Atractocarpus tahitensis (Nadeaud) Puttock

Mouly, Arnaud & Butaud, Jean-François, 2023, The French Polynesian Atractocarpus Schltr. & K. Krause (Rubiaceae): circumscription of A. tahitensis and description of A. teamotuaitaui sp. nov., both microendemic and critically endangered species in the Society Islands, Adansonia (3) 45 (10), pp. 151-159 : 154-156

Atractocarpus tahitensis (Nadeaud) Puttock

( Fig. 3 )

Australian Systematic Botany 12: 316 (Puttock 1999), as ‘tahitiensis’. — Trukia tahitensis (Nadeaud) Fosberg, Phytologia 62: 174 ( Fosberg 1987).

— Basionym: Randia tahitensis Nadeaud, Énumération des plantes indigènes de l’île de Tahiti: 54 ( Nadeaud 1873).

TYPUS. — Society Islands, Tahiti. Tahiti Nui, Tepuna, above Pirae, ridge to Aorai , vers 900-1000 m, fl. & fr., 19.XI.1857, Nadeaud 359 (lecto-, P [ P00703710 ], designated by Fosberg 1987 ; isolecto-, BISH, P [ P00703706 , P00703707 , P00703708 , P00703709 , P00703711 , P 04022077 , P 04022078 , P 04022079 , P 04022080 , P 04022081 ], US [ US00036659 ]) .

OTHER HERBARIUM SPECIMENS EXAMINED. — Society Islands , Raiatea . On ridge of mountain N of Faaroa Bay, fl. fr., 400 m, 20.I.1927, Moore 554 ( BISH, L [ L2897608 ], U[U1575688], US[US01939487, US02496748]); on ridge N end of highest mountain, fl., 800 m, 4.IV.1927, Moore 714 ( BISH, L [ L2897607 ], U[U1575687], US[US02496749]). — Tahiti. Tahiti Nui , Versant Nord-Est du plateau d’Orofero, 653 m, st., 22.IX.2015, Butaud 3447 ( PAP [ PAP015919 ]) ; ibid., 621 m, fr., 22.IX.2015, Butaud & Lenoble 3448 ( PAP [ PAP015920 ]) ; ibid., 653 m, fl., 6.XI.2015, Butaud, Lenoble & Teamotuaitau 3489 ( PAP [ PAP015942 ]) ; ibid., 653 m, fl. fr., 6.XI.2015, Butaud, Lenoble & Teamotuaitau 3490 ( PAP [ PAP015943 ]) ; ibid., 653 m, fr., 6.XI.2015, Butaud, Lenoble & Teamotuaitau 3491 ( PAP [ PAP015944 ]) ; Tahiti Nui , Vallée d’Orofero, flanc Sud, partie Ouest du Plateau Tahiti, 916 m, fl., 30.I.2021, Butaud, Luta, Lenoble & Teamotuaitau 4001 ( PAP) .

PHENOLOGY. — The species seems to bloom from October to February and to rise fruits over the year, ripe fruits being observed mostly from August to November.

DESCRIPTION

Slender treelet 2.5-8(-10) m high, up to 10-15 cm in diameter (at breast height); the young branchlets glabrescent. Stipules connate at the base, 5-7 mm long, hispid to glabrescent. Colleters cylindrical, 0.6-1.1 mm long, c. 2 mm wide. Leaves opposite, elliptical to narrowly obovate, glabrous; petioles 10-15 mm long, hispid or glabrescent; lamina 70-165 mm long, 30-50 mm wide with acuminate apex and attenuate base, glossy dark green, dull grey green below, chartaceous; secondary veins in 6-8 pairs at 45-50° to the midvein, arched to straight (Moore 554), raised below; tertiary venation reticulate and opaque; domatia absent. Inflorescences axillary, unilateral, a single flower or 2-10-flowered, flowers hermaphroditic; perennial on contracted 1-5-branched brachyblasts; bracts narrowly triangular, 1-2 mm long. Pedicels 18-28 mm long, filiform, 0.6-0.9 mm in width. Hypanthium 2-3 mm long, hispid or glabrescent. Calyx tube obconical, 2-3 mm long; lobes truncate, c. 0.5 mm long. Corolla tube 6-9 mm long, urceolate, c. 4 mm diameter at the widest point, constricted at mouth, at the lobe’s sinuses, externally hispid. Corolla lobes lanceolate, 8-14 mm long, 3-4 mm wide, glabrous. Stamens inserted at the base of the urceolate part of the corolla tube, filament 0.4-0.5 mm, anther basi-dorsifixed, 3-3.5 mm long, sagittate at base, acuminate by a sterile appendage, 0.2-0.3 mm long. Style included 3-3.5 mm long, 0.4-0.5 mm wide, glabrous; stigmatic head oblong, deeply bifid, branches 3-3.5 mm long, 1 mm wide. Ovary bilocular, placentas 2, axile, 10-15 ovules per locule. Fruit solitary, on a thin pedicel 20-30 mm long, subspherical to ellipsoid, 22- 45 mm long, 20-34 mm diameter, smooth to slightly pointed, calyx persistent and nectary disc forming a short umbo, 1-2 mm long; exocarp yellow green when mature; placental pulp dark brown. Seeds laterally compressed; 2-4(-6) mm in depth, 6-12 mm in length.

DISTRIBUTION, ECOLOGY AND THREATS

Atractocarpus tahitensis occurs in the understory of forest vegetation dominated by: Syzygium cumini (L.) Skeels, Neonauclea forsteri (Seem.ex Havil.) Merr. , Serianthes myriadenia Planch. ex Benth. , Alphitonia zizyphoides (Sol. ex Spreng.) A.Gray , Metrosideros collina (J.R.Forst. & G.Forst.) A.Gray , Spathodea campanulata P.Beauv. , Coffea arabica L, Macaranga taitensis (Müll.Arg.) Müll.Arg. , Aleurites moluccanus (L.) Willd., Miconia calvescens DC. , Psidium cattleyanum Sabine , Ceodes taitensis (Heimerl) E.F.S.Rossetto & Caraballo , Cyclophyllum barbatum (G.Forst.) N.Hallé & J.Florence , Eugenia reinwardtiana (Blume) DC. , Glochidion spp. , Meryta drakeana Nadeaud , Myrsine spp. , Psychotria spp. , Ixora spp. , Celtis pacifica Planch. , Claoxylon taitense Müll. Arg. , Tarenna sambucina (G.Forst.) T.Durand ex Drake. This vegetation contains numerous indigenous species associated with naturalized species that threaten the survival of the native ones, the former belonging to the genera Coffea L., Miconia Ruiz & Pav. , Psidium L., Spathodea P.Beauv. , and Syzygium Gaertn. The understory is degraded by wild boar grubbing.

OnTahiti, the elevation of occurrence of Atractocarpus tahitensis ranges are 620-680 m on the Tahua Iti plateau and 870-920 m on the Tahiti plateau in Orofero valley. Nadeaud’s location on the slopes of Aorai was around 1000-1100 m. On Raiatea, the two known populations were located between 400 and 800 m in elevation.

Endemic to the Society Islands, Atractocarpus tahitensis has not been reported elsewhere than onTahiti and Raiatea.Moreover,it is only known from the ridges of the Mount Aorai on Tahiti since Nadeaud’s collection in 1857 (another collection by Nadeaud’s son is reported in Nadeaud’s journal for the same population in 1896 but was not located) and from Raiatea since Moore’s two collections in 1927.It has not been collected there since Nadeaud and Moore’s prospections.On the other hand, two new locations were discovered on Tahiti in 2015 and2019, one on the Tahua Iti plateau (often erroneously named Orofero plateau) and one on the Tahiti plateau (also called Taha Iti) in Orofero Valley. These extant populations both hardly exceed 100 mature individuals. The species is protected by the French Polynesian laws and was evaluated as “Critically Endangered” under the IUCN criteria ( UICN France et al. 2015) based on theTahua Iti plateau’s population. The discovery of a second population may not change the CR evaluation under criteria B as both populations belong to the same locality, due to a short separative distance ( Fig. 2 ), identical environments and threats (wild boars, invasive plant species, rat predation…), an area of occupancy less than 10 km 2, and an observed decline of habitat quality.

NOTES

Fosberg (1987) mentioned two collections that possibly could be assigned to this species. According to Nadeaud’s field book, these collections were made by Nadeaud’s son Temarii in Puairi on elevated crests of Pirae, but have not been located so far.Fosberg also made a handwritten note on a collection at P made by Nadeaud in 1896 in Pirae on Tahiti; this collection belongs to Gardenia taitensis DC. and not to Atractocarpus tahitensis . The sterile collection Fosberg 63730 (BISH, US) belongs in fact to Tarenna sambucina (G.Forst.) T.Durand ex Drake. Puttock (1999) assumed that Atractocarpus tahitensis is a dioecious species, based on very few observed herbarium specimens. According to our field observations, individuals produce hermaphroditic flowers. A similar breeding system has been observed for the other Polynesian Atractocarpus species. Finally, a gathering attributed to Atractocarpus tahitensis (as Randia tahitensis ) and collected by M.Hoff on Wallis (Hoff 4281, MNHN-P-P05377792) belongs to Tarenna sambucina .

Figures

FIG. 3. — Atractocarpus tahitensis (Nadeaud) Puttock: A, leafy branch of the species, under the typical vegetation cover; B, unripe fruit; C, flower in lateral view; D, floriferous brachyblast of a perennial inflorescence; E, mature flowers and flower buds. Photos by J.-F. Butaud.

FIG. 2. — Satellite picture of Tahiti and location of extant and extinct populations of both Atractocarpus Schltr. & K.Krause species.