Research Article |
Corresponding author: Jason T. Cantley ( jtc015@bucknell.edu ) Academic editor: Sandy Knapp
© 2016 Jason T. Cantley, Margaret J. Sporck-Koehler, Marian M. Chau.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Cantley JT, Sporck-Koehler MJ, Chau MM (2016) New and resurrected Hawaiian species of pilo (Coprosma, Rubiaceae) from the island of Maui. PhytoKeys 60: 33-48. https://doi.org/10.3897/phytokeys.60.6465
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Two species of Coprosma (Rubiaceae) J.R.Forst. & G.Forst. are described from the island of Maui of the Hawaiian Archipelago. A newly described taxon, Coprosma cordicarpa J.Cantley, Sporck-Koehler, & M.Chau, sp. nov. is locally common in medium to high elevation dry forests and shrublands of leeward East Maui. The second taxon is resurrected from the synonymy of C. foliosa A.Gray as C. stephanocarpa Hillebr. and occurs in mesic to wet rainforests of both East and West Maui. Both taxa are segregated from C. foliosa, with which they share similar morphological characters. A conspicuous and persistent calyx of the fruit and various floral characters most easily differentiate both taxa from other Hawaiian taxa. The newly described Coprosma cordicarpa is further distinguished from C. stephanocarpa by a central constriction of the fruit with a depressed apex, which gives it a characteristic heart shape. Furthermore, the taxa are largely separated phenologically, ecologically, and geographically. Descriptions, conservation status, and specimens examined for the new species are included.
Auwahi, Coprosma , Coprosma cordicarpa , Coprosma stephanocarpa , East Maui, Haleakalā, Hawaiian Islands, Kanaio, Maui, pilo, Rubiaceae , West Maui
There are more than 110 species in the genus Coprosma J.R. Forst. & G.Forst., which consists of species that are predominantly dioecious and wind pollinated. Species range in habit from trailing woody plants to large trees and produce many various colored fruits (e.g. black, blue, orange, red, yellow, and translucent), which are most often two-seeded drupes. The genus is Oceanic in distribution with a primary center of diversity in New Zealand (ca. 55 spp.:
Species belonging to the genus Coprosma were first formally described in the Hawaiian Islands by Asa Gray in 1858 from material gathered by Nelson on Cook’s last voyage to the islands, and by Menzies during Vancouver’s voyage (
Such is the case for currently described C. foliosa, which is a widespread taxon occurring on islands of Kaua‘i, O‘ahu, Moloka‘i, Maui, and Lana‘i (
The (re)discovery of bisulcate fruit with a depressed apex and a persistent crown-like calyx from a locally common Coprosma taxon in the Kanaio Natural Area Reserve on leeward East Maui, plus the difficulty in keying these individuals to the species level, prompted this detailed investigation by the authors. The investigation included in-depth herbarium research, as well as fieldwork to validate findings and to assess the taxon’s abundance and distribution on Maui. This paper recognizes one new distinct species, C. cordicarpa, and unexpectedly confirms the need to resurrect C. stephanocarpa from synonymy. Both taxa are segregated from C. foliosa using morphological, ecological, phenological, and geographical lines of evidence. This study, plus a concurrent study of a new taxon from Kaua‘i (D. Lorence, pers. comm.), increases the total number of endemic Coprosma species in the Hawaiian Islands to 16.
All measurements given herein are taken from dried herbarium specimens. Field observations were performed in September 2013, September 2014, and May 2015 to assess abundance and to take field notes and digital photos. Seeds of C. cordicarpa were collected from two populations at Kanaio Natural Area Reserve and Auwahi totaling 609 seeds from 32 individual plants. All seeds were deposited for long-term germplasm storage at the Seed Conservation Laboratory at Lyon Arboretum. Measurements are presented in the descriptions as follows: length, then width, each followed by units of measurement (mm or cm). More than 80 specimens (including type specimens) from the
Lectotype species (designated by
Shrubs, multi-branched, erect, occasionally creeping and sometimes rooting at the nodes, or occasionally trees, often foetid when bruised. Leaves simple, opposite or rarely ternate, margins entire, petiolate or sessile; stipules interpetiolar, distinct or partly connate, entire or dentate with tooth-like marginal colleters. Flowers unisexual (and the plants dioecious or rarely monoecious), rarely polygamous or in one species perfect, axillary, solitary or in cymes; calyx 4–5(–10)-toothed, often reduced or absent in male flowers; corolla funnelform or campanulate, 4–5(–10)-lobed, lobes valvate in bud; stamens 4–5(–10), inserted at base of corolla tube; filaments long-exserted, erect or pendulous; ovary 2(–4)-celled, ovule 1 per cell, basal, anatropous; style 2(–4)-lobed, divided nearly to base; stigmas long-exserted, papillose-hirsute. Fruits drupaceous, fleshy, ovoid to globose, with 2(–4), 1-seeded, plano-convex pyrenes.
1 | Fruit reddish-orange, ovoid, lacking a central constriction between the two seeds, apex not depressed, calyx conspicuous or not | (2) |
– | Fruit reddish-orange to yellow, cordate (heart-shaped) with a central constriction between the two seeds, apex depressed, calyx conspicuous and persistent, leeward East Maui | C. cordicarpa |
2 | Fruit reddish-orange to yellow, fruit calyx conspicuous and persistent and >1.5 mm long, East and West Maui | C. stephanocarpa |
– | Fruit reddish-orange to yellow, persistent fruit calyx not present or sometimes minute (<1.5 mm), Kaua‘i, O‘ahu, Moloka‘i, Lana‘i, West Maui | C. foliosa s.l. |
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:
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 C. stephanocarpa and C. foliosa s.l.) on male flowers.
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.
Field images of C. cordicarpa and C. 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).
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.
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.
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 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 invaded 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 C. cordicarpa varies from 700 to 1900 mm annually with the highest rainfall occurring from December to January (
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.
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 (
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 (
United States of America. Hawai‘i: Maui, East Maui, Haleakalā, alt. 3000-6000 ft, 1888, J. Hillebrand s.n. (lectotype, designated by
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.
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.
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.
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.
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 (
United States of America. Hawaii: Maui: West Maui: edges of Honokowai gulch, alt. 4500 ft, 24 Aug 1910, J.F.C. Rock 8189 (
When numerous collections of Coprosma foliosa from Maui were run through the most current key to Hawaiian Coprosma (
Phenological observations suggest that C. cordicarpa and C. 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 C. 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 C. ochracea and C. rhynchocarpa from Hawai‘i Island have a peak flowering period during early spring months (March to May;
The taxonomic boundaries between Coprosma stephanocarpa and C. foliosa s.l. are less easily defined, especially from populations of C. foliosa s.l. occurring on the islands of Moloka‘i and Lana‘i. However, C. stephanocarpa is here restricted to Maui only, as taxa elsewhere appear to maintain consistent morphological differences. On Moloka‘i, at least two morphotypes of C. foliosa s.l. exist that are similar to C. 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 C. stephanocarpa. The second Moloka‘i C. 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 C. stephanocarpa.
The recognition of C. cordicarpa and C. 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 C. 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 C. pubens and C. 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.
We would like to thank Ulupalakua Ranch, Keahi Bustamente, Diana Crow, Randy Kennedy, Peter Landon, Hank Oppenheimer, Bryon Stevens, and Casey Stewman for their help and organization to visit the Kanaio Natural Area Reserve and Auwahi populations of C. cordicarpa. Mahalo to Clyde Imada and Barbara Kennedy at the Bishop Museum herbarium (
Coprosma Morphology Data Matrix
Data type: Measurement
Explanation note: Measurements and notes taken from herbaria specimens.