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16.15 Taxon Summary: Hedyotis parvula

2 Photographer: J. Obata 4 Scientific name: Hedyotis parvula (A. Gray) Fosb. 6 Hawaiian name: None known Family: (Coffee family) 8 Federal status: Listed endangered

10 Description and biology: Hedyotis parvula is an erect to sprawling perennial shrub with branches measuring 10-30 cm (4-12 in) long. Its oppositely arranged leaves are 1-4 cm (0.4-1.6 12 in) long. Its inflorescences are borne at the tips of the branches. The flowers’ corollas usually have four lobes, which are white to white tinged with purplish pink towards their tips, and 14 measure 5-6 mm (ca. 0.2 in) long. The flowers are either perfect (possessing both male and female reproductive parts), or pistillate (possessing only female reproductive parts). The 16 capsules are almost round, measure about 3.3-4.0 mm (0.1-0.2 in) long, split open across the top upon maturity, and contain small dull brown seeds. 18 As with certain other Hawaiian cliff (Viola chamissoniana subsp. chamissoniana and 20 Brighamia spp. for instance) the flowers of H. parvula are relatively large and white or light colored, and are prominently displayed above the ’s foliage, suggesting that the species’ 22 pollinating agent are night-flying moths. Flowering and fruiting has been recorded throughout the year. Little is known about H. parvula's breeding system and seed dispersal agents. The 24 longevity of individuals of this species is unknown, but since the plant is a small shrub, its longevity is presumed to be less than 10 years, and it is therefore a short-lived species for the 26 purposes of the Implementation Plan.

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Known distribution: Hedyotis parvula is endemic to the Waianae Mountains, and has been 30 documented throughout the mountain range. Recorded elevations for this species range from 720-830 m (2,350-2,730 ft). 32 Population trends: All of the currently known populations of H. parvula were discovered 34 within the past decade, so little information on the species’ population trends is available. The only colony whose population trend is known is the eastern group of on Ohikilolo Ridge. 36 The colony reportedly had more than 100 plants when it was discovered in 1993. Today it numbers fewer than 20 (Kawelo pers. comm. 2000). 38 Current status: Three H. parvula population units are known, totaling fewer than 150 40 individuals. About 60-70 are found on Ohikilolo Ridge on the Makua Military Reservation. The species' current population units are listed in Table 16.43 and their sites are plotted on Map 42 16.23. All of the sites are proposed for management for stability. Sites are characterized in Table 16.44 and threats to the plants at these sites are identified in Table 16.45. 44 Habitat: Hedyotis parvula typically grows on cliff faces or on exposed rocky ridges. The 46 vegetation in these areas is mesic, usually short and sparse, and includes native herbs, grasses, sedges, and shrubs. 48 Taxonomic background: The Hedyotis is subdivided into a number of sections, several 50 of which are present in Hawaii. Hedyotis parvula belongs to the section Wiegmannii, which includes three taxa native to the Waianae Mountains, namely H. schlectendahliana, H. degeneri 52 var. degeneri, and H. degeneri var. coprosmifolia. Other Hedyotis taxa of the Waianaes include H. terminalis of the section Gouldia, H. centranthoides of the section Gouldiopsis, and H. 54 coriacea of the section Protokadua. All of these relatives of H. parvula potentially occur near H. parvula. 56 Outplanting considerations: The most important Hedyotis taxa to avoid when selecting H. 58 parvula’s potential outplanting sites are the rare ones. These are H. degeneri var. degeneri, which is moderately rare; H. degeneri var. coprosmifolia, which was last seen in the 1980's; and 60 H. coriacea, which has not been reported on Oahu since the 1800's, and is still extant but very rare on Hawaii and West Maui. 62 The co-occurrence of two or more species of Hedyotis is very common in Hawaii. Certain 64 herbarium specimens of Hawaiian Hedyotis have been identified as probable hybrids (Wagner and Lorence 1998), but there has been no in-depth study of hybridization in the genus in Hawaii 66 or the potential for it, either in the wild or in greenhouse experiments. All species of Hedyotis native to the Waianae Mountains have small green or yellow flowers with the exception of H. 68 parvula, with its large white flowers. These marked floral differences suggest that H. parvula’s pollinators are different from those of other species of Hedyotis with which H. parvula 70 potentially occurs. The presumed difference in pollinators lessens the likelihood of hybridization between H. parvula and other Hedyotis species of the Waianae Mountains. The presence of 72 common Hedyotis taxa at potential H. parvula outplanting sites does not appear to be cause for concern since it is natural for H. parvula to grow near other members of the genus. In any case,

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Chapter 16.15 Taxon Summary: Hedyotis parvula 16-93

74 it would be impossible to find sites appropriate for H. parvula where common Hedyotis taxa are absent. 76 There are noticeable morphological differences among herbarium specimens of H. parvula. 78 These differences may be genetically based. Hedyotis parvula forma sessilis is a form that was described based on its leaf shape (Fosberg 1943). It was thought that the plants from the 80 southern Waianae Mountains represented this form, whereas the plants from the northern Waianaes represented the typical form H. parvula forma parvula. Findings from additional 82 study of the morphological differences within the species may result in future alterations of the species’ conservation plans. 84 Threats: Feral goats and pigs constitute major threats to H. parvula. Although many plants 86 grow on steep cliffs where they cannot be reached by ungulates, many others are within their reach. Furthermore, the animals degrade the plants’ habitat by hastening the spread of invasive 88 weeds and by disturbing substrates above the cliffs, thus increasing the size and frequency of landslides and rock falls, which directly affect even the inaccessible plants and their steep cliff 90 habitat. Alien plants threaten H. parvula by altering the species’ habitat and competing with it for moisture, light, nutrients, and growing space. Also, the spread of highly flammable alien 92 grasses increases the incidence and destructiveness of wildfires.

94 Table 16.43 Current Population Units of Hedyotis parvula. The numbers of 96 individuals include mature and immature plants, and do not include seedlings. Population units proposed for management are shaded. Island Population Unit Name Total No Management Number of Management Proposed Individuals Proposed Oahu: Halona 64-79 0 64-79 Ohikilolo Makai 50 0 50 Ohikilolo Mauka 17 0 17 98

100

102

104

106

108

110

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114 Table 16.44 Site Characteristics for Population Units of Hedyotis parvula Proposed for Management for Stability. Population Unit: Site Characteristics: Habitat Quality Terrain Accessibility Existing Fence

Halona Medium-Low to High- Steep to Vertical Low to High None Medium Ohikilolo Makai High- Medium Steep to Vertical Low Large

Ohikilolo Mauka High- Medium Steep to Vertical Low Large

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118 Table 16.45 Threats to Population Units of Hedyotis parvula Proposed for Management for Stability. Population Threats: Unit: Pigs Goats Weeds Rats Black Slugs Other Fire Fire Erosion Human Twig and Arthro- Ignition Fuels Distur- Borer Snails pods bance Halona Low to Low to High Unknown Unknown Unknown Unknown Very Medium Low Low to High Medium A A A A high Medium Ohikilolo Makai Low Low Medium Unknown Unknown Unknown Unknown Very Medium Low Low A A A A high Ohikilolo Mauka Low Low Medium Unknown Unknown Unknown Unknown Very Medium Medium Low A A A A high 120

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