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Cycas micronesica

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Cycas micronesica
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Gymnospermae
Division: Cycadophyta
Class: Cycadopsida
Order: Cycadales
Family: Cycadaceae
Genus: Cycas
Species:
C. micronesica
Binomial name
Cycas micronesica
K.D. Hill, 1994

Cycas micronesica is a species of cycad found on the island of Yap in Micronesia, the Marianaislands of Guam and Rota, and The Republic of Palau. It is commonly known as federico nut or fadang in Chamorro. The species, previously lumped with Cycas rumphii and Cycas circinalis, was described as a unique species in 1994 by Ken Hill.[2] Paleoecological studies have determined that Cycas micronesica has been present on the island of Guam for about 9,000 years.[3] It has been implicated as a factor in Lytico-Bodig disease, a condition similar to amyotrophic lateral sclerosis (ALS), due to the presence of the neurotoxin BMAA found in its seeds. Seeds were a traditional food source on Guam until the 1960s.[4] The neurotoxin is present due to a symbiosis with cyanobacteria.[5][6]

Description

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Stem with ringed leaf scars

Cycas micronesica is a medium-sized tree most commonly 2–5 meters tall but can reach heights up to 15 meters. The tree has a straight palm-like trunk ringed with frond scars.[7]

Leaves

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Leaves are 140–180 cm long, flat in section (opposing pinnae inserted at 180 degrees on rachis), with 130 -150 pinnae, terminated by a spine approximately 4mm long; petiole usually glabrous, usually unarmed, rarely spinescent for up to 20% of length, 35 – 45 cm long; median pinnae at 70-80 degrees to rachis, 240 – 280 mm long, 16 –17 mm wide, 0.35 - 0.45 mm thick, glabrous, dull green or slightly bluish-green when developing, becoming glossy mid-green at maturity, flat in section with slightly recurved margins, strongly discolorous, decurrent for 7–10 mm, narrowed to 5.0-6.0 mm at base, 17 – 20 mm apart on rachis apex attenuate; midrib not sharply raised, more or less equally prominent above and below, 1.2 -1.5 mm wide.[8]

Reproductive organs

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Like all cycads, Cycas micronesica are dioecious. Females possess clusters of ovules situated on modified leaves called megasporophylls. Male reproductive structures consist of modified leaves called microsporophylls, but each modified leaf has small, compact pollen sacks attached to their lower surface.[9] There has been documentation of a symbiotic relationship between Cycas micronesica and an Anatrachyntis moth species on Guam, which depends on male cones (microsporangia) for oviposition and recruitment in return for pollinating the female cone.

Female cones (megasporophylls)

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The female cones are pale fawn to pale orange-brown, narrowly ovoid, 30–50 cm long, 8–10 cm in diameter. Megasporophylls 27–33 cm long, grey- and orange-tomentose, with 2-6 ovules, lamina 45–55 mm wide, broadly ovate to elliptical, regularly dentate with 16-20 lateral spines, apical spine 8–15 mm long, lateral spines 2–6 mm long. Seeds flatten to ovoid, green becoming orange, not pruinose, 50–60 mm long, 45–50 mm in diameter; sarcotesta 3–6 mm thick.[8]

  • Female cone with closed megasporophylls
    Female cone with closed megasporophylls
  • Female cone (megasporophylls) with immature green ovules
    Female cone (megasporophylls) with immature green ovules
  • Female cone with drooping megasporophylls and developing ovules
    Female cone with drooping megasporophylls and developing ovules
  • Fertilized megasporangia with developing seeds
    Fertilized megasporangia with developing seeds
  • Developed seed
    Developed seed
  • Cycas micronesica seed and root. Dededo, Guam
    Cycas micronesica seed and root. Dededo, Guam

Male cones (microsporophylls)

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Microsporophyll laminae are 35–45 mm long, 20–25 mm wide; fertile zone 25–35 mm long; sterile apex 7–10 mm long, not recurved, apical spine somewhat reduced, broad, sharply upturned, 2 mm long.

  • Male cone with closed microsporangia
    Male cone with closed microsporangia
  • Male cone with open microsporangia and pollen
    Male cone with open microsporangia and pollen
  • Microsporangia of male cone with pollen
    Microsporangia of male cone with pollen
  • Microsporangium with pollen sacks and yellow pollen
    Microsporangium with pollen sacks and yellow pollen

Conservation

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Male cone and leaves infested with cycad aulacaspis scale (CAS)

Cycas micronesica is threatened by a combination of introduced species throughout the islands of Guam and Rota. The most notable pest is the diaspidid scale, Aulacaspis yasumatsui, which was first recognized on Guam in December 2003.[10] Other threats include cycad blue butterfly (Luthrodes pandava); the longhorn beetle (Acalolepta marianarum), which causes stem damage; the alien invasive snail Satsuma mercatoria, which feeds on young leaflets; and habitat loss due to the growing human population and military activities.[1] Prior to the invasion of Aulacaspis yasumatsui, it was one of the most abundant plants in Guam's forests.[11] Plant mortality was so rapid that the species was listed as Endangered by the IUCN Red List in 2006, only three years after the devastating invasions began.[12][13] Population counts in northwest Guam had declined from 686 individuals in early 2004 (before Aulacaspis yasumatsui reached this habitat) to 87 individuals in January 2007.[1] Cycas micronesica used to have stable populations across Micronesia, with Guam having the largest. However, the Aulacaspis scale invasion caused an 87% decline in the Guam subpopulation over ten years.[14] In 2004, Rhyzobius lophanthae was introduced on Guam as a biological pest control and has lessened the population decline. However, they were ineffective at protecting cycad seedlings from Aulacaspis yasumatsui predation, as lack of seed vigor is one of the major factors contributing to Cycas micronesica decline.[15] Without effective action against the Aulacaspis scale, the Guam population may become critically endangered.

Threats

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The cycad aulacaspis scale (CAS), an invasive species from Southeast Asia, poses a significant threat to Cycas micronesica, resulting in substantial plant mortality. However, the current plant mortality is not solely due to the scale. The introduction of the cycad blue butterfly in 2005 and the intensified damage caused by pre-existing arthropod pests are additional severe threats to the already weakened cycad population. Longhorn beetles, especially Acalolepta marianarum, are responsible for many recent plant deaths due to stem damage. Moreover, the invasive snail Satsuma mercatoria, has only recently been noted to be feeding on young leaflets. This change in herbivore behavior may be a result of the compromised ability of unhealthy cycad plants to synthesize chemicals that deter herbivores.[14]

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  • Understory habitation
    Understory habitation
  • Stem and palm-like structure
    Stem and palm-like structure
  • Crown
    Crown
  • Pinnate leaf formation
    Pinnate leaf formation
  • Young stem covered in cataphylls, with new leaf emerging
    Young stem covered in cataphylls, with new leaf emerging

See also

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References

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  1. ^ a b c Bösenberg, J.D. (2022). "Cycas micronesica". IUCN Red List of Threatened Species. 2022: e.T61316A68906033. doi:10.2305/IUCN.UK.2022-1.RLTS.T61316A68906033.en. Retrieved 22 August 2023.
  2. ^ Hill, K.D. (1994). Cycas micronesica. Australian Systematic Botany 7: 554-556.
  3. ^ Athens, J., & Ward, J. (2004). Holocene vegetation, savanna origins and human settlement of Guam. Records Of The Australian Museum, 15-30.
  4. ^ Sacks, Oliver. (1996). The Island of the Colour-blind. Pan Macmillan Australia: Sydney. ISBN 0-330-35887-1
  5. ^ Cox PA, Banack SA, Murch SJ, Rasmussen U, Tien G, Bidigare RR, Metcalf JS, Morrison LF, Codd GA, Bergman B (2005). "Diverse taxa of cyanobacteria produce b-N-methylamino-L-alanine, a neurotoxic amino acid". PNAS. 102 (14): 5074–5078. Bibcode:2005PNAS..102.5074C. doi:10.1073/pnas.0501526102. PMC 555964. PMID 15809446.
  6. ^ Esterhuizen M, Downing TG (2008). "β-N-methylamino-L-alanine (BMAA) in novel South African cyanobacterial isolates". Ecotoxicology and Environmental Safety. 71 (2): 309–313. doi:10.1016/j.ecoenv.2008.04.010. PMID 18538391.
  7. ^ Vogt, S., & Williams, L. (2004). Common flora & fauna of the Mariana Islands. Saipan?: S.R. Vogt & L.L. Williams.
  8. ^ a b Hill KD (1994). "The Cycas rumphii complex (Cycadaceae) in New Guinea and the western Pacific". Australian Systematic Botany. 7 (6): 543–567. doi:10.1071/sb9940543. ISSN 1446-5701.
  9. ^ Willis, K., & McElwain, J. C. (2014). The evolution of plants (2nd ed.). Oxford, United Kingdom; New York: Oxford University Press.
  10. ^ Terry, Irene; & Marler, Thomas. (2005). Paradise Lost? Tipping the scales against Guam’s Cycas micronesica. The Cycad Newsletter 28(3-4): 21-23.
  11. ^ Donnegan, J., & Pacific Northwest Research Station. (2004). Guam's forest resources, 2002 (Resource bulletin PNW ; 243). Portland, OR: U.S. Dept. of Agriculture, Forest Service, Pacific Northwest Research Station.
  12. ^ Marler, T.E.; Lawrence, J.H. (2012). "Demography of Cycas micronesica on Guam following introduction of the armoured scale Aulacaspis yasumatsui". Journal of Tropical Ecology. 28 (3): 233–242. doi:10.1017/S0266467412000119.
  13. ^ Marler, T.E. (2010). "Cycad mutualist offers more than pollen transport". American Journal of Botany. 97 (5): 841–845. JSTOR 20700414.
  14. ^ a b "Redlist - Cycas micronesica".
  15. ^ Marler, T.E.; Miller, R.; Moore, A. (2013). "Vertical Stratification of Predation on Aulacaspis yasumatsui Infesting Cycas micronesica Seedlings". HortScience. 48 (1): 60–62. doi:10.21273/HORTSCI.48.1.60.
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"Home". Guam Plant Extinction Prevention Program. Retrieved 2018-06-08.

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