Ceratopteris shingii Y. H. Yan & R. Zhang, 2020

Zhang, Rui, Yu, Jun-Hao, Shao, Wen, Wang, Wei-Qing, Shang, Hui, Zheng, Xi-Long & Yan, Yue-Hong, 2020, Ceratopteris shingii, a new species of Ceratopteris with creeping rhizomes from Hainan, China, Phytotaxa 449 (1), pp. 23-30 : 24-28

Ceratopteris shingii Y. H. Yan & R. Zhang , sp. nov. Fig. 1 .

Type: — CHINA, Hainan Province, Haikou City, Longhua District, Jiangjunshan , in some volcanic lakes, 19°47′N, 110°17′E, elev. 44 m, 12 January 2019. Yue-Hong Yan Fern09770 (holotype, CSH!; isotypes, CSH!, PE!, IBSC!) .

Diagnosis: —Morphological features of the new species are similar to those of C. thalictroides with dimorphic fronds and linear sori attached to the veinlets on both sides of the main vein, but differs by having creeping rhizomes and dense scales.

Description: —Terrestrial and aquatic, 8.3–41 cm tall. Rhizomes: long-creeping to 1 m long, scaly. Scales sparse on stipe apex and dense on the base, brown, and hyaline. Fronds: dimorphic, green and fleshy, and distant with the spacing 1–2 cm; dormant bud initials are often found in the sinuses of the pinnae of both sterile and fertile fronds, and dropped when ripe. Sterile fronds: 8.3–24.2 cm long; stipes 3.5–8.5 cm long; blades 4.7–15.5 cm long, 2.6–5 cm wide; 2–3 pinnate; 4–10 pinnae pairs, ovate to oblong, up to 1 × 0.5 cm; terminal lobes entire, ovate to deltoid to oblong, 0.3–0.4 cm × ca. 0.1 cm; broad wing formed at the base of decurrent along rachis. Fertile fronds: 27.7–41 cm long; stipes 12.3–18.5 cm long; blades 15.5–22 cm long, 7–8 cm wide; three pinnate; 5–9 pinnae pairs, ovate to oblong, up to 22 × 7 cm; terminal lobes linear to siliquiform, 0.4–1.4 cm × ca. 0.1 cm. Spores: tetrahedral and trilete, 99–105 μm in diameter with parallel ridges on the surface. Tetraploid, 2 n = ca. 154 ( Fig. 2 ).

Additional Specimens Examined:— CHINA. Hainan: Longhua district, Poxun village , 13 January 2019, Y. H. Yan Fern09764 ( CSH!) ; Longhua district, West Lake Niangniangmiao , 7 December 2018, X. L. Zheng Fern09739 ( CSH!) ; Baoting County, Diaoluoshan township, Bai Shui Ling , 2 December 1954, Diaoluoshan Team PE00587578 ( PE!) .

Distribution and Habitat:— Ceratopteris shingii has three currently known locations in Hainan Province, China. It grows in some volcanic lakes and even on dry volcanic rocks with elevation 44 m ( Fig. 3 ), where it grows together with several rare Chinese species, such as Ottelia cordata (Wall.) Dandy (1934: 137) , Nymphaea nouchali Burm. f. (1768: 120) , Hydrocera triflora (L.) Wright & Arn. (1834: 140), Oryza rufipogon Griff. (1851: 5) and Myriophyllum tetrandrum Roxb. (1820: 470) . However, C. shingii may be at risk due to invasive alien species, such as Eichhornia crassipes (Mart.) Solms (1883: 527) , Pistia stratiotes L. (1753: 963) and Alternanthera philoxeroides (Mart.) Griseb (1879: 36) , which are commonly seen in its habitat.

Etymology:— In honor of Professor Fu-Wu Xing due to his contribution to plant investigation in Hainan Province.

IUCN Red List category:— Ceratopteris shingii is currently found in three locations in Hainan, and further investigations are still needed. It is considered vulnerable (VU) due to its current narrow geographical distribution, shrinkage of wetland and invasion of alien plants.

Phylogenetic evidence:— A Bayesian phylogenetic tree and maximum likelihood tree were constructed based on the sequences of C. shingii , other Ceratopteris samples, and outgroups ( Fig. 4 ). In agreement with the report of Masuyama & Watano (2010), other Ceratopteris samples could be classified into four well-supported clades: C. thalictroides , C. gaudichaudii var. vuigaris , C. oblongiloba , and C. pteridoides + C. richardii . We find that C. shingii is sister to the other Ceratopteris species. Our results suggest that C. shingii is a lineage independent from other previously reported Ceratopteris groups.

Notes: —Morphologically, C. shingii is close to C. thalictroides , and associated cryptic species. It is characterized by its aquatic habit, unexpanded stipe bases, dimorphic fronds, linear sorus margins, and reflexed lobe margins. The rhizomes of all other Ceratopteris species are erect, whereas C. shingii has creeping rhizomes. In addition, our phylogenetic analysis revealed C. shingii as sister to all other Ceratopteris species.

Figures

FIGURE 1. Ceratopteris shingii Y.H. Yan & R. Zhang. Drawn by Wen Shao based on the holotype Fern 09770 (CSH). A. Habit; B. Enlarged fertile frond anatomy/portion for sporangium; C. Scale; D. Spore.

FIGURE 2. Chromosome number of C. shingii in mitotic root-tip cells. 2n=ca.154.

FIGURE 3. The habitat of C. shingii (photographed by Yue-Hong Yan). A. The landform in Jiangjunshan in Haikou city, Hainan; B. Morphology of the sporophyte; C. C. shingii plants with creeping rhizomes.

FIGURE 4. The phylogenetic tree using MrBayes based on the sequences of rbcL, the intergenic spacer regions of trnL(UAA)-trnF(GAA), psbC-trnS(UGA), trnW(CCA)-trnP(UGG), and rbcL-atpB. Numbers on branches are support values PPBI/ML (Bayesian inference posterior probabilities / maximum likelihood). Dash (-) indicates nodes with PPBI or ML <50%. “//” indicates that the branch length of the outgroups is shortened.