Amaranthus brownii
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| Amaranthus brownii Christoph. & Caum |
Amaranthus brownii is a species of plant in the Amaranthaceae family. It is one of nine species of Amaranthus in Hawaii,[a] but the only native species of the genus in the Hawaiian archipelago. Research scientists from the Tanager Expedition discovered the plant in 1923 while exploring Nihoa, a small island in the Northwestern Hawaiian Islands. This unique plant is endemic to the island of Nihoa and is found nowhere else. The plant shares the island with 12 other endemic plants, two of which—Pritchardia remota and Schiedea verticillata—can only be found on Nihoa like itself. Amaranthus brownii is considered the rarest plant on the island of Nihoa, and has not been observed in situ since 1983.[1]
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[edit] Description
A. brownii is an herbaceous annual plant that grows from 30 to 90 centimeters (1 to 3 feet) in height and has narrow leaves, small, green flowers, and fruit that holds a single, dark red seed. A. brownii is monoecious and the male and female flowers are found together on the same plant.[1] There are nine recorded species of Hawaiian Amaranthus, but A. brownii is the only native species in the islands.[2] A. brownii differs from other Hawaiian species of Amaranthus with its spineless leaf axils, linear leaves, and indehiscent fruits—fruit which does not open to release seeds when ripe.[1]
[edit] Distribution
The plant has a very limited range, as it is endemic to and only found on Nihoa. Nihoa is part of the Hawaiian Islands National Wildlife Refuge and is managed by the United States Fish and Wildlife Service.[3]
A. brownii was first collected on Nihoa by botanist Edward L. Caum[4] during a ten-day visit by the Tanager Expedition beginning on June 10, 1923. Scientists conducting research on the island observed the plant growing in great quantity on the ridges towards Miller's Peak and on eastern ridges of the island. But by 1983, only two populations of 35 plants were thought to exist on the island: 23 plants were found near Miller's Peak and 12 plants in Middle Valley.[3] The two plant populations are separated by a distance of approximately 0.4 km (0.25 mi).[3]
[edit] Habitat
A. brownii grows during the moist, winter season from December through July. It can be found in shallow soil on rocky outcrops in exposed areas between 120 and 215 m (390 and 700 ft).[1] At least ten other native plant species can be found in its habitat,[b] including 'aheahea, kakonakona, kupala, and a non-native amaranth species.[3]
Major threats are invasive species, fire, and possible hybridization with other Amaranthus species.[3] Inbreeding is a serious threat, as the small plant population is forced to reproduce within its own circle resulting in genetic defects.[2] More recently, the invasive Schistocerca nitens, a nonnative grasshopper, has presented an even larger threat to A. brownii. Although present on the island since the early 1980s, S. nitens has increased its population density, resulting in massive defoliation of Nihoa's vegetation, leaving A. brownii at greater risk of predation.[5] It is also forced to compete with non-native Portulaca oleracea (pigweed), the plant's main alien species threat.[1]
[edit] Conservation
A. brownii shares the island with 27 vascular plant species, 21 of which are native and 12 endemic. The plant is one of three endemic and endangered species only found on Nihoa, along with Pritchardia remota and Schiedea verticillata. A. brownii was federally listed as an endangered species in 1996,[4] and internationally classified as critically endangered on the IUCN Red List in 2003.[6] On May 22, 2003, 171 acres (69 hectares) on the island of Nihoa were designated by the United States Fish and Wildlife Service as a critical habitat for A. brownii, as well as Pritchardia remota, Schiedea verticillata, and two other species found on Nihoa and other Hawaiian islands, Sesbania tomentosa (ʻohai) and Mariscus pennatiformis.[1]
Wildlife refuge staff visited Nihoa during the dry season at least 21 times between 1983-1996.[5] In more than a decade of field surveys, no living plants were identified. Because winter surveys of Nihoa tend to be difficult and dangerous due to poor landing conditions,[1] surveys were not conducted during the moist, winter growing season from December through March when the plant is easiest to find.[2] Most of the surveys have been completed during the summer months, when the stems of A. brownii dry up and cannot be distinguished from other herbaceous plants.[5] As a result, additional winter surveys of A. brownii on Nihoa are required to accurately assess its current conservation status.[2] A recent seven day visit to the island in April of 2006 still did not find any specimens. Nevertheless, as of 2007, botanists are optimistic that the species has survived.[5] Ex-situ conservation efforts to propagate A. brownii by seed in botanical gardens have been unsuccessful.[2]
[edit] Nomenclature
The species was named in 1931 by botanists Erling Christophersen and Edward Leonard Caum after the botanist Forest Brown (F.B.H. Brown).[4] The plant is sometimes referred to as Brown's Amaranth, Brown's Pigweed, or Browns Amaranth, although it is unclear which, if any, common name is in use.
[edit] Notes
a. ^ Eight of the nine species of Amaranthus recorded in Hawaii are: A. brownii; A. dubius (spleen amaranth); A. graecizans; A. hybridus subsp. hybridus (green amaranth); A. lividus subsp. polygonoides; A. retroflexus; A. spinosus (spiny amaranth); and A. viridis (slender amaranth).
b. ^ Native plants found in and around the habitat of A. brownii include: Chenopodium oahuense (Hawaiian Goosefoot), Eragrostis variablis, Ipomoea indica, Ipomoea pes-caprae ssp. brasiliensis, Panicum torridum, Scaevola sericea, Schiedea verticillata (Nihoa Carnation), Sicyos pachycarpus, Sida fallax, and Solanum nelsonii (Nelson's Horsenettle).[1]
[edit] References
- ^ a b c d e f g h United States Fish and Wildlife Service 2003, pp. 28054–28075
- ^ a b c d e Evenhuis & Eldredge 2004, pp. 55-57
- ^ a b c d e Hawai'i Department of Land and Natural Resources 2005
- ^ a b c Bruegmann & Ellshoff 1996, pp. 43178-43184
- ^ a b c d Pacific Islands Fish and Wildlife Service 2007
- ^ Bruegmann & Caraway 2003
[edit] Bibliography
- Bruegmann, M.M.; Caraway, V. (2003). Amaranthus brownii. 2007 IUCN Red List of Threatened Species. International Union for Conservation of Nature and Natural Resources. Retrieved on 2008-04-03.
- Christophersen, E.; Caum, E.L. (1931). Vascular plants of the Leeward Islands, Hawaii, Bernice P. Bishop Museum Bulletin; No. 81; Tanager Expedition publication; No. 7. Honolulu, Hawaii: Bishop Museum Press.
- Conant, Sheila (1985). "Recent observations on the plants of Nihoa Island, Northwestern Hawaiian Islands". Pacific Science 39: 135–149. University of Hawaii Press.
- Evenhuis, Neal L. (ed.); Eldredge, Lucius G. (ed.) (2004). Natural History of Nihoa and Necker Islands, Bishop Museum Bulletin in Cultural and Environmental Studies; No. 1. Honolulu, Hawaii: Bishop Museum Press. ISBN 1-58178-029-X.
- Amaranthus brownii fact sheet (PDF). Hawaii's Comprehensive Wildlife Conservation Strategy. Hawai'i Department of Land and Natural Resources (October 1, 2005). Retrieved on 2008-03-31.
- Pacific Islands Fish and Wildlife Service (2007). "Amaranthus brownii (No common name); 5-Year Review; Summary and Evaluation" (PDF). . United States Fish and Wildlife Service Retrieved on 2008-04-04.
- United States Fish and Wildlife Service (May 22, 2003). "Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for Five Plant Species From the Northwestern Hawawiian Islands, Hawai" (PDF). Federal Register 68 (99): 28054–28075. United States Government Printing Office.
- Bruegmann, M. M.; Z. E. Ellshoff (1996). "Endangered and Threatened Wildlife and Plants; Determination of Endangered Status for Three Plants from the Island of Nihoa, Hawaii". Federal Register 61 (163): 43178–43184. United States Government Printing Office.
- Wagner,, W.L.; Herbst, D.R.; Sohmer, S.H. (1999). Manual of the flowering plants of Hawai'i, Revised, Honolulu, Hawaii: University of Hawaii Press. ISBN 0824821661.
