Cyanea macrostegia ssp. gibsonii
Cyanea macrostegia ssp. gibsonii
No Common Name
|Listed||September 20, 1991|
|Description||A tropical tree with attractive, blue flowers.|
|Habitat||Tropical rainforest near streams.|
|Threats||Habitat destruction, feeding by non-native mammalian herbivores, and competition with invasive alien plants.|
Cyanea macrostegia ssp. gibsonii, a member of the bellflower family (Campanulaceae), is a palm-like tree 3.3-23 ft (1-7 m) tall. The leaves are elliptic or oblong, about 7.9-31.5 in (20-80 cm) long and 2.6-7.9 in (6.6-20 cm) wide; the upper surface is usually smooth, while the lower is covered with fine hairs. The leaf stem is often covered with small prickles throughout its length. The inflorescences are horizontal and clustered among the leaves, each bearing five to 15 curved flowers that are blackish-purple externally and white or pale lilac within. The fruit is a yellowish-orange berry about 0.6-1.2 in (1.5-3 cm) long. The following combination of characters separates this species from the other members of the genus on Lanai: calyx lobes are oblong, narrowly oblong, or ovate in shape; and the calyx and corolla are both more than 0.2 in (0.5 cm) wide. Cyanea macrostegia ssp. gibsonii was seen flowering in the month of July, but the details of its flowering period are not known.
The Cyanea macrostegia ssp. gibsonii grows in tropical lowland rainforest on moderate to steep grades, usually in lower gulch slopes and the bottom or edges of streambanks. These relatively inaccessible locations offer some protection from introduced mammalian herbivores. Its sites are sunny to shady, mesic to wet, and with clay or other soil substrates. The Cyanea macrostegia ssp. gibsonii has been reported from elevations of 2,500-3,180 ft (760-970 m). Associated vegetation includes native ferns, shrubs, trees in wet Metrosideros forest or Diplopteryqium-Metrosideros shrubland (sometimes with Dicranopteris ), Perrottetia, Scaevola chamissoniana, Pipturus, Antidesma, Freycinetia, Psychotria, Cvrtandra, Dicranopteris, Broussaisia, Cheirodendron, Clermontia, Dubautia, Hedyotis, Ilex, Labordia, Melicope, Pneumatopteris, and Sadleria, and the alien Rubus rosifolius.
Cyanea macrostegia ssp. gibsonii is historically documented from the summit of Lanaihale and wet forest in the upper parts of the Mahana, Kaiholena, and Maunalei drainages of Lanai at elevations between 2,490-3,180 ft (760-970 m). In 1989, only a single plant could be found at one site in Kaiholena Valley, and it was being overgrown by kahili ginger. The 1991 survey done by the Hawaii Heritage Program of The Nature Conservancy of Hawaii provided virtually the only information on recently observed populations. Populations of Cyanea macrostegia ssp. gibsonii occur on Lanai in two gulches in upper Kaiholena Valley, two feeder gulches into Maunalei Valley, and four sites near the Lanaihale summit. In the Maunalei Valley feeder gulches, the 1991 survey located two populations with a total of four mature plants and two juveniles. In the upper Kaiholena Valley, one mature plant and five seedlings were seen in Waialala Gulch, while 10 mature plants were seen in the gulch between Kunoa and Waialala Gulches. The populations near the Lanaihale summit include one population of 34 mature and eight juvenile individuals and three populations with a total of eight mature plants and one juvenile. The known surviving individuals of the species thus comprise eight populations totaling approximately 75-80 plants.
Deer have not yet fully invaded the current habitat of Cyanea macrostegia ssp. gibsonii, although they have contributed to the decline of this species both directly through browsing and trampling of plants and indirectly through opening up avenues of invasion in damaged habitat for alien species. Browsing and habitat disturbance by axis deer promise to eliminate if drastic management efforts are not undertaken.
Kahili ginger was observed overgrowing the only plant found at one of the Kaiholena sites in 1989.Even small pockets of virtually undisturbed forest in the heads of gulches on the upper slopes of Lanai-hale are being invaded by strawberry guava, fire-tree, manuka, sourbush, molasses grass, Rubus rosifolius, and Paspalum conjugatum.These alien species have become pervasive on adjacent ridges since the forest floor is bombarded by alien propagules, and natural openings, or openings created by habitat disturbance by axis deer, provide ample sites for these aliens to obtain a foothold. Continuing disturbance by axis deer exacerbates the alien plant invasion problem.
The limited local gene pool that is available in a total population of 75-80 individuals in many small occurrences threatens to depress reproductive vigor.
Since native birds may have been the pollinators of Cyanea macrostegia ssp. gibsonii, their decline is very likely to pose a major, although currently undocumented, threat.
Conservation and Recovery
As of August 1992, the Hawaii Plant Conservation Center had in storage a total of 570 seeds of Cyanea macrostegia ssp. gibsonii from Lanai.
U.S. Fish and Wildlife Service
Pacific Islands Ecoregion
300 Ala Moana Boulevard, Room 3-122
Box 50088, Honolulu, Hawaii, 96850
Telephone: (808) 541-3441
Fax: (808) 541-3470
U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Building
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
U.S. Fish and Wildlife Service. 1995. "Lana'i Plant Cluster Recovery Plan: Abutilon eremitopetalum, Abutilon menziesii, Cyanea macrostegia ssp. gibsonii, Cyrtandra munroi, Gannia lanaiensis, Phyllostegia glabra var. lanaiensis, Antalum freycinetianum var. lanaiense, Tetramolopium remyi, and Viola lanaiensis." U.S. Fish and Wildlife Service, Portland, OR.