the uS Army for 23
years. They were restored to Japanin 1968 (Funa-
koshi 1992).
After the return of the Islands, the former
villagers and new settlers have come back to live
on chichijima and Hahajima (the other islands
are uninhabited now). The Japanese Government
and the Tokyo Metropolitan Government invested large sums in the construction of houses,
roads, sea ports, public offices, cultivated fields,
etc. Almost all parts of the Bonins except residential and cultivated areas were designated as a
National Park
in 1972. At
the same time some
endemic animals were appointed as the Natural
Monuments by the Agency for Cultural Affairs.
The total population at present is about z2o0
(1800 at Chichijima, 400 at Hahajima).
There are 599 vascular plant species (83 ferns
and 516 flowering plants; including introduced
ones) reported from the Bonins including Kazanretto (Kobayashi & Ono 1987). 309 species (71
ferns and 238 flowering plants) are indigenous to
Chichijima and Hahajima-rettos, among which
124 species (12 ferns and ll2 flowering plants)
are endemic to the Bonins (Toyoda l98l). The
total endemic ratio is 40. ly6, which is comparable
to that of the Galapagos Islands (42.3%; porter
1984). Two genera, Boninia (Rutaceae) and Den-
drocacalia (Compositae), are endemic
to
the
Bonins. The Bonin plants mainly originated from
the south-East Asian flora. coastal plants consist
of wide-spread species in tropical and subtropical
regions. Some species are from the southern
islands of Micronesia and Polynesia, and the
others are from the mainland of Japan. Judging
from taxonomical characteristics, Polynesian elements seem to have arrived at the Islands earlier
than the South-East Asian elements (Yama zaki
1981). Adaptive radiation is found in several
4 species of Pittospontm and 3
species of Callicalpa, Crepidiastntm, Symplocos,
genera such as
Ilex, Ficus and Boninia (Shimizu & Tabata 199 I ).
According to the plant sociological method,
Okutomi et al. (1983) classified the vegetation of
the Bonins into 89 communities (natural:37, substitutional: 52) and made vegetation maps of all
islands. Shimizu (1989, 1993) classified the natural forests except coastal ones into 7 types based
on the ecological features and dominant
species:
Elaeocarpus-Ardlsra mesic forest (E-A m.f.), Pinus-Schima mesic forest (P-S m.f.), Rhaphiolepis-
Livistona dry forest (R-L d.f.), Distylium-Schima
dry forest (D-S d.f.), Ardisia-Ochrosia dry forest
(A-O d.f.), Distylium-Pouteria dry scrub (D-P d.
s.), and Dendrocacalia-Fatsia mesic scrub (D-F
m.s.). Among them the Distylium dry forest
(Distylium-Schima dry forest and Distylium-
Pouteria dry scrub) which is distributed mainly in
chichijima-retto contains many endemic species
some of which are endangered now (Shimizu
ree2).
2.
Bndangered Species of the Bonins
In general, habitats of insular plant species are
confined to small areas because of limited island
size. Insular species usually have smaller number
of individuals and thus less genetic diversity in
total than continental ones. They can not escape
from islands even though island
environments
change in various ranges of time. In addition,
human activities such as destruction of habitats
and introduction of alien plants and animals have
altered island natures rapidly in recent several
hundred years. On the other hand, oceanic islands have many endemic species that exist only in
specified islands. So insular species are easily
exterminated, and in fact it is reported that many
species have become extinct or endangered or
threatened in oceanic islands in the world (Melville 1979; Stone 1985).
The Environmental Agency carried out a research project of endangered species of the Bonins
in 1984 (Environmental Agency 1985). Based on
the results, Ono et al. (1986) reported the situa-
tion of
endangered plant species
in the Bonins.
They recognrzed that 85 taxa (Pteridophyta: 19
species, Angiospermae: 66 taxa) among 145 endemic taxa (Pteridophyta: 25 taxa, Gymnospermae: I species, Angiospermae: 119 taxa) were
threatened or critically endangered at that time.
The ratio of the endangered species was 38.6%.
They also classified the 85 taxa into two categories, A group: critically endangered and I group:
not so seriously threatened at present. A group
includes four fern species and 17 angiosperm taxa,
and B group includes 15 fern species and 49
angiospenn taxa.
The Japanese
(NACS-J
Red Data Book of Plants
& WWFJ 1989) listed 35 extinct, 147
endangered, 677 vulnerable, and 36 unknown vascular plant species in Japan. It includes 4 extinct,
20 endangered, 38 vulnerable, and I unknown
species
of the Bonin
Islands (Table
I
).
The
number of listed species in the Bonins is 7.0% of
all listed species in Japan. This is a very high ratio
for the small size of the Islands. No other regions
in Japan are comparable to the Bonins except the
一-146-一
Endangered Plant Species in the Bonin (Ogasaw ata) (Shimizu)
Table
l.
Endangered plant species in the Bonin Islands listed in the Japanese Red Data
Book of Plants NACS.J & WWFJ 1989)
Extinctz Paspalidium tuyamae, Malaxis boninensis, Zeuxine boninensis, Cinium toyoshimae
Endangered: Ahrodictium boninense, Asplenium it<cnoi, Alpinia bilamellata, Calanthe hafiorti, Calanthe
hoshii, Cinhopetalum boninense, Corymborchis subdensa, Liparis hostaefolia, Morus boninensis' Ptocrb
boninensis, Pittosporum panifulium, Eurya boninensis, Metpsideros boninensis, Melasnma Etmmerum,
Rhododenitron boninense, Symplocos lcnwakamii, Symplocos pergracilis, Ajuga boninsimae, Crepidiastrum
ameriistophyllum, Crepidiastrum grandicollum
Vulnerable: Psilotum nudum, Ophioderma pendula, Marattia boninensis, Adianthum ogasawarensis, Sciaphila
ol<abeana, Aristiila boninensis, Carcx toyoshimae, Fimbristylis longispica var. hahajimensis, Scirpus grossus,
boninsimensis, Eulophia toyoshimae, Goodyera boninensis, Luisia boninensis, Malaxis hahaiimensis,
Pepetomia boninsimensis, Piper postelsianum, Ficus iidaiana, Santalum boninense, Sedun boninense,
Pittosporum beecheyi, Pittosporum chichisimense, Evodia nishitnurae, Claoxylon centinarium, Ilex beecheyi,
Stachyurus macnocaapus, Stachyurus macrocarpus var. purnifolius, Melastoma pentapetalum, Limonium
wrightii, Pouteria boninensis, Symplocos boninensis, Callicarpa nishimurae, Lycium sandwicense, Orobanche
boiinsimae, Lobelia boninensis, Cirsium boninense, Crepidiastrum linguifolium, Dendruacalia crepidifolia,
Alpinia
Ixeris longirostruta
Unknown: Ctenitis lepigera
Nolet Paryalidium tuyamoe and Malaxis boninensis in the category of extinct
Ototojim, and Chichijima,
Ryukyu Islands, the continental islands being located nearly in the same latitude but having a
total area about 20 times as large as the Bonins. It
may be said that the Bonin Islands are a "hot
spot" of endangered species in Japan. Ono et al.
( 199 1 ) described the latest situation of 44 en-
dangered species in the Bonins.
There are some endangered species whose categories in former research are not adequate for
present situation (Kazaki 1992; Nobushima
1993). New localities were discovered and information of ecological features were added to some
species recently. So this paper shows the present
situation of endangered species in the Bonin Islands with stress on possible causal factors of
endangennent and related ecological features of
each species. The problems in protecting and
restoring endangered species are also discussed.
This study was made by the Grant-in-Aid from
the Ministry of Education, Science and Culture,
Japan (No. 04304m5 to Tetsukazu Yahara; "Extinction of terrestrial plants and biology for conservation").
II.
were re-discovered in
1994
at Hahajima and
respectively.
Causal Factors and Present Situation
As for causal factors of endangerrnent in the
Bonins, Ono et al. (1986) described 4 categories:
reduction of the population size, damage by feral
animals, human impact, and competition with
introduced plants. Iwatsuki & Shimozono ( 1989)
categorized the 7 causal factors in the Bonins as
follows: fluctuation of environment, unusual climate, exploitation of forests, inferiority in numbers, competition with introduced plants, damage
by introduced animals, and collection for com-
use. Shimizu ( 1990, 1992) proposed
nearly the same categories putting a stress on a
long-tenn trend of aridness in the Bonins. In this
mercial
paper these causal factors are elaborated
categories and discussed in detail.
1.
Deterioration
of Habitats by a
into l0
Long'term
Environmental Fluctuation
Extinction of oceanic biota is usually discussed
in the context of direct or indirect human impact.
But there must be extinction of natural phenomenon in oceanic islands as MacArthur & Wilson
(1967) predicted in the dynamic equilibrium
theory. Shimizu ( 1992) proposed a hypothesis to
explain the origin of the Dlstylium dry forest and
the occurrence of many endangered species in the
Bonins as follows (Figure 1)z Distylium dry forest
originated from a kind of cloud forest when the
Islands were once higher than they are at present;
the forest has been declining in area and species
composition with the sinking of the Islands and
the tendency toward increasing aridity over time,
producing many endangered species; this trend
has been accelerated by a rise of sea level of about
100
m after the last Ice Age, during which the
area of the Islands decreased to one-third of
total
the form er area. Twenty-five endangered species
were listed in the papet, whose occurrences were
-147-
STAGE l
STAGE 2
E‐
Am.1
一
D‐ s dof.
｀
D―
Photo
R― Ld.f.
1.
Melastoma tetramerum.
.5m.
P des.
TAGE 3
°
%
０００
丁
AGE4 1llllヱ
・
2足2肇
0
ぃ
Figure 1. The hypothetical process of the origin
of native forest types in Chichiiima-retto.
00
After Shimizu (ly)2).
Chichijima-retto.
There are two endemic species of Melastoma in
∞
0
0
0
8
the Bonin Islands. M. tetramentm inhabits the
Distylium-Schima dry forest at Chichijima, while
Chichijima when the Islands were restored to
Japan (Tokyo Regional Forestry Office 1975).
One individual growing near a road was run over
by a car and another died back from shade of
偽
りb°
F3 。。
closely connected with the Distylium dry forest in
M. pentapetalum is in Dendrocacalia-Fatsia mesic
scrub on Hahajima. The two species of the
Bonins must have been diversified within the Islands. We have another species: M. candidum
growing in a cloud forest in Kazan-retto. The
relationship between the Bonin species and that of
Kazan-retto is not well known (Ono 1994).
M. tetramentm was a tare species occurring at
only one locality (Chuosan-higashidaira) of Chichijima even before World War II (Toyoshima
1938). Although it was once described from
Anijima, the population seems to have become
extinct. 'We could find only three individuals at
00
。
0 0
。
.
0
.00
0
●
0
2. Dishibution of 91 individuds of
Melastoma tctramerum in the newly
discovered habitat. tlnpublished data.
Figure
(Yasui 1993; Ono 1994). About 120 individuals
were growing concentratively in a small valley
(Figure 2). They occur in a secondary forest:
Pinus-Schima mesic forest, where crowns of
canopy trees were seriously damaged by a big
typhoon that attacked in 1983. As the individuals
trees growing nearby until the late 1970s
(Toyoda, prsl. comm.). So it was once believed
are not so old (supposed to be the same age), they
seem to have germinated after the opening of the
that the one left at Chichijima was the last natural
individual in the world (Photo l).
Fortunately, some villagers discovered a new
locality of this species at Chichijima in 1993
canopy by the typhoon damage. The location is
about I km from the suspected last individual,
thus a mother individual must have been left near
this location (it has not been discovered yet).
―-148-―
Endangered Plant Species in the Bonin (Ogasaw ara) (Shimizu)
M. tetramerum requires bright and moist condition for its germination, but juveniles dislike
direct sun light (Iwatsuki & Shimozono 1989).
No seedlings are found in the new locality' even
though almost all individuals bear many fertile
year. Occasional forest disturbances
like typhoon damage must be necessary for regeneration of this kind of shrub. On the other hand,
the recent habitat condition at Chichijima is too
dry for this species to grow well. It seems that
habitats adequate for this species has been disseeds every
appearing from the Bonins due to the tendency of
long-term aridness and recent trend of aridness
accelerates it.
Metrosideros boninensls is one of the Polynesian
elements in the Bonin Islands (Photo 2). Only
several individuals were recognized at Chichijima
just after the restoration of the Islands, thus it was
thought
to be one of the most critically enBut recently, Nobushima
dangered species.
(1993) discovered 215 individuals in total in four
regions at Chichijima (Figure 3) and there are
No.of :ndiv.
◆ 1-5
◆ 6-20
◆ 217
ｍ
ｋ
︲
a
ザ
マ
Ftgure
3.
Ilishibution ol Mettwifuros bonincnsis in Ctichijlne. Lineg on the map ghow the llX)m contour.
Modiffed fton Nobushimr (193).
―-149-―
growing in a disturbed Pれ
sesc力 J′ ηα mesic fbrest.
“ killed by nematode
Allnost all pine trees were
infectiOn in the early 1980s in this fbrest,thus new
indiViduals succeeded in invading the open■
oor
of this ibrest at that tilne.
The locality ofRλ οJο ごθ″ごro″
bο ″J″ θ se is con‐
“
ined tO a五 dge(Asadachiiwa)at ChiChJima.
Only a few individuals were growing there even
before World War II(TOyOShilna 1938)。 When I
visited the place in 1976,I found Only 7 individu‐
Photo
2. Metrosi"deros boninensis
with an endemic
hornet visiting flowers.
als growing c10se to cach othero No seedlings and
saplings were found there. This habitat is sur―
rounded by R力等,力 lioJ響お‐
Po“ た′
Jα dry forest at
present,butit must have been covered with Dお
Jli“
still some more in other places (Nobushima, prsl.
comm.). shimizu (1990) found one individual at
Anijima, too. The habitats of this species are
classified into three types: ( I ) small valley in
Disylium-Schima dry forest, (2) ridge adjacent to
Pinus-Schima mesic forest, and (3) open places in
and around Pinus-Schima mesic forest. Most of
the localities are situated on the north or northeast slope of mountains. Furthennore, all the
localities are commonly located at the altitude
above 160 m, where frequent fog coverage keeps
the air moisture rather high (Nobushima 1993).
This altitude coincides with the occurrence of
Distylium dry forest at Chichijima (Shimizu
1992). Hawaiian Metrodideros (Ohia: M. poly-
_Sc力 J′ηα dry
ク_
forest in the past, because the
“
altitude
of this place(2801n asl。 )is included i五
the habitat zone of DおクJli“ ‐
Sc力 J“ α dry forest.
‐
In fact,a renlnant DおりJli“ 1““
Sc力 J“ 〕
αdry forest is
found not so far from the place.Shimizu(1992)
supposed that Dお
ry″
_Sc力 J“ αdry forest is less
“ R力
tolerant of drought “
than
PO“ たrlila
等,あわ′
ψ お‐
dry forest,thus the forlner has been replaced by
the latter with the long‐ ternl trend of aridity of
the lslandso
This species also produces small
wind‐ dispersed seeds and it needs a bright and
moist gennination condition. It seclns that the
original cloudy and mesic habitat has been dis‐
appearing from ChichJimao That is the basic
reason why,Rttodoご θ ごrO“ bο J“ θ″sθ haS become
critically endangered. “
“
morpha; maybe a relative of the Bonins') forms a
mesic forest in the cloud zone, too (Kitayama &
some individuals in the 1970s,some died
Mueller-Dombois 1993).
drought in the sunllner of 1980, the remainder
M. boninensis bears many small seeds dispersed
Someone cutting branches fbr a graft damaged
ёf severe
were severely ittured by the typhoOn in 1983,and
by wind, and it needs bright and moist seed beds
for germination. These are the common ecological features of pioneer species. Ohia invades
exposed lava flow and grows there to make a
climax ohia forest in Hawaii (Mueller-Dombois &
Howarth 1981). The individuals of the Bonin
Metrosideros having the habitat types ( 1) and (2)
are usually large and old, and maybe suppliers of
seeds to neighboring area. When forests get disturbed and bright and moist conditions good for
germination appear around these trees, new individuals invade and establish themselves at the site
competing with native pioneer species like Schima
mertensiana. This is the habitat type (3) which
occurred in abandoned fields or open lands exploited by man. Nobushima (1993) pointed out
that an introduced pioneer species: Pinus lutchuensis, may have suppressed the establishment of
Metrosideros trees in open places. There is one
locality where young trees of this species are
―-150-―
Photo 3。 The last indi宙 dual of R力
bo4J"θ ttθ in the neld。
bttPИ だ蘭,“
`囲
then they were infected with a kind of tick (Iwatsuki & Shimozono 1989). Now only one individual, the last natural individual on earth, is alive
there (Photo 3).
Dendrocacalia-Fatsia mesic scrub is confined to
the main ridge located at the altitude above 350 m
at Hahajima. The scrub contains several rare
species such as Melastoma pentapetalum, Stachyu-
nts macrocarpus var. purntfolius, Crepidiastram
ameristophyllum and some orchids. Endangerment of these species may also have been related
to the declining of this scrub with the long-term
Photo
trend of aridness.
4.
Old stumps of Morus boninensis
in a mesic forest.
2. Inggng of Particular Tree Species
were found around them (Funakoshi, unpubl.
In the early days of settlement, the Bonin Islands produced good timbers such as Monts boninensis, Hibiscus glaber, Celtis boninensis, Elaeocarpus photiniaefolius, and Melia azedarach. Many
woodmen came to the Islands and stayed in the
mountains for years cutting these trees. Timbers
were shipped to the mainland of Japan. Thus the
timber resource was soon exhausted. The Local
Government made rules of cutting valuable trees,
ms.).
but it was too late (Toyoda 1981; Funakoshi
A palm tree: Clinostigma savoryana is a Polynesian element in the Bonins. A picture of the forest
taken at Chichijima before World War II shows
many boles of this species with conspicuous
reez).
Monts boninensis was an excellent timber not
only for villagers' houses but also furniture, sculpture and interior decoration. It was sold at so
high price that this tree was cut selectively and
concentratively. Ogasawara-Tocho ( l9l4) described that almost all trees of this species were cut
by the time, and most of the remaining individuals
were also nearly dead. As the timber is very hard
and it does not decay for a long time, we can still
find stumps of this species which were felled more
than 100 years ago (Photo 4). A stump left in
Hahajima has a diameter of about 5 m. It is said
that a villager counted its year rings to about
2000, even though the central part of the stump
was vacant (Toyoda 1981). It must have been a
very large tree, which we can see nowhere in the
Islands at present. Only about 20 matured trees
are known at Chichijima and about 40 matured
trees are reco gnized at Hahajima at present (Funakoshi, psnl. comm.). They seem to include some
individuals that were planted before World War
II. No young trees are growing around them.
Fortunately, a new locality was discovered at
Ototojima in 1988. 38 individuals (19 female and
19 male) were growing on a north-facing rocky
slope of a mountain (Mt. Hirone). All of them
were matured trees and no seedlings or saplings
Monts boninensl's is a light-demanding tree, &r
early successional species. Nevertheless, it is one
of the main canopy trees of Elaeocarpus-Ardisia
mesic forest (climax forest in mesic habitat) in the
Bonins because the oceanic biota lacks true climax
trees (Shimizu 1994). It is a key species when we
try to restore the original mesic forest of
the
Bonin Islands.
crowns extruding above the canopy of other
native trees (Toyoshima 1938). Kittlitz (1844)
who visited the Islands prior to the arrival of the
first settlers described this palm tree. This species
must have been very common and widely distributed in the original forest of the Bonins. But
it was once thought to be nearly extinct at the
time of restoration of the Islands, because Japanese soldiers who were stationed during World
War II cut this tree and ate its top leaf bud as a
substitute for fresh vegetables (Toyoda 1981 ).
This palm is called a "cabbage tree" in English,
too.
Fortunately, some mature trees were discovered in several remote areas of the Islands, and
then many young trees were found scattered in
both dry and mesic forests in the 1970s. Now
some of them begin to attain to canopy layers
showing conspicuous crowns.
As for logging of valuable trees in Pacific islands, the decline of sandalwoods (Santalum) are
famous (Culliney 1988; Cuddihy & Stone 1990).
The Bonin sandalwood: Santalum boninense was
described for the first time in 1929. It is known to
be a root parasite of other native plants such as
- lsl -
Distylium lepidotum, Hibiscus glaber and Miscanthus boninensrs in dry type forests (Toyoda 1981;
Ono & Kobayashi 1983). It was lucky that this
little scent and it was never thought
to be a kind of sandalwood by villagers, so it has
not been collected in the Bonins (Tuyama 1970).
species had a
3.
Destruction and Decline of Habitats
It is speculated that lowland areas of Chichijima and Hahajima were once covered with developed Elaeocarpus-Ardisia mesic forest (Shimizu
l99l). Kittlitz visited the Bonins in 1828 and left
three copperplate printings of the vegetation of
Chichijima
184).
with their
explanations (Kittlitz
Those plates show the appearunce of
original mesic forests before the first settlers came
to the Islands. But the lowland areas with deep
soils and moisture were almost cleared and chang-
ed to cultivated fields (mainly for sugar
cane
plantation) until 1900 (Figure 4). Thus this type
of forest almost disappeared from Chichijima,
and only a small area was left as reserve forest at
Hahajima, although valuable trees like Moras
in the past even there.
Now the lowland areas which were once covered
with the original mesic forests are dominated by a
secondary forest: Pinus-Schima mesic forest in
both islands (Shimizu & Tabata 1985).
The remnant original forest at Hahajima contains several rare endemic species. Some of them
boninen^sls had been logged
are designated as endangered species
Hohojimo
Chichijimo
t
l.l:
I
セゝ
Figure
4.
now.
Piper
postelsianum is a perennial herb with oblique
stems about 2m high (Photo 5). Kobayashi
(psnl. comm. ) supposes that this species is related
to Polynesian congeners rather than South-East
Asian ones. It prefers rather bright habitats in
Elaeocarpus-Ardisia mesic forest, such as forest
edges or canopy gaps in the forest. There are two
specimens of this species that were collected at
Distribution of cultivated fields in Chichijima and Hahajima around lg44'.
After Katahira (1981, 1982).
- 152-
4.
Photo
5.
PiPer Pstenianttm-
in 1913 (Ono et al. 1991), but the
population of Chichijima has already been extinct
due to the disappearance of the mesic forest itself.
Only several localities are known at Hahajima
now. As mentioned later, stems of this species
were damaged by an introduced land snail in the
1970s and then eaten by rats in the 1980s, so the
populations have nearly disappeared from these
localities. It is critically endangered now.
Chichijima
A ground orchid:
Corymborchis subdensa was
also described at both Chichijima and Hahajima
before World War II, but it has been extinct at
Chichijima because of the destruction of the original mesic forest (Ono et al. 1991). Claoxylon
centenarium also grows only in the remnant mesic
forest at Hahajima. It is a very rare tree in the
second-layer of the forest. Ficus iidaiana, one of
three endemic Ficus species which diversified in
the Bonins, is another endangered species growing
in the second-layer of the mesic forest at Hahajima. In addition to the declines of original mesic
forests, these two small-tree species are suppressed
by the dominance of an introduced tree: Bischofia
javanica recently.
Only a small population of Alpinia boninsimensr's was left along a stream in a cultivated area
Illegal collection bY man
Some kinds of orchids and ferns have been
collected supposedly by commercial collectors or
amateur nature lovers. It is said that these plants
sell at a high price in the market of mainland
Japan. Soon after Malaxis boninensis, first described in 1918, was re-discovered at Chichijima
in the late 1970s, the population was stolen from
the habitat. The last individual that was found at
a different locality in 1990 seems to have been
eaten by feral goats, so it was designated as extinct in the Japanese Red Data Book. But another
individual was discovered in 1994, so there may
be some more unknown individuals at Chichijima.
Malaxis hahajimensis was discovered at Hahajima
in 1978 (Kobayashi 1980). Only a few individuals are known in some localities at Hahajima now.
In the early 1970s we could easily find epiphytic
orchids and ferns such as Cinhopetalum boninense and Luisia boninensls (orchids), and Selagin'
ella tamariscina, Crepidomanes acuto-obtusum
and Psilotum nudum (ferns) at Chichijima and
Hahajima. But they have been collected so much
since then, that they have become endangered.
An endemic ground orchid: Calanthe hattorii
with beautiful yellow flowers (Photo 6) was
widely distributed in the floor of Distylium-
Schima dry forest at Chichijima and Anijima in
the early 1970s. But it has been stolen from the
habitats of Chichijima and shipped to the mainland of Japan by stealth. It is said that horticultural shops in the mainland sent collectors to the
Islands or asked villagers to collect and send the
plants to them. The populations of this species
were extinct at some localities, and the number of
individuals decreased greatly at other localities at
Chichijima (Tokyo Regional Forestry Office 1994
a). Collectors began to enter the habitats of
(Kitafukurozawa) at Chichijima. The original
habitat must have been destroyed by exploitation
before World War II. Recently another population was discovered at the upstream of the former
locality in more natural condition.
The construction of roads and National Park
facilities also destroyed some localities
of
en-
dangered species. It is said that a locality with the
largest population of Pittospontm parvtfolium was
destroyed by making a rest place in the National
Park in the early 1970s at Chichijima (Toyoda
1984). The last individual of Crepidiastram ameristophyllum at Chichijima was killed in the course
of road construction in the early
″
rЙ口胸だj.
Photo 6。 CaJa“ ″
1980s.
-1s3-
Endangered Plant Species in the Bonin (ogasawara) (Shimizu)
Anlima WhiCh had so far escaped their attentions
from the late 1980so
This orchid has become
critically endangered.
cara“ 励θ ヵosLゴ J was desc五 bed in 1983 as an
endemic species of Hahttima.It grOws at ttesic
habitats in EJagocα ″ s―A■ ダ
おlia mesic forest. It
“ it was irst describede
was already very rare when
Nevertheless,it was c011ected by unthinking men
(Nobushima 1992).Only a few indi宙 duals are
protected in the nelds at present.
As for woOdy plants, branches of」
ごro“
bo41i4θ
Rλ odoご θ ‐
w andル化Jasro“ α たrra“ θ″
“
were
Photo 7.助 ″ J000S h聞施 ″JJ.
once cut by “
someone perhaps ibr grafts. “
It must
have hurt the individuals tO some extent。
5).助 p″ηJOCOsメ
Unusual Clilnate
5。
species inシ
"″
α′
機 JJ,one of three endemic
which d市 ersined in the
りJOCos “
“
Bonins, is a small
shrub with thick and curled
Big typhoons and severe drought are twO unu‐
sual climatic events that arect the existence of
Ondangered species in the Bonins. These events
leaves(PhOt0 7). ThiS Shrub growing only at
Chichlima seems to have a drought_tolerant abil―
ity,but some individuals died of the 1980's dro―
are natural phenomena that occur once in several
ughto Several localities disappeared at that tilne.
decades,so they urge canopy gap formation and
About 15 individuals inake a local population in
one locality(Yoakedaira),and the other individ‐
promote regeneration process of fbrests in gener‐
al.
But they could push endangered species to
extinction or to a more endangered state.
There was a severe drought in the sunllner of
1980. The rain fall was only 189ろ of usual years
through March tO November(Shimizu 1982).It
damaged many individuals Of a va五 ety of species
growing in DJsク ″ ‐
PO"″ Jα dry scrub(Figure
ualS(less than 10 in total)are diStl威 buted in
isolation from each other.Pli″ ″
θ
ψ O″
Jli"″ 2
,1器
g“
.lm.
lili
was also damaged by the drought to some extent.“
Some individuals ofR力 Odode″ グro“ bο ″J″ θ sc also
“
died of this drought,and the remaining individu‐
als grew weaker。
““
o no damage
′α″ル ‐
growing in the same habitat as Siた “
α″αたα
A big typhoon (′ ryph。。n No. 17) hit the
Bonins in Novettber, 1983. It caused damage to
the native forests, especially to EJaθ ocattp“ s‐
Иだおlia mesic forest at Hahttima(shimizu 1994
‐
a)O Many big trees sucl aS EJacocarp“ s′ 力ο″
J“
S,PiSO“
lia“
bθ
〃
raθ
/0″
,Ilib淑 ,“s grabθ r and
ψ
Po““
′
θrlia ObOッ α″
α“
fell to the ground,Inaking large
lilaθ
canopy gaps in the forest(Figure 6).ProCr,s
bo4J“ θ sお ,a perennial herb creepinか on calCare‐
“ is known at only one 10cality (Sek‐
ous rocks,
imOn)in Hahttima.ThiS species almost dis‐
appeared just after the typhoon attack perhaps
because it got salty spray carrled by windo Fortu‐
nately,it has recovered little by little. The indi‐
viduals Of」 R力 odode“ ごrO“ bο
J“
θ sθ , WhiCh sur‐
“ again
“ damaged by
vived the 1980's drought,were
the typhoon,so this species became the only indi―
vidual left in the habitato The crown of the last
individual was also severely dalmaged(seC PhOto
3).
Figure
5. Damage of unusual drought on a
Distylium-Pouteria dry scrub
at Chichijima in 1980.
6. Attack of lnsects or Pests
From Shimizu (1982).
Pli“
sJ“ ″
c力 θ
″sお
“
―-154-―
“
was introduced to the Bonins
Endangered Plant Species in the Bonin (Ogasawata) (Shimizu)
conopy gqp
ノ
ｏヽ，′ 呻 “
ヽ
0RJ
Ar=
、
｀
｀ヽ
イ
_…
…
ノ
レ/1Sヽヽ
fO
語
:ス
。。
二
,LT
`‐
‐
´
・ ‐
´
´
・
′
′
′
f・
′
1
・
￨■
:・
‐‐ ‐
・・、
、
随Wi
一
´一
ヽ
・
・
．
﹁
ド、
6.
′
︰
Figure
A「 =
／
ォ
﹁
・・
.
∵
D・
F・
ん
拿
:
ヽ
電日`
｀
｀
・
5し〆
雀11」
．
′
´
︲
・
ざ〈
・
グ
二
〃
'bMe
で
￨ヽ
El°
ノ
ヽ平::P
`°
。ゝ
ヽ
3‐
。
・′
蹴
．Ｅ鴫
・
・
爵
。
場ｏ
'巫
ヽ一
・ ′
・
句
Fシ
・
み卜4m・￨:卜
、ヽ
１
卜０一
Ｅ
の︶
︶
・
ー
縦身‖ ・
ベ
Ar=5ヽ6h・
′
′
ぷ
∂く
′ ｀
r黎 :レ 1/二
一︲Ｏ
Ｅ
総′
．
″一
ヮ土
、
′
NVふ
/ .￨
´′
′´
・
√
ゎ。
１ヽり ‘
‘
t
ヽ
/メヽ
「
・ジ
、
′嶽．
グ
一
ヽ
.1弓ガ
￨ゝ
、
Ｉ．４
ヽ、Ｅ
ヽ
゛
ｔｉ
′
、
ゝ
昴
メ
︶・
ル
¨
fl3
10m
14
熔
.
。RII
P
Typhoon damage and canopy gap formation in a Elaeocarpus-Ardisia
mesic forest at Hahttima in 1983。
From Shimizu(199色 ).
in 1899 from the Ryukyu Islands. It became
naturalized invadin g a vacant niche in the Bonins
where gymnosperms like pine trees did not exist
(Shimizu & Tabata 1985). It established itself in
a wide range of abandoned cultivated fields just
after the World War II, and then made PinusSchima mesic forest, a typical secondary forest in
the Bonins.
A pine wood nematode invaded the Bonins
from the mainland of Japan in the late 1970s. It
spread very rapidly over the Islands and killed
matured pine trees selectively (Figure 7). About
80% of adult pine trees was dead at Chichijima
until 1982 (Shimizu 1986, 1987b). It seems that
the canopy of native species got damaged by the
1983's typhoon more seriously than expected in
dry type forests because wind easily entered the
forests without pine crowns which had taken the
role of wind shields before the nematode attack.
It
became brighter and drier on the forest floor
after the nematode attack and the typhoon
damage. This environmental change may have
had a negative impact on some herbs growing in
shady condition like Calanthe hattorii (Tokyo Regional Forestry Office 1994a).
On the other hand, this disturbance (opening of
canopy) gave a chance to regenerate for some
rare species that demanded light for germination
of seeds. It
seems that Metrosideros boninensis
and Melastoma tetrameram could invade new
open places made by the death of pine trees and
the following typhoon damage (Nobushima 1993;
Yasui 1993).
A
severe drought occurred
at Hahajima
in
1991, then a beetle : Acalolepta boninensis attacked
Fatsia oligocarpela, an endemic shrub in Dendrocacalia-Fatsia mesic scrub (Esaki 1993). Almost
all adult trees of this species disappeared from the
habitats (Nobushima 1992). Only saplings were
alive and they are growing up now.
Pouteria obovata is distributed widely in almost
all islands and it becomes a sub-dominant species
in several forest types. This species is not endemic
to the Bonins, but there is an endangered endemic
congener: P. boninensls that was derived from P.
obovata in the Bonins. The two species were
seriously attacked by a moss larva: Achaea sema in
1984 and 1993 (Kurozumi 1985; Chiba 1993).
Almost all leaves were eaten in many individuals,
thus some died after this event. Pouteria boninensis may have become more endangered by the
insect attack. The sunlight penetrated into the
forest floor through the naked crowns of Pouteria
trees giving negative influence to some shady species.
7.
Damage by Introduced Animals
Domestic animals introduced by man became
naturalized and gave serious damage to native
―-155-―
Endangered Plant Species
in the Bonin (Ogasaw ara) (Shimizu)
□ areC Wilthout pine
_● ―Dr:dge
‐
1979
_1980
- 1981082
Figure
7.
Infection process of pine wood nematode together with concentrated death
of introduced pine trees (Pinus lutchuensis) in Chichiiima.
After Shimizu (1987a).
plant species or vegetation itself in many oceanic
islands whose ecosystems had been developed
without such big mammals (Stone 1985; Tsuneda
1992; Lever 1994). A variety of domestic animals
were introduced to the Bonin Islands historically,
but only goats and pigs have survived in 7 islands
and in one island, respectively. Especially, feral
goats are the most harmful for plants (Toyoda
1981; Ichikawa 19921. Shimizu 1993). They prefer
to eat herbaceous plants of Compositae, Campanulaceae, Liliaceae that grow on rocky habitats
such as sea coasts and cliffs (Environmental
Agency 1985).
Lobelia boninensr's, one of Polynesian elements
in the Bonins (Photo 8), was common on rocky
coasts of Chichijima. An old photograph taken
before World War II shows a population of this
at a place (Minamizakr) in Chichijima
(Toyoshima 1938), but we can not find any individuals there now. Only a small number of individuals were alive in a few localities in the 1970s,
but they were almost exterminated by feral goats
in the 1980s at Chichijima. Only a few are known
at one locality (Nishikaigan) of Chichijima at
species
一-156-―
Endangered Plant Species in the Bonin (Ogasawara) (Shimizu)
present where feral goats can not reach (Yasui
1994). There are still many individuals of this
species left at a small islet (Higashijima) adjacent
to Chichijima (Yasui, psnl. comm.) and some
islands of Hahajima-retto (shimizu 1994b) where
feral goats were exterminated before.
Cirsium boninense and Ixeris longirostrata have
nearly the same habitat as Lobelia
boninensis.
These species were also grazed by feral goats and
have become nearly extinct at Chichijima. The
local population of these species are recovering at
Minamijima, a small calcareous island located
south-west of Chichijima (Toyoda et al. 1994).
The vegetation of Minamijima was once destroy-
ed nearly completely by feral goats, but
Photo 8. Loレ
a bo“ j"θ パ r.
“
1969
0
1979
1∞
1993
200m
／丁ト
Ｋ
Ｋ
Ｋ
川い＼
Figure
8.
it
has
been recovering rapidly since the time when the
goats were shot for the sake of nature conservation in 1972 (Figure 8).
Crepidiastram has diversified into three endem-
Vegetation recoyery at Minamijima after the extermination of feral goats
From Toyoda et al. (1994).
―-157-―
in
1972.
ic species in the Bonins (Ito & Ono 1990) . C.
grandicollum, a perrenial herb on rocky habitats
in Distylium-Pouturta dry scrub at chichijima and
Anijima, has been damaged by feral goats, thus it
is seriously endangered at present. A few individuals of C. ameristophyllum were found near the
peak of the highest mountain (Mt. Chuo) at
Chichijima in the early 1970s, but then they disappeared little by little, and the last individual was
killed by road construction in the 1980s. Feral
goats may have eaten these individuals at Chichij-
ima. We can find
some populations of this species
at several localities in Hahajima-retto.
The habitats of Ajuga boninsimae are open
places such as forest edges and sea cliffs. These
places are preferred by feral goats as grazing
fields. This species is also nearly exterminated at
Chichijima.
Angiopteris lygodiifolia was not included in the
food menu of feral goats before the 1980's drought. But goats found this fern was edible when
usual food stock became short due to the severe
drought in 1980. They began to eat this species
after that event (Yasui 1992b), so this fern
became critically endangered at Chichijima. But
recently it has recovered again because the density
of feral goats became low by shooting. There are
still many at Hahajima.
The harm of feral goats extends not only to
herbaceous species but also to small shrubs. Callicarpa nishimurae is a small endemic shrub occurr-
Photo
9.
Callicarpa nishimurae.
ing in Distylium-Pouteria dry scrub at Chichijima
9). Feral goats seemingly
liked the soft hairy leaves and ate almost all
saplings of this species at Chichijima in the 1980s
(No adult was found at Chichijima even in the
1970s). It is supposed to be exterminated at
Chichijima. Anijima is following the situation of
and Anijima (Photo
Chichijima. Only a few adult individuals
O
soil erosion
@ exposed rock
C) gross lond
@ forest
Figure
9.
are
confirmed at some localities of Anijima at present,
where feral goats cannot reach because of dense
thickets. It is one of the most endangered species
in the Bonins (Kazaki 1992).
Feral goats checked the regeneration of ArdisiaOchrosia dry forest by grazing all seedlings and
saplings of trees, therefore the forest changed to
grassland after disturbances like typhoon damages
in the three islands of Mukojima-retto (Toyoda
Vegetation degradation and soil erosion by feral goats at Nakodojima.
From Ichikaws (1992).
-158-
then. It is not clear whether this decrease is a
passing phenomenon or not (Koyano 1992).
1981; Ichikawa 1992; Shimizu 1993). Forests
themselves are disappearing from these islands.
Especially, soil erosion proceeded in a wide area,
and basal rocks being exposed in some places in
8.
Nakodojima (Figure 9). Though plant species
endemic to Mukojima-retto are not recorded,
Shimizu (1989) discussed the influence of three
introduced plants on the native species. Pinus
lutchuensis spread into open places like abandoned fields to make a wide range of secondary
forests with an endemic pioneer: Schima mertensiana, and it also invaded canopy gaps of dry type
local populations of species endemic to the Bonins
living in Mukojima-retto will be exterminated in
the near future.
As mentioned in causal factor 2, Piper postelsianurz was confined to only several localities at
Hahajima. It grew in a rather good condition
until 1985, but rats (not native) became to bite its
stems giving fatal damage to the individuals suddenly in the late 1980s. The natural populations
are about to disappear at present (Ono et al.
forests and exposed lava. As
Leucaena leucocephara formed monotypic
stands on disturbed habitats near villages or along
roads. It was difficult for native plants to establish
themselves in the stands, and this light-demanding
species could not invade native forests if the
canopy was closed. So this species is not a menace
to native plants (Kimura et al. 1983).
On the contrary, Bischofia javanica was a very
disruptive invader.
It
invaded canopy gaps of
mesic type forests, grew rapidly, and continued to
occupy the place. As saplings of this species have
shade-tolerant ability to some extent, they can
wait for the next disturbance under the canopy.
This species takes the place of native species little
by little and makes a Bischofia monotypic forest at
a
calcareous rock of only one locality (Sekimon) at
Hahajima. As it was eaten by the snail, only a few
small individuals lived there in the 1970s. A
villager voluntarily covered the habitat with a net
last (Shimizu 1988; Tokyo Regional forestry
Office 1994b). Especially, it spread to a wide area
and increased rapidly after the 1983 typhoon
and put an anti-snail pesticide around the place to
prevent the snail. This fern was once thought to
be an endemic genus of the Bonins, but the same
species was found in Kitadaitojima in 1972
damaged the native forests at Hahajima (Figure
l0). Mt. Kuwanoki of Hahajima was once covered with a developed Elaeocarpus-Ardisia mesic
(Toyoda 1981).
The endangered orchids such as Calanthe hoshii
forest, but now most of the area is replaced by
Bischofia dominant forests. Rare species such as
Claoxylon centinarium and Ficus iidaiana growing
and Malaxis hahajimensis, both endemic to Haha-
jima, were also damaged by the snail. Only a few
individuals of both species are recognized in the
fields at present. Crepidiastntm linguifolium, one
of three Crepidiastrum species in the Bonins, was
also eaten by the snail. I observed that a popula-
in the native forest were
eliminated from the
forests with the dominance of ^Bischofia javanica.
Bischofia dominant forests shaded out some native
herbs and ferns growing on the ground (Tokyo
Regional Forestry Office 1994b).
Alien weeds are a threat to some endemic gra-
tion (5-6 individuals) on Mt.
Sakaigatake of
Hahajima was exterminated by the snail's attack
1979.
This snail preferred the bark of Claoxylon centinarium, a small tree in Elaeocarpus-Ardisia mesic
forest at Hahajima. As the snail ate the bark of
this tree in a ring stopping the flow of phlo€ffi,
some trees attacked by the snail died in the 1980s.
Fortunately, the snail decreased suddenly in
1988 probably because of the attack of a small fly
(Tomiyama, 1994). Damage to the native plants
by the snail have become greatly reduced since
-
occupied a vacant
(Shimizu & Tabata 1985).
A land snail: Achatina fulica was introduced to
the Bonins around 1935, and then it escaped and
became wild, spreading all over the Islands (Tomiyama 1988). Many shells of this species were
found at mesic habitats of Chichijima and Hahajima until the late 1980s. This snail ate not only
agricultural products but also native plants, and
some rare orchids and ferns were damaged. Asp-
in
it
in the Bonins, the influence of this pine
species on the native plants was not so great
niche
leel).
lenium ikenoi was a small fern growing on
Competition with Introduced Plants
sses such as Ischaemum ischaemoides, Rhynchosp-
ora boninensis, Aristida boninensis and Digitaria
platycarpha. Open places on exposed lava, road
side, and abandoned land have been occupied by
alien weeds such as Srachytarpheta jamaicensis,
Bidens pilosa var. bisetosa, Lantana camara, Chloris barbata, and Sporobolus diander at Chichijima
and Hahajima. The dominance of these weeds is
closely related with the degree of human disturb159
-
before
Figure
10.
Invasion of an introduced tree species: Bischofia javanica into native forests
at Hahqiima. After Tokyo Regional Forestry Office (1994b).
ance. The endemic grasses are preserved in good
condition only at Anijima, which man has nct
inhabited and the alien weeds listed above are
seldom found (Table 2).
9.
2. Comparison of herbaceous species
between Chichijima and An[iima
Species with frequency more than lO%
are listed. N: native, B: endemic,
I: introduced. After Shimizu (1991).
Table
Loss of Pollinators
Average frequency
Pollination is important for outcrossing of
plant species. Especially it is indispensable for
dioecious plants. The high ratio of dioecism is a
characteristic of oceanic island biota (Carlquist
1974). Among ll2 native woody species in the
Bonins, about n% is dioecious (unpubl. data). It
is noteworthy that the three endemic species of
the Bonin Callicarpa (C. subpubescens, C. glaber,
C. nishimurae) developed a kind of functional
dioecy within the Islands, while mainland congeners are all hermaphrodite (Kawakubo 1990). A
male tree has real stamina and degenerated pistils,
and a female tree has stamina with sterile pollens
and real pistils in these species.
Recently Kato (1994) discovered that Dendrocacalia crepidifolia (endemic genus in Compositae
of occurrence (%)
Species name
Chichijima Anijima
Fimbristylis dichotomd
(N)
74.1
84.1
Stachytarpheta jamaicensr (I)
Sporobolus diander (l)
Digitaria violascens (I)
Bidens pilosa var. bisetosa (l)
Paspalum orbiculare (I)
68.3
Digitaria ciliaris (I)
10.8
10.0
5.8
10.0
0.8
9.2
9.2
10.8
8.3
20.8
Carex hattoriana (E)
Cenchrus brownll (I)
Digitaria platycarpha (E)
Tridatc procumbens (I)
Aristida boninensls (E)
Rhynchospora boninensis
Ischaemum ischaemoides
- 160-
(E)
(E)
33.3
25.8
22.5
t4.2
20.8
14.2
5.8
52.5
2.5
74.1
and an example of insular woodiness) bears dioecious flowers (Photo 10), even though dioecism is
not known in the related genera of the mainland.
There are 9 endemic bees that are pollinators of
the Bonin plants. But most of them were
ex-
terminated at Chichijima and Hahajima. Instead,
a honey bee: Apis mellifera, introduced to the
Bonins before World War II for the sake of
apiculture, has become naturalized to pollinate
many endemic plants (Kato 1992). The loss of
endemic bees and perhaps unknown indigenous
pollinator insects must have influenced seed production and regeneration of some endemic plant
species. Shimizu (1983) pointed that many plant
species of the Bonins bear little fruit for the
Photo
10.
Dendrocacalia crepi.difolia.
quantity of flowers.
Calanthe hatorii mentioned in causal factor 3
blooms well in the fields, but it seldom produces
fertile seeds (Shimozono 1994). Scutellarta longituba, an undergrowth herb in Distylium-Schima
dry forest, has a very long corolla (Photo I 1).
This species also produces few fertile seeds though
flowers are found every year. It is known that
Santalum boninensis mentioned in causal factor 2
bears fruit very rarely in the fields (Toyoda 1981).
These phenomena may be related to the loss of
original pollinators. These species seem to maintain their populations by vegetative reproductions
like back bulbs, tubers, and rhizomes, respectively.
For endangered dioecious plants, effective pollination is rather difficult even though original pollinators exist. Pittosporam panrfolium with dioecious habit is one of 4 endemic congeners which
diversified in the Bonins and a member of Distytium-Pouteria dry scrub (Photo l2). Only two
individuals (one male and one female) are recognized in the fields at present, and they are located
about 25Om apart from each other (Yasui 1992
a). Thus the pollination in the fields is hopeless.
10.
Photo
11.
Scutellaria longituba with a long corolla.
Hybridization with Inhoduced Relatives
The biota of oceanic islands is isolated from
that of the mainland by physical barriers (sea and
long distance), thus reproductive isolation between the island and the mainland biotas is not
necessarily complete. Island species possibly
make hybrids with introduced related species.
As mentioned in causal factot 2, Monts boninensis was critically endangered because of selective cutting before World War II. A mainland
mulberry: Monts australis was introduced to the
Bonins for sericulture before World War II be-
Photo
cause leaves
12. Pittasporum
parvifolium.
of the Bonin mulberry is too hard to
feed silkworms (Toyoda 1981).
became
M. australis
wild soon and spread rapidly to a wide
area at Chichijima and Hahajima (Photo 13).
The two Morus species are dioecious. As a result,
pollens of M. boninensis were contaminated with
those of M. australis, and hybrids of these species
-161 -
Photo
13.
Morus boninensis (left) and
M. australis (right).
appeared (Toyoda 1981). According to germination test, seedlings that germinated from the seeds
collected from matured trees of M. boninensls at
Hahajima showed some characters of M. australis
(Iwatsuki et al. 1990). Isozyme analysis also
showed hybridization between the two species in
Chichijima and Hahajima (Ito, unpubl. data). As
M. australis was not introduced to Ototojima, the
individuals of M. boninensl's seem to keep genetic
genuineness at Ototojima even now. A germination test and isozyme analysis also supported it
(Iwatsuki et al. 1990).
III.
1.
Discussion
Propagation and Planting
The Botanical Garden, Llniversity of Tokyo, is
carrying out research and propagation of endangered species of the Bonin Islands. They
succeeded in reproducing some critically endangered species in the Garden such as Melastoma tetrameram, Rhododendron boninense and
Metrosideros boninensrs, from the seeds or cuttings
collected in the fields (Iwatsuki & Shimozono
1989). Furtherrnore, they are trying to plant the
saplings and restore populations in the original
habitats (Shimozono & Iwatsuki 1986; Iwatsuki er
al. 1993). The Tokyo Metropolitan Government
supported this project financially from 1988-1993,
and the Environmental Agency of the Japanese
Government is succeeding to this project from
1994. They also succeeded in propagating many
other endangered species of the Bonins including
critically endangered species like Pittosporum parvifolium and Callicarpa nishimurae. To collect
fertile seeds they carried out artificial pollination
on Pittospontm parrrfolium and Calanthe hattorii
in the fields. They are keeping 83 endemic species
of the Bonins in the Garden. Some of them were
sent to other botanical gardens to keep the strains
more securely (Iwatsuki & Shimozono 1989).
The aim of the propagation and planting is to
restore the natural population in which the species
reproduces and establishes itself without human
assistance. But the largest problem is the loss of
the original habitats from the Bonins. According
to the research in the Garden, a number of endangered species of the Bonins need much humidity for germination (Iwatsuki et al. 1990), but
such environment has been almost lost in the
Islands maybe because of a long-term aridness
(causal factor 1) and destruction of the original
forests by man (causal factor 3). The reasons
that made many Bonin species become endangered are themselves an obstruction to their
restoration in the original habitats.
Another problem is that genetic variation is
limited in many endangered species. Especially,
we can get only self-pollinated seeds or cuttings of
one individual in Rhododendron boninense. The
situation is nearly the same in Melastoma tetrame-
ntm, Pittospontm parntfolium and Piper postelsianum. Even though we plant many clonal
individuals in the fields, inbreeding depression is
inevitable over the long term, and they are susceptible to environmental fluctuations or infection of
disease. They will need continuous human care in
the fields for a long time.
We must take into account genetic variation
among different island populations within a species. As mentioned before, it is difficult to collect
pure Monts boninensrs seeds from Chichijima and
Hahajima because of the genetic contamination
by M. australis (causal factor 10). We can get
them only from the population of Ototojima, but
it is disputable whether we should plant saplings
of the Ototojima population to other islands. Scientific researches including genetic variation
among islands must be done before we can reach
a conclusion.
It is necessary
that precise procedure of
the
planting project is recorded and the report is
opened for researchers. Otherwise, we will not be
able to differentiate natural populations from planted ones in the future. Continual monitoring of
planted populations is also desirable to prevent
such confusion. One problem is that we cannot
open to the public the information on localities of
endangered species, especially valuable orchids,
because unthinking men will soon take the plants
from the habitats.
一-162-一
2.
Conservation Facilities and Cooperation of
Villagers
Almost all areas except residential places and
cultivated fields are designated as the Ogasawara
National Park. About 70% of the Islands atea,
most of them covered with forests, are owned by
the Japanese Government (Tokyo Regional Forestry Office 197 6). The Environmental Agency
should have an office and put rangers in the Islands, but due to shortage of budget and staff, it
entrusts the Natural Park Section, the Bonin
branch of Tokyo Metropolitan Government, with
But no endangered
to prevent
illegal
collection. If we propagate an endangered plant
(i.e. Calanthe hattorii) in gardens and supply a
number of individuals to markets, the economic
value of the plant would be decreased, and the
motive of collecting natural individuals would
disappear (Ono 1994b). But this cause and effect
has not been verified yet.
3.
Extermination of Introduced Biota and Prevention of Invasion
As mentioned in the causal factor 7 , feral goats
the care of the National Park. On the other hand,
of Minamijima were exterminated in 1972.
the Bonin branch of Tokyo Regional Forestry
The
result was outstanding (see Figure 8). Shooting
of feral goats was sometimes carried out at Chichijima from the late 1970s by the Tokyo Metropolitan Government, but the number of goats soon
recovered. Several rare endemic herbs almost
disappeared in the 1980s at Chichijima. Researchers repeatedly proposed to exterminate
feral goats from the Bonins to protect endemic
plants and vegetation. But it was difficult to shoot
them in uninhabited islands, because the budget
for shooting feral goats was usually admitted only
for prevention of agricultural damage, and not for
Office, the Forestry Agency, manages the national
forests. They established 10 reserve forests in the
Bonin Islands in 1975 (Tokyo Regional Forestry.
Office 1976), and revised them in 1993. A new
category, Forest Ecosystem Reserve Site, was ap-
plied to the eastern part of Hahajima. Tokyo
Metropolitan University or ganizes the Ogasawara
Research Committee, which manages a laboratory at Chichijima and publishes an annual report
"Ogasawara-Kenkyu-Nenpo" and a research
magazine "Ogasawara Research" periodically.
There are some islanders who know the nature
of the Bonins very well. They love to walk around
nature conservation. The Tokyo Metropolitan
Government will start a project to reduce feral
the islands, observe the nature, sometimes find
new things, and give valuable information to researchers. They have also taken care of en-
goats, stop the soil erosion, and restore vegetation
on the exposed area at Nakodojima from 1995.
But it is said that the Government is hesitating to
exterminate feral goats, because they are worrying about criticism of Animal Rights Associations. What they should do is not to fear criticism
but to persuade critics.
voluntarily. The Tokyo Metropolitan Government formally asks some of them
to promote nature conservation of the Bonins.
They have organrzed a circle to help research or
propagation projects, give suggestions to local
administration on nature conservation, ask visitdangered plants
As for the prevention of a plant invader:
Bis-
hofia javanica, the Forest Agency carried out a
research project in 1993 (Tokyo Regional Forestry Office 1994b). According to the results of the
project, they started a test to reduce the number
ing researchers to give lectures to villagers, and
publish a newsletter about the nature of the
Bonins.
Though there are some conservation laws that
are related with the protection of endangered
species in Japan, it is difficult to prevent unthinking men from collecting valuable species. To
protect endangered species more effectively, the
organrzations mentioned above must be more
active than at present. In addition, we need
cooperation of all villagers, who understand value
of the nature and can watch out for illegal or
unthinking deed. The Law concerning Conservation of Wildlife Species Threatened to Extinction
coming into effect in 1993 can designate rare
plants and animals as endangered species, then
of individuals of the species at Hahajima. Now
that this plant has already spread all over the
island, it is impossible to exterminate the species
(see Figure 10). So we must first prevent the
further invasion of this species into the natural
forests that have so far escaped invasion. On the
other hand, we should start a project to reduce the
number of individuals (i.e., cutting of female
adult trees and planting endemic tree species)
little by little in the perspective of 100 years.
There is one successful example of exterminating a harmful insect in the Bonins (Koyano &
Takeuchi 1992). That is a kind of fruit fly: Dacus
prohibit the business of the designated species.
-
species have been designated
from the Bonins yet.
There is another proposal
163
-
dorsalis. Because of this fly farmers could not
Eco-tourism is being introduced in the Bonins
ship local fruits to the mainland of Japan after the
restoration of the Islands. So the Tokyo Metropolitan Government started a project to extermi-
recently. But there are no official guidelines or
guide systems. Nature conservation is not fully
considered by tour agencies. It is necessary to
nate this insect from the Islands. They made a
laboratory at Chichijima, produced sterile male
flies by applying radiant rays, and dispersed them
in the fields by helicopters. The number of individuals decreased little by little and at last became
zero in 1985. A new project to research a harmful
land snail: Achatina fulica began after that project, but effective methods to exterminate it have
not been developed yet. As mentioned before, this
snail suddenly decreased from 1988 due to the
attack of small parasitic fly.
The invasion of pine wood nematode into Chichijima in 1979 is thought to be caused by bringing infected pine wood for construction materials
from the mainland. If a pest that affects endangered endemic species were introduced, it
might have exterminated the species. Kai (1994)
discussed the impacts of infectious disease on
endangered species showing several examples of
the world. Apart from plants, a green anole:
Anolis carolinensl,s introduced to the Bonins in the
1960s as a pet escaped and became naturalized in
the early 1970s, and it has been spreading rapidly
at Chichijima and then at Hahajima (introduced
from Chichrjima in 1984), eliminating a native
lizard: Cryptoblepharus boutoni (Hasegawa, et al.
1988). A pet green iguana was caught at Chichijima about one year after it escaped from a cage
(Kamdo 1993). There is no check on bringing in
alien plants and animals to the Islands, while
taking out of some harmful animals from the
Islands is checked by the Quarantine. Bringing in
alien biota should also be under control. It is also
necessary that villagers understand the danger of
bringing in alien plants and animals and watch for
their
4.
escape.
Tourism and Development
More than 20,000 tourists visit the Bonins an-
nually. Many tourists enjoy diving, fishing, whale
watching, dolphin swimming and other marine
leisure, and land plants and animals are not so
popular among tourists. Tourist activities are not
such serious threats to land biota at present except
for a small island: Minamijima. It is reported that
tourists brought weeds from Chichijima to Minamijima, and endemic herbs recovering from the
make formal rules for the Bonin eco-tourism as
soon as possible.
Only one steamer is put on the Bonin line
(Tokyo-Chichijima) 5 or 6 times a month. It
takes about 28 hours one way. The Tokyo Metropolitan Government has a plan to construct a big
air port at Anijima. Furthermore, this plan is
supposed to be connected with a bigger resort
development
inhabited and an intact native ecosystem has been
preserved (Figure 1 I ) (Shimizu et al. 1991 ).
Most of the island area is covered with DistyliumShima dry forest and Distylium-Pouteria dry
scrub including many endangered species mentioned in this paper (Shimizu l99l; Shimizu &
Yasui L992). So scientists concerning the Bonin
biota are opposing this plan (Kitayama l99l;
Funakoshi 1992b).
Propagation and planting of endangered species
is a kind of emergency step. The last aim is for
these plants to live in the original habitats by
themselves. Even if we succeeded with propagation in the garden, w€ could not restore native
population in the Islands if the original habitats
have already disappeared. The largest priority
must be put on the protection of intact native
ecosystems which have so far miraculously escaped past human activities. An airport should be
constructed in some places other than Anijima.
Environmental assessment is important to prevent destruction of habitats. There is a regulation
of environmental assessment issued by the Tokyo
Metropolitan Government. But the regulation
does not apply for small projects such as construction of walking trails and rest facilities in the
National Park of the Bonins. In fact, some habitats of endangered species were destroyed by the
construction of these facilities in the past (causal
factor 3 ). Furthermore, there is criticism that
environmental assessment is not effective for protecting nature in Japan, because it is usually carried out after the complete project plan is decided
and only minor change of the project is admitted
even if serious damage is considered to occur to
the nature. In the Bonins, environmental assessment must be strictly applied for all construction
projects even if it is not obligatory.
past damage by feral goats may compete with
alien weeds (Toyod a et
al.
project. But Anijima is the only
island in the Bonins which humans have never
1994).
一-164-一
Endangered Plant Species
5.
in the Bonin (Ogasawata) (Shimizu)
Integration of Causal Factors and Monitoring
factors are threatening the endangered species
even now in the Bonins. Plural causal factors
often affect one endangered species. For example,
As mentioned in this paper a vatiety of causal
Ototttima
degree of intactness
5(111)
4(□ )
3(目匡
ヨ)
2(□ )
Rhododendron boninense seemingly decreased
little by little with the long-term aridity of the
Islands (causal factor 1 ), human activity in the
past may have destroyed the habitat (causal
factor 3), unusual drought in 1980 killed some
individuals (causal factor 5), concentrated death
of pine trees by nematode infection in the early
1980s made the habitat more open and drier than
before (causal factor 6), taxing branches by someone had a negative impact on them (causal factor
l(Z互 2)
4), the typhoon in
1983 caused fatal damage on
them except one (causal factor 5), and a kind of
tick infested the last individual (causal factor 6).
Environmental fluctuations are natural pheAntjima
Chichuima
nomena. Even unusual climatic events (long drought, big typhoon) are involved with natural regeneration mechanisms of native species (Shimizu
L994). But once a species becomes endangered
(the number of individuals decreases so much and
the locality is confined to small area), these events
are sometimes fatal for them. Furthermore, repeated damage in a short interval deprives the
plants of a chance to recover. Recently unusual
climatic events seem to occur more frequently
than before. This seems to increase the possibility
of extinction of the Bonin species.
Monitoring
of the present situation of
en-
dangered species is indispensable for prevention
of extinction. We have mapped the location of
the Bonin endangered species. Especially, all
individuals of Melastoma tetramentm and Metro-
sideros boninensis were tagged
with plastic
number plates and the habits of each individual
were recorded (Nobushima 1993;
Shimizu,
unpubl. data). We will be able to know the
change when we check the habits of these individuals again in the future. But these were carried
out not as routine work of organizations but as
personal (volunteer) work. It is necessary to
locate monitoring work as formal activities of
concerned organizations.
As for the invasion of Bischofia javanica, Tokyo
Regional Forestry Office (1993) set two perma-
nent quadrats at Hahajima in 1993, and they are
going to monitor them once every 5 years.
6.
11. Evaluation of the nature (degree of
intactness) in Chichijima-retto. The larger the
degree is, the better the nature is.
From Shimizu et al. (1991).
Figure
Network with other Pacific Islands
Problems on endangered species are common to
many oceanic islands. It is useful to exchange
information among peoples who are engaged in
一-165-一
research, protection
and restoration of
the Bonins must be helpful for the Galapagos
Islands, too.
To begin with, we construct networks with the
Galapagos and the Hawaiian Islands, and then
spread them to other oceanic islands in the world.
To realize this we must establish an information
center in the Bonin Islands.
References
Asami, S. (1970) Climate and ocean (in Japanese) , The Nature in the Bonin Islands, p. 8790, Hirokawa-shoten, Tokyo.
Chiba, H. ( 1993) Note on the mass occurrence of
a kind of moth: Achaea serna in the Bonin
Islands (in Japanese), Bonin-HakubutsuTsushin No. 20:
1.
Cuddihy,L. W. & Stone, C. P. (1990) Alteration
of Native Hawaiian Vegetation-Effects of
Humans, their Activities and Introductions, 138
pp., University of Hawaii Press, Honolulu.
Culliney, J. L. (1988) Islands in a Far Sea-Nature
and Man in Hawaii, 410 pp., Sierra Club
Books, San Francisco.
Environmental Agency ( 1985) Report
on
sis on Chichi-jima, the Bonin Islands, Japan,
en-
dangered species in each islands. The Bonin
Islands is called "the Orient Galapagos" according to the characteristics of island history and
biological contents. The Bonins are so small that
the problems are more clear and severer than
other big islands. On the other hand, we have the
advantage that we can deal with the problems
rapidly and completely if we intend to. We have
many things to learn from the Galapagos Islands,
especially the way of coexistence of man and
nature (Itow 1994), and the experience we have in
the
Japanese Journal of Herpetology 12: 115-118.
Hirai, K. (1990) Orchids of the Bonin
Honma, S. (1992) Invitation to the nature of
Ogasawara (in Japanese), Field Guide-The
Nature of Ogasawara, p. l-17, Kokon-shoin,
Tokyo.
Ichikaw&, M. (1992) Present situation of vegetation and evaluation of feral goat's impact (in
Japanese), p. 5l-83, Report of the Urgent
Study to Evaluate Impact of Feral Goats on
Native Plants and Animals in the Bonin Islands, Japan Wildlife Research Center, Tokyo.
Ito, M. & Ono, M. ( 1990) Allozyme diversity and
the evolution of Crepidiastrum (Compositae)
on the Bonin (Ogasawara) Islands, Bot. Mag.
Tokyo 103: 449-459.
Ito, M., Soejima, A., Endo, C. & Ono, M. (1991)
Adaptive radiation of endemic plants in the
Bonin Islands-diversification from the view-
point of allozyme diversity data (in Japanese),
Ogasawara-Kenkyu-Nenpo No. 14: 15-20.
Itow, S. (1992) Eco-tourism in the Galapagos
National Park (in Japanese), National Park
No. 501: 8-13.
Iwatsuki, K. & Shimozono, F. (1989) Science to
Save Endangered Plants-A Trial to Propagate
Melastoma tetramerum in the Bonin Islands
(in Japanese), 155 pp. Kensei-sha, Tokyo.
Iwatsuki, K., Shimozono, H. & Hirai, K. (1990)
Research on the propagation of endangered
plants endemic to the Bonin Islands (in Japanese), p. 5-38, Report on the Studies of Greening, Tokyo Metropolitan Government, Tokyo.
Iwatsuki, K., Shimozono, H. & Hirai, K. ( 1993)
Propagation and restoration of endangered
plants in the Bonin Islands (in Japanese) , Ogasawara-Kenkyu-Nenpo No. 16: 78-95.
Urgent Study to Protect Endemic Plants in the
Bonin Islands (in Japanese), pp. 89, Tokyo-
Landscape-Kenkyusho, Tokyo.
Esaki,
K.
( 1993) Notes on the Acalolepta boninen-
srs Hayashi (Coleoptera, Cerambycidae) (in
Japanese), The Nature and Insects 28(5): 3842.
Funakoshi, M. (1992a) History of exploitation
and nature destruction (itr Japanese), Field
Guide-The Nature of Ogasawara, p. 38-45,
Kokon-shoin, Tokyo.
Funakoshi, M. (1992b) Natural preservation and
an airport proposal at Anijima, Ogasawara
(Bonin) Islands (in Japanese) , Ann. Environ.
Kai, C. (1994) Prevailing of infectious disease
in wildlife animals (in Japanese), Kagaku 64:
625-632.
Kaizuka, S. (1981) Macro-geographical location
and climate of the Bonin Islands (in Japanese),
p. 65-84, Report on the Assessment of the
Nature of Ogasawara (2) , Tokyo Metropolitan
University, Tokyo.
Kamijo, A. ( 1993) I caught an iguana in the
Orient Galapagos ! (itt Japanese), BoninHakubutsu-Tsushin No. 2O: 3.
H. (1981) Characteristics of land use
on Chichijima Island before World War II (in
Japanese), p. 155-162, Report on the Assess-
Katahira,
Sci., Shinshu Univ. 14: 101-119.
Islands-
Propagation of Calanthe hoshii (in Japanese),
Planta No. 8: 6l-67.
Hasegawa, M., Kusano, T. & Miyashita, K.
(1988) Range expansion ofr{nolis c. carolinen-
- 166-
ment of the Nature of Ogasawara (2), Tokyo
Metropolitan Government, TokYo.
Katahira, H. (1982) Characteristics of land use
on Hahajima Island before World War II (in
Japanese), p. l4L-144, Report on the Assessment of the Nature of Ogasawara (3), Tokyo
Metropolitan Government, TokYo.
Kato, M. ( 1992) Partnership between plants and
insect pollinators in Ogasawara Islands (in
Japanese with English summary), WWFJ Science Report 1(1): 51-61.
Kato, M. ( 1994) Formation and destruction of
partnerships between plants and other biota
(in Japanese), Kagaku 64: 633-640.
134, Kokon-shoin, TokYo.
Kurozumi, T. ( 1985) Unusual occurrence of Ophiusa coronata and Achaea serua in the Bonin
Islands (in Japanese) , Insects of Ryukyus No.
10: 142-146.
Lever, C. (1994) Naturalized Animals-The Ecology of Successfully Introduced Species, 354 pp.,
T & AD Poyser Ltd, London.
MacArthur, R. H. & Wilson, E. O. (1967)
Melville, R. (1979) Endangered island floras, p.
361-377, Plants and Islands, Academic Press,
London.
Mueller-Dombois, D. & Howarth, F. G. (1981)
Niche and life form integration in island com-
(
Kazaki, H. (1992) Present situation of rare plants
munities,
in Anijima (in Japanese), Ogasawara-Kenkyu'
Nenpo No. 15: 1l-19.
Kimura, M., Muto, N., Funakoshi, M., Sudo, S.
& Masuzawa, T. (1983) Dynamics of Leucaena leucocephala forest at Chichijima in the
Bonin Islands (it Japanese), Report on the
& WWFJ (1989) Japanese Red Data
Book of Plants (Present Situation of Important
Plant Species for Protection in Japan) (in Japa'
nese)
, 320 pp. NACS-J & WWFJ, Tokyo.
F. (1992) Report of some plants
from Hahajima (in Japanese), Bonin-
Nobushima,
a3Q-\:
Hakubutsu-Tsushin No. t5: 2-3.
Nobushima, F. (1993) Distribution and ecology
of an endemic Metrosideros (M. boninensis
Tuyama) in the Bonin Islands (in Japanese),
altitudinal transect analysis of windward vegetation on Haleakala, a Hawaiian island moun-
Ogasawara-Kenkyu-Nenpo No. t6: 37-77
.
Ogasawara-Tocho (1914) Outlines of the Forests
in the Bonin Islands (itt Japanese), 231 pp.,
Ogasawara-Tocho, Tokyo.
Okutomi, K., Iseki, T.,Hioki, Y., Kitayama, K. &
Sumihiro, H. (1983) Vegetation of the Ogasawara Islands (in Japanese) , p. 97-268, Endemic Species and Vegetation of the Bonin Islands,
Tokyo Metropolitan Government, Tokyo.
Ono, M. (I994a) Discovery of a new locality of
tain: (2) vegetation zonation, Phytocoenologia
24: 135-154.
Veget-
ations-Ansichten von Kustenlandern und Inseln
des Stillen Oceans: Aufgenommen in den
Jahren 1827, 1828 und 1929 auf der Entdeckungsreise der Kaiserlich-Russischen Corvette
Senjawin unter Capitain Lutke, 68 pp.*24
plates, Friedrich'sche Verlagsbuchhandlung,
an endangered species: Melastoma tetramerum
Siegen.
in Chichijima (itt
Kobayashi, S. ( 1980) A new orchid in the Bonin
Islands, Journ. Jap. Bot. 55: 303-305.
Kobayashi, S. & Ono, M. (1987) A revised list of
vascular plants indigenous and introduced to
the Bonin (Ogasawara) and the
Ecosystems-
Company, Stroudsburg.
9-10.
Kitayama, K. & Mueller-Dombois, D. (199a) An
Kittlitz, F. H. ( 1844) Vier und Zwanzig
337-364, Island
NACS-J
Kitayama, K. ( l99I) Threatened endemic species
of the Bonin (Ogasawara) Islands, Pacific Sci-
Information Bulletin
p.
Biological Organization in Selected Hawaiian
Communities, Hutchinson Ross Publishing
Study of the Grant-in-Aid of the Ministry of
Education, Science and Culture, 114 pp.
ence Association
The
Theory of Island Biogeography, 203 pp. Princeton University Press, Princeton.
1990) Dioecism of the genus
Kawakubo,
Callicarpa (Verbenaceae) in the Bonin (Ogasawara) Islands, Bot. Mag. Tokyo 103: 57-66.
N.
in the Bonin Islands, Field Guide-The
p. 132-
pests
Nature of Ogastwara (in Japanese),
Japanese), Ogasawara-
Kenkyu-Nenpo No. t7 : 74-76.
Ono,
M.
(1994b) Biotas
in Isolated
Galapagos and Ogasawarc
Islands-
(in Japanese),239
Volcano pp., Iwanami-shoten, Tokyo.
13: Ono, M. Kobayashi, S. & Kawakubo' N' (1986)
(Kazan) Islands, OgasawaraResearch No.
l-55.
Present situation of endangered plant species
in the Bonin (Ogasawara) Islands, Ogasawara
Koyano, S. (1992) Present situation of Giant
Research No. 12: l-32.
African snail (in Japanese), Subtropical AgriOno, M., Ito, M., Toyoda, T., Kobayashi, S. &
culture Center News No. 18.
Yasui, T. (1991) Present situation of vascular
Koyano, S. & Takeuchi, K. (1992) Agricultural
-
167
-
Island group in the Bonin (Ogasawara) Islands with reference to the ecology of Ardisia
dominant forest and the influence of feral
plants and endangered species endemic to the
Bonin Islands, p. l-12, Report of the Second
General Surttey on Natural Environment of the
Ogasawara (Bonin) Islands, Tokyo Metropolitan University, Tokyo.
Porter, D. M. (1984) Endemism and evolution in
terrestrial plants, p. 85-99, Galapagos, Pergamon Press.
Shimizu, Y. ( 1982) Influence of the drought in
1980 on the vegetation of Chichijima (in Japanese), p. 3l-37 , Report on the Assessment of the
Nature of Ogasawara (3), Tokyo Metropolitan
Government, Tokyo.
Shimizu, Y. (1986) Serious damage to Pinus lutchuensis by the attack of the pine wood nematode at Chichijima in the Bonin (Ogasawara)
Islands, Journal of the Faculty of Letters, Komazawa University 44: 169-178.
Shimizu, Y. ( 1987a) Process and distribution of
concentrated death of pine trees at Chichijima
in the Bonin Islands (in Japanese), p.201-203,
Ecological Studies in the Environmental Effects
of Insecticides on the Pine Forest Ecosystem,
goats (in Japanese) , Komazawa Geography. 29:
9-5 8.
Shimizu, Y. (1994a) Regeneration of mesic forest
at Sekimon, Hahajima in the Bonin (Ogasawara) Islands with reference to disturbance of
the forest by the Typhoon No. 17 (1983) (in
Japanese), Regional Views No. 7: 3-32.
Shimizu, Y. ( 1994b) Vegetation of small islands
in Hahajima Island Group, the Bonin (Ogasawara) Islands, with reference to the distribution, composition, structure of dry forest (in
Japanese), Komazawa Geography No. 30: l768.
Shimizu,
12: 195-207.
Shimizu, Y. & Tabata,
lease and speciation, Pactfic Science
Shimizu,
4z 67-86.
Shimizu, Y. & Yasui, T. (1992) Flora of Anijima
and distribution of rare plant species (in Japanese with English summary), WWFJ Science
zawa Geography 23: 33-60.
Report 1( 1) : 107-122.
& Iwatsuki,
Shimozono, F.
Stone, C. P. ( 1985) Alien animals in Hawaii's
native ecosystems: Toward controlling the adverse effects of introduced vertebrates, p. 251297 , Hawaii's Terrestrial Ecosystems Preserl,ation and Management, Cooperative National
Park Resources Studies Unit and University of
Hawaii, Honolulu.
Tokyo Regional Forestry Office (I97 5) Vegetation
Tokyo.
Shimizu, Y. (1990) Endangered plant species on
the Bonin Islands (in Japanese), Heredity 44
( 10): 5-6.
Shimizu, Y. (1991) Vegetation of Anijima Is. in
the Bonin (Ogasawara) Islands-Distribution,
composition, structure of dry forest (in Japanese) , Komazawa Geography No. 27: 77-130.
Shimizu, Y. (1992) Origin of Distylium dry forest
and occurrence of endangered species in the
Bonin Islands, Pacific Science 46: 179-196.
of National Forests and Reserve Forests in the
Bonin Islands (in Japanese), 73 pp., Tokyo
Regional Forestry Office, Tokyo.
Tokyo Regional Forestry Office Q99aa) Report
on the Study for Protection and Management of
Calanthe hatorif (in Japanese), 135 pp., Tokyo
Regional Forestry Office, Tokyo.
Tokyo Regional Forestry Office (1994b) Report
Mukojima
-
K. (1986) Botanical
gardens and the conservation of an endangered
species in the Bonin Islands, AMBIO 15: 1921.
species (Bischofia javanica) (in Japanese) , Regional Views No. 1: 3l-46.
-Shimizu, Y. (1989) Ecological characteristics of
forest vegetation on oceanic islands, Ogasawara (in Japanese), p. 159-203, Vegetation of
Japan: Okinawa & Ogasawara, Shibundo,
of
45:28-49.
Y., Tomiyama, K., Yasui, T., Funa-
nature of Chichijima-retto in the Ogasawara
(Bonin) Islands (in Japanese), Regional Views
Shimizu, Y. ( 1988) Vegetation of Mt. Kuwanoki
in the Bonin (Ogasawara) Islands with reference to the invasion of an introduced tree
1993) Vegetation
a
koshi, M., Ito, M., Kawakubo, N. & Honma,
S. (1991) Evaluation of human impacts on the
in the Bonin
(Ogasawara) Islands with special reference to
forest floor vegetation (in Japanese), Koma-
(
Forest struc-
Pacific Island, with reference to ecologieal re-
tode infection at Chichijima
Y.
H. (1991)
tures, composition, and distribution on
particularly the Change of the Pine Forest Ecosystem Caused by the Pine Wood Disease,
Nature Conservation Society of Japan, Tokyo.
Shimizu, Y. (1987b) Changes in species composition and structure of Pinus lutchuensis-Schima
mertensiana forest after the pine wood nema-
Shimizu,
Y. & Tabata, H. ( 1985) Invasion of
Pinus lutchuensis and its influence on the
native forest on a Pacific island, .,I. Biogeogr.
168
-
on the Study to Prevent an Alien Plant (Bischofia javanica) from Invading Native Forests (itt
Japanese), 153 pp., Tokyo Regional Forestry
Office, Tokyo.
Tomiyama, K. ( 1988) Giant African snail (Ach-
atina fulica) in the Bonin Islands (itt Japanese) , Ogasawara-Kenkyu-Nenpo No. lt:2-16.
Tomiyaffi&, K. (1994) Factors affecting the extinction of land snails on the Ogasawara Islands (in Japanese) , Venus 53: 152-156.
Toyoda,
T. (1931) Flora of Bonin .Is. (in
Japa-
nese), 380+ 16 pp., Aboc-sha, Kamakura.
Toyoda,T. ( 1984) To realize conservation of endemic plants in the Bonin Islands (itt Japa'
nese) , Ogasawara-Kenkyu-Nenpo No. 7: 42-45.
Toyoda, T., Shimizu, Y.& Yasui, T. (1994) Vegetation recovery of 25 years after the extermination of feral goats at Minamijima in the Bonin
(Ogasawara) Islands (in Japanese) , Ogasawa'
ra-Kenkyu-Nenpo No. 17: I-24.
Toyoshima, K. ( 1938) Vegetation and useful tropical plants in the Bonin Islands (in Japanese),
Bull. Forestry Forest Producls Res. Inst. 36: 1-
25r.
Tsuned&,
K. (1992)
population, p. 3I-49, Report of the Urgent
Study to Evaluate Impact of Feral Goats on
Native Plants and Animals in the Bonin Islands
(in Japanese), Japan Wildlife Research
Center, Tokyo.
T. (1970) Plants of Ogasawara (in Japanese), p. 109-141, Nature in the Bonin /slands, Hirokawa-shoten, TokYo.
Yamazaki, T.(1981) Floristic position of the flora
of the Bonin Islands (in Japanese), p. 303-308,
Flora of Bonin Is., Aboc-sha, Kamakura.
Yasui, T. (1992a) Discovery of a new individual
of Pittosporum parntfolium (in Japanese) , Bonin-Hakubutsu-Tsushin No. 1 1: 1-3.
Yasui, T. (1992b) Recovery of Angiopteris lygod-
Tuyam&,
iitolia after the shooting of feral goats (in
Japanese), Bonin-Hakubutsu-Tsushin
No. 16:
t.
Yasui, T. (1993) Notes on the habitat and popu-
lation of Melastoma tetramerum newly
covered
at
Chichijima
(in
dis-
Japanese), un-
published manuscript.
Yasui, T. ( 1994) Lobelia boninensr in Chichijima
(in Japanese), Bonin-Hakubutsu-Tsushin 25: 2.
Present situation of feral goat
- 169-

Endangered Plant Species in the Bonin (Ogasawara) Islands

Transcription

Similar documents

Tiki Wiki - Miss Maggie Sings!

Presentation

by rinsing and using mortars and pestles for grinding the

September 2010 - 1000 Islands Environmental Center

Sea Of Green - A Visit To The Aeolian Islands

Thousand Islands Secondary School

anthias ventralis

Promote exchanges in the arts and culture based on city diplomacy

SUSTAINABLE PACIFIC GROVE APRIL MEETING

You Can Help These Animals