Status of native flowering plant species on the south slope of Haleakala, East Maui, Hawaii

Abstract

In an attempt to provide a basis for conservation measures for the remaining leeward native vegetation of East Maui, an assessment was made of the past and present status of all flowering plant species known from the area. The unpublished 1920 field notes of C. N. Forbes provided a major source of information on past status. Present status was determined by field exploration. A total of 237 native species in 70 families and 139 genera once occurred in the study area, which extends from sea level to 3000m (10,000 ft). Of the native flowering plants of the study area 86% are endemic to the Hawaiian Islands; 28% are endemic or have infraspecific taxa endemic to the island of Maui. Fourty-six (19%) of the species once present in the study area have neither been encountered by this survey nor recently noted by others and are considered extirpated. Of these, 23 species have surviving populations elsewhere in the Hawaiian Islands, though in some cases the study area populations represent endemic subspecific taxa. The remaining 23 species (10%) are apparently extinct. Of these extinct species, 20 species were endemic to East Maui. Extinct endemic species of the study area include: Canavalia forbesii, Cladocarpa hispida, Cyanea arborea, C. comata, Cyrtandra begoniaefolia, Gouania lydgatei, G. pilata, Hedyotis foliosa, Hibiscadelphus wilderianus, Pelea tomentosa, Phyllostegia hillebrandii, Schiedea implexa, Sicyos hillebrandii, Solanum haleakalaense, Stenogyne cinerea, S. glabrata, S . haliakalae, and S. vagans. Major factors currently contributing to the continuing serious decline of native vegetation and flora of leeward East Maui include : browsing and grazing by feral goats and feral and domestic cattle; feeding and digging by feral pigs; and displacement of reproduction of native plant species by introduced plant species - especially Pennisetum clandestinum, Holcus lanatus, and Bidens pilosa. Although most native species consistently produce flowers and fruits, this survey found little or no evidence of successful reproduction of most woody species. Dodonaea eriocama and Wikstroemia monticola are the only native species which appear to be maintaining vigorous, abundantly reproducing populations in spite of habitat degradation. Although Haleakala National Park appears to provide a relatively secure "refuge" for many species of the study area, the park by no means includes a representative sample of the vegetation and flora of leeward East Maui. Of the 237 species of native flowering plants recorded in the study area by this survey, only 108 species (46%) have also been recorded as naturally occurring within the park. However, in spite of the advanced deterioration of East Maui's native leeward vegetation, sites containing significant remnants of the former vegetation still exist outside the park and provide opportunities for preservation.