Hibiscadelphus distans 

Scope: Global

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Taxonomy [top]

Kingdom Phylum Class Order Family
Plantae Tracheophyta Magnoliopsida Malvales Malvaceae

Scientific Name: Hibiscadelphus distans
Species Authority: L.E.Bishop & D.R.Herbst
Taxonomic Source(s): Wagner, W.L., Herbst, D.R. and Lorence, D.H. 2005 onwards. Flora of the Hawaiian Islands website. Available at:
Identification information: Small tree in Malvaceae family. Flowers have small green bracts & petals with a magenta staminal column. Immature fruit are green, Mature fruit arebrown.

Assessment Information [top]

Red List Category & Criteria: Critically Endangered B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v); C2a(i,ii); D ver 3.1
Year Published: 2016
Date Assessed: 2016-07-01
Assessor(s): Clark, M.
Reviewer(s): Walsh, S.
Contributor(s): Wood, K. & Nyberg, B.
Hibiscadelphus distans is assessed as Critically Endangered. The taxon is endemic to Kauaʻi and only ten individuals, within a single subpopulation and location remain. The extent of occurrence and area of occupancy of these remaining individuals both equate to only 0.09 km2. Impacts to the species from non-native invasive species remain a major factor in the survival of this species.
Previously published Red List assessments:

Geographic Range [top]

Range Description:This Hawaiian taxon is endemic to Kauaʻi. It is only known from a single population on the bluff above Koaie Stream in Waimea Canyon between 425 and 800 m elevation.
Countries occurrence:
United States (Hawaiian Is.)
Additional data:
Estimated area of occupancy (AOO) - km2:.09Continuing decline in area of occupancy (AOO):Yes
Estimated extent of occurrence (EOO) - km2:.09
Continuing decline in extent of occurrence (EOO):Yes
Number of Locations:1
Lower elevation limit (metres):425
Upper elevation limit (metres):800
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:In 1998, between 50 and 100 individuals were known. In 2004, that number dropped down to 15. Only 10 individuals are currently known, all occurring within a single subpopulation.
Current Population Trend:Decreasing
Additional data:
Number of mature individuals:10Continuing decline of mature individuals:Yes
No. of subpopulations:1Continuing decline in subpopulations:Yes
All individuals in one subpopulation:Yes

Habitat and Ecology [top]

Habitat and Ecology:The taxon is a large shrub found in mixed, dry shrub-forest. The single remaining population occurs in a cliff patch receiving full sun in summer, with no direct sun in winter. Substrate is of basaltic rock; surrounded by dry, crumbly red-brown clay soil. Associated native plant species include Sapindus oahuensis, Psydrax odoratum, Myrsine sp., Bidens sandwicensis, Schiedea spergulina, Dodonaea viscosa, Lobelia niihauensis, Erythrina sandwicensis, Nototrichium sandwicensis, Artemisia australis, Xylosma hawaiiense, Euphorbia celastroides var. hanapepensis, Acacia koaia, Chenopodium oahuense, Neraudia melastomifolia, Sida fallax, Lipochaeta connata var. acris, Plectranthus parviflorus, Dianella sandwicensis, Sicyos sp., Alyxia stellata, Carex meyenii, C. wahuensis, Eragrostis variabilis, Panicum beecheyi, P. lineale, Doryopteris decora, Diospyros hillebrandii, D. sandwicensis, Metrosideros polymorpha var. glaberrima, Chrysodracon aurea, Melicope barbigera, Pouteria sandwicensis, Santalum freycinetianum var. pyrularium, Kadua affinis, Sideroxylon polynesicum, Pteralyxia kauaiensis, Flueggea neowawraea, Myoporum sandwicens, Hibiscus waimeae subsp. waimeae, Bobea timonioides, Canavalia kauaiensis, Smilax melastomifolia, Spermolepis hawaiiensis, Korthalsella complanata, Microlepia strigosa, Dicranopteris linearis, Psilotum nudum, Pteris xhillebrandii and Selaginella arbuscula. Outplanted taxa nearby include Polyscias racemosum,Caesalpinia kavaiensis, Rauvolfia sandwicensis, and Kokia kauaiensis.
Continuing decline in area, extent and/or quality of habitat:Yes

Threats [top]

Major Threat(s): Major threats to this taxon include the following invasive, non-native plant taxa: Lantana camara, Opuntia ficus-indica, Triumfetta semitriloba, Hyptis pectinata, Grevillea robusta, Leucaena leucocephala, Agave sp., Kalanchoe sp., Aleurites moluccanus, and Melia azedarach. Direct predation to plants and habitat degradation is caused by goats, also causing rock falls, landslides, and erosion. Floods, droughts, human disturbance, fire, and hurricane damage have impacted the population. Rats, grasshoppers and rose beetles eat fruit and foliage, and insect larvae eat seeds. Reduced reproductive vigour due to the few individuals remaining is also a threat.

Conservation Actions [top]

Conservation Actions: The taxon is listed on the U.S. Endangered Species Act, thus a recovery plan exists. It is also managed under the Plant Extinction Prevention Program of the state of  Hawaiʻi, and is monitored regularly. The single population remaining is included in and managed as Conservation District Forest Land, under the jurisdiction of the State Division of Forestry and Wildlife (DOFAW). DOFAW has constructed enclosures around naturally occurring plants that require protection from feral goat browsing, and has undertaken a program of outplanting of propagated seedlings into exclosure sites. Exclusion of the goats, weeding, watering, and fertilizing have in a short time resulted in the regeneration of Hibiscadelphus distans in the Lower Koaie Canyon area. To achieve recovery of H. distans, steps to control and minimize the threats acting upon the existing population must be undertaken. Surveys within likely habitat areas in Waimea Canyon may determine whether any other populations currently exist, and all newly discovered populations must be adequately protected. Seeds are in storage at the National Tropical Botanical Garden and Lyon Arboretum. It has been propagated and outplanted both ex situ (in gardens) and in situ (back in the wild).

Citation: Clark, M. 2016. Hibiscadelphus distans. The IUCN Red List of Threatened Species 2016: e.T30930A83801583. . Downloaded on 25 October 2016.
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