Euonymus aquifolium Loes. & Rehder in Sargent 1913: 484

Hu, Jun, Zhang, Jun-Yi, Yu, Ding-Xiang, Jiang, Hong, Xu, Bo, Liu, Qing & He, Hai, 2022, Euonymus aquifolium (Celastraceae): Rediscovered in flowering with respect to its taxonomy, nomenclature, and rarity, PhytoKeys 201, pp. 139-151 : 139

Euonymus aquifolium Loes. & Rehder in Sargent 1913: 484

Figs 1 , 2

Glyptopetalum aquifolium ≡ Glyptopetalum aquifolium (Loes. & Rehder) C.Y.Cheng & Q.S.Ma in Cheng et al. 1999: 93

Type.

China. Sichuan [Szechuan]: Wa-shan , on cliffs, elev. ca. 2200 m, in fruiting, November 1908, E. H. Wilson 1366 (holotype A00049691 (Fig. 4A ); isotypes K000669647 & US 00096036).

Description.

Evergreen shrubs, 1-3 m tall, glabrous throughout; young branches firstly 4-angular and green, later turning almost terete and grey-brown. Leaves opposite, leaf blade leathery, oblongly ovate, ovate to orbicularly ovate, 4-7 × 2.5-4.5 cm, uneven on both surfaces, adaxially dark green, abaxially slightly pale green, glossy, margin with clear and irregular large spines, apex acute or short acuminate, base slightly cordate and often marginally clasping the branch, more or less oblique; lateral veins 6-10 pairs, curved and distally ca. 1/4 its length near margin connected with tertiary veins, midrib and lateral veins visibly elevated on both surfaces, transverse veins obscure; subsessile or petiole to 2 mm long. Cymes in leaf axils or extra-axillary, nearly on the adaxial side of branchlet when extra-axillary, with 1 to several (mostly 5-7) flowers; peduncle 1.5-5 cm long; pedicel 0.6-1.2 cm long, usually with two opposite bracteoles at base; bracteoles subulate, 0.4-0.8 cm long, ca. 2 mm wide, persistent. Flowers red-brown, 1-1.5 cm in diameter, 5-merous; calyx 5-lobed to middle, lobes triangular, red-brown, margin with fleshy projections, persistent; petals 5, fleshy, 0.5-0.8 cm long, 0.3-0.6 cm wide, broad-ovate, slightly revolute; disc pentagonal, deep red, fused to ovary; stamens 5 on disk, filaments very short, anthers small and yellow; ovary partly exposed outside disk, reddish brown, style absent, stigma rounded, white with yellowish tinge; ovary 5-locular; ovules 2 per locule. Capsule, subglobose, mostly yellowish green when immature, glabrous, 8-10 mm high, 1.2-1.5 cm in diameter, 5-loculed, sometimes only 4(-2)-loculed owing to infertile of one or more locules, with 2 seeds per locule, or only one seed with another ovule aborted. Seeds brown, oblong, 0.4-0.8 cm long, with orange-yellow aril, more than 1/2 covered by aril.

Phenology.

Flowering was observed in August, and it could start earlier; fruiting from August to November.

Habitat.

The newly discovered site (elevation ca. 1850 m) is located under the cliff of a small ditch in the Dadu River Basin. The place is located in the so-called 'Rain Zone of Western China’, where it is commonly rainy most of the year. The habitat is further shady and humid due to the gorge landform (Fig. 1A, B ). Based on the records of type specimens, Euonymus aquifolium can grow on the cliffs within the evergreen broadleaf forest or evergreen and mixed deciduous broadleaf forest at an elevational range of 1800-2200 m in Dadu River Basin.

Additional specimens examined.

China. Sichuan: Jiulong County, Wanba , elev. ca. 1850 m, in flowering, 10 August 2021, J. Hu et al. hujun20210810B01 (CDBI! NAS! PE!) (Fig. 4B ) .

Nomenclatural note.

The species epithet of Euonymus aquifolium had been changed to " Euonymus aquifolius " to agree with the generic gender based on the assumption that this epithet was used as adjectival in form, and this was generally followed (e.g., Chang 1988; Cheng et al. 1999; Ma et al. 2008; IPNI 2022). However, when it was originally proposed, the initial letter of the epithet was capitalized as " Aquifolium " ( Sargent 1913), and that was customary then to indicate the epithet was applied after a proper noun, such as a person or a genus ( Clifford and Bostock 2007). Aquifolium Miller (1754) is an illegitimate superfluous generic name of Ilex Linnaeus (1753), though it could also be used as an adjective ( Euonymus aquifolius ). Loesener & Rehder also capitalized the epithet when describing other species in the same publication ( Sargent 1913). For example: Euonymus sargentianus Loes. & Rehder in Sargent (1913) by naming the epithet as " Sargentiana " (named after a person), and E. oblongifolius Loes. & Rehder in Sargent (1913) as " oblongifolia ". This conclusion is further supported based on a review of the handwriting annotations by those authors on the type material of these taxa, where the species epithets of E. aquifolium (E. H. Wilson 1366, A) and E. Euonymus sargentianus (E. H. Wilson 1187, A) were written in uppercase, while that of E. oblongifolius (E. H. Wilson 3125, A) was in lowercase. Therefore, the species epithet of Euonymus aquifolium should retain its own gender and termination according to Art. 23.5 of ICN ( Turland et al. 2018).

Rarity and conservation status.

The type material of Euonymus aquifolium was collected by E. H. Wilson in November 1908 in Washan, Sichuan. Further geographical information concerning the type locality could not be traced by the related references (such as Wilson 1913, 1929; Yin et al. 2010). Owing to the historical vicissitudes, the picture named as "Wa Shan" in Wilson (1913, 1929) was traced by Yin et al. (2010; Fig. 5 ) to Jinkouhe District, Leshan City, Sichuan. A few botanists and amateurs (K. P. Yin, pers. comm.) had made attempts to find the living plants of this species around this area without result.

Another gathering (P. N. Qin et al. 104) identified as this species is recorded in Cheng et al. (1999) without mention of the herbarium where the specimen(s) were deposited. The collectors were a team of younger volunteers assigned by Tsofu Lu (1893-1952), the director of the then newly established Science Institute of West China, to survey in western Sichuan along the water courses in 1929 ( Hou 2012), and most of their collections include duplicates bequeathed to the present Chongqing Natural History Museum (CQNM). An extensive search at CQNM did not identify any material from this gathering (Feng Chen, pers. comm.). It is unimaginable that it lacked leaves as commented in Cheng et al. (1999) since this is an evergreen thick leathery leaved plant. Searches by enthusiastic amateurs previously and Jun Hu’s team recently for living individuals near the locality of this gathering (Fig. 5 ) were also unsuccessful.

We conclude that Euonymus aquifolium is a rare and vegetatively distinctive species, and this rediscovery uncovered the only presently confirmed living individuals more than 110 years after its description, which are distributed more than 100 km westward from its type locality (Fig. 5 ). Although it is located in difficult-to-access valleys on, and living on a cliff that is unlikely to be destroyed intentionally, natural hazards might still totally damage its habitat. With just ~ 15 individuals, it should still be assessed as Critically Endangered (CR) according to the IUCN (2022) Red List Categories and Criteria.

Figures

Figure 1. Euonymus aquifolium Loes. & Rehder A habitat B habit on cliff C branch with a flower D a flower and an immature fruit E axillary inflorescence F extra-axillary inflorescence G leaves in adaxial (G 1) and abaxial views (G 2) H an inflorescence showing peduncle (H 1) and pedicel (H 2) I close-up of a flower and an immature fruit (I 1), showing disk and calyx (I 2), a detached petal (I 3), an immature fruit in side view (I 4) and front view (I 5), and two immature seeds in a fertile locule with the lower right one covered by aril.

Figure 2. Euonymus aquifolium Loes. & Rehder A flowering and fruiting branches B leaves in abaxial view C a flower in side view D a flower in rear view showing abaxial calyx, attached pedicel and a pair of bracteoles at its base E a flower in front view F a flower with petals removed showing disk G a detached petal H an immature fruit in front view I an immature fruit in side view [Drawn by Cong-Ying Li from live specimens J. Hu et al. hujun 20210810 B 01].

Figure 4. Selected specimens of Euonymus aquifolium Loes & Rehder A holotype of this species (E. H. Wilson 1366, A 00049691) B a duplicate of J. Hu et al. hujun 20210810 B 01 (CDBI).

Figure 5. Distribution map of Euonymus aquifolium Loes & Rehder based on three collections.