Ko'oloa'ula

Abutilon menziesii

Description

Abutilon menziesii is a shrub in the mallow family that stands 6.6-8.2 ft (2-2.5 m) tall. It has coarsely toothed, silvery, heart-shaped leaves 0.8-3.2 in (2-8.1 cm) long. The flowers are medium red to dark red and about 0.8 in (2 cm) across. The capsules are hairy and five-to eight-parted, usually with three seeds per cell.

All known populations of A. menziesii are frequently exposed to severe drought and periodic flooding. Due to the presence and abundance of alien grasses surrounding stands of A. menziesii throughout its current range, range expansion through natural seedling establishment appears virtually impossible. Seedlings are becoming established to a limited extent within existing stands of the species, but survival potential is probably reduced by deer browsing. It has been noted that the species is somewhat fire tolerant.

Since A. menziesii may produce new leaves only during a flush growth period in the wet season, defoliation by such pests as the Chinese rose beetle may have a significant negative impact on the survival of the species. Carpenter bees and honey bees have been observed on the flowers, although honey bees seem to have difficulty accessing nectar because of the small size of the flowers. The native bee Nesoprosopis has rarely been observed on flowers of this species and may have been more important as a pollinator in the past. A dual cycle of flowering has also been observed: some flowers open in early morning, staying open throughout the day; others open in the evening and remain open during the night. That may imply the past existence of a nocturnal pollinator, although no such pollinator has been observed.

Habitat

On Lanai, A. menziesii occurs in psyllid-damaged (plant lice-damaged) stands of koa haole with an understory of Guinea grass. The currently known habitat of A. menziesii on Maui is gentle leeward slopes of summer-dry shrubland areas (part of the lowland dry shrubland zone) with open to scattered closure and a substrate of rocky 'a'a (rough) lava or red soil, in communities usually dominated by alien plants.

A. menziesii has been reported from elevations of 500-1,400 ft (152.4-426.7 m). Associated species observed include the native Sida fallax, Dodonaea viscosa, and Waltheria indica, as well as the alien Rhynchelytrum repens, Cenchrus ciliaris, Prosopis pallida, lantana, Guinea grass, koa haole, and Casuarina. All known populations of A. menziesii are frequently exposed to severe drought and periodic flooding.

Distribution

A. menziesii has apparently been uncommon since its discovery in the 1800s. It once occurred locally in dryland forest habitats on the islands of Lanai, Maui, Hawaii, and possibly Oahu.

Of the historic locations on Lanai, Pu'u Mahanalua (Twin Peaks) is the only site known to have surviving plants. Fifty to 100 plants with flowers and fruits were observed in 1990, and about 33 plants were observed nearby at an elevation of 1,200 ft (365.8 m). There are an estimated 200 scattered plants in this population. These plants are generally 3-10 ft (0.9-3 m) tall. In 1991 a second site containing three populations of approximately 400 total scattered plants was reported at an elevation of approximately 1,050-1,150 ft (320-350.5 m) in an area north of Kaumalapau Road (on land formerly grazed by cattle) in psyllid-damaged stands of koa haole with an understory of Guinea grass.

Five known sites with single small populations of A. menziesii —totaling approximately 45 individuals—survive on Maui; three are on red soils in the Kalialinui Gulch drainage at elevations of 690-750 ft (210.3-228.6 m) near Pukalani, and two are on 'a'a lava at elevations of 500-1,400 ft (152.4-426.7) on lava flows in the vicinity of Pu'u o Kali near Kihei. In 1990 two to three clumps of this species—with at most 12 total plants—were observed at an elevation of 1,150 ft (350.5 m) at Pu'u o Kali. All Maui populations are subject to grazing. No conservation measures are being taken for these populations.

A. menziesii was once believed extirpated from the island of Hawaii but was rediscovered in 1995 at Puaks. This population is on private property; efforts by the landowner are facilitating the protection of this population.

A single plant of A. menziesii was reported from Barbers Point on Oahu in 1981, although this plant may have been an escapee from cultivation. At that time all cultivated plants were descended fom the Hawaii population at Puaks; however, this plant may represent a natural occurrence. Some botanists feel that, due to differences in leaf morphology of progeny from this plant as compared with other populations, it is likely that it actually did represent a separate natural population. The current status of this plant is unknown, but it is assumed to be gone. The area in which it formerly occurred was subject to development at the time the plant was last sighted.

A. menziesii was reportedly available in 1995 for sale from three commercial nurseries in the state of Hawaii. Plants are said to thrive and bloom regularly under nursery conditions, and propagation by seed is usually successful. Cuttings can also be cultivated successfully; cultivation requirements are similar to those of hibiscus. This species has also reportedly been planted at Kalopa State Park on the island of Hawaii. Plants from Hawaii, Lanai, Maui, and Oahu are now each represented in at least one cultivated situation.

Threats

Although populations of A. menziesii have been drastically reduced in the past by habitat destruction and browsing, primarily by cattle and goats, the major populations of the species on Lanai are now largely safe from those threats, except in cases of food shortage for axis deer caused by drought or other factors. Fire is still a potential threat. Careful management involving research, monitoring, and manipulation when necessary can probably assure its survival. The main management problem is that disturbance from browsing by axis deer both directly threatens the species and may also aid it by controlling invasive plants, especially Guinea grass.

A. menziesii may illustrate the precarious existence of a species that does not compete well without moderate disturbance. Some plant species, of which A. menziesii is probably one, are dependent on occasional environmental perturbations to provide open areas for recolonization. These plants have only a tenuous foothold in situations and conditions like the ones in which A. menziesii grows, where introduced alien plants have aggressively overtaken some varieties of native plants and have altered the very habitat they are coming to dominate in the process. Human land alterations, the presence of easily ignitable alien grasses, and other unnatural environmental disturbances can make the situation even more precarious for these kinds of sensitive plants.

Guinea grass and koa haole are presently the primary competitors of A. menziesii in its habitat on Lanai. Although koa haole has undergone extensive dieback due to defoliation by an immigrant psyllid that arrived in the early 1980s, it is fully capable of recovery if the psyllid were to undergo a decline (a likely circumstance). Browsing by axis deer seems to have a significant effect on koa haole at present and would have more effect if the psyllid were to decline. By the mid-1990s koa haole was increasing in vigor on Lanai. The most serious threat, though, may be from the Guinea grass, which would be much more dense and robust in the absence of deer.

Although not a preferred food of axis deer, A. menziesii is significantly browsed by deer. Cattle browsing probably contributed to the decline of the species on Lanai, where cattle were eliminated in the 1950s. One population on the island of Hawaii was completely destroyed by cattle during an unusually dry year. Most of the plants at Pu'u o Kali on Maui are periodically subjected to cattle browsing. On Lanai, deer browsing in current A. menziesii habitat appears to have a positive aspect, since Guinea grass and koa haole seem to be directly affected by browsing more than A. menziesii. However, browsing and trampling of seedlings by axis deer or mouflon (wild sheep) may inhibit regeneration.

Fire has occurred occasionally in the habitat of Abutilon and may be more frequent in the future now that surrounding lands are no longer in pineapple production. Populations of A. menziesii have not fared too badly in past fires but could undoubtedly be threatened by intense fires in dense Guinea grass.

The Chinese rose beetle has been documented to feed on leaves of A. menziesii and is a potential threat.

Since native insects—especially Nesoprosopis bees—may have been the pollinators of A. menziesii, their decline is very likely to pose an additional threat, although the flowers now are frequently visited by introduced insects. Pineapple fields adjacent to current populations probably destroyed some A. menziesii habitat, and a road and garbage dump have been proposed within its range.

Conservation and Recovery

Management efforts are being carried out to protect the only known population of A. menziesii on the island of Hawaii. This population is on private land that is being developed for residential purposes; the landowning corporation, Nansay Hawaii, is cooperating with the U. S. Fish and Wildlife Service to implement plans for protecting this population.

A. menziesii is represented in the National Tropical Botanical Garden, the Waimea Arboretum and Botanical Garden, the Honolulu Botanic Gardens, and the Amy Greenwell Ethnobotanical Garden. The Hawaii Plant Conservation Center, as of August 1992, had in storage a total of more than 4,000 A. menziesii seeds from the islands of Lanai, Hawaii, and Maui (from several plants); this institution also had 72 plants in cultivation. Research on this species includes isozyme analysis and some research into pollination biology.

In cultivation, A. menziesii seeds germinate readily in a cinder medium in as little as one week, and they grow quickly after transplanting to individual containers. Cultivated plants are reported to be thriving on windward Maui in an area 125-185 ft (38.1-56.4 m) in elevation that receives approximately 50-75 in (127-190.5 cm) of annual rainfall.

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/

Pacific Remote Islands Ecological Services Field Office
300 Ala Moana Blvd., Room 3-122
P. O. Box 50088
Honolulu, Hawaii 96850
Telephone: (808) 541-1201
Fax: (808) 541-1216

References

Char, W., and N. Balakrishnan. 1979. Ewa Plains Botanical Survey. Department of Botany, University of Hawaii, Moanoa.

Funk, E., and C. W. Smith. 1982. "Status Report on Abutilon menziesii. " U. S. Fish and Wildlife Service, Portland, Oregon.

Hillebrand, W. [1888] 1965. Flora of the Hawaiian Islands. Reprint. Hafner Publishing, New York.