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Plants of Concern in American Samoa
Art Whistler (2005)

Purpose | Introduction | Previous Botanical Work | The Flora | References | Search Checklist

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.

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").