Wikstroemia fragrans W.B.Liao, Q.Fan & J.R.Chen, 2022

Chen, Jing-Rui, Lee, Shiou Yih, Guo, Jian-Qiang, Jin, Jie-Hao, Fan, Qiang & Liao, Wen-Bo, 2022, Wikstroemia fragrans (Thymelaeaceae, Daphneae), a new species from Mount Danxia, China based on morphological and molecular evidence, PhytoKeys 213, pp. 67-78 : 67

Wikstroemia fragrans W.B.Liao, Q.Fan & J.R.Chen sp. nov.

Figs 2 , 3 , 4

Type.

China. Guangdong Province, Danxia National Park , 25.0°N, 113.7°E, 74 m alt., 16 March 2022 [fl.], Qiang Fan, DNPC 1597 (Holotype SYS! Barcode SYS00236854, Isotypes SYS! Barcode SYS00236855, CSFI!) .

Diagnosis.

Wikstroemia fragrans differs from W. trichotoma , by its smaller leaves (1.2-1.6 × 0.5-0.9 vs. 1.2-3.5(-8) × (0.5-)1-2.2(-4) cm), densely racemose to nearly capitate inflorescence (vs. loose panicle), yellowish green calyx (vs. white), and strigose-pubescent ovary (vs. apically strigose ovary). Wikstroemia fragrans differs from W. fargesii by its strigose-pubescent ovary (vs. apically strigose) and a disk scale 2- or 3-dentate apically (vs. entire or slightly retuse apically).

Description.

Shrub, 0.6-1.6 m tall; perennial branches reddish brown, rugose, annual branches yellowish green, glabrous. Leaves opposite or subopposite, ovate to ovate-lanceolate, 1.2 - 1.6 × 0.5 - 0.9 cm, thinly papery, grayish green adaxially, light yellowish green abaxially, glabrous on both surfaces, apex acuminate or obtuse, margin entire, base cuneate or subrounded, midrib flat adaxially, prominent abaxially, secondary veins 4-8 pairs per side, slightly prominent abaxially; petiole ca. 1 mm long. Inflorescence 4-8-flowered, densely racemose to capitate; peduncle 5 - 15 mm long, glabrous; pedicels absent or ca 0.4-0.7 mm long, glabrous. Calyx tube yellowish green; 9-11 mm long, exterior glabrous, lobes 5 (sometimes abnormally 6), elliptic, 2.5-3.3 × 1.2-1.7 mm, margin undulate, glabrous on both surfaces. Stamens 10 (sometimes abnormally 11), lower whorls of 5 anthers inserted 2-4 mm above middle of hypanthium, upper whorl of 5 anthers at throat; free portion of filaments ca 0.3 mm long; anther linear-oblong, ca 0.8 mm long; subgynoecial disk scale 1, linear or linear-oblong, apex 2- or 3-dentate, 0.8-1.0 × 0.3-0.7 mm, membranous, glabrous. Ovary obovoid, 3-4 mm long, ca 0.6 mm in diam., subsessile, strigose pubescent; style ca 0.2 mm long, glabrous; stigma yellow, globose, ca 0.5 mm in diam., surface papillate. Drupe ca. 6 mm long, yellowish green, ovoid-globose, glabrous, 1-seeded, enclosed by persistent calyx; fruiting pedicel ca 8 mm long. Seed ovoid, ca. 4 mm long, black, glabrous.

Distribution and habitat.

Wikstroemia fragrans is currently known only from the type locality, Danxiashan National Nature Reserve (Ba Zhai, Mount Shaoshi, Shuang He Zhai, Yu Nv Lan Jiang), Guangdong, China. It occurs in xerophytic hillside thickets on sandstone and conglomerate based soil at 100-300 m elevation. In this habitat, the most common shrubby and herbaceous species are Lagerstroemia indica Linn. ( Lythraceae ), Symplocos tanakana Nakai ( Symplocaceae ), Decaspermum gracilentum (Hance) Merr. et Perry ( Myrtaceae ), Viola hybanthoides W. B. Liao & Q. Fan ( Violaceae ) and Salvia scapiformis Hance ( Lamiaceae ).

Phenology.

Wikstroemia fragrans was observed flowering from March to April, fruiting from April to June.

Etymology.

Latin Wikstroemia fragrans , smell or odor, alluding to sweet-scented flowers. The Chinese name is given as 香花荛花 ( xiāng huā ráo huā).

Conservation status.

During our intensive floristic inventories in Danxiashan National Nature Reserve from September 2021 to May 2022, only 5 populations of Wikstroemia fragrans comprising 5-20 individuals each were found. Due to the limited extent of occurrence (ca. 40 km2) and area of occupancy (ca. 5 km2) and small population sizes (<100 individuals totally), W. fragrans is proposed to be classified as Critically Endangered (CR B1ac(i)+2ac(i)) according to the IUCN Categories ( IUCN 2012).

Additional specimens examined (paratypes).

China, Guangdong Province, Danxia National Park , 25.0°N, 113.7°E, 384 m alt., 14 August 2022, Wan-yi Zhao & Jing-rui Chen, DNPC 2966 (SYS) ; China, Guangdong Province, Danxia National Park , 24.9°N, 113.7°E, 162 m alt., 17 August 2022, Wan-yi Zhao & Jing-rui Chen, DNPC 3029 (SYS) .

Figures

Figures 2. Wikstroemia fragrans W. B. Liao, Q. Fan & J. R. Chen, sp. nov. A flowering branch B flower C subgynoecial disk scale opened out D dissected flower showing the normal condition of 10 stamens E strigose ovary and glabrous disk scale A-E DNPC 1597 deposited in SYS. Drawn by Rong-En Wu.

Figure 3. Habitat and morphological features of Wikstroemia fragrans W. B. Liao, Q. Fan & J. R. Chen, sp. nov. A, B habitat, hillsides thickets of Danxiashan National Park C flowering branches D immature fruits E densely racemose inflorescence F, G flowers, showing 5 - lobed calyx. (A-C, E-G photographs by Jing-Rui Chen of unvouchered plants in the original habitat in April 2022 D photograph by Jian-Qiang Guo taken in April 2021).

Figure 4. Wikstroemia fragrans W. B. Liao, Q. Fan & J. R. Chen, sp. nov. A hypanthium dissected showing 10 stamens B hypanthium dissected showing abnormal 11 stamens C subgynoecial scale disk, linear-oblong, apex 2 - 3 dentate D pistil with strigose-pubescent ovary, glabrous style, and light green stigma. A-D DNPC 1597 deposited in SYS.