Mitrephora sukhothaiensis Leerat., Chalermglin & R.M.K.Saunders, 2023

Leeratiwong, Charan, Chalermglin, Piya & Saunders, Richard M. K., 2023, Three new species of Mitrephora (Annonaceae) from Thailand, PhytoKeys 218, pp. 93-107 : 93

Mitrephora sukhothaiensis Leerat., Chalermglin & R.M.K.Saunders sp. nov.

Figs 6 , 7

Diagnosis.

Mitrephora sukhothaiensis is distinct from all other species in having a combination of outer petals that reflex at maturity as well as inner petals that have inwardly folded marginal protrusions at the midpoint adaxially.

Types.

Thailand: Central: TISTR Annonaceae collection plot, Khlong Luang district, Pathum Thani Province, Central Thailand, ca. 5 m alt., 10 December 2021, P. Chalermglin 641210 (originally from Si Satchanalai District, Sukhothai Province, Northern Thailand, ca. 360 m alt.) (holotype PSU; isotypes BKF, KKU).

Description

(from cultivated material). Shrubs, to 2 m (in cultivation). Young branches densely pubescent. Leaf laminas coriaceous, (elliptic-)lanceolate or rarely ovate-lanceolate, 6-22 by 2.5-8 cm, base rounded to slightly cordate, apex acute to acuminate, glossy, glabrous (except midrib pubescent) adaxially, moderately to sparsely pubescent abaxially, secondary veins 6-14 pairs per leaf, with domatia; petioles 3-8 mm long, moderately pubescent. Inflorescence rachides simple, with rachis internodes remaining short, 1-3 mm long, 2-3-flowered, densely pubescent; pedicels 8-17 mm long. Sepals united at base, broadly ovate, not imbricate, 4-5.5 by 4-5.5 mm, densely pubescent ab- and adaxially. Outer petals creamy white to yellow, ovate, 12-17 by 9-12 mm, reflexing when mature, not clawed, margin not undulate, apex obtuse, densely pubescent ab- and adaxially. Inner petals greenish-yellow with purple spot towards apex, 10-12 by 5-6 mm, claw incurved, densely pubescent abaxially, densely hairy with long hairs towards apex adaxially, with inwardly folded marginal protrusions at the midpoint adaxially. Stamens 0.8-1.3 mm long, connective truncate, glabrous. Carpels 12-20 per flower, 1.6-2 mm long; ovary ellipsoid to oblong-ellipsoid, 1.3-1.5 mm long, moderately hairy; stigma globose, 0.3-0.5 mm long, hairy; ovules 6-10 per carpel. Fruits with up to 16 monocarps, borne on a pedicel 15-25 mm long, 4-6 mm wide, densely pubescent. Monocarps yellow when ripe, (ellipsoid-)ovoid to subglobose, 13-20 by 10-16 mm, smooth, without longitudinal ridge, densely pubescent; stipes 15-22 mm long, densely pubescent. Seeds 2-6 per monocarp, semi-lenticular (lowermost and uppermost within monocarp) or discoid (others), 5-10 by 5-6 mm, glabrous, pitted.

Phenology

(in cultivation). Flowering between December and March to June; fruiting between May and July.

Distribution and habitat.

Endemic to Sukhothai Province, Northern Thailand (Fig. 3 ). Growing in mixed deciduous forest; ca. 360 m alt.

Etymology.

From the name Sukhothai province.

Local name.

Phrom sukho (พรหมสุโข) (general).

Additional specimens examined

(paratypes). Thailand: Pathum Thani Province, Khlong Luang District, TISTR Annonaceae collection plot, ca. 5 m alt., 20 November 2020, P. Chalermglin 631120 (originally from Si Satchanalai District, Sukhothai Province, Northern Thailand , ca. 360 m alt.) (SING) ; ibid. 1 May 2022, P. Chalermglin 650501 (KKU, PSU); ibid., 23 June 2022, P. Chalermglin 650623/2 (PSU) .

Discussion.

Mitrephora sukhothaiensis is easily distinguished from all other species in two key characters: its outer petals that reflex at maturity, and its inner petals that have inwardly folded marginal protrusions at the midpoint adaxially.

Mitrephora sukhothaiensis also resembles M. tomentosa in the appearance of the fruit (monocarp shape and surface) and seeds, but differs in its shrubby habit, growing to 2 m in height (vs small to medium trees to ca. 20 m), sparsely to moderately hairy leaf indument abaxially (vs densely hairy), outer petals that reflex at maturity and without undulate margins), inner petals with inwardly folded marginal protrusions, and narrower seeds (5-6 mm vs ca. 8 mm).

Figures

Figure 3. Distributions of Mitrephora langsuanensis, M. sirindhorniae and M. sukhothaiensis.

Figure 6. Mitrephora sukhothaiensis sp. nov. A, B leaves (ad- and abaxial) C flower buds D flower (slightly immature) E-G flowers, F, G showing the outer petals reflexed when mature, with insert in F showing adaxial surface of inner petal with inwardly folded marginal protrusions H fruit (mature). Photos by P. Chalermglin.

Figure 7. Mitrephora sukhothaiensis sp. nov. A vegetative branch B, C flowers D, E sepals (ab- and adaxial) F, G outer petals (ab- and adaxial) H, I inner petals (ab- and adaxial, showing marginal protrusions) J, K stamens (ab- and adaxial) L carpel M fruit, composed of separate monocarps. Drawn by A. Somphrom, A-L from P. Chalermglin 641210 (PSU), M from P. Chalermglin 650501 (PSU).