Fagraea christinae Y.W. Low & V.A. Albert

Low, Yee Wen, Wanma, Jimmy F., Ibrahim, Bazilah, Heatubun, Charlie D. & Albert, Victor A., 2023, Taxonomic appraisal of Fagraea ceilanica (Gentianaceae), and description of a new tree species from the Bird's Head Peninsula, western New Guinea, Candollea 78 (2), pp. 167-175 : 167-175

Fagraea christinae Y.W. Low & V.A. Albert , sp. nov. (F ig. 2, 3).

Holotypus: INDONESIA. Prov. West Papua: Maybrat Regency , Ajamaru [Ayamaru], [1°16'31"S 132°11'44"E], 240 m, 7.III.1962, Vink BW15226 ( L [ L.2687803 ] image!; iso-: K!, WAG [ WAG.1807281 , WAG.1807284 , WAG.1807285 ] images!) .

Fagraea christinae Y.W. Low & V.A. Albert is morphologically similar to F. annulata Hiern in having stamens inserted upon a fleshy ring around the mid-portion of the corolla tube but differs in having the margins of bracteoles and calyx lobes distinctly crenate (vs. entire in F. annulata ).

Tree to 10 m tall, trunk to 12 cm diam., glabrous throughout; bark smooth, dark grey-brown. Petioles (6–) 10– 15 mm long, to 3 mm wide, petiolar sheaths present and not fused along the interpetiolar median. Leaves lamina elliptic to obovate, (4–)6–12 × (2–) 3–6 cm, thin-leathery; base cuneate, slightly decurrent, without auricles; apex acute to short acuminate; margin entire; midrib flat to sunken above, prominent below; secondary veins 4– 9 pairs, distinct to faintly visible (rarely inconspicuous) on upper side, inconspicuous on lower side; tertiary venation inconspicuous on both sides. Inflorescences terminal, a solitary to 3-flowered branched cyme, up to 5 cm long. Pedicels up to 3 mm long, up to 4 mm diam.; floral bracts broadly triangular, up to 1 cm long, apex ± acute to obtuse, margin crenate, inserted below the calyx. Calyx 25–30 mm long, sparsely glandular on outer surface; calyx mouth up to 15 mm diam.; calyx lobes 5, broadly elliptic, 15–20 × 12–17 mm, margin crenate. Corolla salver-shaped, green on outer surface, white on inner surface; tube up to 50 mm long, up to 9 mm wide at the mid-portion, up to 23 mm wide at the throat; lobes 5, broadly obovate, c. 8 × 12 mm, left-contorted at bud stage. Stamens 5, inserted upon a fleshy ring around the mid-portion of the corolla tube, dorsifixed, included inside the corolla tube; filaments up to 14 mm long; anthers up to 7 mm long. Style up to 40 mm long; stigma clavate with a shallow depression at the top, inserted in the corolla tube; ovary unknown. Fruits globose when mature, depressed globose and somewhat 4-lobed when immature, 25–30 × 25–30 mm; apex conspicuously beaked upon drying; base tightly clasped by the calyx lobes; surface in fresh mature specimens smooth (epidermis wrinkled conspicuously upon drying), green, maturing pinkish red. Seeds numerous, kidney-shaped, c. 1 × 0.5 mm; testa surface areolate.

Etymology. – This species is dedicated to Christina Soh Jeng Har (1955–2020) of the Singapore Botanic Gardens’ library. Chris, as she was fondly known amongst patrons of the library, colleagues and friends, was the longest-serving librarian who played an important role in overseeing the expansion and modernisation of the Gardens’ botanical literature for close to 40 years before she passed away in 2020 (LOW, 2021). She was also one of the sponsors for YWL’s doctoral scholarship from the National Parks Board, Singapore, to study Syzygium Gaertn. ( Myrtaceae ) in the Bird’s Head Peninsula , New Guinea.

Distribution, ecology and phenology. – Fagraea christinae is endemic to the Ayamaru Lakes, Maybrat Regency in the Southwest Papua Province, Indonesia (F ig. 4), where it occurs in tall and moist primary rainforest to secondary forest on loam over uplifted ancient corallite limestone. F lower buds, open flowers, immature fruits and mature fruits have been collected in March.

Conservation Status. – Fagraea christinae is rare and known from four locations in primary rainforest to secondary forest around the Ayamaru Lakes, where its habitat is threatened by the rapid growth of settlements around the lakes (SOLOSSA et al., 2013). The extent of occurrence (EOO) of the species is estimated to be c. 156 km ² (which falls within the 100 km ² upper limit for CR status under the subcriterion B1), whereas its area of occupancy (AOO) is estimated to be 16 km ² (which falls within the 500 km ² lower limit for EN status under the subcriterion B2). Based on satellite data on forest cover obtained for Indonesian New Guinea between 2001 to 2019, GAVEAU et al. (2021) estimated that 83 % (34.29 million hectares) of the region remains forested, with a predicted deforestation rate on an upward trend. Over 19 years, 2 % (0.75 million hectares) of forest was cleared (GAVEAU et al., 2021).

As the over 4,000 km Trans-Papua Highway, a much-needed public infrastructure for social development in Indonesian New Guinea, is being completed in stages, an acceleration in development is predicted and if not planned carefully and sustainably, it will lead to severe deforestation as seen in Borneo (GAVEAU et al., 2014, 2016). Fagraea christinae is provisionally assessed as “Critically Endangered” [CR B1ab(iii,iv)] using the IUCN Category and Criteria ( IUCN, 2012).

Notes. – An unpublished phylogenomic result of an ongoing study (Albert et al., in prep.) of Southeast Asian Fagraea s.s. including representatives from Cyrtophyllum , Limahlania K.M. Wong & Sugumaran, Picrophloeus and Utania , places Fagraea christinae in one of the sister clades within Fagraea s.s. The robustly supported clade consists of New Guinean and Australian taxa with stamens inserted upon a fleshy ring, namely F. berteroana , F. salticola and F. christinae. In contrast, the other sister clade includes mostly West Malesian taxa with stamens inserted upon the inner surface of the corolla tube wall, such as F. ceilanica s.s. The preliminary finding of Albert et al. (in prep.) confirmed the topology of the ‘ Fagraea’ clade proposed by SUGUMARAN & WONG (2012) but with robust support obtained for the two sublineages, including relationships between species.

Additional specimens examined. – INDONESIA. Prov. West Papua: Maybrat Regency, Tubun, North of Ajamaru [Ayamaru], 260 m, 12.III.1962, Vink BW 15361 (K, L); west of Ayawasi , track to plot 6, 1°08'24"S 132°07'12"E, 9.XI.1995, Polak MP 923 (K, L); Aitinyo, Athabu, 1°24'15"S 132°15'15"E, 359 m, 1.III.2019, Wanma et al. MAN-SING45 (BO, BRI, G, K, MAN, SING [2 sheets]) .