Adiantum × ailaoshanense Y.H.Yan & Y.Wang, 2015

Wang, Ying, Shang, Hui, Zhou, Xi-Le, Zhao, Guo-Hua, Dai, Xi-Ling & Yan, Yue-Hong, 2015, Adiantum ailaoshanense (Pteridaceae), a new natural hybrid from Yunnan, China, Phytotaxa 236 (3), pp. 266-272 : 267-270

Adiantum × ailaoshanense Y.H.Yan & Y.Wang , nothosp. nov. ( Figs. 1 & 2 A)

A. × ailaoshanense is most similar to A. × meishanianum morphologically. However, they differ because in A. × ailaoshanense , the upper margins of the false indusia is flat and straight, and each pinna has less sori. Moreover, A. × ailaoshanense differs from A. sinicum because the pinna of A. × ailaoshanense is stalked, and its rachis and pinna are sparsely hairy. Furthermore, the new hybrid is also similar to A. menglianense , but A. × ailaoshanense has shorter pinna stalks (1.5–2.5 mm vs. 10–25 mm in A. menglianense ) (Fig. 2 & Tab. 1).

Type:— CHINA. Yunnan: Yuanjiang County, Ailao Mountain National Natural Reserve, 1120 m, 4 June 2013, Yan 12410 (holotype CSH!).

FIGURE 2. A. A. × ailaoshanense . B. A. × meishanianum . C. A. sinicum . D. A. malesianum . E. A. menglianense . F. A. philippense . Photos by the author.

Plants 15–40 cm tall. Rhizomes erect, short; scales brown with black center, linear–lanceolate, 3–4 mm, margins entire. Fronds clustered; stipe castaneous, lustrous, 10–20 cm, base with same scales as rhizome; rachis glabrous or with sparse multicellular hairs; lamina 1-pinnate, lanceolate in outline, 15–35 × 2.5–5.0 cm; apex usually prolonged into a whip-like appendage and rooting to form new plantlets; pinnae 15–25 pairs, mostly horizontally spreading, basal pair reflexed, sub-orbicular flabellate, 1.2–2.5 × 1.0– 1.5 cm, progressively smaller distally, herbaceous, both surfaces with sparse multicellular hairs when young, sub-glabrous when mature, base asymmetrical, outer margins undulate-lobed or lobed for 1/3–1/2 of breadth of pinnae, with 4–7 lobes; stalk distinct, 1.5–2.5 mm; terminal pinna small, obtriangular, base cuneate, outer margins rounded and 2–4 lobed; veins dichotomously forked, visible on both surfaces. Sori 4–10 per pinna; false indusia sparsely hairy or nearly glabrous, dark brown, rectangular, papery, upper margins flat and straight, entire, persistent. Spores abortive, dark brown, radially symmetrical, and trilete, ornamentation tuberculate.

Etymology: —The specific epithet is derived from the type locality, Ailao Mountains, Yunnan Province, China.

Distribution and habitat: — Adiantum × ailaoshanense grows in shaded wet areas of the forests at 1120 m with its parents in same population ( Fig. 4 ). Its distribution area is known only from the type locality.

Additional specimens examined (paratype): — CHINA. Yunnan: Ailao Mountain National Natural Reserve, Yuanjiang County, 1120 m, 4 June 2013, Yan 12413 (CSH!).

IUCN Red List category: — Adiantum × ailaoshanense has a restricted geographic distribution. It has not been found in other areas except for one population in the Ailao Mountains. Based on the IUCN Red List criteria, it should be considered Critically Endangered ( IUCN 2014).

Remarks: —The spore of the hybrid is abortive. Spore germination rate was ca. 10% and the gametophyte could not develop well. Its ornamentation is tuberculate like that of its female parent Adiantum sinicum , whereas the spores of its male parent are granulate ( Fig. 3 ).

The Adiantum menglianense range overlaps with the southern portion of the A. sinicum range, in Yuanjiang and Cangyuan County ( Lin 1990; Lin et al. 2013). Adiantum × ailaoshanense was collected from the Ailao Mountains where the range of these two species overlaps. Both A. sinicum and A. menglianense have been found in the vicinity of the A. × ailaoshanense . The hybrid species is suggested to arise when the distribution ranges of the parents overlap. Thus, A. × ailaoshanense might be established at some sites across the overlapping range of the two parents. A future field investigation will be undertaken in places where the ranges of the two parental species overlap ( Fig. 4 ).

Figures

FIGURE 1. Adiantum × ailaoshanense Y.H. Yan & Y. Wang. A. Habit. B. Pinna abaxial. C. Pinna adaxial. D. Sporangia. E. Multicellular hair. F. Rhizome scale. Drawn from the holotype Yan12410 (CSH).

FIGURE 3. SEM photographs of the spore morphology of Adiantum × ailaoshanense (B, D and E) and its parents. A. A. sinicum. C. A. menglianense.

FIGURE 4. Distribution of Adiantum × ailaoshanense(Ì). A. sinicum(●) and A. menglianense(▲).