Hayun Lagu

Serianthes nelsonii

Description

The tronkon guafi (on Rota), also known as the hayun lagu (on Guam), is one of the largest native trees in the Mariana Islands, It grows as tall as 118 ft (36 m) and has a diameter of up to 6 ft (1.8 m).

Habitat

The tronkon guafi occurs in habitats with limestone-derived soil. Most of the surviving trees on Rota grow on or near steep hillsides and cliffs at elevations of 490-1,380 ft (150-420 m) on the western side of the island. Trees in Guam grew at elevations of 400-575 ft (120-175 m).

Distribution

The tronkon guafi is a locally evolved (or endemic) species that only occurs on the islands of Guam and Rota in the Mariana Islands of the western Pacific Ocean.

Threats

Although there are no historical data, it is likely that the tronkon guafi was once more abundant and widespread on both Guam and Rota. It has apparently declined because of deforestation to develop land-uses for agricultural, residential, and military purposes, and harvesting as a source of timber and firewood. There are now only two surviving populations of the tronkon guafi, consisting of about 121 mature trees on Rota, and only one mature tree on Guam. Little or no reproduction appears to be taking place in either population, probably because of unsustainable browsing of seedlings by introduced deer and predation on seeds by non-native insects. Other threats include browsing by introduced pigs and cattle; typhoon damage; inbreeding in its small populations; wildfire; and insect infestations.

Conservation and Recovery

The U. S. Fish and Wildlife Service has created a National Wildlife Refuge on Guam, and is out-planting the tronkon guafi into that protected area. The only surviving natural tree is now enclosed in a fence that excludes deer and pigs. Attempts have been made to cultivate the tronkon guafi by: the Department of Land and Natural Resources of the Commonwealth of the Northern Mariana Islands; the Guam Division of Forestry and Soil Resources; the College of Agriculture and Life Sciences of the University of Guam; and the Waimea Arboretum. However, success in these ventures has been poor, with most seedlings dying within several years. Conservation of the tronkon guafi requires the strict protection and appropriate management of its surviving habitat, and further research into its captive-propagation so that stock can be raised for out-planting to supplement the sparse regeneration of wild populations.

Contacts

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
(503) 231-6121
http://pacific.fws.gov/

U. S. Fish and Wildlife Service, Pacific Region, Guam
Haloda Building
P.O. Box 23774-GMF
Barrigada, Guam 96921-3774
(671) 472-7146

References

Wiles, G.J.; Schreiner, I.H.; Nafus, D.; Jurgensen, L.K.; Manglona, J.C. 1996. "The Status, Biology, and Conservation of Serianthes nelsonii (Fabaceae), an Endangered Micronesian Tree." Biological Conservation 76: 229-239.

U.S. Fish and Wildlife Service. 1999. "The Recovery Plan for the Serianthes nelsonii. " Threatened and Endangered Species: Threatened and Endangered Plants in the Pacific. (http://www.r1.fws.gov/pacific/wesa/serianthesnels.html). (7/5/00).