Adiantum menglianense

Kuo, Li-Yaung, Hsu, Tian-Chuan, Chang, Yi-Han, Huang, Yao-Moan & Chiou, Wen-Liang, 2016, Systematics of the Adiantum philippense complex (Pteridaceae, Polypodiales) in Taiwan, Phytotaxa 263 (2), pp. 113-121 : 116-117

Adiantum menglianense –a newly recorded species in Taiwan

In this study, we confirmed that the sexual diploids of Adiantum philippense in Taiwan are A. menglianense , and that A. menglianense is a distinct species from A. philippense . Morphologically, these sexual diploids in Taiwan are similar to type description of A. menglianense having more dissected fertile pinnules than A. philippense ( Qian 1992) . They also tend to have narrower false indusia (2–6 mm) than that in A. philippense subsp. philippense (2–12mm),

which apparently agree with the morphological differences revealed by Wang et al. (2014). In addition, same as the type description of A. menglianense , they have 64-spored sporangia (i.e. the indication of sexual reproduction; Table 1). 64-spored sporangium is a very useful character to distinguish from A. philippense subsp. philippense , which is referred to apomictic triploid (i.e. with 32-spored sporangia) and most widespread distributed among the three subspecies. Comparing to A. philippense subsp. teestae , a sexual diploid subspecies ( Verma & Fraser-Jenkins 2008), A. menglianense has much larger plant sizes and the lowest pinna with basal angles>180° (vs. ≤150°). Phylogenetically, Adiantum menglianense and A. philippense , including three subspecies, belong to two separate and sister monophyletic groups ( Fig. 1 ), and such relationship is congruent with previous phylogenies ( Wang et al. 2014; Wang et al. 2015). Taiwanese and Chinese A. menglianese populations share a very high sequence identity in trnL-L-F and rbcL (as detailed in result section), and both phylogenies based on these two genetic regions also support the monophyly of A. menglianense sister to A. philippense (data not shown). In addition, phylogeny of low-copy nuclear gene, CRY2 intron 1, further implies that A. menglianense is unlikely involved in the reticulation (i.e. polyploidization and hybridization) within A. philippense ( Zhang et al. 2014) . Based on above evidences, A. menglianense should be regarded as a species biologically independent from A. philippense although two species are very similar in morphology.

To reveal distribution of Adiantum menglianense in Taiwan, the herbarium collections were examined. Based on frond morphology and spore number in sporangia, we report three populations in Taiwan. All the known distribution records of A. menglianense in Taiwan are mapped on Fig. 2, and their voucher specimens are cited in Appendix 2.

Figures

FIGURE 1. Plastid phylogeny of the Adiantum philippense complex in Taiwan. ML bootstrap support (MLBS) values, the posterior probabilities of Bayesian phylogenetic inference (PP), and MP bootstrap support (MPBS) are indicated on each branch, as MLBS/PP/MPBS. The plus (+) sign represents MLBS = 100, PP = 1.00, or MPBS = 100. The thickened branch indicates MLBS ≥ 70 and PP ≥ 0.95.