Hesperomannia lydgatei

No Common Name

Description

Hesperomannia lydgatei is a sparsely branched small tree of the aster family that stands 6.5-13 ft (2-4 m) high. Its alternately arranged lance-shaped or elliptic leaves are broader above the middle, paler beneath, 4-12 in (10.2-30.5 cm) long, and 1.4-3.5 in (3.6-8.9 cm) wide. The flower heads cluster in groups of four and five on slender stems at the ends of branches, pendant only when mature. Flower heads consist of four to eight circles of overlapping bracts, of which the outer are purplish or brownish and the inner are silver; these surround slender tubular yellow florets that are 0.9-1 in (2.3-2.5 cm) long. Flowering material was collected from July to November. Almost no mature fruits develop, and it is possible that H. lydgatei is self-infertile and fails to set seed unless cross-pollinated with other individuals. The abortive fruits are crowned by a plume-like cap of light brown hairs 0.8 in (2 cm) long. The purple flower heads with long tubular florets suggest pollination by long-tongued insects such as moths or butterflies, although field observations are required to confirm this. Absence of the appropriate pollinator or pollinators could be responsible for the observed lack of viable seeds. However, several seeds collected from plants at Waioli Stream Valley apparently possessed embryos and germinated successfully at the Hawaii Plant Conservation Center nursery. Also, since 31% of the current population is made up of juvenile plants, this species appears to be reproducing adequately in the wild.

The plumelike hairs crowning the fruit of H. lydgatei strongly suggests dispersal by wind, as in many members of the aster family. This species grows almost exclusively along streams, however, so dispersal by water currents is also likely. Specific details regarding growth rates, the age at which trees begin flowering in the wild, the length of time they remain reproductive, and the longevity of the plants are unknown.

Habitat

The original Forbes and Lydgate collections of H. lydgatei were made in the Wahiawa Mountains in 1908 and 1909. They noted it to be rare and local in occurrence, appearing only in dense wet forest in the Wahiawa drainage at 1,970-2,460-ft (600.5-749.8-m) elevations. The species was not re-collected again until 1955.

The habitat of H. lydgatei in the upper Waioli Stream Valley below Namolokama Mountain, similar to its habitat in the Wahiawa Drainage, consists of lowland rain forest dominated by Metrosideros and Dicranopteris at an elevation of 1,300 ft (396.2 m).

Distribution

H. lydgatei, by far the most abundant of the listed species in this ecosystem, has 281 individuals—195 adults and 86 juveniles—recorded at eight localities in the Wahiawa Drainage. Judging by the substantial number of juveniles, this species seems to be regenerating well. In December 1991 a disjunct population of three plants was located in the upper Waioli Stream Valley below Namolokama Mountain. Two of these plants were killed and the third damaged by Hurricane Iniki in September 1992. Further fieldwork is needed in the Waioli Stream Valley to determine the vigor of this individual and to survey for others that may be in the area.

Threats

Low numbers and the presence of alien plant species threaten H. lydgatei.

Conservation and Recovery

Examination of numerous fruiting heads of H. lydgatei plants from the Wahiawa area revealed that virtually all of the seeds were aborted. Efforts to germinate seeds from Wahiawa plants at the National Tropical Botanical Garden and at the Honolulu Botanical Gardens have failed. Several viable seeds were collected from a plant in Waioli Stream Valley, although most of the seeds were insecteaten. Five seeds were planted at the National Tropical Botanical Garden's Hawaii Plant Conservation Center nursery, four of which germinated. No conservation efforts at natural sites have been attempted.

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/

Pacific Remote Islands Ecological Services Field
Office
300 Ala Moana Blvd., Room 3-122
P.O. Box 50088
Honolulu, Hawaii 96850
Telephone: (808) 541-1201
Fax: (808) 541-1216

References

Carlquist, S. 1957. "Systematic Anatomy of Hesperomannia. " Pacific Science 11: 207-215.

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

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

Stone, C.P., and J.M. Scott, eds. 1985. Hawaii's Terrestrial Ecosystems: Preservation and Management. Cooperative National Park Resources Study Unit, University of Hawaii Press, Honolulu.

Wagner, W.L., D.R. Herbst, and S.H. Sohmer. 1990. Manual of the Flowering Plants of Hawaii. University of Hawaii Press and Bishop Museum Press, Honolulu.