Goniothalamus palawanensis C.C.Tang & R.M.K.Saunders, 2013

Tang, Chin Cheung, Xue, Bine & Saunders, Richard M. K., 2013, A new species of Goniothalamus (Annonaceae) from Palawan, and a new nomenclatural combination in the genus from Fiji, PhytoKeys 32, pp. 27-35 : 27-29

Goniothalamus palawanensis C.C.Tang & R.M.K.Saunders sp. nov. Figs 1 , 2

Diagnosis.

Similar to Goniothalamus amuyon (Blanco) Merr. except with shorter inner petals (11-16 mm), hairy ovaries, and filiform pseudostyles with funnel-shaped stigmas.

Type.

Palawan: Puerto Princesa, Corrigutor, 31 May 2012, C.C. Tang TCC10 (holotype: L; isotypes: PNH).

Description.

Small trees, to 5 m tall, to 3 cm d.b.h. Young shoots (densely) hairy. Leaf laminas 18-31 cm long, 5.8-11 cm wide, length/width ratio 2.3-3.5, broadly elliptic or oblong elliptic, apex (long) acuminate, base acute, papyraceous to coriaceous, 50-100 μm thick, glabrous both ab- and adaxially; midrib slightly pubescent and very prominent abaxially; secondary veins 8 to 10 pairs per leaf, prominent adaxially; tertiary veins reticulate (sometimes slightly percurrent towards base of leaf), distinct; petioles 8.5-15.5 mm long, 1.5-2.8 mm in diameter, hairy. Flowers axillary, solitary, on young branches, pendent; pedicels 8-13(-16.5) mm long, 0.8-1.2(-1.7) mm in diameter, (sparsely) hairy; bracts 2 to 5. Sepals 3-4(-5) mm long, 3.5-4.5(-6.5) mm wide, length/width ratio 0.6-0.9, generally not reflexed at anthesis, not connate, triangular, 170-250 μm thick, (sparsely) hairy abaxially, glabrous to very sparsely hairy adaxially, green, venation indistinct. Outer petals 20.5-34 mm long, 5.5-13.5 mm wide, length/width ratio 2.4-4.9, broadly to elongated lanceolate, 450-1100 μm thick, (densely) hairy both ab- and adaxially, with glabrous region at base of adaxial surface, greenish yellow, venation indistinct. Inner petals 11-16.5 mm long, 5-9.5 mm wide, length/width ratio 1.6-2.5, with 2.3-3.4 mm wide basal claw, 330-800 μm thick, densely hairy abaxially, sparsely hairy adaxially, greenish yellow; apertures between inner petals 3.5-4.5 mm long, 3.5-5 mm wide. Stamens ca. 100 per flower, 1.9-2.2 mm long, 0.3-0.5 mm wide; connectives rounded, 0.2-0.5 mm long, papillate-hairy. Carpels 10 to 15 per flower; ovary 0.8-1.8 mm long, 0.4-0.7 mm wide, densely hairy with long golden-brown hairs; stigmas and pseudostyles 2.4-4 mm long; pseudostyles 0.1-0.3 mm wide, glabrous; stigma funnel-shaped, glabrous. Fruits unknown.

Phenology.

Flowering specimens collected in May and June; fruiting specimens unknown.

Distribution and habitat.

Endemic to Palawan ( Fig. 3 ), in mixed dipterocarp and limestone forests; 50-120 m.

Etymology.

The specific epithet reflects the geographical distribution of the species in Palawan.

Additional specimens examined (paratypes).

Philippines. Palawan: Bloomfield, St. Pauls Bay, Mt. Bloomfield, lowlands to the SSE, 4 May 1984, A. C. Podzorski SMHI2012 (K, L); Iraan Mountains, Aborlan, 29 May 1950, M. D. Sulit 14792 (L); Puerto Princesa, Corrigutor, 31 May 2012, C.C. Tang TCC06 (HKU), C.C. Tang TCC09 (HKU), C.C. Tang TCC11 (HKU), C.C. Tang TCC14 (HKU), C.C. Tang TCC17 (HKU).

Discussion.

Phylogenetic analysis of chloroplast DNA sequence data (C.C. Tang et al., unpubl.) indicates that this new species, Goniothalamus palawanensis , is sister to Goniothalamus amuyon (Blanco) Merr. with moderate to strong support (posterior clade probability = 0.97 and bootstrap support = 74%), and more distantly related to Goniothalamus costulatus Miq., Goniothalamus rufus Miq., Goniothalamus sawtehii C.E.C.Fischer, Goniothalamus tomentosus R.M.K.Saunders, Goniothalamus undulatus Ridl. and Goniothalamus velutinus Airy-Shaw. These species are all characterised by a distinct indument of rusty-red hairs on the young shoots and petals. Amongst these species, Goniothalamus amuyon and Goniothalamus palawanensis are distinct in possessing fewer secondary veins per leaf (8 to 11, compared with 11 to 25 in the other species, with the exception of Goniothalamus rufus ), and in having indistinct sepal venation (although similar venation is observed in Goniothalamus velutinus ). Goniothalamus palawanensis is furthermore geographically close to Goniothalamus amuyon , which occurs in Luzon, Visayas and Mindanao ( Guzman et al. 1986). Morphological differences between Goniothalamus palawanensis and Goniothalamus amuyon include: inner petal length (11-16.5 mm vs 15-29 mm, respectively: Ying 1991; Liao 1996); ovary indument (hairy in Goniothalamus palawanensis [Fig. 1G] vs glabrous in Goniothalamus amuyon ); and pseudostyle/stigma shape (filiform pseudostyle with small, funnel-shaped stigma in Goniothalamus palawanensis [Fig. 1G], vs relatively enlarged, fleshy pseudostyle with entire stigma in Goniothalamus amuyon ).

The flora of Palawan shows close biogeographical affinities with Borneo, reflecting the extensive connectivity that existed between the two regions ( Hall 2009). Two of the species listed above as close relatives of Goniothalamus palawanensis occur in Borneo, viz. Goniothalamus rufus and Goniothalamus velutinus . In addition to the differences in leaf and sepal venation alluded to above, these species differ from Goniothalamus palawanensis in possessing greatly enlarged and warty pseudostyles/stigmas ( Mat-Salleh 1993).

There is only one Goniothalamus species, Goniothalamus obtusifolius Merr., that is sympatric with Goniothalamus palawanensis in Palawan. These two species are clearly distinct, however, as Goniothalamus obtusifolius has much smaller (15-18 × 6-8 cm) coriaceous leaves, and large (ca. 5 × 3.5 cm) membranous outer petals ( Merrill 1906).

IUCN conservation status.

EN B1ab(iii) (IUCN, 2001). Goniothalamus palawanensis is endemic to Palawan, with an extent of occurrence of ca. 1,800 km2. The species is only known from three periods of collection (1950, 1984 and 2012), and from fewer than five localities. The region is subject to continuing habitat decline due to logging of low altitude forests ( DENR/UNEP 1997), hence the endangered red list category recommendation.

Figures

Figure 1. Goniothalamus palawanensis, sp. nov. A Flowering branch B Flower C Sepal (ab and adaxial) D Outer petal (ab- and adaxial) E Inner petal (ab- and adaxial) F Stamen (ab- and adaxial) G Carpel. Scale bars: A = 5 cm; B, D, E = 1 cm; C = 5 mm; F = 2 mm, G = 1 mm; A from C. C. Tang 10 (HKU); B-G from C. C. Tang 14 (HKU); drawing by Caren Pearl Shin.

Figure 2. Goniothalamus palawanensis, sp. nov. A Habit (mature individual with flowers) B Branch with leaves (abaxial) C Branch with leaves (adaxial) D, E Flower F Sepals (abaxial) G Very mature flower with two outer petals and one inner petal removed, showing stamens and stigmas H Perianth parts (abaxial; left to right: sepal, inner petal, outer petal) I Perianth parts (adaxial; left to right: sepal, inner petal, outer petal). Scale bars: H, I = 1 cm; A, D from C. C. Tang 09 (HKU); B, C, F, G from C. C. Tang 06 (HKU); E, H, I from C. C. Tang 14 (HKU). Photos by C. C. Tang.

Figure 3. Distribution of Goniothalamus palawanensis, sp. nov., in Palawan.