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Research Article
Goniothalamus roseipetalus and G. sukhirinensis (Annonaceae): Two new species from Peninsular Thailand
expand article infoCharan Leeratiwong, Piya Chalermglin§, Richard M. K. Saunders|
‡ Prince of Songkla University, Hat Yai, Thailand
§ Thailand Institute of Scientific & Technological Research, Pathum Thani, Thailand
| The University of Hong Kong, Hong Kong, China
Open Access

Abstract

Two new Goniothalamus species (Annonaceae), G. roseipetalus sp. nov. and G. sukhirinensis sp. nov., are described from the southern limits of Peninsular Thailand (Narathiwat and Yala Provinces). Both new species resemble G. macrophyllus, G. scortechinii and G. uvarioides. The addition of these two new species brings the total number of Goniothalamus species in Thailand to 27. Separate identification keys are provided for flowering and fruiting specimens of the Thai species.

Keywords

Annonaceae, Goniothalamus roseipetalus, Goniothalamus sukhirinensis, new species, Thailand

Introduction

The genus Goniothalamus (Blume) Hook.f. & Thomson (Annonaceae subfam. Annonoideae tribe Annoneae: Chatrou et al. 2012; Guo et al. 2017) is widely distributed in lowland and submontane tropical forests across Southeast Asia (Thomas et al. 2017). It is characterised by pendent, protogynous flowers with two trimerous petal whorls, with the inner whorl forming a mitriform dome over the reproductive organs (a ‘type III’ chamber sensu Saunders 2010). The outer petals are typically larger than the inner and periodically block the apertures between the inner petals, thereby controlling pollinator access and enabling the flower to temporarily trap the pollinating beetles (Lau et al. 2016). The timing of the petal movements that regulate pollinator trapping and release are synchronised with the circadian rhythms of the beetles (Lau et al. 2017; Saunders 2020); this allows the plant to utilise beetles with diverse circadian activities, and also allows the staminate floral phase to be extended to promote pollen deposition and enhance interfloral movement of beetles. These floral characteristics provide a possible biotic explanation for the statistically significant increase in the evolutionary diversification rate recently reported for the genus (Xue et al. 2020).

Goniothalamus fruits are apocarpous, with distinct fleshy ‘monocarps’ that develop from individual carpels after fertilisation. Two contrasting seed dispersal systems have been inferred, correlated with differences in fruit and seed morphology (Tang et al. 2015a): the species that are dispersed by non-volant mammals typically have ramiflorous or cauliflorous fruits with large (often sessile) monocarps and hairy seeds; whereas the species that are bird-dispersed have fruits that are borne on young growth and have small stipitate monocarps with glabrous seeds.

Goniothalamus is comparatively species-rich, with over 130 species. Although the genus has never been comprehensively revised, there are several recent regional taxonomic studies, including Thailand (Saunders and Chalermglin 2008), Peninsular Malaysia (Saunders 2003), Sumatra (Saunders 2002) and Borneo (Turner 2014). Twenty-five Goniothalamus species have been recorded from Thailand (Saunders and Chalermglin 2008), with the majority (14 species) occurring in Peninsular Thailand, viz. G. expansus Craib, G. giganteus (Wall. ex) Hook.f. & Thomson, G. latestigma C.E.C.Fisch., G. macrophyllus (Blume) Hook.f. & Thomson, G. malayanus Hook.f. & Thomson, G. ridleyi King, G. rotundisepalus M.R.Hend., G. scortechinii King, G. tapis Miq., G. tavoyensis Chatterjee, G. tenuifolius King, G. tortilipetalus M.R.Hend., G. undulatus Ridl. and G. uvarioides King. Several other Goniothalamus species are recorded from Peninsular Malaysia, close to the Thai border (Saunders 2003), viz. G. curtisii King, G. montanus J.Sinclair and G. subevenius King. Recent fieldwork in Narathiwat and Yala Provinces of Peninsular Thailand has resulted in collections of two new species that are described here as G. roseipetalus and G. sukhirinensis. The species descriptions provided here are based on observations and measurements from living material.

New species descriptions

Goniothalamus roseipetalus Leerat., Chalermglin & R.M.K.Saunders, sp. nov.

Figs 1, 2, 3

Diagnosis

Goniothalamus roseipetalus resembles G. scortechinii and G. uvarioides but is distinguished by its leaves with generally fewer secondary veins (15–22 pairs), wider sepals (24–35 mm), and wider inner petals (8–11 mm). It is also distinguished from G. scortechinii by its wider outer petals (14–25 mm), and is distinguished from G. uvarioides by its smaller, single-seeded monocarps (8–15 by 7–9 mm), borne on shorter stipes (3–5 mm).

Figure 1. 

Goniothalamus roseipetalus sp. nov. A flowering branch B flower C calyx of fused sepals (abaxial) D calyx of fused sepals (adaxial) E outer petal (abaxial) F outer petals (adaxial) G inner petal (abaxial). H inner petal (adaxial) I stamen (abaxial) J stamen (adaxial) K carpel (abaxial) L carpel (adaxial) M fruit, composed of separate monocarps. N–P seeds (different orientations). Drawn by A. Somphrom A–L from C. Leeratiwong 211708 (PSU) M–P from C. Leeratiwong 211707 (PSU).

Types

Thailand: Narathiwat: Cha Nae, Du Son Yo subdistrict, 400 m alt., 15 April 2021, C. Leeratiwong 211706 (holotype PSU; isotypes BKF, KKU).

Figure 2. 

Goniothalamus roseipetalus sp. nov. A branch with leaves (adaxial) B fruiting branch with leaves (abaxial) C, D flowers. Photos by P. Chalermglin.

Description

Shrubs to small trees, to 4 m. Young branches glabrous. Leaf laminas 15–40 by 3–13 cm, length/width ratio 2.8–5, elliptic to oblanceolate, apex generally acuminate (rarely acute to obtuse), acumen 3–10 mm long, base broadly cuneate, chartaceous, glabrous ab- and adaxially (sometimes sparsely pubescent over midrib); midrib strongly prominent abaxially, sunken adaxially; secondary veins 15–22 pairs, plane adaxially; tertiary veins percurrent, slightly distinct, lacking a ‘granular’ appearance abaxially; petioles 12–22 mm by 1.5–2.5 mm, glabrous to sparsely pubescent. Flowers solitary, often on main trunk (cauliflorous), rarely on older branches (ramiflorous), pendent; flowering pedicels 10–17 mm long, sparsely hairy; pedicel bracts ovate to broadly lanceolate, 2–4 by 2–3 mm. Sepals (violet-)pink, broadly ovate, 20–30 by 24–35 mm, basally connate (10–17 mm from base), apex rounded, glabrous ab- and adaxially, with sparsely hairy margins, venation distinct, 5–7-veined. Outer petals greenish-pink when young, (violet-)pink (green at claw) when mature, 25–45 by 14–25 mm with 4–10 mm-long claw, length/width ratio 1.7–2.2, fleshy, (lanceolate-)ovate, apex obtuse to mucronate, reflexed, sparsely hairy abaxially (more densely along margins basally), sparsely hairy (more densely apically) adaxially with velutinous basal region facing apertures between inner petals, midrib and venation indistinct ab- and adaxially. Inner petals 12–20 by 8–11 mm with 2–5 mm-long claw, length/width ratio 1.5–1.8, oblanceolate, densely hairy ab- and adaxially, greenish-pink when young, pale pink when mature, apex acute, lacking a glabrous lasteral flange on the inner petal claws. Stamens numerous, narrowly oblong, 3–4 mm long; connectives apiculate, papillate. Carpels 20–35 per flower, ovary oblong, 2–2.5 mm long, with white hairs; stigma and pseudostyle 2–3 mm long, stigma subulate, glabrous. Fruits with persistent calyx, immature fruits greenish-pink, mature fruits (pinkish-)red; fruiting pedicels 10–20 by 2–2.5 mm, sparsely hairy to glabrous. Monocarps 5–20 per fruit, 1–2-seeded, 8–17 by 7–10 mm, length/width ratio 1.1–1.7, ellipsoid to ovoid, apex apiculate, apicule 0.5–1.5 mm long, smooth, sparsely hairy, glossy, pericarp 1–2 mm thick, stipes 3–6 by 1.5–2 mm, moderately hairy. Seeds with mucilage, 9–11 by 8–9 mm, length/width ratio 1.1–1.6, ovoid, testa sparsely pubescent, rugose.

Figure 3. 

Goniothalamus roseipetalus sp. nov. A, B flowers C, D fruits showing persistent calyx. Photos by P. Chalermglin.

Phenology

Flowering in March and April; fruiting in August (based on limited data).

Distribution and habitat

Endemic to Peninsular Thailand, where it occurs in Narathiwat and Yala Provinces (Fig. 4). Growing in shady and moist areas of tropical rainforests and forest margins between para-rubber plantations and remnant rainforests; 100–400 m alt.

Figure 4. 

Distributions of Goniothalamus roseipetalus and G. sukhirinensis.

Etymology

In reference to the red pigmentation of the petals.

Local name

Panan klip muang (ปาหนันกลีบม่วง) (general).

Additional specimens examined (paratypes)

Thailand: Yala Province, Bannang Sata, 350 m alt., 1 August 2020, C. Leeratiwong 201684 (PSU); Narathiwat Province: Cha Nae District, Du Son Yo subdistrict, 100 m alt., 6 March 2021, C. Leeratiwong 211705 (PSU).

Discussion

Although G. roseipetalus is yet to be included in a molecular phylogenetic analysis, it shares several morphological similarities with species in a clade (nested within clade ‘A1a’ sensu Tang et al. 2015a, b) that comprises G. loerzingii R.M.K.Saunders, G. macrophyllus, G. scortechinii, G. uvarioides and G. wrayi King. These species were previously classified by Bân (1974) within Goniothalamus subgen. Goniothalamus sect. Goniothalamus, and are characterised by their essentially glabrous vegetative shoots and petioles, percurrent tertiary leaf venation, generally fused sepals with distinct venation, short inner petals, apiculate staminal connectives, relatively few carpels per flower, thick-cylindrical pseudostyles with a broad, hairy stigma, and seeds with a hairy testa. Although G. roseipetalus shares most of these diagnostic characters, its stigmas are glabrous.

Goniothalamus roseipetalus is morphologically most similar to G. scortechinii and G. uvarioides. It differs from these species, however, as it generally has fewer secondary veins in its leaves (15–22 pairs, vs [18–]21–26[–32] in G. scortechinii and 24–35 in G. uvarioides), larger sepals (20–30 by 24–35 mm, vs 8–24 by 8–23 mm in G. scortechinii and 12–16 by 5–13 mm in G. uvarioides), and wider inner petals (8–11 mm, vs 5–8 mm in G. scortechinii and 7–8.5 mm in G. uvarioides). It also has wider outer petals (14–25 mm) than G. scortechinii (8–14 mm), and can be distinguished from G. uvarioides by reference to its smaller monocarps (8–15 by 7–9 mm, vs 31–44 by 15–18 mm) with a single seed (vs four or five seeds per monocarp) and shorter stipes (3–5 mm, vs 12.5–17.5 mm). Goniothalamus roseipetalus also resembles the widespread species G. macrophyllus, although the latter species has creamy-white petals.

Goniothalamus roseipetalus also resembles G. calycinus J. Sinclair, a species that is endemic to Terengganu in Peninsular Malaysia (Saunders 2003). Goniothalamus roseipetalus differs, however, in its flower position (with flowers borne on young or older branches in G. calycinus), larger sepals (only 4.5–17 by 4–17 mm in G. calycinus), wider outer petals (only 7–14 mm wide in G. calycinus), larger inner petals (only 8–14 by 5–7.5 mm in G. calycinus), and by the absence of a persistent calyx in fruits of G. calycinus.

Goniothalamus sukhirinensis Leerat., Chalermglin & R.M.K.Saunders, sp. nov.

Figs 5, 6

Diagnosis

Goniothalamus sukhirinensis resembles G. macrophyllus and G. scortechinii, but is distinguished by its densely hairy shoots, numerous secondary veins (32–40 pairs per leaf), generally longer pedicels (flowering: 12–18 mm; fruiting: 20–25 mm), larger outer petals (34–37 by 18–22 mm), larger monocarps (20–27 by 9–13 mm) that are densely hairy, and longer seeds (13–17 mm).

Figure 5. 

Goniothalamus sukhirinensis sp. nov. A vegetative branch B petiole, showing base of leaf lamina C flowers D sepal (abaxial) E sepal (adaxial) F outer petal (abaxial) G outer petals (adaxial) H inner petal (abaxial) I inner petal (adaxial) J stamen (abaxial) K stamen (adaxial) L carpel (abaxial) M carpel (adaxial) N fruit, composed of separate monocarps O seed with hairy surface. Drawn by A. Somphrom from C. Leeratiwong 211708 (PSU).

Types

Thailand: Narathiwat: Sukhirin, Ban Yade village, Ma Mong subdistrict, 167 m alt., 6 March 2021, C. Leeratiwong 211708 (holotype PSU; isotypes BKF, KKU).

Figure 6. 

Goniothalamus sukhirinensis sp. nov. A leaf (abaxial) B, C flowers D fruit. Photos by P. Chalermglin.

Description

Shrubs to small trees, to 4 m. Young branches densely appressed-pubescent. Leaf laminas 28–50 by 7–16 cm, length/width ratio 3.1–4, (lanceolate-)oblong, apex generally acuminate to caudate (rarely acute to obtuse), acumen 7–20 mm long, base broadly cuneate, subcoriaceous, glabrous abaxially (sparsely hairy over midrib), sparsely pubescent adaxially (densely hairy over veins); midrib strongly prominent abaxially, sunken adaxially; secondary veins 32–40 pairs, plane adaxially; tertiary veins percurrent, distinct, lacking a ‘granular’ appearance abaxially; petioles 20–30 mm by 4–6 mm, densely pubescent. Flowers solitary or paired, often on main trunk (cauliflorous), rarely on older branches (ramiflorous), pendent; flowering pedicels 12–18 mm long, densely hairy; pedicel bracts ovate-triangular, 2.5–3 by 1–1.5 mm. Sepals greenish-pink, broadly ovate, 7–9.5 by 7.5–10 mm, basally connate (2.5–3 mm from base), apex acute, moderately hairy abaxially, sparsely hairy adaxially, venation indistinct. Outer petals greenish-yellow when young, whitish-yellow (green at claw) when mature, 34–37 by 18–22 mm with 3–5 mm-long claw, length/width ratio 1.6–1.9, fleshy, (lanceolate-)ovate, apex acuminate, densely hairy abaxially, moderately hairy adaxially with velutinous basal region facing apertures between inner petals, midrib raised adaxially, venation indistinct ab- and adaxially. Inner petals 13–15 by 7–8 mm with 2–3 mm long claw, length/width ratio 1.8–1.9, ovate-lanceolate, densely hairy abaxially, sparsely hairy distally adaxially, yellowish-green when young, pinkish-orange to reddish-brown when mature, apex acuminate, lacking a glabrous lasteral flange on the inner petal claws. Stamens numerous, oblong, 2.5–3.7 mm long; connectives apiculate, papillate. Carpels 11–20 per flower, ovary oblong, 2–3 mm long, with white hairs; stigma and pseudostyle 2–2.5 mm long, stigma funnel-shaped, hairy. Fruits sometimes with persistent calyx, immature fruits brownish-green, mature fruits not seen; fruiting pedicels 20–25 by 2–3.5 mm, sparsely hairy. Monocarps 5–14 per fruit, single-seeded, 20–27 by 9–13 mm, length/width ratio 2–2.7, (obovoid-)ellipsoid, apex apiculate, apicule 5–8 mm long, smooth, densely hairy, glossy, pericarp 1–2 mm thick, stipes 7–15 by 2–3 mm, densely hairy. Seeds 13–17 by 8–10 mm, length/width ratio 1.6–1.7, ellipsoid, testa densely villose, slightly rugose.

Phenology

Flowering and fruiting in February and March (based on limited data).

Distribution and habitat

Endemic to Narathiwat Province, Peninsular Thailand (Fig. 4). Growing in shady and moist areas of tropical rainforests; 167–200 m alt.

Etymology

From the name Sukhirin, Narathiwat Province.

Local name

Ratchakhru khao (ราชครูขาว) (Narathiwat).

Additional specimen examined (paratype)

Thailand: Narathiwat Province: Sukhirin District, Ban Yade village, Ma Mong subdistrict, 200 m alt., 28 February 2021, C. Leeratiwong 211707 (PSU).

Discussion

As with the previous species, G. sukhirinensis is yet to be included in a molecular phylogenetic analysis but has strong morphological affiliations with a clade that comprises G. loerzingii R.M.K.Saunders, G. macrophyllus, G. scortechinii, G. uvarioides and G. wrayi King (nested within clade ‘A1a’ sensu Tang et al. 2015a, b). The morphological characteristics of this clade are detailed under G. roseipetalus, above.

Goniothalamus sukhirinensis resembles G. macrophyllus and G. scortechinii, but differs in several key characters: densely hairy shoots (vs glabrous to medium-hairy); numerous secondary veins (32–40 pairs per leaf, vs 12–23 in G. macrophyllus and [18–]21–26[–32] in G. scortechinii); generally longer flowering pedicels (12–18 mm, vs 5–11.5 mm in G. macrophyllus and 8–13 mm in G. scortechinii); larger outer petals (34–37 by 18–22 mm, vs 10–28 by 4.5–11.5 mm in G. macrophyllus and 20–33 by 8–14 mm in G. scortechinii); longer fruiting pedicels (20–25 mm, vs 7–19 in G. macrophyllus and 8–20 mm in G. scortechinii); larger monocarps (20–27 by 9–13 mm, vs 8–15 by 7.5–10 mm in G. macrophyllus and 9–18 by 6–10 mm in G. scortechinii) that are densely hairy (vs subglabrous to medium-hairy); and longer seeds (13–17 mm, vs 8.5–12 mm in G. macrophyllus and 8–11 mm in G. scortechinii). Goniothalamus sukhirinensis also differs from G. macrophyllus as its leaves lack the fine ‘granular’ appearance of the latter species (due to the immersion of tertiary and higher-order veins: Saunders, 2002), and has longer monocarp stipes (7–15 mm, vs up to 1.8 mm in G. macrophyllus).

Key to Goniothalamus species in Thailand (flowering specimens)

1a Stamen connective apex apiculate 2
2a Young branches densely hairy to velutinous 3
3a Leaf laminas 28–50 cm long, with 32–40 pairs of secondary veins; sepals 7–9.5 by 7.5–10 mm; outer petals 34–37 by 18–22 mm; inner petals 13–15 by 7–8 mm G. sukhirinensis sp. nov.
3b Leaf laminas 50–76 cm long, with 24–32 pairs of secondary veins; sepals 30–40 by 28–30 mm; outer petals 60–80 by 30–40 mm; inner petals ca. 35 by ca. 17 mm G. cheliensis H.H.Hu
2b Young branches glabrous to hairy 4
4a Flowers in large fascicles, exclusively from woody tubercles at base of trunk G. ridleyi King
4b Flowers solitary or in pairs, not exclusively from base of trunk 5
5a Adaxial surface of outer petals with glabrous or sparsely hairy region facing apertures between inner petals 6
6a Leaves with 24–35 pairs of secondary veins G. uvarioides King
6b Leaves with 11–22 pairs of secondary veins G. tapis Miq.
5b Adaxial surface of outer petals with velutinous region facing apertures between inner petals 7
7a Flowering pedicels 20–37 mm long; carpels 50–100 per flower G. tortilipetalus M.R.Hend.
7b Flowering pedicels 5–19 mm long; carpels 8–50 per flower 8
8a Leaves with 9–12 pairs of secondary veins; stamen connective apex distinctly tapered; carpels 8–10 per flower G. tavoyensis Chatterjee
8b Leaves with 12–26(–32) pairs of secondary veins; stamen connective apex not distinctly tapered; carpels 11–50 per flower 9
9a Tertiary venation reticulate 10
10a Sepals 11–18.5 mm long, 8–15.5 mm wide; outer petals 21–46 mm long, 4.5–18 mm wide, yellow; inner petal length/width ratio 3–6.5; stamens 95–120 per flower G. calvicarpus Craib
10b Sepals 14–29 mm long, 12–26 mm wide; outer petals 36–104 mm long, 14–24 mm wide, green; inner petals length/width ratio 1.8–3.6; stamens 100–200 per flower G. griffithii Hook.f. & Thomson
9b Tertiary venation percurrent 11
11a Sepals 24–35 mm wide; outer petals 14–25 mm wide G. roseipetalus sp. nov.
11b Sepals 4–23 mm wide; outer petals 4.5–14 mm wide 12
12a Leaf laminas (sub-)coriaceous, with fine “granular” texture abaxially (due to immersion of tertiary and lower order veins); leaves with 12–23 pairs of secondary veins G. macrophyllus (Blume) Hook.f. & Thomson
12b Leaf laminas papyraceous, without fine ‘granular’ texture abaxially; leaves with (18–)21–26(–32) pairs of secondary veins G. scortechinii King
1b Stamen connective apex truncate 13
13a Inner petal claws with distinct glabrous lateral flange 14
14a Flowering pedicels 7–23 mm long; stigma subulate 15
15a Outer petals 23–43 mm long, 12–23 mm wide; carpels 40–100 per flower G. sawtehii C.E.C.Fisch.
15b Outer petals 10.5–32 mm long, 5.5–17.5 mm wide; carpels 10–54 per flower G. undulatus Ridl.
14b Flowering pedicels 2–11.5 mm long; stigma fusiform or funnel-shaped 16
16a Young branches densely hairy to velutinous G. tamirensis Pierre ex Finet & Gagnep.
16b Young branches glabrous to hairy 17
17a Flowering pedicels 5–11.5 mm long; sepal venation generally indistinct; outer petals 12.5–73 mm long; stigma fusiform G. laoticus (Finet & Gagnep.) Bân
17b Flowering pedicels 2–6 mm long; sepal venation distinct; outer petals 8.5–39 mm long; stigma funnel-shaped 18
18a Leaf laminas 8–14 cm long, 1.5–4 cm wide; petioles 3.5–7 mm long; sepals 3–9 mm long, 3.5–6 mm wide; outer petals 8.5–15 mm long, 3.5–8 mm wide, very densely hairy ab- and adaxially; inner petals 6.5–10 mm long, 3–4.5 mm wide; ovary glabrous G. elegans Ast
18b Leaf laminas 12.5–24.5 cm long, 4–8.5 cm wide; petioles 5–15 mm long; sepals 7.5–12.5 mm long, 5.5–11 mm wide; outer petals 23–39 mm long, 7–15 mm wide, glabrous to hairy ab- and adaxially; inner petals 10–16 mm long, 5.5–9 mm wide; ovary sparsely hairy G. latestigma C.E.C.Fisch.
13b Inner petal claws without glabrous lateral flange 19
19a Tertiary leaf venation generally reticulate; outer petals with velutinous region at base of adaxial surface (facing aperture between inner petals); inner petals velutinous adaxially 20
20a Sepals 2.5–3.5 mm long, basally connate, venation indistinct; outer petal venation distinct; stigma fusiform G. repevensis Pierre ex Finet & Gagnep.
20b Sepals 4.5–19 mm long, free, venation distinct; outer petal venation indistinct; stigma subulate or funnel-shaped 21
21a Young branches glabrous; outer petal length/width ratio 3.4–5.2 G. expansus Craib
21b Young branches very sparsely to densely hairy; outer petal length/width ratio 1.6–3.8 22
22a Leaves with fine “granular” texture abaxially (due to immersion of tertiary and lower order veins); flowers slightly supra-axillary G. rotundisepalus M.R.Hend.
22b Leaves without fine “granular” texture abaxially; flowers axillary G. tenuifolius King
19b Tertiary leaf venation percurrent; outer petals with glabrous or sparsely hairy region at base of adaxial surface (facing aperture between inner petals); inner petals glabrous to densely hairy adaxially 23
23a Flowering pedicels 20–48 mm long; sepals 7–15 mm long; outer petals 68–113 mm long, 28–63 mm wide G. giganteus (Wall. ex) Hook.f. & Thomson
23b Flowering pedicels 8–16(–21) mm long; sepals 2–8 mm long; outer petals 16–50(–62) mm long, 7–22(–32) mm wide 24
24a Inner petals glabrous adaxially; ovaries densely hairy G. malayanus Hook.f. & Thomson
24b Inner petals (densely) hairy adaxially (sometimes glabrous towards base); ovaries glabrous to sparsely hairy 25
25a Leaf laminas 23–32 cm long, with 14–21 pairs of secondary veins; stamens 50–160 per flower; carpels 4–11 per flower G. aurantiacus R.M.K.Saunders & Chalermglin
25b Leaf laminas 17–25.5 cm long, with 13–16 pairs of secondary veins; stamens ca. 180–200 per flower; carpels ca. 18–20 per flower 26
26a Flowering pedicels densely hairy; outer petals densely hairy abaxially, very densely hairy adaxially, venation indistinct; inner petals very densely hairy abaxially G. maewongensis R.M.K.Saunders & Chalermglin
26b Flowering pedicels very sparsely hairy; outer petals subglabrous abaxially, glabrous adaxially, venation distinct; inner petals sparsely hairy abaxially G. rongklanus R.M.K.Saunders & Chalermglin

Key to Goniothalamus species in Thailand (fruiting specimens)

1a Adaxial surface of leaves with very prominent secondary veins 2
2a Leaf laminas 50–76 cm long, 13–22 cm wide, with 24–32 pairs of secondary veins; leaf midrib densely hairy to velutinous; petioles 17–30 mm long, velutinous; monocarps densely hairy G. cheliensis H.H.Hu
2b Leaf laminas 12.5–39.5 cm long, 3.5–9.5(–11.5) cm wide, with 10–22 pairs of secondary veins; leaf midrib glabrous to sparsely hairy; petioles 4–16 mm long, glabrous to hairy; monocarps glabrous to hairy 3
3a Monocarps distinctly warty G. giganteus (Wall. ex) Hook.f. & Thomson
3b Monocarps smooth or finely rugulose 4
4a Fruits restricted to trunk; fruiting pedicels 19–36 mm long G. tortilipetalus M.R.Hend.
4b Fruits not restricted to trunk; fruiting pedicels 10–19 mm long 5
5a Tertiary leaf venation percurrent; fruits without persistent calyx; monocarps 16–40 mm long, 8–13(–17) mm wide; seeds 13–20 mm long, with (sparsely) hairy testa G. malayanus Hook.f. & Thomson
5b Tertiary leaf venation reticulate; fruits with persistent calyx; monocarps 10–14 mm long, 7–8 mm wide; seeds 10–12 mm long, with glabrous testa 6
6a Monocarps red; seeds slightly rugose G. calvicarpus Craib
6b Monocarps yellow-brown; seeds smooth G. griffithii Hook.f. & Thomson
1b Adaxial surface of leaves with impressed or only slightly prominent secondary veins 7
7a Tertiary leaf venation percurrent 8
8a Monocarps apiculate 9
9a Young branches densely hairy; leaves with 32–40 pairs of secondary veins; fruiting pedicels 20–25 mm long; monocarps 20–27 mm long, densely hairy; monocarp stipes 7–15 mm long G. sukhirinensis sp. nov.
9b Young branches glabrous to hairy; leaves with 12–23 pairs of secondary veins; fruiting pedicels 7–20 mm long; monocarps 8–15 mm long (very) sparsely hairy; monocarp stipes up to 5 mm long 10
10a Fruits without persistent calyx G. macrophyllus (Blume) Hook.f. & Thomson
10b Fruits with persistent calyx G. roseipetalus sp. nov.
8b Monocarps not apiculate 11
11a Monocarps 7–18 mm long, 6–10 mm wide 12
12a Leaf laminas 22–40(–50) cm long, 5.5–12(–19.5) cm wide, with (18–)21–26(–32) pairs of secondary veins G. scortechinii King
12b Leaf laminas 8–20 cm long, 2.5–6 cm wide, with 8–14 pairs of secondary veins G. tenuifolius King
11b Monocarps 16–56 mm long, 13–29 mm wide 13
13a Leaf laminas 32–48 cm long, 7–15.5 cm wide, with 24–35 pairs of secondary veins; fruits without persistent calyx G. uvarioides King
13b Leaf laminas 14–32 cm long, 3.5–9.5 cm wide, with 11–21 pairs of secondary veins; fruits with persistent calyx 14
14a Fruits restricted to base of trunk; fruiting pedicels 30–130 mm long G. ridleyi King
14b Fruits not restricted to base of trunk; fruiting pedicels 10–22 mm long 15
15a Monocarps subsessile or with stipe ≤ 1 mm long; seeds 18–19 mm wide, rugose G. maewongensis R.M.K.Saunders & Chalermglin
15b Monocarp stipes 2–8 mm long; seeds 13–17 mm wide; smooth to slightly rugulose 16
16a Leaf laminas 23–32 cm long, with 14–21 pairs of secondary veins; fruiting pedicels ca. 14 mm long; seeds 19–27 mm long, length/width ratio 1.5–1.7 G. aurantiacus R.M.K.Saunders & Chalermglin
16b Leaf laminas 17–25 cm long, with 13–16 pairs of secondary veins; fruiting pedicels 16–22 mm long; seeds 15–22 mm long, length/width ratio 1.1–1.5 G. rongklanus R.M.K.Saunders & Chalermglin
7b Tertiary leaf venation reticulate 17
17a Monocarps 22–56 mm long, 14–21 mm wide, with prominent longitudinal ridge; up to 7 seeds per monocarp G. laoticus (Finet & Gagnep.) Bân
17b Monocarps 8.5–26 mm long, 6–11 mm wide, without longitudinal ridge; 1 or 2 seeds per monocarp 18
18a Fruiting pedicels 8–20 mm long 19
19a Young branches (very densely) hairy 20
20a Leaf laminas glossy adaxially; monocarp stipes 6.5–16.5 mm long; seeds 9–11.5 mm long G. undulatus Ridl.
20b Leaf laminas matt adaxially; monocarp stipes 3–6 mm long; seeds 11–14 mm long G. sawtehii C.E.C.Fisch.
19b Young branches glabrous to hairy 21
21a Leaf lamina tertiary venation (clearly) distinct G. expansus Craib
21b Leaf lamina tertiary venation indistinct to ± distinct 22
22a Leaf laminas with 9–12 pairs of secondary veins; monocarps greenish-yellow, ca. 19 mm long; seeds 17–18 mm long G. tavoyensis Chatterjee
22b Leaf laminas with 11–16 pairs of secondary veins; monocarps (dark) red, 10–14 mm long; seeds 9–12 mm long G. tapis Miq.
18b Fruiting pedicels 4–8 mm long 23
23a Monocarps greenish-yellow 24
24a Young branches hairy; leaf laminas 12.5–24.5 cm long, 4–8.5 cm wide; monocarps smooth; seeds ca. 17.5 mm long G. latestigma C.E.C.Fisch.
24b Young branches (very) sparsely hairy; leaf laminas 10.5–13.5(–16) cm long, 3–5 cm wide; monocarps very finely rugulose; seeds ca. 9.5 mm long G. repevensis Pierre ex Finet & Gagnep.
23b Monocarps red 25
25a Fruits without persistent calyx; seeds subglabrous to hairy G. tapis Miq.
25b Fruits with persistent calyx; seeds glabrous 26
26a Leaf laminas 1.5–4 cm wide, ± glossy adaxially G. elegans Ast
26b Leaf laminas 3.5–8.5 cm wide, (±) matt adaxially 27
27a Monocarps glabrous; monocarp stipes 4.5–13 mm long G. tamirensis Pierre ex Finet & Gagnep.
27b Monocarps very sparsely hairy; monocarp stipes 2–3 mm long G. rotundisepalus M.R.Hend.

Acknowledgements

The authors would like to thank Mr Abdulromea Baka and Mr Isma-ael Sama-ae for field assistance, Ms Arisa Somphrom for the line drawings, and Dr Thomas Couvreur, Prof. David Johnson and two anonymous reviewers for their invaluable input. The first author would like to thank the Faculty of Science, Prince of Songkla University, for financial support.

References

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