Alphonsea glandulosa Y.H. Tan & B. Xue, 2017

Xue, Bine, Shao, Yun-Yun, Saunders, Richard M. K. & Tan, Yun-Hong, 2017, Alphonsea glandulosa (Annonaceae), a New Species from Yunnan, China, PLoS ONE (e 0170107) 12 (2), pp. 1-16 : 11-13

Alphonsea glandulosa Y.H. Tan & B. Xue , sp. nov. [urn:lsid:ipni.org:names:77159533–1] ( Figs 2 , 3 , 4 , 5 and 6 )

Type: CHINA. Yunnan Province, Meng-la County, Meng-lun , Man-zhang Reservior , 21˚ 55 0 53 @ N, 101˚10 0 58 @ E, alt. 625 m. Y. H. Tan 1014*, 2016.04.07 (fl.) (holotype HITBC; isotypes IBSC, KUN)

Diagnosis. Alphonsea glandulosa is unique amongst Alphonsea species in having a nectar gland at the base of the adaxial surface of each inner petal. It is most similar to A. philastreana (Pierre) Finet & Gagnep. , but differs in having a greater number of secondary veins on each side of the leaf, greyish to yellowish pubescent flower buds, longer pedicels, a greater number of carpels per flower, a smaller number of ovules per carpel, and globose to shallowly bilobed stigmas.

Description. Trees to 15–20 m tall, ca. 25–30 cm dbh. Bark brownish, fissured. Young twigs green, puberulent, soon become greyish and glabrous. Petioles 3–8 mm long, 1–2 mm in diameter, transversely densely striate; leaf laminae narrlowly elliptic, elliptic or ovate, 6–19 × 3–6.7 cm, base cuneate, apex acuminate, slightly coriaceous, abaxially sparsely pubescent to glabrescent, adaxially glabrous; midrib impressed and glabrous above, raised and hairy to glabrous below; secondary veins 8–18 on each side of the leaf, parallel, diverging at 45–60˚ from midrib, anastomosing within margin, distinctly raised below; tertiary veins reticulate, prominent abaxially. Inflorescences leaf-opposed or supra-axillary; (3–)5–9(–13) flowers per inflorescence ( Fig 2A–2C ). Peduncles absent or up to 3 mm long ( Fig 2A–2C ). Pedicels 10–20 mm long, 1–1.5 mm in diameter, pubescent, with one densely pubescent median bract ( Fig 2A–2C ). Sepals ovate, 1.5–2 × 1.5–2.5 mm, hairy abaxially, glabrous adaxially; outer petals ovate, 10–14 × 6–8.5 mm, base acute, apex acute, tomentose abaxially, sparsely hairy to glabrous adaxially; inner petals narrower, 10–14 × 5–8 mm wide, hairy abaxially, glabrous adaxially, with glandular tissue near the base ( Fig 4A–4D ), apparent as ridge in fresh ( Fig 4A and 4B ) and FAA-fixed ( Fig 4C ) material, and as distinct groove in dried specimens ( Fig 4D ). Stamens ‘miliusoid’ with very short connective prolongation not extending over pollen sacs, 26–35 per flower, ca. 1 mm long, in 3 whorls ( Figs 3C , 4A and 4F ). Carpels 4–7 per flower, ca. 3 mm long, with short brown hairs ( Figs 2B and 4B ); ovules 10–13 per carpel, biseriate ( Fig 3D ). Fruiting pedicels 7–20 mm long, 3 mm in diameter; monocarps 1–7 per fruit, subglobose to cylindrical, ca. 2–4 cm long, 1.5– 3 cm in diameter, yellow when mature, greyish pubescent, smooth, sometimes with a longitudinal ridge or

groove, apex rounded; stipe to 10 mm long, ca. 4 mm thick ( Fig 2D and 2E ). Seeds flattenedellipsoid, up to 13 per monocarp ( Fig 2E ). Pollen grains solitary, subspherical, 30–40 μm in diameter, rugulate ( Fig 3E and 3F ).

Etymology. The specific epithet reflects the presence of nectar glands at the base of the adaxial surface of each inner petal.

Additional specimens examined (paratypes). China. Meng-la , Yunnan , 2009-03-25, Chun-fen Xiao C100647 ( HITBC) ; 2015-04-29, B. Xue 188 ( IBSC) ; 2016-04-26, B. Xue 26* ( IBSC, KUN) ; 2016-04-27, B. Xue 268 ( IBSC, SING) .

Distribution. Only known from two localities in Yunnan, China ( Fig 7 ).

Ecology and phenology. In evergreen forests. Flowering specimens collected in March to May, and fruiting specimens in June to July.

IUCN Conservation Status. Only two individuals were found in Meng-la County, Yunnan Province. The primary forests in Xishuangbanna have been under severe pressure from agricultural expansion over the last 30 years, and below 900 m elevation most unprotected forest has been replaced by rubber plantations [ 57]. The tree growing in the forests close to Man-zhang Reservoir in Meng-la County is located at the edge of a rubber plantation. One of the authors, Yun-Hong Tan, has undertaken an extensive field survey in Xishuangbanna, but was unable to locate other individuals. Perhaps because of the dearth of individuals, the level of fruitset in the two trees is poor. On the basis of current IUCN red list categories and criteria [ 58], we therefore recommend critically endangered status, CR D.

Figures

Fig 2. Flower and fruit morphology of Alphonsea glandulosa. A, Branch, showing leaf-opposed inflorescence position,and lanceolate leaves. B, Abaxial view of the inflorescence, showing 5–6 carpels per flower. C, Adaxial view of the inflorescence, showing pubescent pedicels with one densely pubescent medial bract (arrowed). D, Fruit with subglobose monocarps. E, Single monocarp, dissected to show seed arrangement.—Photos: A–E, Yun-hong Tan. doi:10.1371/journal.pone.0170107.g002

Fig 3. Morphology of the surface of the inner petal glands, stamen, carpel and pollen of Alphonsea glandulosa (scanning electron micrographs). A, Surface of the glandular tissue, showing the nectary stomata (arrowed). B, Close-up of the nectary stomata. C, Stamen. D, Carpel, dissected to show biseriate ovules. E, Pollen grain. F, Rugulate pollen exine ornamentation. doi:10.1371/journal.pone.0170107.g003

Fig 4. Glandular tissue, nectar and flower visitors of Alphonsea glandulosa. A, Nectar at pistillate phase.B, Nectar at the end of staminate phase. C, Morphology of the glandular tissue after FAA fixation. D, Morphology of the glandular tissue after rehydration from dried specimens. E, Small curculionid beetles observed visiting the flowers. F, Bee observed visiting the flower.—Photos: A, C, F, Yun-Yun Shao; B, D, E, Bine Xue. doi:10.1371/journal.pone.0170107.g004

Fig 5. Anatomical structure of the inner petal glands and adjacent non-glandular part of the inner petals (paraffin sections). A, Section of the inner petal nectary gland, showing the nectary epidermis (E), secretory parenchyma (SP), ground parenchyma (GP), and vascular tissue (V). B, Section of the non-glandular part of the inner petals, showing the epidermis (E), parenchyma (P) and vascular tissue (V). doi:10.1371/journal.pone.0170107.g005

Fig 6. Alphonsea glandulosa sp. nov. A, Flowering branch. B–D, Flower (B, Lower view. C, Lateral view. D, Top view, showing six carpels and three rows of stamens). E–F, Outer petal (E, Abaxial view. F, Adaxial view). G–H, Inner petal (G, Abaxial view. H, Adaxial view,with nectar glands at the base). I, Flower with petals removed,showing the attachment of stamens and carpels. J–K, Stamen (J, Adaxial view. K, Abaxial view). L. Carpel, longitudinal section, showing ovule arrangement. M, Fruit, composed of separate monocarps. N, Single monocarp. O, Longitudinal section of monocarp, showing seed arrangement. Drawn by Yun-xiao Liu. doi:10.1371/journal.pone.0170107.g006

Fig 7. Distribution of Alphonsea glandulosa. doi:10.1371/journal.pone.0170107.g007