Amaranthus brownii

Taxobox
name = "Amaranthus brownii"


image_caption =
image_width = 250px
status = CR
status_system = iucn2.3
regnum = Plantae
divisio = Magnoliophyta
classis = Magnoliopsida
ordo = Caryophyllales
familia = Amaranthaceae
genus = "Amaranthus"
species = "A. brownii"
binomial = "Amaranthus brownii"
binomial_authority = Christoph. & Caum

"Amaranthus brownii", also known as Brown's amaranth, or more commonly pigweed, is an annual herb in the Amaranthaceae family. It is one of nine species of "Amaranthus" in Hawaii,Ref_label|A|a|none but the only endemic Hawian species of the genus. Botanists from the Tanager Expedition first collected 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 Nihoa, and has not been observed "in situ" since 1983.

Morphology

"A. brownii" is an herbaceous annual plant that grows from 30-90 cm (1-3 ft) in height and has narrow, linear 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. There are nine recorded species of Hawaiian Amaranthus, but "A. brownii" is the only native species in the islands. "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) that are ovoid and between 0.8-1 mm long and 0.6-0.8 mm wide.

Distribution and habitat

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 in the Papahānaumokuākea Marine National Monument and is managed by the United States Fish and Wildlife Service.

"A. brownii" was first collected on Nihoa by botanist Edward Leonard Caum on 17 June 1923, [Nihoa: fl, fr, June 17 1923, E. L. Caum No. 73. Type, B. P. Biship Mus.] during a ten-day visit by the Tanager Expedition. [The visit began on 10 June 1923.] Botanists observed the plant growing in great quantity on the ridges towards Miller Peak and on eastern ridges of the island. [ Another specimen was collected by C. S. Judd: Nihoa: fl, fr, June 20, 1923, C. S. Judd No. 2] Expeditions in the early and mid-1960s failed to identify any specimens, but in 1969, ethnobotanist Douglas E. Yen of the Bishop Museum Project collected specimens near Miller Peak. Sheila Conant found "A. brownii" growing on the island in 1981 and 1983, by which time only two populations of 35 plants were thought to exist:cite journal
last = Conant
first = Sheila
title = Recent observations on the plants of Nihoa Island, Northwestern Hawaiian Islands
journal = Pacific Science
volume = 39
issue = 2
pages = 135–149
publisher = University of Hawaii Press
date = 1985
url = https://scholarspace.manoa.hawaii.edu/bitstream/10125/921/1/v39n2-135-149.pdf
format = PDF
accessdate = 2008-07-22] 23 plants were found near Miller Peak and 12 plants in Middle Valley. The two plant populations are separated by a distance of approximately 0.4 km (0.25 mi).

"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). At least ten other native plant species can be found in its habitat,Ref_label|B|b|none including 'aheahea, kakonakona, kupala, and a non-native amaranth species.

Major threats are invasive species, fire, and possible hybridization with other "Amaranthus" species.cite web
title = Amaranthus brownii fact sheet
work = Hawaii's Comprehensive Wildlife Conservation Strategy
publisher = Hawai'i Department of Land and Natural Resources
date = October 1, 2005
url = http://www.state.hi.us/dlnr/dofaw/cwcs/files/Flora%20fact%20sheets/Ama_bro%20plant%20NTBG_OK.pdf
format = PDF
doi =
accessdate = 2008-03-31 ] Inbreeding is a serious threat, as the small plant population is forced to reproduce within its own circle resulting in genetic defects. In 2002 and 2004, the invasive "Schistocerca nitens", a nonnative grasshopper, presented an even larger threat to "A. brownii". Although it was first recorded on the island in 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. "A. brownii" is also forced to compete with non-native "Portulaca oleracea" (pigweed), the plant's main alien species threat.

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".cite web
author = Pacific Islands Fish and Wildlife Office
title = Recovery Plan for Three Plant Species on Nihoa Island
work = Endangered Species in the Pacific Islands
publisher = United States Fish and Wildlife Service
date = 2008
url = http://www.fws.gov/pacificislands/flora/nihoaplants.html
accessdate = 2008-09-05] "A. brownii" was federally listed as an endangered species in 1996,cite journal
last = Bruegmann
first = M. M.
coauthors = Z. E. Ellshoff
title = Endangered and Threatened Wildlife and Plants; Determination of Endangered Status for Three Plants from the Island of Nihoa, Hawaii
journal = Federal Register
volume = 61
issue = 163
pages = 43178–43184
publisher = United States Government Printing Office
date = 1996
url = http://www.fws.gov/Endangered/pdfs/FR/f960821.pdf
format =
accessdate = 2008-04-12] and internationally classified as critically endangered on the IUCN Red List in 2003.cite web
last = Bruegmann
first = M.M.
coauthors = Caraway, V.
title = "Amaranthus brownii"
work = 2007 IUCN Red List of Threatened Species
publisher = International Union for Conservation of Nature and Natural Resources
date = 2003
url = http://www.iucnredlist.org/search/details.php/44077/summ2007
accessdate = 2008-04-03] 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" ("okinaohai") and "Mariscus pennatiformis".cite journal
author = United States Fish and Wildlife Service
title = Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for Five Plant Species From the Northwestern Hawawiian Islands, Hawai
journal = Federal Register
volume = 68
issue = 99
pages = 28054–28075
publisher = United States Government Printing Office
date = May 22, 2003
url = http://www.fws.gov/pacificislands/CHRules/nwhifinal.pdf
format = PDF
accessdate = 2008-03-31]

[
cite book
last = Wagner
first = W.L.
coauthors = Herbst, D.R.; Sohmer, S.H.
title = Manual of the flowering plants of Hawai'i
publisher = University of Hawaii Press
volume = I
pages = 185-189
edition = Revised
date = 1999
location = Honolulu, Hawaii
isbn = 0824821661] ] Wildlife refuge staff visited Nihoa during the dry season at least 21 times between 1983-1996.cite paper
author = Pacific Islands Fish and Wildlife Office
authorlink =
coauthors =
title = "Amaranthus brownii" (No common name); 5-Year Review; Summary and Evaluation
version =
publisher = United States Fish and Wildlife Service
date = 2007
url = http://www.fws.gov/pacific/ecoservices/endangered/recovery/Documents/Amaranthusbrownii.pdf
format = PDF
accessdate = 2008-04-04 ] 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, surveys were not conducted during the moist, winter growing season from December through March when the plant is easiest to find. 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. As a result, additional winter surveys of "A. brownii" on Nihoa are required to accurately assess its current conservation status. 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.

Ex-situ conservation efforts to propagate "A. brownii" by seed in botanical gardens have been unsuccessful.cite book
last = Evenhuis
first = Neal L. (ed.)
coauthors = Eldredge, Lucius G. (ed.)
title = Natural History of Nihoa and Necker Islands
publisher = Bishop Museum Press
series = Bishop Museum Bulletin in Cultural and Environmental Studies; No. 1
date = 2004
location = Honolulu, Hawaii
isbn = 1-58178-029-X] During the 1981 expedition, "A. bronwii" seeds were collected by Sheila Conant and presented to the Waimea Arboretum on the Hawaiian island of Oahu and the Kew Gardens in London, England. Although the seeds at the Waimea Arboretum germinated and grew for a while, no plants survived beyond the stage of seedling development. Information about the outcome of the seeds sent to Kew Gardens is unavailable.

Nomenclature

The species was named in 1931 by botanists Erling Christophersen and Edward Leonard Caum after the botanist Forest Brown (F.B.H. Brown). The plant is sometimes referred to as Brown's Amaranth,cite web
title = PLANTS Profile: "Amaranthus brownii" Christoph. & Caum (Brown's amaranth)
work = USDA PLANTS Database
publisher = Natural Resources Conservation Service
url = http://plants.usda.gov/java/profile?symbol=AMBR5
accessdate = 2008-08-24] Brown's Pigweed,cite web
title = Threatened and Endangered Plant Species Found on the National Wildlife Refuge System
work = America's National Wildlife Refuge System
publisher = United States Fish and Wildlife Service
url = http://www.fws.gov/refuges/habitats/EndSpPlants.html
accessdate = 2008-08-24] or Browns Amaranth.cite web
title = Amaranthus brownii (Brown's Amaranth, Brown's Pigweed, Browns Amaranth)
publisher = ZipcodeZoo
url = http://zz4k.com/Plants/A/Amaranthus_brownii/default.asp
accessdate = 2008-08-24]

ee also

*List of species of the Northwestern Hawaiian Islands

Notes

a. Note_label|A|a|none Wagner and Herbst list five naturalized species of "Amaranthus" in Hawaii in addition to the endemic "A. brownii". The authors note that the information may be both inaccurate and incomplete due to errors caused by a lost collection and lack of data. "A. graecizans", "A. retroflexus", and a third unknown species (possibly extinct or reclassified) have been proposed as additional naturalized candidates.

b. Note_label|B|b|none 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).

References

Further reading

*cite book
last = Carr
first = Gerald D.
authorlink =
coauthors =
chapter = Chromosome evolution and speciation in Hawaiian flowering plants
editor = Tod F. Stuessy, Mikio Ono
title = Evolution and Speciation of Island Plants
publisher = Cambridge University Press
date = 1998
location =
pages =
url = http://www.cambridge.org/catalogue/catalogue.asp?isbn=0521496535
isbn = 0521496535
*cite book
last = Christophersen
first = Erling
coauthors = Caum, Edward L.
title = Vascular plants of the Leeward Islands, Hawaii
publisher = Bishop Museum Press
series = Bernice P. Bishop Museum Bulletin No. 81; Tanager Expedition Publication No. 7
date = 1931-07-01
location = Honolulu, Hawaii
isbn =
*cite news
last = Gagné
first = W.C.
coauthors = S. Conant
title = Nihoa: biological gem of the Northwest Hawaiian Islands
publisher = Newslett. of the B.P. Bish. Mus. Assoc.
date = July 1983