Research Article |
Corresponding author: Marc S. Appelhans ( marc.appelhans@biologie.uni-goettingen.de ) Academic editor: Pedro Acevedo-Rodríguez
© 2017 Marc S. Appelhans, Kenneth R. Wood, Warren L. Wagner.
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:
Appelhans MS, Wood KR, Wagner WL (2017) Reduction of the Hawaiian genus Platydesma into Melicope section Pelea (Rutaceae) and notes on the monophyly of the section. PhytoKeys 91: 125-137. https://doi.org/10.3897/phytokeys.91.21363
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Platydesma, an endemic genus to the Hawaiian Islands containing four species, has long been considered of obscure origin. Recent molecular phylogenetic studies have unequivocally placed Platydesma within the widespread genus Melicope as sister to the rest of the Hawaiian species of Melicope. This makes submerging Platydesma into Melicope necessary. We make the necessary new combinations: Melicope cornuta (Hillebr.) Appelhans, K.R. Wood & W.L. Wagner, M. cornuta var. decurrens (B.C.Stone) Appelhans, K.R. Wood & W.L. Wagner, M. remyi (Sherff) Appelhans, K.R. Wood & W.L. Wagner, and M. rostrata (Hillebr.) Appelhans, K.R. Wood & W.L. Wagner. An additional species that has been recognized within Platydesma should now be recognized under its original name M. spathulata A. Gray. All Hawaiian species belong to Melicope section Pelea. Our molecular phylogenetic studies also showed that in addition to merging Platydesma into section Pelea, five species described from New Caledonia need to be excluded from the section in order to achieve monophyly of section Pelea.
Hawaiian Islands, Melicope , New Caledonia, Platydesma , Rutaceae
The genus Melicope J.R. Forst. & G. Forst. is the largest genus within Rutaceae, with approximately 230 species ranging throughout the Malagasy and Indo-Himalayan regions, Southeast Asia, Australasia, and across the Pacific Islands (
The immediate relationships of the Hawaiian endemic genus Platydesma (Rutaceae) have puzzled taxonomists due to the divergent floral morphology and hermaphroditic breeding system of Platydesma (
Recent molecular phylogenetic studies provided unequivocal evidence for the placement of Platydesma within Melicope, as sister to the Hawaiian taxa in Melicope section Pelea (
Phylogenetic affinities of Hawaiian Melicope section Pelea (incl. Platydesma) based on five plastid and nuclear markers (modified from
The Hawaiian Islands have the highest rate of dioecy in the world, evolving in situ in at least 12 lineages, possibly as a selective force to avoid inbreeding depression, affect resource allocation, and sexual selection (
The copious nectar production and the stamens connate into a cup-like structure that holds accumulating nectar in Platydesma flowers suggest adaptations to bird-pollination. A similar case of adaptation to bird-pollination can be found in Hawaiian Schiedea/Alsinidendron (Caryophyllaceae) (
To preserve the monophyly of Melicope section Pelea, Platydesma must be merged with Melicope and the New Caledonian species of section Pelea have to be excluded (Fig.
With four species of Platydesma included and five New Caledonian species excluded, Melicope section Pelea consists of 86 currently recognized species (
We propose the following taxonomic changes for Platydesma:
Platydesma H. Mann, Proc. Bost. Soc. Nat. Hist. 10: 317. 1866. – Type: Platydesma campanulata H. Mann (=Melicope spathulata A. Gray)
Platydesma sect. Cornutia B.C. Stone, J. Arnold Arbor. 43: 422. 1962. – Type: Platydesma cornuta Hillebr. (=Melicope cornuta (Hillebr.) Appelhans, K.R. Wood & W.L. Wagner).
Pelea clusiifolia A. Gray (=Melicope clusiifolia (A. Gray) T.G. Hartley & B.C. Stone).
Platydesma cornuta Hillebr., Fl. Hawaiian Isl. 72. 1888.
As was typical for Hillebrand in the Flora of the Hawaiian Islands, he cited localities for which he saw collections and would only sometimes cite collector information (when someone other than himself made the collection). In this case he cited three localities (Halemano, Wailupe, and Pauoa) indicating he collected or saw material from each one of them. As such these collections must be considered syntypes.
O‘ahu: s. l., W. Hillebrand s.n. (lectotype, designated by Stone, J. Arnold Arbor. 43: 423. 1962: K [K000717606, image!]; isolectotype: GH [GH00044164, image!]. Additional syntypes: O‘ahu, Halemanu, Hillebrand s.n. (BISH [BISH1016374, specimen!], US [US00101497, specimen!]); O‘ahu, Pauoa Valley, Hillebrand & J. M. Lydgate s.n. (BISH [2; BISH1016375, BISH1016476, specimens!]; O‘ahu, Wailupe (MEL [MEL587728, image!], with a photo at BISH); and a fragment made by J. Rock of B sheet, without locality (BISH [BISH1016377, specimen!]).
A, B Melicope rostrata, flower (field images of Appelhans et al. MA683, BISH, GOET), fruit (Wood and DeMotta 14490, US, and Flynn 4626, US) CMelicope cornuta var. decurrens flower (field images by Sebastian Marquez and Dave Fahrenwald in the Wai‘anae Mountains) DMelicope cornuta var. cornuta fruit (field images by Joel Lau in Nui, Ko‘olau Mountains).
Platydesma cornuta var. decurrens B.C. Stone, J. Arnold Arbor. 43: 423. 1962.
O‘ahu: Wai‘anae Mountains, Munia-Kanehoa trail, wet fern-covered banks by stream in valley just southeast of trail, [200 m], 26 March 1960, B.C. Stone & G. Pearsall 3263 (holotype: BISH-579783 [BISH1016373, specimen!]).
Claoxylon remyi Sherff, Publ. Field Mus. Nat. Hist., Bot. Ser. 17: 557. 1939. Platydesma remyi (Sherff) O. Deg., I. Deg., Sherff & B.C. Stone, Fl. Hawaiiensis. 6: Fam. 179. 1960.
Platydesma campanulatum var. sessilifolia Rock, Indig. Trees Haw. Isl. 243. 1913. – Type: Hawai‘i: in dense forests of the summit mountain of the Kohala range, 12 July 1909, J. F. Rock 4222 (holotype: BISH, not located; isotype: GH [mounted on two sheets, GH00044160, GH00044161, images!]).
These two sheets are the only type material of this collection located. They were labelled as co-type, which was used at the time Rock published for the equivalent of isotype. Rock stated in his book that most of the specimens mentioned in the text were in the “college of Hawaii Herbarium”, which are now incorporated into BISH. He specifically indicated the type of this new variety to be there, so the presumed holotype should be at BISH, but could not be located.
Hawai‘i: 1851–1855, J. Remy 604, (holotype: P [P00636836, image!]; isotype: P [P00636837, image!]).
Platydesma rostrata Hillebr., Fl. Hawaiian Isl. 72. 1888.
At the time Hillebrand described this species there was a single specimen known, the type. When Rock brought fragments from B back to BISH the label information was not well transcribed, but all have printed labels indicating they were from the B collection. There were no other collections in the B herbarium so despite the lack of information this must be a fragment of the holotype.
Kaua‘i: V. Knudsen 68 (holotype: B-destroyed, fragment BISH-581794 [BISH1016395, specimen!]).
Melicope ? grandifolia A.Gray Bot. U.S. Expl. Exped. 1: 354. 1854. – Type: Hawai‘i: forests of Mauna Kea, 1840, U.S. Expl. Exped. s.n. (holotype: US-15033 [US00101457, specimen!]; isotype: GH [GH01153097, image!]).
Platydesma campanulata H. Mann, Proc. Bost. Soc. Nat. Hist. 10: 317. 1866. – Type: O‘ahu: on the mountains behind Honolulu, at middle heights, H. Mann & W. T. Brigham 94 (holotype: CU, not located; isotypes: BISH [4 sheets, BISH1016385, BISH1016386, BISH1016388, BISH1016390, specimens!], G [G00380101, image!], GH [2 sheets, GH00044158, GH00044159, images!], MASS [MASS00320396, image!], MO [MO-251520, specimen!], NY [NY00067067, specimen!], US [US00101498, specimen!]).
Platydesma campanulata f. coriaceum Rock, Indig. Trees Haw. Isl. 243. 1913. – Type: Hawai‘i: Kohala Mts., [W of] Honokanenui gorge, June 1910, J. F. Rock 8367 (holotype: BISH-586927 [BISH1016394, specimen!]; isotypes: BISH [BISH1016441, specimen!], GH [2 sheets, GH00044162, GH00044163, images!]).
Platydesma campanulata var. macrophylla Hillebr., Fl. Hawaiian Isl. 71. 1888. – Type: Kaua‘i: V. Knudsen s.n. (holotype: B-probably destroyed, fragment of holotype BISH-581799 [BISH1016383, specimen!]).
Platydesma campanulata var. pallida Hillebr., Fl. Hawaiian Isl. 71. 1888. Platydesma spathulatum var. pallidum (Hillebr.) B.C. Stone, Madroño. 16: 165. 1962. – Type: O‘ahu: Ka‘ala, Hillebrand s.n.; E. Maui, Hamakua, Lydgate s.n. (syntypes: B-destroyed); Maui: along pipe-line trail, Olinda, in dark forest, 29 July 1927, O. Degener & L. Topping 8615 (neotype [designated by Stone, J. Arnold Arbor. 43: 420. 1962]: BISH-68071 [BISH1016379, specimen!]; isoneotypes: B [B_10_0296003, image!], BH [BH000121710, image!], K [K000342164, image!], MASS [MASS00320397, image!], NY [NY02859241]).
Platydesma campanulata var. pubescens Skottsb., Acta Horti Gothob. 15: 388. 1944. Platydesma spathulatum var. pubescens (Skottsb.) B.C. Stone, Madroño. 16: 165. 1962. – Type: O‘ahu: Wai‘anae Mountains, slope of Ka‘ala, 25 September 1938, O. Selling 3710 (holotype: GB [GB-0048636, image!]; isotype: S [S08-7736, image!]).
Platydesma oahuensis H. Lév., Repert. Spec. Nov. Regni Veg. 10: 154. 1911. – Type: O‘ahu: Punalu‘u, May 1910, U. Faurie 243 (holotype: not located; isotypes: A [A00044165, image!], BM [BM000798124, image!]), P [P00639232, image!]).
Platydesma spathulatum f. kalalauense O. Deg. & I. Deg., Fl. Hawaiiensis. 7: Fam. 179. 1960. – Type: Kaua‘i: east rim of Kalalau Valley, 16 Nov 1960, O. Degener, I. Degener, & W. Cadenhead 27150 (lectotype [designated here]: US-2604492 [US00101496, specimen!]).
Platydesma spathulatum f. stonei O. Deg. & I. Deg., Fl. Hawaiiensis. 7: Fam. 179. 1960. – Type: O‘ahu: Ko‘olau range. Punalu‘u, summit of Castle trail, B.C. Stone 3551 (holotype: BISH, not located; lectotype [designated here]: fig. 2, Stone, J. Arnold Arbor. 43: 418. 1962).
Kaua‘i: mountains, 1840, U.S. Expl. Exped. s.n. (holotype: US-15031 [US00101445, specimen!]).
Melicope spathulata A habit with flower (Wood 15091, Kaua‘i, Kohua Ridge, US) B flower, lateral view (Ishikawa 302, Kaua‘i, Koke‘e, US) C flower, top view (Ishikawa 302, US) D flower, longitudinal section (Ishikawa 302, Kaua‘i, Koke‘e, US) E fruit (Herbst & Mull 5507, Hawai‘i, Ola‘a, US and Takeuchi et al. 1997, O‘ahu, Ko‘olau Mountains, US).
Platydesma auriculifolia (A. Gray) Hillebr., Fl. Hawaiian Isl. 72. 1888. Pelea auriculifolia A. Gray, Proc. Amer. Acad. Arts 3: 50. 1853. – Type: Hawai‘i: forests of Mauna Kea, U.S. Expl. Exped., s.n. (holotype: US-15020 [US00101488, specimen!]. [= Melicope clusiifolia (A. Gray) T.G. Hartley & B.C. Stone]. – Note: Hillebrand cited the second source of the name in Pelea by Gray (U.S. Expl. Exped., Phan. 343. 1854) and also used part of the description (fruit). Hillebrand cites among the three collections the type of Pelea auriculifolia A. Gray as well as a specimen of Platydesma (Hillebrand s.n.), and the third one can’t be located (Lydgate s.n.). So his cited collections are a mixture as is the description. This Hillebrand name must be taken as a new combination. The critical facts are: Hillebrand cited the basionym, used the same epithet, and did not exclude the holotype of the basionym. It does not matter that Hillebrand cited a later publication of the cited basionym. Since this is a pre-1953 publication, it is not mandatory to cite the original publication of the basionym.
Platydesma fauriei H. Lév., Repert. Spec. Nov. Regni Veg. 10: 153. 1911. – Type: O‘ahu: Punaliuu [Punalu‘u], May 1910, U. Faurie 242 (Isotypes: BM [BM000994065, image!], P [P00311275, image!]. – Note: The holotype was expected to be stored at E but no specimen could be located there. [=Nothocestrum longifolium A. Gray].
The identification keys included in the “Manual of the Flowering Plants of Hawaii” (
Key to the genera of Rutaceae (p. 1175 in
1 | Leaves simple, opposite or whorled | 2. Melicope |
– | Leaves pinnately compound, opposite, or alternate (2). | |
2 | Leaves alternate; seeds not winged | 3. Zanthoxylum |
– | Leaves usually opposite; seeds winged | 1. Flindersia |
Key to the species of Pelea/Melicope (p. 1178 in
1 | Shrubs, shrubby trees, or with palmoid habit; flowers perfect; petals slightly imbricate; filaments nearly completely connate into a staminal tube; ovules 5–8 per carpel; fruit a subglobose or cruciate capsule, indehiscent or tardily dehiscent |
use original key for Platydesma (p. 1209 in |
– | Trees, shrubs, or subscandent; flowers functionally unisexual (and the plants polygamous) or rarely perfect; petals valvate; stamens in 2 whorls, distinct, reduced but always present in functionally pistillate flowers, longer fertile stamens equal to or exserted from corolla; ovules 2 per carpel; fruit composed of 4 nearly distinct follicles or a 4-lobed, 4-valved, cruciate or cuboid capsule, dehiscent |
use original key to species of Pelea/Melicope (p. 1178 in |
We are grateful to Danica Harbaugh for assembling a first draft of the taxonomic section of this article and the curators of B, BISH, CU, E, GH, K and NY for providing photographs of type specimens. We are grateful to Alice Tangerini for her excellent illustrations of this group of Melicope species. We thank Dave Fahrenwald, Joel Lau and Sebastian Marquez for providing photographs. We appreciate comments by Kanchi Gandhi on several nomenclatural issues and we thank Cynthia Morton for constructive comments on the manuscript. We acknowledge support by the German Research Foundation (DFG; grant number AP 251/3-1 to M.S. Appelhans) and the Open Access Publication Funds of Goettingen University.