Ko'oko'olau (Bidens micrantha ssp. kalealaha)
Bidens micrantha ssp. kalealaha
|Listed||May 15, 1992|
|Description||Erect perennial herb with narrow, tapering leaves and yellow flowers clustered at the top.|
|Habitat||Open canopy dry montane forests to dry shrublands, on sheer rock walls.|
|Threats||Habitat destruction by feral animals, alien plant species, low numbers.|
Ko'oko'olau (Bidens micrantha ssp. kalealaha ), an erect perennial herb in the aster family, is slightly woody at the base and 1.6-4.9 ft (.5-1.5 m) tall. The leaves are 2.4-7.5 in (6.1-19.1 cm) long and usually have three to seven—sometimes even nine—lanceolate leaflets. The flower heads are arranged at the top of the plant and on side branches in open clusters of 15-50. Each flower head is 1-1.8 in (2.5-4.6 cm) in diameter and comprises five sterile, yellow-ray florets, ranging from 0.6 to 1.1 in (1.5 to 2.8 cm) long and 0.2 to 0.3 in (5.1 to 7.6 mm) wide.
B. micrantha is known to hybridize with B. mauiensis and B. menziesii; it may also hybridize with B. conjucta, another native Bidens.
B. micrantha ssp. kalealaha is found in open canopy dry montane forests to dry shrublands 1,600-9,800 ft (487.7-2,987 m) in elevation. Annual precipitation ranges from 10 to 50 in (25.4 to 127 cm) in seasonally dry montane forests to about 60 in (152.4 cm) in subalpine shrublands. The substrate is comprised mostly of blocky lava flows with little or no soil development. The species typically grows on sheer rock walls at an elevation of 5,200-7,600 ft (1,585-2,316.5 m). Associated vegetation includes pilo, 'a'ali'i, and na'ena'e.
B. micrantha ssp. kalealaha was known historically from Lanai, the south slope of Haleakala on East Maui, and from one locality on West Maui. Hillebrand and Lydgate collected this species around 1869 on East Maui at Kula. Forbes collected it in 1920 above Lualailua Hills and east of Puu Keokea, on the south slope of Haleakala. When B. micrantha was collected in 1950, it was noted that the 5-ft-tall (1.5-m-tall) shrub had shiny leaves and was growing at the precipitous headwall of a small canyon 200 yd (182.9 m) west of the Kahua cabin on the south slope of Haleakala at an elevation of 7,000 ft (2,133.6 m). It was also noted that these plants appeared to be palatable to feral goats, which had almost destroyed the climax subalpine woodland of the region, forcing the native vegetation to persist only in inaccessible places.
In 1983 the species was observed on the leeward slopes and inner crater walls of Haleakala at elevations of 2,460-7545.9 ft (749.7-2,300 m). The four remaining populations of B. micrantha ssp. kalealaha number no more than 2,000 individuals scattered over 9.3 by 1.8 mi (15 by 2.9 km) of federal and state land on leeward East Maui. These populations are distributed 1) on the southern slope of East Maui at elevations of 5,200-6,400 ft (1,585-1,950.7 m), primarily on drainage headwalls between Manawainui and Wallaulau; 2) farther west, with Dubautt'a platyphylla, in several deep pit craters south of Kahua cabin at about 6,840 ft (2,084.8 m); 3) within Haleakala National Park, sporadically along cliff walls in western Kaupo Gap at 6,000-6,400 ft (1,828.8-1,950.7 m); and 4) within this park on the inner walls of Haleakala Crater at about 7,200-7,600 ft (2,194.6-2,316.5 m).
In October 1990, three years after feral goats were eliminated from Haleakala Crater, eight juvenile plants 1.5-24.4 in (3.8-62 cm) tall were noted in Haleakala National Park at elevations of 5,906-6,334 ft (1,800.1-1,930.6 m). The plants were growing at the base of the steep walls of western Kaupo Gap, on talus slopes and along stream courses, below cliff faces inhabited by mature B. micrantha. The largest of the young plants was flowering. This was the first time this species was observed away from its typical near-vertical rock wall habitat. There appears to be ample habitat nearby for a much greater increase of this species now that the effect of feral goat browsing has been eliminated.
Continuing habitat destruction by feral goats and pigs are major threats to the long-term survival of B. micrantha ssp. kalealaha. On leeward East Maui, within the habitat of this species outside Haleakala National Park, feral goats have destroyed much of the original native vegetation, except in those areas inaccessible to them such as sheer rock faces and steep watercourse sides. In these areas, ridge tops and flat areas are often eroded and pasturelike, with an abundance of alien plants.
B. micrantha ssp. kalealaha, quite conspicuous when flowering, is restricted to largely inaccessible sites. While feral goats are no longer an immediate threat to this plant within Haleakala National Park, the potential still exists for the ingress and reestablishment of goats. Feral pigs are also present on the leeward slopes of East Maui within the habitat of this species, but outside of the park. They pose a moderate threat to this plant, although modest in comparison to that of feral goats.
Cattle ranching occurs on the southern slope of Haleakala in the vicinity of B. micrantha ssp. kalealaha. Escaped domestic cattle pose a moderate threat to the long-term survival of this species.
Competition from a variety of invasive plant species threatens B. micrantha ssp. kalealaha, especially in conjunction with ecosystem damage caused by hoofed mammals. Alien plant cover within Haleakala National Park slows the recovery of this species; establishment of new individuals is largely limited to stream beds and talus slopes, where competition with alien grasses is not intense.
Fire is a major potential threat to the survival of this species because a single blaze could destroy a significant portion of one or more of its remaining populations
Conservation and Recovery
Propagating this species by seed is easy, and it is now being grown by several horticulturists of native species.
Control of feral goats has been a priority within Haleakala National Park since the late 1970s. By the late 1980s feral goats had been largely eliminated from Haleakala Crater and Kaupo Gap for the first time since their introduction almost 200 years before. Within a few years, new plants of B. micrantha ssp. kalealaha were noted growing in the rocky scree slopes directly below the sheer cliffs where the species had escaped the feeding of feral goats; this is apparently the first significant recruitment of new plants of this species in decades. These new plants were flowering and producing seed by the early 1990s.
Without protection, this subspecies will continue to decline due to degradation of habitat by feral animals, although individuals will survive on vertical and near-vertical rock faces. Enclosures for protection of this plant could also include Huperzia mannii, Cyanea comata, Ranunculus spp., Clermontia lindseyana, and other endangered species of the area.
This genus in Hawaii—and this taxon specifically—are morphologically and genetically complex. Each population is likely to have its own unique characteristics. Maintenance of the individual characteristics of discrete populations is always an important factor to consider, but perhaps more so in this genus and species. Populations of this plant should be kept discrete, and outplanting done in a manner that would preserve genetic distinctiveness of individual populations. It would be appropriate and beneficial to establish new populations within probable former range in Haleakala National Park and into the Nature Conservancy of Hawaii Kapunakea Reserve on West Maui.
U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
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
U. S. Fish and Wildlife Service. 15 May 1992. "Endangered and Threatened Wildlife and Plants; Determination of Endangered or Threatened Status for 15 Plants from the Island of Maui, Hawaii." Federal Register 57 (95): 20772-20787.