CPC Plant Profile: Dwarf Iliau
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Plant Profile

Dwarf Iliau (Wilkesia hobdyi)

Closeup of flowering plant. Notice the lax inflorescences specific to this species. Photo Credit: D. Ragone
Description
  • Global Rank: G1 - Critically Imperiled
  • Legal Status: Federally Endangered
  • Family: Asteraceae
  • State: HI
  • Nature Serve ID: 128454
  • Date Inducted in National Collection: 05/28/1986

The genus Wilkesia (Asteraceae) contains two species endemic to Kauai. One of these, Wilkesia hobdyi, is threatened. This plant is currently found only on nearly vertical rock outcrops in western Kauai, and is threatened by the actions of feral goats. Goats were brought to the islands of Hawaii by Europeans as a food source in the late 1700s, and quickly spread throughout even the most remote areas of the islands. Goats caused extensive damage to Hawaiian plant species, as they evolved in the absence of grazing mammals and therefore had no defense mechanisms to limit the detrimental effects of browsing. Since then, feral goats have reduced or eliminated whole populations of native plants, leaving remnant plant populations behind only on the steepest and most inaccessible cliffs, where even the sure-footed goat doesnt venture. Such is the fate of this species, the dwarf iliau. This small member of the sunflower family (Asteraceae) is a short-lived perennial shrub, which branches from the base and can grow up to 60 centimeters tall. The tip of each branch bears a cluster of narrow leaves (about 7.5 to 15 centimeters long) growing in whorls joined together into a short sheathing section at their bases. The cream-colored flower heads grow in clusters that are about 2 centimeters in diameter (USFWS 1995). Flowering plants have been observed in June, September, October, and December (Wagner et al. 1999). Wilkesia hobdyi (Asteraceae), a conspicuous, cliff-dwelling Kauai endemic in the Silversword radiation, is known only from the highly fragmented dry cliffs of the iconic and rugged Na Pali Coast. It is the diminutive cousin of the more widespread Kauai Greensword, W. gymnoxiphium (Iliau in Hawaiian), and is also sometimes referred to as Dwarf Iliau or the Dwarf Greensword.

Participating Institutions
Updates
  • 10/15/2020
  • Propagation Research

The laboratory germination time was 2 months (Yoshinaga 2002).

  • 10/15/2020
  • Orthodox Seed Banking

The seeds of W. hobdyi have been tested at the National Tropical Botanical Garden (NTBG) finding that they are orthodox and can tolerate freezing.

  • 10/15/2020
  • Living Collection

In addition, there is one plant growing in the nursery and 14 individuals representing two out of the five populations growing in the grounds of the botanical garden.

  • 10/15/2020
  • Orthodox Seed Banking

The National Tropical Botanical Garden (NTBG) currently has ex situ holdings of 1,480 seeds in its seed bank, which represents four out of the five populations.

  • 10/15/2020
  • Propagation Research

For these accessions, initial viability tests are still ongoing and the germination after about nine months is 1.5-5.5% on agar substrate with all germination so far occurring within about a month.

Adam M. Williams, Ben Nyberg, Anna Sugiyama
  • 10/29/2019

In addition to competition from naturalized plants, introduced goats are the primary threat to its continued survival through direct browsing of all plants they can reach. Consequently, W. hobdyi is restricted to nearly vertical cliff faces where the goats are unable to reach, mostly on North-facing slopes from Haeleele Ridge in the Southwest to Waiahuakua Ridge in the Northeast.
 
UAS (unmanned aircraft systems, a.k.a. drone technology) have provided a platform for in-depth inventory and monitoring of cliff habitat, which often serves as refugia from invasive goats and pigs. In the last several years, development of UAS survey techniques has led to the discovery of new Endangered plant populations and range extensions for multiple rare plant species on Kauai.
 
The use of UAS will be continued to be refined in combination with rope-trained field botanists by focusing on the Endangered W. hobdyi. When utilized for survey and mapping, the UAS has allowed for remote observation of phenology, the creation of detailed maps of individuals and populations, and has led to a tremendous increase in known plants, from approximately 750 to 5,923. On the ground, the drone assists in locating fruiting plants and guiding collectors directly to them, greatly improving safety and efficiency while working on ropes, and leading to improved collections for ex situ conservation facilities. Building on these successes will allow for future habitat assessmen t and niche modeling to inform climate change adaptation efforts and guide in situ restoration and research activities.
 
For these accessions, initial viability tests are still ongoing and the germination after about nine months is 1.5-5.5% on agar substrate with all germination so far occurring within about a month. Storability of this species is unknown but seeds of a congener Wilkesia gymnoxiphium is storable for 10+ years at -18ºC. Seeds stored at -18ºC are scheduled to be tested for long-term viability tests in 10 years.

Nature Serve Biotics
  • 05/02/2017

G1S1.2 Endemic to the northwestern coast of the island of Kauai. This species is known from fewer than 10 occurrences, totaling fewer than 1,000 plants. The cliffs of northwestern Kauai are experiencing heavy degradation by feral goats, affecting all of the Wilkesia hobdyi occurrences. Goats are also known to browse on the species. Other threats include alien plants.

  • 01/01/2010

Threats to W. hobdyi include habitat disturbance and browsing by feral goats. Although the low number of individuals and their restricted habitat could be considered a potential threat to the survival to the species, the plant appears to have vigorous rep

  • 01/01/2010

Number of Populations: 5 (USFWS 2001) Number of Plants: <300 (USFWS 2001)

  • 01/01/2010

Essential habitat areas for all listed, proposed, and candidate plants and evaluated species of concern were identified to determine if essential habitat areas would provide for their habitat needs (USFWS 2002). The seeds of W. hobdyi have been tested at the National Tropical Botanical Garden (NTBG) finding that they are orthodox and can tolerate freezing. The laboratory germination time was 2 months (Yoshinaga 2002).

  • 01/01/2010

A recovery goal stated for W. hobdyi included the establishment of eight to ten populations with a minimum of 300 individuals per population on Kaua'i (USFWS 2002). The National Tropical Botanical Garden (NTBG) currently has ex situ holdings of 1,480 seeds in its seed bank, which represents four out of the five populations. In addition, there is one plant growing in the nursery and 14 individuals representing two out of the five populations growing in the grounds of the botanical garden.

  • 01/01/2010

1. Pollination biology and seed dispersal mechanism studies need to be done. 2. Map genetic diversity in the surviving populations of W. hobdyi. 3. Test the influence of weeding and fencing on populations of W. hobdyi. Recommendations derived from M.H. Chapin and M. Maunder.

  • 01/01/2010

1. Establish secure ex situ stocks with full founder representation. 2. Develop proper horticultural protocols and pest management for W. hobdyi. 3. Survey ex situ holdings and conduct molecular fingerprinting. Recommendations derived from M.H. Chapin and M. Maunder.

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Photos
Nomenclature
Taxon Wilkesia hobdyi
Authority H. St. John
Family Asteraceae
CPC Number 4421
ITIS 196323
USDA WIHO3
Common Names dwarf liau | dwarf iliau
Associated Scientific Names Wilkesia hobdyi
Distribution W. hobdyi, an endemic to Kauai, was first collected in 1968 on Polihale Ridge, and was not formally described until 1971. W. hobdyi occurs on State and privately owned lands and may occur on or near F

Elevation between 275 m and 400 m. Polihale and Kaaweiki, Kauai. Only very restricted Kauai endemic are presently known.
State Rank
State State Rank
Hawaii S1
Habitat

W. hobdyi grows on coastal dry cliffs or very dry ridges from 275 to 400 meters (900 to 1,310 ft) elevation (USFWS 2000).Associated species of W. hobdyi include Artemisia sp. (sagebrush), W. gymnoxiphium (iliau), Lipochaeta connata (nehe), Lobelia niihauensis (no common name [NCN]), Peucedanum sandwicense (makou), Hibiscus kokio subsp. saint johnianus (kokio), Canthium odoratum (alahee), Peperomia sp. (ala ala wai nui), Myoporum sandwicense (naio), Sida fallax (ilima), Waltheria indica (uhaloa), Dodonaea viscosa (aalii), and Eragrostis variabilis (kawelu).

Only from highly fragmented dry cliffs of the iconic and rugged Na Pali Coast. Occurring on very dry rdiges.

Ecological Relationships

W. hobdyi is probably pollinated by insects and is probably self-incompatible. Flowering was observed most often in the winter months, but also during June. Fruits may be dispersed when they stick to the feathers of birds. Hybridization with W. gymnoxiphium may be occurring. (Sakai et al. 1995)

Pollinators
Common Name Name in Text Association Type Source InteractionID
Other
Insects Suspected Pollinator Floral Link

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