Plants
of Concern in American Samoa
Art Whistler (2005)
Purpose
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PURPOSE
There are currently no federally listed "threatened or endangered" plant
species in American Samoa. This does not mean no plants are threatened or endangered
in the Territory, it simply means that none have been put through the laborious
listing process. Indeed, there are a number of plant species among the approximately
343 native plant species recorded in the Territory so far whose existence there,
or even in the world as a whole, is precarious. A previous study of the plants
rare in American Samoa was prepared several years ago (Whistler 1998), but since
that time virtually no work has been done on these species or on the preparation
of any listing of threatened or endangered plant species for the Territory.
The
purpose of the following study, entitled "Plants of Concern in American Samoa,"
is to determine which plant species may in the future need some kind of protection
in the Territory. It is intended to be a follow-up to the 1998 work, primarily
to enter the records (i.e., collection data) of the plants considered to be "of
concern" in the Territory of American Samoa into a GIS data base, and map
these collection records. Because of field work done in the last five years (only
a small portion of which was done for this survey), the list of "Plants of
Concern," as they are referred to here, has been updated to reflect changes
of status of the species (e.g., new rare species being found, other species determined
not to be as rare as previously thought). From the 109 Plants of Concern included
on this list (Appendix A), 21 (Table 4) have been recommended for the next step,
the listing process to determine if these plants meet criteria that would allow
them to become federally listed threatened or endangered plant species.
INTRODUCTION
American
Samoa
Samoa is a volcanic archipelago running in a north-northwest direction
east of Fiji, north of Tonga, and east of the Cook Islands and Tahiti. It is divided
politically into Samoa (referred to here as "independent Samoa" to avoid
confusion with the term Samoa, which refers to the geographical entity, the archipelago),
which is an independent country, and American Samoa, which is an unincorporated
territory of the United States. The archipelago, lying at a longitude of 168-173°
W and a latitude of 11-15° S, comprises nine inhabited volcanic islands, plus
Swains Island and uninhabited Rose Atoll, with a total area of just over 3100
km2. The main islands of independent Samoa, which comprise the western portion
of the archipelago, are Savai'i (1820 km2 area, 1860 m elevation) and 'Upolu (1110
km2, 1100 m). These two islands represent about 94% of the total area of the island
chain.
American Samoa, which comprises the eastern end of the archipelago,
consists of five volcanic islands (Tutuila, 'Aunu'u, Ofu, Olosega, and Ta'u) and
two atolls (Rose and Swains). Tutuila is the westernmost and by far the largest
of the islands of American Samoa. It has an area of approximately 142 km2 (55
mi2) and a maximum elevation of 653 m (2140 ft) at the summit of Matafao. Lying
off its southeastern end is the small tuff cone island of 'Aunu'u that has an
area of less than 2 km2 (ca. 0.6 mi2). Approximately 100 km (62 miles) to the
east lie the three islands, Ofu, Olosega, and Ta'u, that comprise the group known
as Manu'a. Ta'u, which is the easternmost of the volcanic islands, has an area
of 39 km2 (15 mi2), and a maximum elevation of ca. 960 m (3150 ft) at the summit
of Mt. Lata. The much smaller islands of Ofu and Olosega, with areas of 5 km2
(2 mi2) and 4 km2 (1.6 mi2) and elevations of 495 m (1625 ft) and 640 m (2100
ft), respectively, lie together within a common reef about 10 km (6 miles) to
the west of Ta'u. East of Manu'a about 140 km (84 mi) lies uninhabited Rose Atoll,
and 320 km (192 mi) north lies Swains Island, which is home to a small population.
The current population of American Samoa is over 60,000.
Previous Botanical Work
The first collection of the flora of American Samoa
was made during the ill-fated La Pérouse expedition that landed on the
north coast of Tutuila in 1787, but the specimens were later lost when the ships,
along with everyone on board, subsequently disappeared in Melanesia. A second
collection was made in 1838 by another French expedition, this one under the command
of Dumont D'Urville, but little is known about the specimens, which are deposited
in the Paris Museum. The first significant collections were made in 1839 during
the visit of the United States Exploring Expedition (USEE) to Samoa. Unfortunately,
the specimens were poorly curated, and mistakes in locality are not uncommon.
In fact, some specimens of endemic Samoan plant species were incorrectly labeled
as having been collected in Tahiti. Even the correctly labeled USEE specimens
cite only "Samoa" as the locality, so it is not certain on which islands
of the archipelago they were collected-although there is some indication from
the published list of specimens of Pickering (1876) and the work of Gray (1854).
The next plant collector to visit Tutuila was apparently the Rev. T. Powell, an
amateur English botanist employed as a missionary by the London Missionary Society
in ca. 1850-1885. Unfortunately, most of his specimens also lack localities, so
it is impossible to determine which ones were collected on Tutuila and Manu'a
and which ones on the other islands (he is known to have collected on Savai'i
and 'Upolu as well). The only relevant publication by Powell was a list of Samoan
plant names (Powell 1868). Another amateur botanist, Dr. E. Graeffe, a Swiss physician
who traveled extensively in the region in the 1860s and 1870s, is known to have
collected specimens in American Samoa (Tutuila) at about the same time. Unfortunately,
many of his specimens, like those of the earlier collectors, lack specific localities
and some are apparently mislabeled (i.e., some specimens apparently collected
in Fiji are labeled as coming from Samoa).
The last botanist in the 19th
century to work in Samoa was F. Reinecke, who wrote the first flora of Samoa (1896,
1898). Unfortunately, a number of Reinecke's specimens cited from American Samoa
may be incorrectly labeled, since he collected some species that no one else has
collected there (but which are found in independent Samoa). Several other collectors
visited Tutuila before 1920, but their contributions to the flora of American
Samoa are minor. The best known of these was K. Rechinger, who visited a decade
after Reinecke (in 1905) and collected a few specimens on Tutuila, but the bulk
of his collections were made in independent Samoa. He published his information
several years later (Rechinger 1907-1915). Another botanist visited American Samoa
in 1905, C. Lloyd, but the report on his work (Lloyd and Aiken 1934) does not
cite any specimen numbers and it is not clear how much of the work applies to
American Samoa rather than independent Samoa.
The first major collector in
American Samoa since the USEE was W. A. Setchell, who visited Tutuila in 1920
and published a flora of the island (Setchell 1924). His collection includes about
580 numbers, which makes it larger than the one collected in the whole archipelago
during the USEE. He was soon followed by D. W. Garber, who collected about 578
numbers on Tutuila and in Manu'a between 1921 and 1925. Garber never published
any of this Samoan work, but most of his collections were listed by Christophersen
(1935, 1938) and/or Yuncker (1945). Other minor collections in American Samoa
from that decade were those made by Eames in 1921 with about 30 specimens, Bryan
in 1924 with about 68, and Diefenderfer in 1929 and 1930 with about 48. These
minor collections were included in Christophersen's publications.
The
next major collection in American Samoa after the one of Setchell was made by
E. Christophersen in 1929 and 1931 (about 407 specimens from Tutuila), and were
included in his two publications on the flora of Samoa, which still form the most
complete published account of the flora of the archipelago. Later collections
were made by W. and A. Harris (with about 350 specimens from Manu'a, mostly weeds)
in 1938 and T. Yuncker (with about 444 specimens from Tutuila and Manu'a) in 1939.
Both of these collections (except for Yuncker's Tutuila specimens) were listed
by Yuncker (1945) in his flora of Manu'a. Other minor collections from Ta'u were
made by Judd, McMullin, Swezey, and Schultz, but only a few specimens are known
from each.
More recent collections have been made on Tutuila, including
those of A. Wisner in 1955 (about 163 specimens, only 2/3 of which have been accounted
for), C. Lamoureux (about 80 specimens) in 1965, and C. Long (about 200 specimens)
also in 1965. The original botanist on the study of American Samoa by Amerson
et al. (1982), J. Kuruc, collected a number of specimens from American Samoa in
1975, but most of his collections were lost or are without any data. Another collection
of undetermined size was made by P. Cox from Manu'a in 1987, but no record of
these has been published other than those in the genus Meryta (Cox 1985). The
largest collection from American Samoa, with nearly 2050 numbers, was made by
the present author from 1972 to 2003. Little of this work has heretofore been
published other than in revisions of two genera (Whistler 1986, 1988a). Additionally,
specimen numbers with little collection data are included in two National Park
studies of American Samoa (Whistler 1992b, 1994).
The
Flora
The angiosperm flora of the Samoan archipelago is about one third
as large as that of Fiji, which lies just 1140 km (700 mi) to the west, but it
is larger than that of any other tropical Polynesian archipelago or island except
Hawai'i, which has more species but fewer genera. The flora is estimated to comprise
about 540 native species of flowering plants (Whistler 1992a), two thirds of them
dicots. These are included in about 283 genera in 95 plant families. The level
of endemism of the angiosperms is estimated to be about 30% at the species level,
but only one genus, Sarcopygme of the Rubiaceae family, is endemic to the archipelago.
An additional 250 or so species are naturalized or adventive (Whistler 1988b).
The fern flora is estimated to comprise 230 species, with a much lower rate of
endemism. The only comprehensive publication on the ferns of Samoa was done by
Christensen (1943), who never himself collected in Samoa.
The most extensive
work on the flora, until recently, was done by Christophersen, who collected in
Samoa in 1929 and 1931, but his work (Christophersen 1935, 1938) is not an actual
flora since it lacks taxonomic keys, descriptions, and specimen citations other
than those of his own collections. Some of the knowledge of the flora has been
filled in by more recent monographs and revisions of Pacific genera and families.
The three largest genera, Psychotria, Syzygium, and Cyrtandra, have recently been
revised for Samoa (Whistler 1986; Whistler 1988a; Gillett 1973, respectively).
Many other genera and families in Samoa have also been revised, including Araliaceae
(Smith & Stone 1968), Ascarina (Smith 1976), Clusiaceae (Smith & Darwin
1974), Cunoniaceae (Smith 1952c; Bernardi 1964; Hoogland 1979), Diospyros (Smith
1971b), Elaeocarpus (Smith 1953), Geniostoma (Smith & Stone 1962; Conn 1980),
Macropiper (Smith 1975), Meliaceae (Smith 1952b), Metrosideros (Smith 1973b),
Myrsinaceae (Smith 1973a), Orchidaceae (Cribb & Whistler 1996), Rutaceae (Smith
1952a), and Terminalia (Smith 1971a). However, many of these revisions are now
out-of-date because of more recent collections, and since they are widely scattered
through the literature, most are relatively inaccessible, except for those included
in Smith's flora of Fiji (1979-1996).
The native vascular flora of American
Samoa, based upon Whistler 1980, 1992b, 1994, 1998, and the present work, is now
estimated to be about 343 flowering plants, 135 ferns, and 9 fern allies. These
are listed in Appendix A of the Whistler 1998 report, except for a few additions
collected since then. The largest flowering plant families represented in the
flora are Orchidaceae (65 native species), Rubiaceae (19), Fabaceae (18), Cyperaceae
(17), Poaceae (15), Euphorbiaceae (12), and Urticaceae (10). As noted earlier,
the rate of endemism in Samoa is about 30%, but the local endemism for American
Samoa is only about 1%, i.e., only about 1% (seven or eight species) of the flora
of American Samoa is endemic to the Territory (see Table 1). Another 200 or so
species of vascular plants (all angiosperms) have been introduced and naturalized
in American Samoa. Some of these were brought in by Polynesians ("Polynesian
introductions") prior to the European Era, but most were brought in during
recent times ("modern introductions") after about 1830. Some of these
were "intentional introductions" brought in with a purpose in mind (e.g.,
food plants, like breadfruit and taro), while others were "unintentional
introductions" that were inadvertently brought in stuck to the clothing or
livestock of the Polynesian voyagers (and which have since become "weeds").
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