Viola kauaensis A. Gray var. hosakae (H.St.John) Havran & Ching Harbin, 2014

Havran, J. Christopher, Harbin, Susan Ching & Portner, Talia, 2014, Viola kauaensis var. hosakae (Violaceae), a new variety of endemic Hawaiian violet, PhytoKeys 39, pp. 35-48 : 44-45

Viola kauaensis A. Gray var. hosakae (H.St.John) Havran & Ching Harbin comb. et. stat. nov. Figure 1B , 3 Additional figures: St. John (1989) Bot. Jarb. Syst. 111(2) 165-204 (Figure 4).

Basionym.

Viola hosakae H.St.John, Botanische Jarbücher für Systematik, 111(2), 173, 1989.

Type.

Hawai`i, O`ahu Island, Ko`olau Range, divide between head of Kawainui and Kaipaupau Gulches, rare in bog, 860 m elev., E.Y. Hosaka 2504; July 3, 1938 (holotype: BISH! Sheet no: 72125).

Description.

Rhizomatous herb, rhizome creeping rhizome stipules 1.5-3.0 mm long, 1-2 mm wide, often overlapping and scaly in appearance; vertical stems produced from rhizome, internodes on vertical stem longer than on rhizome, stipules 2.0-5.0 mm long, 1.0-2.5 mm wide. Flowers solitary on terminal peduncle, flower subtended by opposite pair of small linear bracts on peduncles. Chasmogamous flower characteristics as in St. John (1989): dorsal sepal 5 × 1.4 mm, elliptic; lateral sepal 4.5 × 1.4 mm, obovate elliptic; ventral sepal 5.6 × 1.4 mm, lance elliptic; dorsal petals 15 × 3.3 mm, with a 4 mm claw and an elliptic blade; lateral petals 14 × 2.6 mm, with a broad 4 mm claw and an elliptic blade; ventral petal 16 mm long, with a curved 6 mm channeled claw, and an elliptic blade that is 5 mm wide; dorsal stamen 3.9 mm long, filament 0.5 mm long, stout, oblique, anther 2.5 mm long, narrowly obovoid ellipsoid, sterile tip 1.3 mm long, ovate; lateral stamen 3.9 mm long, filament 0.5 mm long and broad, anther 2.3 mm long, narrowly cuneoid, sterile tip 1.3 mm long, ovate, acute; ventral stamen 3.6 mm long, filament 0.5 mm long and wide, anther 2.3 mm long oblanceoloid, sterile tip 1.5 mm long, lanceolate, nectary 1.5 mm high, 0.8 mm wide, arcuate oblong, basal; pistil 2.8 mm long; style 1 mm long; stigma discoid, divergent at 45°; chasmogamous flowers not seen (see methods). Cleistogamous flowers with linear sepals 5, green, 5-6 mm long, 1 mm wide, bases auriculate, apices acuminate, enclosing all other floral organs; petals 5 or fewer, up to 3 mm long, 1 mm wide, white, with withered appearance; stamens 2, 1.5 mm long, filament 1 mm long, anthers 0.5 mm long and at end of filament, anther in direct contact with stigmatic surface of pistil; pistil 2 mm long, ovary 1.5 mm long, style 0.5 mm long, curved at approximately 180˚ towards ovary. Fruit a capsule, capsule valves 7-9 mm long.

Distribution.

Hawaiian Islands, O`ahu: Poamoho summit region of Ko`olau Mountains.

Specimens Examined.

Hawaiian Islands: O`ahu: Laie, 19 Dec 1937, Hosaka 1927 (BISH); Main divide, crest of Ko`olau Mts, above Kaipapau Gulch, 31 May 1937, Fosberg 13973 (BISH); Main divide, crest of Ko`olau Mts, above Kaipapau Gulch, 24 Jul 1937, Fosberg 14229 (BISH); About one half mile south of Poamoho trail along the Ko`olau Summit trail, 20 May 2013, Havran 2013.4 (BISH); About one half mile south of Poamoho trail along the Ko`olau Summit trail, 20 May 2013, Havran 2013.5 (BISH); Ko`olau Mt summit, on small hill at Puu Pauau, between Poamoho and Schofield-Waikane trail, on west side of Summit trail, about 50 ft. from trail, 12 Mar 1995, Perlman 14704 (PTBG); Ko`olau Mts. Between summit of Poamoho trail and Schofield trail, along summit crest on small hill, about 0.5 miles south of cabin, 7 Sep 1987, Perlman 6456 (PTBG).

Conservation status.

Viola kauaensis var. hosakae appears very rare on O`ahu. Despite frequent and thorough conservation work by multiple organizations in the summit area of the Ko`olau Mountains, only one population of the variety is known to exist. The population is threatened by grazing ungulates. In addition, island tropical montane environments, like the ones harboring Viola kauaensis var. hosakae, are incredibly susceptible to global climate change ( Loope and Giambelluca 1998).

Viola kauaensis var. hosakae is best classified as Critically Endangered (CR) according to the IUCN Red List Criteria as it meets the following criteria: B. Area of occupancy less than 10 km2, number of populations = 1, and continuing decline inferred from extent of occurrence and area of occupancy as indicated from herbarium records and personal communication; C. Number of mature individuals less than 250 and an estimated continuing decline (C2) with less than 50 mature individuals in each subpopulation (C2i).

The Plant Extinction Prevention Program (PEPP) branch on O`ahu will work to preserve this taxon on by collecting and germinating seeds when possible. Efforts are underway to enclose the population within an ungulate fence by the end of 2014. An additional population can be started with propagules from the extant population. The cleistogamous reproduction of the variety should help to facilitate seed production in the absence of pollinators at a new location.

Figures

Figure 1. Viola kauaensis var. hosakae on O'ahu. A Habitat composed of mossy slope B Individual in fruit. (Photo credits: A J. C. H., B Joel Lau).

Figure 3. Type of Viola kauaensis var. hosakae.