Po'e

Portulaca sclerocarpa

Description

Po'e, Portulaca sclerocarpa, is a perennial herb with a fleshy, tuberous taproot that becomes woody, and has stems up to about 7.9 in (20 cm) long. The stalkless, succulent, grayish-green leaves are almost circular in cross-section, 0.3-0.8 in (0.8-2 cm) long, and about 0.06-0.1 in (1.5-2.5 mm) wide. Dense tufts of hairs are located in each leaf axil and underneath the tight clusters of three to six stalkless flowers grouped at the ends of stems. Sepals are about 0.2 in (5 mm) long and have membranous edges. Petals are white, pink, or pink with a white base, about 0.4 in (10 mm) long, and surround about 30 stamens in an eight-branched style. The hardened capsules are about 0.2 in (5 mm) long, have walls thick, open very late or not at all, and contain glossy, dark reddish-brown seeds about 0.02 in (0.5 mm) long. This species differs from other native and naturalized species of the genus in Hawaii by its woody taproot, its narrow leaves, and the color of its petals and seeds. Its closest relative, P. villosa, differs mainly in its thinner-walled opening capsule.

This species was observed in flower during December 1937, March 1977, and June 1978. The presence of juveniles indicates that pollination and germination are occurring.

Habitat

This species typically grows in montane dry shrub-lands, often on bare cinder, and even near steam vents, at elevations of 3,380-5,340 ft (1,030-1,630 m). Associated species include mamane and 'ohi'a.

Distribution

Historically, this species was found on an islet off the south coast of Lanai, and at several locations on the island of Hawaii: in the Kohala Mountains, on the northern slope of Haualalai, the northwestern slope of Mauna Loa, and near Kilauea Crater.

Since 1975, one extant population that consists of ten individuals is known to occur off the coast of Lanai on Poopoo and 11 extant populations, numbering more than 1,000 plants, are known to occur on federal, state and private lands on the island of Hawaii.

Individuals were found on three puu (hills) on the Parker Ranch in the early 1980s. The individuals appeared healthy, but not in flower or fruit. The populations within Hawaii Volcanoes National Park occur primarily in the Puhimau geothermal (fumarole) area. In 1983, approximately 4,300 plants were counted but, in 1993-94, the number had declined to 970. The reason for this decline is unknown. The taxon is currently known at two other locations in the park: Keanakakoi Crater Rim (less than 10 plants), and Hilina Pali Road (less than 10 plants). The Footprints Trail population in the Kau Desert consisted of less than 10 plants in the 1970s, but had not been observed in the late 1990s.

In 1991, a single individual was found growing on the western portion of the U. S. Army's Pohakuloa Training Area. In 1993 and 1994, two more populations were discovered in the southwestern portion of the training area. The populations occur approximately 1.5 mi (2.4 km) apart and grow in pockets of eroded pahoehoe lava. Individuals in both populations were healthy, flowering, and producing seed. Numerous juveniles were present in both populations. In 1995, two more plants were found on the 1859 lava flow in the Puuanahulu area. One plant was producing seed.

Threats

A major threat to P. sclerocarpa is competition from alien grasses such as Pennisetum setaceum (fountain grass) and Andropogon virginicus. Although no browsing has been observed, goats, pigs, and sheep trample and disturb the habitat, damaging the understory and providing suitable sites for noxious invaders such as Heterotheca grandifiora. Fire is also a pervasive problem in such dry habitat. The unknown reason for the decrease in numbers from 4,300 in 1983 to 970 in 1994 in the Puhimau geothermal (fumarole) area within Hawaii Volcanoes National Park is of concern. Small numbers of populations and individuals and their scattered distributions decrease reproductive viability and increase vulnerability to random events.

Conservation and Recovery

The National Tropical Botanical Garden has germinated seeds and propagated the taxon. Colorado State University staff germinated seeds in 1993-94. The individuals flowered and set seed.

Propagation and maintenance of ex situ genetic stock should continue. The habitat of this species must be protected from feral ungulates, and competition from alien grasses controlled. Research into the cause of decline in the fumarole area of Hawaii Volcanoes National Park should be undertaken. Efforts should be made to ensure that both Lanai and Hawaii Island populations remain viable. Out-planting of propagated plants may be necessary to augment wild populations.

Contacts

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
http://pacific.fws.gov/

U. S. Fish and Wildlife Service
Pacific Remote Islands Ecological Services Field
Office
300 Ala Moana Blvd., Room 3-122
P.O. Box 50088
Honolulu, Hawaii 96850-5000
Telephone: (808) 541-1201
Fax: (808) 541-1216
http://www.r1.fws.gov/pacific/

Reference

U. S. Fish and Wildlife Service. 4 March 1994. "Determination of Endangered or Threatened Status for 21 Plants from the Island of Hawaii, State of Hawaii." Federal Register 59 (43): 10305-10325.