Coprosma stephanocarpa Hillebr.

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 : 39-43

Coprosma stephanocarpa Hillebr. Figure 1G-I ; Figure 3

Type.

United States of America. Hawai‘i: Maui, East Maui, Haleakalā, alt. 3000-6000 ft, 1888, J. Hillebrand s.n. (lectotype, designated by Oliver 1935, pg. 164: isolectotype: BISH!)

Description.

Shrubs to small trees 2-6 m tall, with one to many main stems; young stems sparsely pubescent. Leaves opposite, blades 6-50 × 4-15 mm, elliptic or sometimes lanceolate, sparsely pilose on both surfaces, midrib puberulent, domatia present on abaxial surface in secondary vein axils, apex acute, base cuneate to attenuate, petioles 3-5(-10) mm long; stipules narrowly deltate, often recurving away from stem, 2-4 × 2-3 mm, connate 1/4 to 1/2 of their length, base puberulent to lanate, margins lanate with one apical colleter and no marginal colleters, band of glabrous tissue immediately below the margin. Inflorescences axillary, male inflorescence a 3(-5) flowered cyme on an unbranched peduncle 3-5 mm long; female inflorescence solitary or occasionally 2-3, sessile or subsessile, peduncle 0-3(-6) mm long, unbranched, flowers terminal. Flowers male calyx lobes 3-5, irregularly toothed 0.25-2 mm long, corolla 5-6-merous, funnelform, 3-4 mm long, lobes 0.5-1.5 mm long, tube 3-4 mm long beyond calyx, stamens 5-6, anthers inserted at base of corolla, filaments 7-13 mm long, exserted beyond corolla, pendulous at maturity; female calyx 3-5 lobes 0-2 mm long, corolla funnelform to campanulate, only lobes exserted beyond calyx, recurving 360 degrees at maturity, lobe apices often touching calyx, styles 2, divided to base, exserted 3-4 mm beyond corolla. Fruit reddish-orange to yellow, ovoid, 4-10 × 3.5-6 mm, crowned with a conspicuous persistent calyx. Seeds 2 plano-convex pyrenes, yellowish-white.

Phenology.

Most flowering specimens were collected from December to February and a lesser number from July to August. Specimens from Lihau (West Maui) are only known to flower in July. No individuals were fruiting or flowering in late September 2014 in Makawao Forest Reserve, but immature fruits and flowers were observed in May 2015. Most fruiting specimens occurred in July, but collections were made across many months.

Distribution.

Known from East and West Maui, but apparently more prevalent on East Maui. The taxon occurs from approximately 975m to 1700m elevation. On East Maui, it is known from mesic sites from Kīpahulu Valley to Olinda. Collections on West Maui are collected from Lihau and Honokawai.

Ecology.

Found in mesic to wet forests and shrublands with both native and non-native plant communities. Occurs primarily as an understory shrub to small tree. The rainfall varies dramatically across its distribution and precise collection localities should be geo-referenced to provide an accurate range of precipitation requirements for this taxon’s distribution.

Etymology.

The specific epithet refers to the persistent calyx on the fruit apex that looks like a crown (crown in Greek = stephanos) due to its persistence, connation, and irregular dentations.

Conservation status. This taxon occurs as scattered individuals that are locally common on two volcanoes within one island. When evaluated using the IUCN criteria for extinction risk ( IUCN 2012), Coprosma stephanocarpa 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, and an observed continuing decline in habitat quality overall. Suitable habitat may continue decreasing in size without active conservation management, and currently none of the populations occur in protected areas.

Specimens examined.

United States of America. Hawaii: Maui: West Maui: edges of Honokowai gulch, alt. 4500 ft, 24 Aug 1910, J.F.C. Rock 8189 (BISH); Manawainui Gulch, alt. 820 m, 8 Mar 1988, W.L. Wagner 5857 (BISH, PTBG); Lahaina District, Lihau, alt. 3200 ft, 28 Oct 1991, P. Welton 1379 (BISH); Lahaina District, Lihau, alt. 3250 ft, 9 May 1991, P. Welton 911 (BISH); Lahaina District, Lihau, alt. 3700 ft, 9 May 1991, P. Welton 954 (BISH); Lahaina District, Lihau, alt. 3800 ft, 25 Aug 1991, P. Welton 1237 (BISH); Lahaina District, Lihau, alt. 3800 ft, 26 Aug 1991, P. Welton 1261 (BISH); Lahaina District, Lihau, alt. 3900 ft, 9 May 1991, P. Welton 955 (BISH); Lahaina District, Lihau, alt. 4000 ft, 24 Aug 1991, P. Welton 1177 (BISH); Lahaina District, Lihau, alt. 4000 ft, 24 Aug 1991, P. Welton 1178 (BISH); Lihau, alt. 4100 ft, 13 Jul 1991, P. Welton 1091 (BISH); Lahaina District, Lihau, alt. 4120 ft, 25 Aug 1991, P. Welton 1200 (BISH); Kukui watershed area, ridge towards Kahana Valley between Kahana and Kahana Iki valleys, M. Kiehn MK-990913-2/4 (PTBG). East Maui: Olinda Forest Reserve, 26 Mar 1952, O. Degener 22116 (BISH); Olinda Forest Reserve, 26 Mar 1952, O. Degener 22116 (BISH); Makawao, Olinda pipe line road, lower fork, alt. 4650 ft, 25 Dec 1951, A.K. Chock 298 (BISH); Olinda FR, Waikamoi Flume, 12 Jan 1985, L. Pyle & W. Takeuchi 1923 (BISH); Olinda FR, alt. 4025 ft, 12 Jan 1985, L. Pyle & W. Takeuchi 1922 (BISH); Olinda, 24 Apr 1918, G.C. Munro 482 (BISH); Olinda, 3 May 1967, N.L.H. Krauss 1128 (BISH); 2 mi. E of Olinda, alt. 4200 ft, 27 Jun 1969, J.S. Henrickson 3738 (BISH); Haleakalā, below Olinda, 24 Apr 1918, G.C. Munro 648 (BISH); lower Olinda Flume, between gate and road, alt. ca. 4000 ft, 19 Jul 1964, M.R. Crosby 1804 (BISH); above Olinda, alt. 4200 ft, 30 Sep 1945, A.L. Mitchell 65 (BISH); Kula pipe line, Olinda, 4500 ft, 11 Feb 1930, H. St. John 10296 (BISH); Kula Pipe Line, 25 May 1930, O.H. Swezey s.n. (BISH); Makawao Forest Reserve, Olinda pipe line, alt. 4300 ft, 25 Dec 1955, H.A. Woolford 137 (BISH); Makawao, Olinda pipe line road, lower fork, alt. 4650 ft, 25 Dec 1951, A.K. Chock 298 (BISH); Kula pipe line, 18 Oct 1922, C.J.F. Skottsberg 892 (BISH); Makawao Forest Reserve, alt. 4300 ft, 16 Jul 1980, K.T. Adee s.n. (BISH); Makawao District, Kalialinui, NW Haleakala, Pu'u Luau, ca. 5720 ft, 10 Jun 1980, P.K. Higashino 9340 (BISH); Ko'olau Forest Reserve, S of W Wailuaiki Stream on pali, alt. ca. 5310 ft, 31 May 1980, P.K. Higashino 9047 (BISH); E of Ukulele, 17 Jul 1919, C.N. Forbes 816M (BISH); Ukulele, 1 Jul 1919, C.N. Forbes 748M (BISH); Ukulele, 1 Jul 1919, C.N. Forbes 758M (BISH); Ukulele, 1 Jul 1919, C.N. Forbes 769M (BISH); Ukulele, 1 Jul 1919, C.N. Forbes 936M (BISH); Ukulele, 1 Jul 1919, C.N. Forbes 748M (BISH); Ukulele, 1 Jul 1919, C.N. Forbes 738M (BISH); Ukulele, 1 Jul 1919, C.N. Forbes 7 69M (BISH); above Ukulele, 1 Jul 1910, C.N. Forbes 215 M (BISH); Ukulele, C.N. Forbes s.n. (BISH); Pu‘u Pani, 4 Mar 1920, C.N. Forbes 1836M (BISH); Waikamoi, alt. 4250 ft, 14 Aug 1933, M.C. Neal s.n. (BISH); Makawao Forest Reserve, Waikamoi Flume Rd, 9 Jan 1997, C.R. Annable 3231 (BISH); N slope of Haleakalā, between Hanawī and E fork of Kopiliula streams, alt. ca. 5750 ft, 13 Jul 1980, P.K. Higashino 9375 (BISH); Hana, E of Kuhiwa Stream and Valley, ca. 5540 ft, 13 Jun 1980, P.K. Higashino 9146 (BISH); Kīpahulu, L side of valley, 15 Nov 1919, C.N. Forbes 1639M (BISH); Kipahulu, ridge L side of valley, 15 Nov 1919, C.N. Forbes 1648M (BISH); Hana, ridge of central part of Kipahulu Valley, alt. 3780 ft, 22 Jul 1980, P.K. Higashino 9407f (BISH); Kipahulu Forest Reserve, ridge N of Pu‘u Ahuli‘i, alt. ca. 5400 ft, 23 Aug 1980, F.R. Warshauer 3113 (BISH); 1-3 km E of Kaupo Gap, Kipahulu Forest Reserve, alt. ca. 5750 ft, 27 May 1980, F.R. Warshauer 2560 (BISH).

Discussion.

When numerous collections of Coprosma foliosa from Maui were run through the most current key to Hawaiian Coprosma ( Wagner et al. 1999), it was clear that at least two taxa subsumed under that species merited taxonomic recognition. Both taxa failed to key out, and specimens did not closely match the taxonomic description of Coprosma foliosa or any other species. After multiple field visits, herbarium specimen measurements, and an in-depth literature review, it was concluded that the two Coprosma foliosa segregates, Coprosma cordicarpa and Coprosma stephanocarpa , maintain rather consistent morphologies on leeward East Maui ( Coprosma cordicarpa ) and mesic areas of East and West Maui ( Coprosma stephanocarpa ). They can easily be segregated from the variable Coprosma foliosa s.l. found on other islands and effectively replace Coprosma foliosa s.l. on East Maui, although at least one form of Coprosma foliosa s.l. is still found on West Maui. Coprosma cordicarpa is most easily distinguished from Coprosma foliosa s.l. by its heart-shaped fruit characters, which include a depressed apex crowned by a persistent connate calyx and the tendency to become bisulcate, particularly when dry. Male individuals of Coprosma cordicarpa are easily differentiated as the calyx is nearly double in size (2-4 mm) than that of Coprosma foliosa s.l. (0.25-2 mm), and Coprosma stephanocarpa (0.25-2 mm). The male calyx ontogeny of Coprosma cordicarpa is quite striking; the irregularly toothed calyx initially appears to be completely connate (or nearly so) when in bud, but due to expansion of the growing corolla, the calyx is mechanically split (often in two locations) becoming deeply incised, and then brown callus tissue forms. Ecologically, Coprosma cordicarpa is found in a unique habitat niche (dry forest/shrubland) compared to Coprosma foliosa s.l. and Coprosma stephanocarpa . The niche requirements of Coprosma cordicarpa should be studied in more detail, but it is clear that the areas where it occurs receive much less precipitation than Coprosma stephanocarpa habitat, which include mesic to wet locations of East and West Maui.

Phenological observations suggest that Coprosma cordicarpa and Coprosma stephanocarpa have different flowering periods that are primarily non-overlapping. Coprosma cordicarpa has a primary flowering period in late summer (August to September). The flowering period of Coprosma stephanocarpa is primarily the winter (December to February), with a less pronounced period of flowering from July to August. Scant information about Hawaiian Coprosma phenology has been published, but Coprosma ochracea and Coprosma rhynchocarpa from Hawai‘i Island have a peak flowering period during early spring months (March to May; Lamoureux 1973), which is different from the summer flowering Coprosma cordicarpa , and winter flowering Coprosma stephanocarpa . Phenological differences among the evolution of Lord Howe Island species of Coprosma have proven to be evolutionarily significant ( Papadopolos et al. 2011), and a similar case could also be true for Hawaiian taxa. However, it should be noted that while most, if not all, taxa of Hawaiian Coprosma have a primary robust flowering period each year, a small percentage of individuals in any population can occasionally be sporadically flowering across many different months (J. Cantley, pers. obs.). The stochasticity of flowering times could help explain the presence of occasional hybrids that are thought to exist among many sympatrically occurring Coprosma taxa in Hawai‘i.

The taxonomic boundaries between Coprosma stephanocarpa and Coprosma foliosa s.l. are less easily defined, especially from populations of Coprosma foliosa s.l. occurring on the islands of Moloka‘i and Lana‘i. However, Coprosma stephanocarpa is here restricted to Maui only, as taxa elsewhere appear to maintain consistent morphological differences. On Moloka‘i, at least two morphotypes of Coprosma foliosa s.l. exist that are similar to Coprosma stephanocarpa . One of these taxa has smaller fruits that are globose with a naked apex, smaller floral characters, and smaller leaves in general, but other vegetative characters (e.g. stipule size & pubescence) are similar to Coprosma stephanocarpa . The second Moloka‘i Coprosma foliosa s.l. morphotype has broad stipules that are more or less glabrous and ellipsoid to globose fruits with a small persistent crown that is not longer than 0.75 mm in length. Concerning Lana‘i specimens, few collections have been made, but these agree in morphology with the former described small-fruited, small-leaved Moloka‘i taxon, although much less morphological variation was noted. Fieldwork is needed on both islands to better understand these taxa and their relationship with Coprosma stephanocarpa .

Conclusions.

The recognition of Coprosma cordicarpa and Coprosma stephanocarpa brings the total number of Coprosma species described in the Hawaiian Islands to 15. A concurrent study of material collected on Kaua‘i will increase the total number of taxa described to 16 (D. Lorence, pers. comm.). Ongoing investigation of the Coprosma foliosa s.l. complex on Maui and other islands ( Kaua‘i, O‘ahu, Moloka‘i, and Lana‘i) is currently being pursued by the authors. Preliminary investigation suggests that perhaps morphology is correlated with geographical location, which may support the need for resurrection of other currently synonymized or novel taxa not discussed in this paper. Moreover, detailed investigations of other currently valid taxa, such as the variable Coprosma pubens and Coprosma ochracea , could reveal cryptic taxa by understanding their diversity in better detail at the population level. Ultimately, it is suggested that a molecular study be undertaken to help shed light on the interesting evolutionary patterns of speciation for this dynamic genus in the Hawaiian Islands.

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 3. Photo of the holotype specimen of Coprosma stephanocarpa (BISH).