Validation of Hymenasplenium laterepens (Aspleniaceae): evidence from morphology and molecular analyses

Abstract

The name Hymenasplenium laterepens was first proposed by Cheng and Murakami in 1998 but was not validly published. We recently collected and studied this taxon at its locus classicus in Xishuangbanna, Yunnan Province in China. Molecular phylogenetic analyses and morphological observation of H. laterepens and related species clearly indicate that this is a distinct taxonomic entity worthy of species rank. Phylogenetically, H. laterepens is closely related to H. apogamum and may be involved in the reticulate evolution of the H. apogamum complex, which is comprised of several taxa with different levels of ploidy. Morphologically, H. laterepens is distinguished by the combination of its triangular laminae, large pinnae with acute apices and deeply serrated margins, and ca. 117 chromosomes at meiosis I and 32 spores in each sporangium. This work provides a complete species description and comparison to related species within the genus Hymenasplenium, particularly to other relatives of the “H. unilaterale” group. Hymenasplenium laterepens is described here with diagnosis and type designation.

Molecular and morphological evidence reveals a new fern species of Hymenasplenium (Aspleniaceae) from south and southwestern China

“…The new taxon presented in this study referred to one of the four numbered species (sp8-sp11) in the H. excisum subclade proposed by Xu et al (2018a) in a phylogenetic study of Hymenasplenium. The founding of this new species is consistent with the results of the previous studies that cryptic speciation exists and reinforces that urgent study is necessary for species diversity and delimitation within Hymenasplenium (Chang et al 2018;Xu et al 2018a).…”

Hymenasplenium tholiformis (Aspleniaceae), a new fern species from southeastern Xizang, China based on morphological and molecular evidence

“…The genus is characterized by the stelar structure of the long-creeping rhizome, dorsiventrally symmetrical steles, swollen petiole bases, and unique rachis-costae structure ( Murakami 1995 ; Xu et al 2018b ). Extensive cryptic speciation in Hymenasplenium has been demonstrated based on recent studies ( Chang et al 2018 ; Xu et al 2018b ), which resulted in the discovery of a large number of new species ( Chang et al 2018 ; Xu et al 2018a , 2019a , 2019b ).…”

“…; Zhang et al 7750 (CDBI, MO, VNMN); Thua Thien-Hue, Vietnam; MH065437 (Xu et al 2018); MH065604 (Xu et al 2018); MH065376 (Xu et al 2018); MH065518 (Xu et al 2018); –. H. apogamum ; Chang 1040 (HITBC); Yunnan, China; MH884808 ( Chang et al 2018 ); –; MH884830 ( Chang et al 2018 ); –; MH884838 ( Chang et al 2018 ). H. cardiophyllum (Hance) Nakaike; Sysu 2; Cult.…”

“…Nakaike; Murakami 596920 (KYO); Kouchi, Japan; AB014705 (Murakami et al 1999); –; –; –; –. H. hondoense ; Chang1062 (HITBC); Yunnan, China; MH884814 ( Chang et al 2018 ); –; MH884833 ( Chang et al 2018 ); –; MH884840 ( Chang et al 2018 ). H. laetum (Sw.) L. Regalado & Prada; Jones 1155 (TUR); –; –; –; –; KM114105 (Lehtonen,S et al, Unpublished); –.…”

“…& X. Cheng ex Y. Fen Chang & K. Hori; Chang 2655 (HITBC); Yunnan, China; MH884806 (Ohlsen et al 2015); –; –; –; –. H. laterepens ; Chang 1039 (HITBC); Yunnan, China; MH884807 ( Chang et al 2018 ); –; MH884829 ( Chang et al 2018 ); –; MH884837 ( Chang et al 2018 ). H. latidens (Ching) Viane & S. Y. Dong; Knapp 3672 (P); Taiwan, China; –; MH065566 (Xu et al 2018); –; –; –.…”