- Source: Cycas micronesica
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. Paleoecological studies have determined that Cycas micronesica has been present on the island of Guam for about 9,000 years. 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. The neurotoxin is present due to a symbiosis with cyanobacteria.
Description
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.
= Leaves
=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.
= Reproductive organs
=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. 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)
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.
Male cones (microsporophylls)
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.
Conservation
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. 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. Prior to the invasion of Aulacaspis yasumatsui, it was one of the most abundant plants in Guam's forests. 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. 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. 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. 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. Without effective action against the Aulacaspis scale, the Guam population may become critically endangered.
Threats
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.
Gallery
See also
List of endemic plants in the Mariana Islands
References
External links
The Cycad Pages – Cycas micronesica Archived 2014-06-23 at the Wayback Machine
Plants of Guam [Botanical]- University of Guam College of Natural Arts and Sciences
Flickr: Plants of Guam by Lauren Gutierrez - Cycas micronesica K.D. Hill
Guam Plant Extinction Prevention Program
"Home". Guam Plant Extinction Prevention Program. Retrieved 2018-06-08.
Kata Kunci Pencarian:
- Pakis haji
- Cycas micronesica
- Cycas
- Cycas circinalis
- Lallemandana phalerata
- Cycasin
- List of cycad species by country
- Lytico-bodig disease
- List of endemic plants in the Mariana Islands
- List of threatened, endangered and extinct species in the Mariana Islands
- Β-Methylamino-L-alanine
