Tetramolopium remyi

No Common Name

Description

Tetramolopium remyi, a member of the aster family (Asteraceae or Compositae), is a much branched, decumbent (reclining, with the end ascending) or occasionally erect shrub up to about 15.8 in (40.1 cm) tall. Its leaves are firm, very narrow, 0.6-0.98 in (1.5-2.5 cm) long, and with the edges rolled inward when the leaf is mature. There is a single flower head per branch. The heads are 0.4-0.6 in (1.0-1.5 cm) in diameter and on stalks 1.6-4.7 in (4-12 cm) tall; each comprises 70-100 yellow disk and 150-250 white ray florets. The stems, leaves, flower bracts, and fruit are covered with sticky hairs. T. remyi has the largest flower heads in the genus. Two other species of the genus are known historically from Lanai, but both have purplish rather than yellow disk florets and from four to 60 rather than one flower head per branch.

T. remyi flowers between April and January. Field observations suggest that the population size of the species can be profoundly affected by variability in annual precipitation; the adult plants may succumb to prolonged drought, but apparently there is a seed-bank in the soil that can replenish the population during favorable conditions. Such seed banks allow populations of arid-dwelling plants to persist even through very adverse conditions. The aridity of the area, possibly coupled with human-induced changes in the habitat and subsequent lack of availability of suitable sites for seedling establishment, may be a factor limiting population growth and expansion. Requirements of this species in these areas are not known, but success in greenhouse cultivation of these plants with much higher water availability implies that, although these plants are drought-tolerant, perhaps the dry conditions in which they currently exist are not optimum. Individual plants are probably not long-lived. Pollination is thought to be done by butterflies, bees, or flies.

Habitat

The habitat of T. remyi is lowland dry shrubland on dry, exposed ridges or flats. Its elevational range has historically been 500-2,500 ft (152.4-762 m). The only known extant population occurs at about 660 ft (201.2 m) elevation on nearly barren red lateritic soils in a highly overgrazed area in Dodonaea viscosa-Heteropoqon contortus shrubland. Associated native species include Bidens mauiensis, Bidens menziesii, Eragrostis grandis, Lipochaeta heterophylla, and Waltheria indica. Associated alien species include lantana, fountain grass, and Acacia farnesiana.

Distribution

T. remyi has been collected in the past in widely scattered localities on dry ridges of Lanai at elevations between 330 and 820 ft (100 and 250 m). The only known current population of T. remyi is very small and probably dwindling, although a substantial seed bank may exist in the vicinity of this occurrence, which consisted of six individuals as of July 1992 and seven individuals as of October 21, 1992. Deer had eaten all adults and all but two seedlings as of May 21, 1993. The population is, or was, in an area of about 2,475 sq ft (230 sq m) in dry shrubland on the north side of Aualua Ridge at approximately 720 ft (219.5 m) elevation. Although this population has fluctuated from between six and 100 individuals in 1978 to a confirmed six individuals in the summer of 1992, this is not complete proof of a terminal decline. Population size in T. remyi can fluctuate quite dramatically depending on the timing and amount of seasonal rainfall. Since the plants are not conspicuous and the area is not regularly explored by botanists, there is clearly a possibility that additional Lanai populations exist.

This species also had historical occurrences in dry exposed ridges or flats and in the foothills of southern West Maui above Ma'alaea Bay; not documented from Maui since 1944, it is probably extirpated from this island.

Threats

Only one population of two individuals of T. remyi is known. This tiny population automatically means a very limited gene pool, which may depress reproductive vigor. Whether or not genetic limitations pose a problem, any natural or man-caused environmental disturbance could easily destroy the remaining individuals.

Although the vegetation near the last known occurrence of T. remyi is largely native and dominated by Heteropogon contortus and Dodonaea viscosa, alien plant species are invading the vicinity. The immediate threats are broomsedge and Guinea grass, both established near T. remyi habitat; if they invade, the tiny plants of this species could easily be displaced and eliminated by the aggressive exotics.

The habitat of T. remyi has been severely degraded by grazing and browsing of livestock and exotic game animals. Much of the native vegetation has been removed, increasing wind erosion of the fragile soils. Axis deer and mouflon are both occasionally present in the vicinity of the only known population of this species. A single incident of grazing or trampling by these animals could easily destroy any or all of the few remaining individuals of this species.

Because the only population of T. remyi grows on a dry part of the island where fires do occasionally occur, a single fire could cause extinction of the species.

Due to the extremely small number of individuals in a single population and the vulnerability of the site to predation by herbivores, invasion by alien weeds, and drought, mismanagement of the population is a particularly critical potential threat to the existence of the species.

Management tactics must be well thought out and closely monitored to ensure that they do not jeopardize the population in unexpected ways. Fencing to exclude herbivores without provisions to remove weeds could allow unrecoverable invasion by alien plants; excessive seed collection for propagation could lead to insufficient seeds at the site for natural reproduction; collection of meristem tissue for tissue culture could kill individuals or allow pathogens to become established due to tissue damage; and site disturbance by improper or careless management efforts such as trampling or unmonitored fencing could adversely affect the survival of the sole remaining population.

Conservation and Recovery

The Hawaii Plant Conservation Center collected fruit from T. remyi from Lanai in May 1990. Two hundred ninety-five seeds were stored in the Hawaii Plant Conservation Center collection as of June 1993. The species has also been grown by the Hawaii Department of Land and Natural Resources on Maui, although no material is currently in cultivation there. Research has been conducted on various aspects of T. remyi, including its evolutionary relationships.

Contact

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/

References

Cuddihy, L.W., and C.P. Stone. 1990. Alteration of Native Hawaiian Vegetation: Effects of Humans, Their Activities and Introductions. University of Hawaii Cooperative National Park Resources Study Unit, Honolulu.

Culliney, J.L. 1988. Islands in a Far Sea: Nature and Man in Hawaii. Sierra Club Books, San Francisco.

Lowrey, Timothy K. 1990. " Tetramolopium." In Manual of the Flowering Plants of Hawai'i, by W.L. Wagner, D.R. Herbst, and S.H. Sohmer. University of Hawaii Press and Bishop Museum Press, Honolulu.

Tomich, P.Q. 1986. Mammals in Hawai'i. 2d ed. Bishop Museum Special Publication 76. Bishop Museum Press, Honolulu.