Hawaii Plant Extinction Prevention Program

Working Together for Cyanea horrida

With approximately 30 Cyanea horrida known to occur on East Maui, the conservation of this PEP species illustrates how island species have evolved and interact together, requiring innovative partnerships working together to prevent its extinction.

Cyanea horrida is a member of the Bellflower family (Campanulaceae) and is found only in the upper elevation wet forests on the windward slopes of Haleakala, East Maui between 4,500 and 6,000 ft. in elevation. The Hawaiian name was originally considered hāhā nui, however, the late Joseph Rock listed holokea as the name for C. horrida.

Cyanea horrida differs from other species of Cyanea (an endemic Hawaiian genus with over 80 taxa descended from a common ancestor) in having divided leaves similar to ferns, presence of thorn-like prickles, and large purplish- green flowers that mature into bright orange berries covered by small prickles. The divided, fern-like leaves make it difficult to spot the plant by the untrained eye. Fern like leaves and prickles in some species of Cyanea are thought to be traits derived as camouflage and a defense strategy from grazing by now-extinct flightless geese and ibises, called moa nalo.

The habitat of holokea is wet, shady ‘ohia forest or `ohia/ koa forest . It often grows in company with trees such as `olapa (Cheirodendron trigynum), kawa`u (Ilex anomala), alani (Melicope spp.), and pilo (Coprosma spp.). Understory shrubs include `akala (Rubus hawaiiensis), kanawao (Broussaisia arguta), manono (Kadua affinis), and kolea (Myrsine spp.). A diverse assemblage of ferns are common including pohole (Diplazium sandwichianum), ama`u (Sadleria spp.), hoe a Maui (Elaphoglossum spp.), several species of Asplenium, and many small epiphytic ferns as well as mosses and bryophytes. Cyanea horrida grows in cold regions and the flowering and fruiting process is therefore extremely slow- some individuals have been observed to begin flowering as early as February with fruit maturing as late as November. Seedlings are rarely observed.

Most of the remaining plants occur on steep gulch walls in small colonies of one to four plants. I`iwi (Vestiaria coccinea), red honeycreeper birds, have been observed at the flowers of holokea, and there is evidence that Maui Parrotbill (Pseudonestor xanthophrys), a critically endangered honeycreeper, disperse the seeds by feeding on insects in the mature fruit.

Threats to this species include habitat degradation and direct predation by feral pigs; herbivory by slugs; small populations isolated from others individuals preventing cross pollination; decline and/or loss of avian pollinators and dispersal agents (e.g. Maui Parrotbill); rats that eat bark and seeds; and erosion. A single devastating event such as a hurricane could conceivably drive the species over the brink and into extinction. Global warming is also considered a potential threat as the upper elevation wet forests become too warm, and mosquitoes move up the slopes and impact native birds essential for pollination and dispersal.

The conservation of C. horrida is linked to maintaining its associated habitat of montane wet forest as well as healthy populations of native bird pollinators and seed dispersers such as ‘i‘iwi and Maui Parrotbill. However, PEP does not have the expertise or capacity to extend conservation measures beyond the immediate biology of the plant. To enhance these conservation measures, PEP has partnered with the Nature Conservancy’s Waikamoi Preserve, the State of Hawai`i Hanawi Natural Area Reserve, and Haleakalā National Park where the remaining natural populations of C. horrida can be found. These areas are also part of the East Maui Watershed Partnership, a 100,000 acre forested area (including critical wet, ‘ōhi‘a forests) managed for watershed purposes. Within this area, the Maui Forest Bird Recovery Project conducts research and management of essential bird habitat, including ‘i‘iwi and Maui Parrotbill.

Currently there are several dozen seedlings being raised for eventual outplanting back into secure habitat. The Olinda Rare Plant Nursery and Haleakalā National Park have material from several different founder plants, and PEP field work to collect seeds from all mature plants and search remaining habitat for new plants is ongoing.

States PEP Maui Nui coordinator Hank Oppenheimer, “it would be truly tragic to lose this unique element of Hawai‘i’s natural history. With the collaborative effort to protect its habitat, learn more about its biology, and manage individual plants one-on-one, there is every reason to be hopeful this species will continue to play its role in Haleakalā’s rain forests for generations to come.”