Coprosma cordicarpa J.Cantley, Sporck-Koehler, & M.Chau, 2016

Cantley, Jason T., Sporck-Koehler, Margaret J. & Chau, Marian M., 2016, New and resurrected Hawaiian species of pilo (Coprosma, Rubiaceae) from the island of Maui, PhytoKeys 60, pp. 33-48 : 36-38

Coprosma cordicarpa J.Cantley, Sporck-Koehler, & M.Chau sp. nov. Figure 1A-F ; Figure 2

Type.

USA. Hawai‘i: Maui: East Maui: Kanaio Natural Area Reserve, near cabin, 29 Sep 2014, J.T. Cantley, M.J. Sporck-Koehler & M.M. Chau JC-479 (holotype: BISH 763458).

Diagnosis.

Differs from other currently recognized species of Coprosma in the Hawaiian Islands primarily by its cordiform fruits formed by a depressed apex and central constriction on female plants, and by large calyces (lobes 2-4 mm vs., for example, 0.25-2.00 mm of Coprosma stephanocarpa and Coprosma foliosa s.l.) on male flowers.

Description.

Shrubs to trees 2-7 m tall, with one to many main stems; young stems sparsely pubescent to puberulent; Seedlings and Juveniles with significantly more trichomes than mature individuals; Leaves opposite, blades 20-56 × 8-25 mm, lanceolate, both surfaces sparsely pilose or glabrous, midrib sparsely puberulent towards base, domatia present on abaxial surface in secondary vein axils, blade apex acute or sometimes rounded, base cuneate; petioles 5-12 mm long; stipules deltate 2-3 mm long, connate 25-50% of their length, base puberulent to lanate with band of glabrous tissue immediately below margin, margin lanate with a conspicuous apical colleter sometimes obscured by two marginal colleters. Inflorescences axillary; male inflorescences a 3-flowered cyme on an unbranched peduncle (3-)7-9(-17) mm long or sometimes trichotomously branched at base, with flowers terminal in groups of 3 on each branch, internodes 5-25 mm long, central branch up to twice as long; female inflorescence solitary, 3-7(-13) mm long or sometimes trichotomously branched at base with solitary flowers terminally occurring on lateral branches and central branch a 3-flowered cyme with sessile central flower, and two lateral flowers on short pedicels, internodes 5-25 mm long, central branch up to twice as long. Flowers: male calyx irregularly toothed, urceolate to campanulate in early development, becoming deeply split due to corolla growth, 2-4 mm long, sheathing basal 1/8-1/4 of the mature corolla, apex red-purple at maturity, corolla 5-6(-8)-merous, campanulate to widely funnelform, lobes 3 × 0.5 mm, stamens 5-6, inserted at base of corolla, filaments exserted to 7 mm, pendulous at maturity; female calyx irregularly toothed at margin, completely connate or nearly so, forming a cylindrical tube around the corolla or occasionally only 1/4 connate, 1.5-3.5 mm long, corolla 5-6-merous, narrowly funnelform to tubular, only lobes exerted beyond calyx, recurving 360 degrees at maturity, lobe apices often touching upper calyx near teeth, styles 2, divided to base, 3 cm long, ca. 0.5 mm diam. Fruit reddish-orange to lemony-yellow, sometimes with red to reddish-purple colored epidermal flecks, cordiform, tapering towards the base, 7-10 × 5-7 mm when dry, with central constriction (furrow) from base to apex present between two seeds, apex depressed between the two seeds, crowned with a conspicuous persistent calyx, drying brown. Seeds 2(-3) plano-convex pyrenes, yellowish-white, 2.3-6.3 × 2.5-5.0 mm × 1.0-3.0 mm, seed operculum 0.5-2.1 mm long.

Phenology.

Flowering specimens were collected from August to September except for one individual in March. Field observations of September 2013 and 2014 found that most individuals of the population at Kanaio Natural Area Reserve and Auwahi were fruiting, and only few flowering. Fruiting specimens were collected across many months, but it is unknown how long fruits were mature on individuals prior to collection.

Distribution.

Known only from southern, leeward slopes of East Maui ( Haleakalā) at elevations of approximately 1000-2000 m, roughly spanning east to west from the Kanaio Natural Area Reserve to the Kaupō Gap Trail. The linear distance is estimated at approximately 21 km, but populations may be disjunct, especially in poor, degraded habitat where ungulates and invasive plant species (i.e. Cenchrus clandestinus (Hochst. ex Choiv.) Morrone) are dominant. Known locations include Kanaio Natural Area Reserve, Auwahi, Kahikinui Forest Reserve, Nu‘u, and the Kaupō Gap Trail. Modern observations of abundance (2013-2015) at Kanaio Natural Area Reserve, Auwahi and Kaupō Gap Trail indicate that it is locally common at all sites. Its present abundance in Nu‘u and Kahikinui Forest Reserve is not known.

Ecology.

In native habitats, Coprosma cordicarpa occurs in dry forest/shrubland habitat with Chrysodracon auwahiensis (H. St. John) P.L.Lu & Morden, Dodonaea viscosa Jacq., Euphorbia celastroides (Boiss) Croizat & Degener var. lorifolia A.Gray, Osteomeles anthyllidifolia (Sm.) Lindl., Leptecophylla tameiameiae (Cham. & Schltdl.) C.M.Weiller, and an understory of Carex wahuensis C.A.Mey. It is often present in in vaded habitats with Cenchrus clandestinus . It occurs primarily in open habitat receiving direct sunlight, but was observed in gulches and high elevation forests along the Kaupō Gap Trail (Seana Walsh, pers. comm.). The rainfall in the distribution of Coprosma cordicarpa varies from 700 to 1900 mm annually with the highest rainfall occurring from December to January ( Giambelluca et al. 2013). Flowering occurs during the dry season, and fruits appear to mature shortly preceding the wettest months, which may represent a germination strategy for this dry habitat taxon.

Etymology.

The specific epithet refers to the heart-shaped fruit, which is a product of the central constriction of the fruit and depressed apex. This character is unique among Hawaiian Coprosma taxa.

Conservation status.

This taxon occurs as scattered individuals that are locally common within five populations on one volcano. When evaluated using the IUCN criteria for extinction risk ( IUCN 2012), Coprosma cordicarpa falls into the Vulnerable (VU) category under Criterion B1ab(iii)+2ab(iii). The VU designation is the lowest of three threatened categories, but indicates the taxon still faces a high risk of extinction in the wild. It has an area of occupancy <2000 km2 and extent of occurrence <20,000 km2, less than 10 known locations that are possibly fragmented, and an observed continuing decline in habitat quality overall. Such suitable habitat may continue decreasing in size without active conservation management. In areas where the landscape has been actively managed for ungulates and invasive plant species (i.e. Auwahi, Kanaio Natural Area Reserve), Coprosma cordicarpa purportedly has displayed a marked natural increase in population size. Further conservation measures may lower extinction risk and change the threatened status of Coprosma cordicarpa .

Specimens examined.

United States of America. Hawai‘i: Maui: East Maui: Hana District, Kaupo Gap, ≈1.75 mi S of Paliku Cabin, alt. 5000 ft, 16 Jul 1969, J.S. Henrickson 5000 (BISH); Haleakalā, Kaupo Gap, 2nd cove S of Waikeke'ehia, 6000 ft, 27 Jun 69, H. St.John 21189 (BISH); Auwahi, 4000 ft, 30 Jun 72, H. St. John 26860 (BISH); Auwahi District, S slope, 18 Dec 1981, A.C. Medeiros 195 (BISH); Auwahi District, S slope, 18 Dec 1981, A.C. Medeiros 195 (BISH); Auwahi, 0.5 km SE of Pu‘u O‘uli, alt. ca. 4000 ft, 24 Jun 1980, P.K. Higashino 9254 (BISH); Auwahi, 24 Nov 1920, C.N. Forbes 2096M (BISH); Auwahi, 20 Mar 1920, C.N. Forbes 2043M (BISH); Auwahi, 1 Feb 1953, J.F.C. Rock 27003 (BISH); 8 mi. E of Ulupalakua, S slope of Haleakalā, alt. 3000-3500 ft, 26 Aug 1976, E.L. Little Jr. 31132 (BISH); SW slope of Haleakalā, Kahikinui FR, S of Kahua Cabin Rd, alt. ca. 4900 ft, 24 Jun 1980, F.R. Warshauer 2684 (BISH); Kahikinui, S Haleakalā, 0.1-0.5 km W of Manawainui Gulch, alt. ca. 4840 ft, June 20, 1980, P.K. Higashino 9234 (BISH); Kanaio NAR, 13 Sept 2013, M.J. Sporck-Koehler s.n. (BISH); Nui, S slope of Haleakalā, 6 Mar 1920, C.N. Forbes 1858M (BISH); Near Kanaio NAR Cabin, 29 Sep 2014, J.T. Cantley, M.J. Sporck-Koehler & M.M. Chau JC-475 (BISH); Near Kanaio NAR Cabin, 29 Sep 2014, J.T. Cantley, M.J. Sporck-Koehler & M.M. Chau, JC-476 (BISH); Near Kanaio NAR Cabin, 29 Sep 2014, J.T. Cantley, M.J. Sporck-Koehler & M.M. Chau JC-477 (BISH); Near Kanaio NAR Cabin, 29 Sep 2014, J.T. Cantley, M.J. Sporck-Koehler & M.M. Chau JC-478 (BISH); Near Kanaio NAR Cabin, 29 Sep 2014, J.T. Cantley, M.J. Sporck-Koehler & M.M. Chau JC-479 (Holotype: BISH); Auwahi restoration unit #1, 29 Sep 2014, J.T. Cantley, M.J. Sporck-Koehler & M.M. Chau JC-480 (BISH); Kahikinui, area east of Manawainui, alt. 5000-6000 ft, K.R. Wood 6247 (PTBG).

Figures

Figure 1. Field images of Coprosma cordicarpa and Coprosma stephanocarpa. A-F Coprosma cordicarpa. A habit and habitat of whole plant with JTC B male stem and inflorescences C female stem and inflorescences D-F fruits illustrating population variation in color and degree of calyx connation G-H Coprosma stephanocarpa G male stem and inflorescence H female stem and inflorescences I immature fruits. All images were taken by the authors, A-C, E from Kanaio Natural Area Reserve D, F from Auwahi G-I from Makawao Forest Reserve. Black scale bar at bottom right indicates the following lengths: 0.5 m (A), 1.5 cm (B-C, E-F), 5 cm (D), 2 cm (G-I).

Figure 2. Photo of the holotype specimen of Coprosma cordicarpa (BISH).