A tree's tribulations: rats and other nonnative creatures imperil the existence of the Hibiscadelphus giffardianus in the state most plagued by endangered species. (Rare & Endangered).
Hibiscadelphus giffardianus, also called hau kuahiwi, is endemic to Hawaii Volcanoes National Park. The species was first described in 1911 by Austrian botanist Joseph Rock. Before the original tree died in 1930, cuttings were collected and at least one tree was propagated on land adjacent to what is now Hawaii Volcanoes. This tree died in 1940, but one cutting remained, keeping the species alive. The plant survived in cultivation and was replanted in the park in the 1950s. The species has been reduced to a single tree at least three times. Each tree is derived from the 1911 original.
H. giffardianus is one of seven Hibiscadelphus species, each endangered or extinct. Only ten adult trees remain in Hawaii Volcanoes, each at least 40 years old, and only 11 young plants survived plantings that occurred in 1995 and 1997. The trees look much like a large hibiscus, not surprising since Hibiscadelphus means "brother of hibiscus." They typically grow 30 to 50 feet tall and have multiple trunks. The tree has rounded leaves that are large and rough. During the spring and summer, dull maroon flowers cover the tree. The curving flowers are narrow, reaching two to three inches in length. The tree produces yellowish-green seedpods, or dry fruit, about an inch long, most commonly during the summer and fall.
The Kamehameha butterfly has been observed feeding on the trees' flowers, and native birds were once known to feast on the nectar, though this is seldom seen today. Alien insects, such as the two-spotted leafhopper and the Japanese rose beetle, feed on the leaves. The insects may be contributing to the trees' demise, but rats are a bigger culprit, says Thomas Belfield, a rare and endangered species propagation specialist at Hawaii Volcanoes. "Rats are the biggest threat facing the trees," Belfield says. "Rats eat seeds and girdle branches." For H. giffardianus, which propagates from its seeds, this causes a serious problem. In addition to the threat posed by alien species, the trees suffer from the loss of a native bird species. The long-billed honeycreeper, likely the flowers' original pollinator, is rare--if present at all--in the park.
Steps are being taken to increase the tree population, although currently Belfield, Linda Pratt, a botanist working for the U.S. Geological Survey Pacific Islands Ecosystems Research Center, and Tim Tunison, chief of resources management at Hawaii Volcanoes, are the only scientists dedicated to the recovery effort. The tree has no specific recovery program, but Belfield is working on the park's Rare Plants Stabilization Project, which began last year. The project focuses on examining the status of rare and endangered plant species, including the H. giffardianus, in four ecological zones in the park. Seeds, fruit, and cuttings are collected and raised in the park's greenhouse, then planted in the park.
More than 200 trees have been planted in the last few years as part of an experiment conducted by U.S. Geological Survey researchers to study damage caused by rats. Despite these efforts, more work remains before the trees can make it off the endangered list. "It is unrealistic to imagine that this species will ever be delisted unless it goes extinct," Pratt says, adding, that reintroducing the species to its natural habitat and having it be self-sustaining is the park's goal.
JENELL TALLEY is publications coordinator.
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|Article Type:||Brief Article|
|Date:||Jul 1, 2002|
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