Polyscias racemosa

Polyscias racemosa, or false 'ohe,[3] is a species of flowering plant in the family Araliaceae. As Munroidendron racemosum, the species was until recently considered to be the only species in the monotypic genus Munroidendron. With the change in classification, Munroidendron is now obsolete. Polyscias racemosa is endemic to the Hawaiian island of Kauai.[4] It is very rare in the wild and some of its original habitat has been replaced by sugar cane plantations.[5] It was thought for some time to be probably extinct, but was rediscovered a few years prior to 1967.[6]

Polyscias racemosa
Polyscias racemosa growing in Maui Nui Botanical Gardens, Maui, Hawaii.

Critically Endangered  (IUCN 3.1)[1]
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Apiales
Family: Araliaceae
Genus: Polyscias
Species:
P. racemosa
Binomial name
Polyscias racemosa
(C.N.Forbes) Lowry & G.M.Plunkett
Synonyms[2]
  • Munroidendron racemosum (C.N.Forbes) Sherff
  • Tetraplasandra racemosa C.N.Forbes

Using cladistic methods, phylogenetic studies of DNA have shown that the closest relative of Munroidendron racemosum is Reynoldsia sandwicensis.[7] These two species are now known as Polyscias racemosa and Polyscias sandwicensis, respectively. They are two of the 21 species now placed in Polyscias subgenus Tetraplasandra.[8]

Polyscias racemosa is known in cultivation in Hawaii.[9] Cultivation procedures for Polyscias racemosa have been studied.[10]

Description

Polyscias racemosa is a small tree growing to 25 ft (7.6 m) tall, with a straight trunk, spreading branches, and smooth, grey bark.[11] Like many members of Polyscias, it is sparingly branched and thick-stemmed, with large imparipinnate leaves, but not as extreme in these characteristics as is Polyscias nodosa.

Its leaves are pinnate, 12 in (30 cm) long, with oval leaflets, each of which is over 3 inches (7.6 cm) long. These trees are dry season deciduous, dropping most of their leaves during their summer blooming season. Its small, pale yellow flowers hang in long, rope-like strands.[12] The inflorescence is racemose in form, with up to 250 flowers.[13]

  • Flowers
  • Inflorescence
  • Leaves
  • New Leaves

Habitat and range

Polyscias racemosa occurs in coastal mesic and mixed mesic forests at elevations of 120–400 m (390–1,310 ft), where it grows on exposed cliffs and ridges. Associated plant species include papala kepau (Pisonia umbellifera), ʻāwikiwiki (Canavalia galeata), ʻilima (Sida fallax), ʻōlulu (Brighamia insignis), alaheʻe (Psydrax odorata), kōpiko (Psychotria spp.), olopua (Nestegis sandwicensis), ʻahakea (Bobea timonioides), hala pepe (Pleomele aurea), and ʻālaʻa (Pouteria sandwicensis).[14] It occurs naturally in only three locations on Kauaʻi: Nounou Mountain, the cliffs of the Nā Pali Coast, and Haʻupu Ridge near Nāwiliwili Bay.

History

Polyscias racemosa first entered the botanical literature in 1917, when it was described and named as Tetraplasandra racemosa by Charles Noyes Forbes.[15]

Earl Edward Sherff felt that this species was uniquely distinct from the rest of Tetraplasandra, so he erected a new genus for it, Munroidendron, in 1952.[16] The genus was named for George Campbell Munro (1866-1963), described by Umberto Quattrocchi as "a pioneer in Hawaiian ornithology, botany, and horticulture; plant collector in the Hawaiian Islands".[17] Dendron is a Greek word for "tree". Munro was apparently the first collector to see his eponymous genus, Munroidendron.[18]

Sherff separated Munroidendron from Tetraplasandra on the basis of five characters: the absence of umbellules, the arrangement of the flowers in a raceme, the sunken, diamond-shaped pedicel scars, the long, persistence of the subtending floral bracts, and the insertion of the stamens in only one whorl, even when numerous.[18] It has been shown that, in spite of its appearance, the inflorescence is not truly a raceme because it is determinate.[11]

Sherff divided the species now known as Polyscias racemosa into three varieties: var. racemosa, var. forbesii, and var. macdanielsii. These have been described as "not sufficiently distinct to be retained".[11]

The establishment of Munroidendron was contentious from the beginning. William R. Philipson said that Munroidendron "comprises a single species with such a distinct inflorescence and corolla that it can well claim generic status.[19] In 1971, a pollen study indicated that Munroidendron might be embedded in Tetraplasandra.[20] This result was not supported by molecular phylogenetic studies based on DNA sequences of nuclear and chloroplast DNA regions.[7] These studies show that Polyscias sandwicensis (formerly Reynoldsia sandwicensis is not most closely related to other species of Reynoldsia, but is sister to Polyscias racemosa, (formerly Munroidendron).[21] This pair is then sister to a monophyletic Tetraplasandra in the sense of Philipson (1970).[19] This pair of species and the nine species formerly in Tetraplasandra form a clade and comprise all of the Hawaiian species of Polyscias.[21] The 11 species of this "Hawaiian clade" and 10 species from Malesia, Melanesia, and southern Polynesia constitute Polyscias subgenus Tetraplasandra.[8]

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References
  1. Adams, J.W.A. (2016). "Polyscias racemosa". IUCN Red List of Threatened Species. 2016: e.T34055A83787166. doi:10.2305/IUCN.UK.2016-2.RLTS.T34055A83787166.en.
  2. "Polyscias racemosa (C.N.Forbes) Lowry & G.M.Plunkett". World Checklist of Selected Plant Families (WCSP). Royal Botanic Gardens, Kew. Retrieved 3 April 2014 – via The Plant List.
  3. "Munroidendron racemosum". Natural Resources Conservation Service PLANTS Database. USDA. Retrieved 14 July 2015.
  4. David G. Frodin and Rafaël Govaerts. 2003. World Checklist and Bibliography of Araliaceae. Royal Botanic Gardens, Kew. ISBN 978-1-84246-048-1. (See External links below).
  5. Earl Edward Sherff. 1956. "Some Recently Collected Dicotyledonous Hawaiian Island and Peruvian Plants". American Journal of Botany 43(7):475-478.
  6. Benjamin C. Stone. 1967. "A review of the endemic genera of Hawaiian plants" Botanical Review (Lancaster) 33(3):216-259.
  7. Gregory M. Plunkett and Porter P. Lowry II. 2010. "Paraphyly and polyphyly in Polyscias sensu lato: molecular evidence and the case for recircumscribing the "pinnate genera" of Araliaceae". Plant Diversity and Evolution (formerly Botanische Jahrbucher) 128(1-2):23-54. doi:10.1127/1869-6155/2010/0128-0002.
  8. Porter P. Lowry II and Gregory M. Plunkett. 2010. "Recircumscription of Polyscias (Araliaceae) to include six related genera, with a new infrageneric classification and a synopsis of species". Plant Diversity and Evolution (formerly Botanische Jahrbucher) 128(1-2):55-84. doi:10.1127/1869-6155/2010/0128-0003. (See External links below).
  9. Clyde T. Imada, George W. Staples, and Derral R. Herbst. undated. Annotated Checklist of Cultivated Plants of Hawai‘i. (See External links below).
  10. Kerin E. Lilleeng-Rosenberger. 2005. Growing Hawaiʻi's Native Plants. Mutual Publishing. ISBN 978-1-56647-716-1
  11. Warren L. Wagner, Derral R. Herbst, and Sy H. Sohmer. Manual of the Flowering Plants of Hawaii, Revised Edition, 1999. Bishop Museum Press: Hololulu
  12. "Munroidendron racemosum". Hawaiian Native Plant Propagation Database. University of Hawaiʻi at Mānoa. Retrieved 2009-03-03.
  13. Peter S. Green (author) and Mary Grierson (illustrator). 1996. A Hawaiian Florilegium: Botanical Portraits from Paradise. University of Hawaii Press: Honolulu, Hawaii. ISBN 978-0-915809-20-2.
  14. "Munroidendron racemosum". CPC National Collection Plant Profiles. Center for Plant Conservation. 2008-07-22. Archived from the original on 2012-02-23. Retrieved 2009-11-14.
  15. Charles Noyes Forbes. 1917. "New Hawaiian Plants.-VI." Occasional Papers of the Bernice Pauahi Bishop Museum 6(4):51. (See External links below).
  16. Munroidendron in International Plant Names Index. (see External links below).
  17. Umberto Quattrocchi. 2000. CRC World Dictionary of Plant Names, volume III. CRC Press: Baton Rouge, New York, London, Washington DC. ISBN 978-0-8493-2673-8 (vol. III). (see External links below).
  18. Earl Edward Sherff. 1952. "Munroidendron, a new genus of Araliaceous trees from the island of Kauai". Botanical Leaflets 7(section V):21-24. published by the author.
  19. William R. Philipson. 1970. "A redefinition of Gastonia and related genera (Araliaceae)". Blumea 18(2):497-505.
  20. Charles C. Tseng. 1971. "Light and Scanning Electron Microscopic Studies on Pollen of Tetraplasandra (Araliaceae) and Relatives". American Journal of Botany 58(6):505-516.
  21. Annemarie Costello and Timothy J. Motley. 2007. "Phylogenetics of the Tetraplasandra Group (Araliaceae) Inferred from ITS, 5S-NTS, and Morphology". Systematic Botany 32(2):464-477.
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