Melicope iolensis K. R. Wood, Lorence & W. L. Wagner 2024, sp. nov.
Creators: name: Wood, Kenneth R.
name: Lorence, David H.
name: Wagner, Warren L.
name: Appelhans, Marc S.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Sapindales
Rutaceae
Melicope
Melicope iolensis

description: Melicope iolensis K. R. Wood, Lorence & W. L. Wagner sp. nov.
Figs 2, 3, 4 A, B, 5
Diagnosis.
Melicope iolensis is morphologically most similar to M. wawraeana (Rock) T. G. Hartley & B. C. Stone, but differs by its combination of leaves abaxially glabrate to pilose-pubescent (vs. glabrous), inflorescence ramiflorous, rarely axillary (vs. axillary), shorter sepals on staminate flowers, 0.3–0.5 mm long (vs. 3.5 mm) and smaller seeds 3–3.5 mm long (vs. 5–8 mm). Phylogenetically, M. iolensis is most closely related to M. nealae (B. C. Stone) T. G. Hartley & B. C. Stone, yet starkly differs by its tree habit (vs. shrub), flowers usually 9–18 per inflorescence (vs. 1–5), carpels with exocarp glabrous, connate 1 / 6–1 / 5 their length (vs. puberulent, connate 1 / 2–3 / 4 length) and seeds 3–3.5 mm long (vs. 5–8 mm long).
Type.
USA • Hawaiian Islands, Kaua‘i: Līhu‘e District, ‘ Iole headwaters, ♀, 22.042, - 159.497, 872 m alt., 8 Sep 2022 (fr.), K. R. Wood, S. Heintzman & S. Deans 19143 (holotype: mounted on 2 sheets, PTBG 1000096868, PTBG 1000096869!; isotype (to be distributed): US!).
Description.
Trees 3–8 m tall, trunks up to 20 cm diameter, bark smooth, mottled grey-brown, ultimate stems brown-red, new growth and young branchlets sparsely tan puberulent, glabrate in age. Leaves opposite, unifoliolate; petiole (20 –) 30–70 mm long, strigose-pubescent, adaxially glabrous, shallowly canaliculate; the blade subcoriaceous to coriaceous, ovate, oblong-ovate, oblong-elliptic, (8 –) 14–25 (– 33) × (6 –) 10–18 cm, margin entire; base truncate to obtuse, rarely acute; apex rounded, often emarginate; secondary veins 15–20 pairs, connected by an arched vein 4–20 mm from margin; higher order venation reticulate; adaxial surface glabrous; abaxial surface minutely black glandular punctate, pilose-pubescent, tan-yellow, or glabrate; mid-rib usually densely pilose-strigose; secondary veins pilose-strigose. Inflorescences in ramiflorous, densely fasciculate cymes, occasionally axillary, (4 –) 9–18 flowered, to 40 mm long, purple-red when fresh; peduncles 2–5 mm long, glabrate, branched to second degree; primary branches 2–4 pairs; pedicels 4–14 mm long, glabrate; bracteoles triangular-ovate 0.3–0.4 mm long. Flowers unisexual, 4 - merous; perianth glabrate; androecium, nectary disc and gynoecium glabrous; ovary greenish glabrous; stigma 4 - lobed ca. 0.5 mm diameter; staminate flowers with sepals orbicular-ovate, free, 0.3–0.5 × 0.5–0.7 mm, glabrate; petals green with purple streaks, narrowly deltate to ovate, 2.5–4.0 mm long; stamens 8; antisepalous filaments ca. 3.5 mm long; antipetalous filaments ca. 2.5 mm long; anthers ellipsoid ca. 0.5–0.6 mm long, with pollen; style obsolete; pistillate flowers with sepals orbicular-ovate, free, 1.0 × 1.3–1.5 mm; petals green, dorsally purple, narrowly deltate to ovate, free, 2.8–3.0 mm long; staminodes 8; antisepalous filaments ca. 0.5 mm long; antipetalous filaments ca. 0.4 mm long; anthers ovoid-ellipsoid ca. 0.5–0.6 mm long, no pollen observed; style 1.5 mm long. Capsules green with purple irregular streaking when fresh, 3–4 × 10–14 mm; carpels basally connate 1 / 6 to 1 / 5 their length, exocarp glabrous; endocarp glabrous. Seeds 1–2 per carpel, ovoid, 3–3.5 mm long.
Additional specimens examined (paratypes).
USA. Hawaiian Islands, Kaua‘i: Līhu‘e District; all collections from ‘ Iole headwaters • 1 ♂; 884 m alt.; 20 Oct 2021 (fl.); Wood et al. 18830 (PTBG) • 1 ♀; 884 m alt.; 20 Oct 2021 (fr.); Wood et al. 18831 (PTBG, US) • 1 ♂; 884 m alt.; 20 Oct 2021 (fl.); Wood et al. 18832 (BISH, PTBG) • 1 ♀; 884 m alt.; 20 Oct 2021 (fr.); Wood et al. 18833 (PTBG) • 1 ♀; 884 m alt.; 8 Sep 2022; Wood et al. 19146 (PTBG, US) • 1 ♀; 900 m alt.; 8 Sep 2022 (fl.); Wood et al. 19148 (UC, PTBG) • 914 m alt.; 8 Sep 2022; Wood et al. 19151 (BISH, NY, PTBG, UC, US) • 890 m alt.; 29 Dec 2022; Wood & Perlman 19245 (PTBG) • 1 ♂; 884 m alt.; 10 Aug 2023 (fl.); Wood et al. 19367 (PTBG) • 1 ♂; 884 m alt.; 10 Aug 2023 (fr.); Wood et al. 19368 (PTBG); • 884 m alt.; 10 Aug 2023 (fl.); Wood et al. 19369 (PTBG) • 1 ♀; 911 m alt.; 10 Aug 2023 (fl.); Heintzman et al. KP 08102301 (PTBG).
Phenology.
Melicope iolensis has been observed with flowers during the months of August and October and with fruit in August, September and October.
Etymology.
The name Melicope is derived from the Greek meli, honey and kope, cut in pieces, alluding to the lobed floral nectary (Lorence and Wagner 2020) and the species epithet represents the holotype locale, ‘ Iole, which literally means “ rat ” in the Hawaiian language (Pukui et al. 1974).
Affinities.
Molecular phylogenetic analyses, based on RADseq datasets (Restriction-Site Associated DNA-sequencing; see Paetzold et al. (2019) for methodology), resolve Melicope iolensis in a clade that includes all taxa belonging to Cubicarpa and Megacarpa and as being most closely related to M. nealae (Appelhans et al., in preparation). Melicope iolensis can be distinguished from the latter species by its tree habit (vs. shrub); flowers usually 9–18 per inflorescence (vs. 1–5); sepals of staminate flowers 0.3–0.5 mm long (vs. 2.5 mm long); capsules with green and purple streaking, up to 14 mm wide (vs. green, up to 27 mm wide), carpels with exocarp glabrous, connate 1 / 6–1 / 5 their length, (vs. puberulent, connate 1 / 2–3 / 4 length); and seeds 3–3.5 mm long (vs. 5–8 mm long) (Table 1). Melicope nealae was previously thought extinct with only two known collections made in 1909 and 1960 and has long been looked for by NTBG Science staff. It was recently rediscovered in transitional mesic to wet forests of western Kaua‘i (Wood and Walsh 2022), is currently known from only 11 individuals and is being monitored and conserved by PEPP and NTBG.
Morphologically, Melicope iolensis is most similar to M. wawraeana, but can easily be separated by its combination of leaves abaxially glabrate to pilose-pubescent (vs. glabrous on M. wawraeana); inflorescence ramiflorous, rarely axillary (vs. axillary); sepals on staminate flowers glabrous, 0.3–0.5 mm long (vs. puberulent, 3.5 mm long); capsules with endocarp and exocarp glabrous, connate 1 / 6–1 / 5 their width, up to 14 mm wide, with green and purple streaking (vs. endocarp and exocarp usually sparsely puberulent, connate 1 / 2 width, up to 20 mm wide, dark green); and seeds 3–3.5 mm long (vs. 5–8 mm) (Table 1). Melicope wawraeana is quite common and known from Kaua‘i and O‘ahu (Wagner et al. 1990, 1999).
Melicope iolensis is not closely comparable morphologically to any of the remaining Hawaiian Megacarpa taxa. Specifically on Kaua‘i, as a tree up to 8 m tall, it differs from the shrubs M. feddei (H. Lév.) T. G. Hartley & B. C. Stone, M. kavaiensis (H. Mann) T. G. Hartley & B. C. Stone and M. macropus (Hillebr.) T. G. Hartley & B. C. Stone. It also differs from those three shrub species in having longer petioles and leaves, inflorescence ramiflorous, rarely axillary, shorter sepals and smaller capsules and seeds (Table 1). The only two remaining Megacarpa taxa on Kaua‘i are M. cruciata (A. Heller) T. G. Hartley & B. C. Stone and M. puberula (H. St. John) T. G. Hartley & B. C. Stone, from which M. iolensis also starkly differs in having longer petioles and leaves, inflorescence ramiflorous, rarely axillary, shorter sepals, glabrous endocarp and smaller capsules and seeds (Table 1).
Distribution and ecology.
Melicope iolensis is endemic to the volcanic island of Kaua‘i (Fig. 1), where it is known from only 15 individuals located in the remote, upper headwater valley of ‘ Iole. The type location is in a hanging valley, having vertical cliffs above and a series of cliffs and waterfalls below, isolating its accessibility (Fig. 4 C).
The plant community where Melicope iolensis occurs is a Metrosideros Banks ex Gaertn. (Myrtaceae) / Cheirodendron Nutt. ex Seem. (Araliaceae) montane wet forest with matting ferns of Dicranopteris Bernh. and Diplopterygium (Diels) Nakai (Gleicheniaceae) and a dissecting riparian drainage. The forested slopes are steep with a diverse mixture of native sedges, grasses, ferns, herbs, shrubs and trees, along with a high density of terrestrial and epiphytic bryophytes throughout. Associated genera of trees include Polyscias J. R. Forst. & G. Forst. (Araliaceae); Pritchardia Seem. & H. Wendl. (Arecaceae); Dubautia Gaudich. (Asteraceae); Cyanea Gaudich. (Campanulaceae), Perrottetia Kunth (Dipentodontaceae); Antidesma L., Euphorbia L. (Euphorbiaceae); Hydrangea Gronov. (Hydrangeaceae); Geniostoma J. R. Forst. & G. Forst. (Loganiaceae); Eurya Thunb. (Pentaphylacaceae); Myrsine L. (Primulaceae); Syzygium Gaertn. (Myrtaceae); Bobea Gaudich., Coprosma J. R. Forst. & G. Forst., Kadua Cham. & Schltdl., Psychotria L. (all Rubiaceae); Melicope J. R. Forst. & G. Forst. (Rutaceae); and Pipturus Wedd. and Touchardia Gaudich. (Urticaceae). Genera of sedges and grasses include Carex L., Cyperus L., Machaerina Vahl (Cyperaceae); Eragrostis Wolf, Panicum L. (Poaceae); herbs and shrubs include Bidens L. (Asteraceae); Vaccinium L. (Ericaceae); Cyrtandra J. R. Forst. & G. Forst. (Gesneriaceae); and the woody climber Freycinetia Gaudich. (Pandanaceae). Genera of ferns include Asplenium L., Hymenasplenium Hayata (Aspleniaceae); Deparia Hook. & Grev., Diplazium Sw. (Athyriaceae); Sadleria Kaulf. (Blechnaceae); Cibotium Kaulf. (Cibotiaceae); Microlepia C. Presl (Dennstaedtiaceae); Ctenitis (C. Chr.) C. Chr. (Dryopteridaceae); Hoiokula S. E. Fawc. & A. R. Sm. and Menisciopsis (Holttum) S. E. Fawc. & A. R. Sm. (Thelypteridaceae).
description: Published as part of Wood, Kenneth R., Lorence, David H., Wagner, Warren L. & Appelhans, Marc S., 2024, Melicope iolensis (Rutaceae), a new tree species from Kaua'i, Hawaiian Islands, pp. 237-249 in PhytoKeys 250 on pages 237-249, DOI: 10.3897/phytokeys.250.128963