Species delimitation of the Selaginella delicatula group in China

doi:10.17520/biods.2021273

Abstract

Abstract:

Aims: Species delimitation of Selaginella remains largely based on morphological characters, however, many closely related species are morphologically indistinguishable from each other. This study aims to (1) explore phylogenetic relationships within the S. delicatula group; and (2) evaluate the utility of nuclear and chloroplast DNA markers for the classification of Selaginella.
Methods: A total of 73 individuals were sampled, covering the geographical distribution and morphological variation of this group. We sequenced three chloroplast markers (rbcL, psbA, and atpI) and two nuclear markers (26S nrDNA and pgiC) to infer the phylogenetic relationships and haplotype network.
Results: We detected incongruence within S. delicatula-S. picta clade between chloroplast and nuclear phylogenies. The chloroplast dataset indicated S. delicatula is not monophyletic, with S. delicatula B sister to S. delicatula A-S. picta. In contrast, nuclear dataset discovered the monophyly of all three species, with S. delicatula sister to S. picta and S. wallichii sister to the S. delicatula-S. picta clade. Morphological characters, including main stem and branches, sporophylls, sterile leaves (ventral, dorsal, and axillary leaves) and spores were carefully observed and assessed. Morphological comparisons indicated that the samples of S. delicatula A and B clades are only distinct in branch patterns and the micromorphology of megaspores surface, not differential in morphology of leaves, strobili and microspores.
Conclusion: As a result of available evidence, three taxa were recognized in the S. delicatula group. It is necessary to perform further studies with cytological evidence and more samples of S. delicatula from type locality in order to obtain a better understanding of the species delimitation. We suggested that the taxonomic work of Selaginella should focus on the closely related species and multiple lines of evidence should be considered, including morphological characters, cytological evidence, molecular data (nuclear and chloroplast DNA markers), and geographical distribution.

Key words: 26S nrDNA, pgiC, chloroplast markers, lycophytes, Selaginella delicatula group

Menghua Zhang, Xianchun Zhang. Species delimitation of the Selaginella delicatula group in China[J]. Biodiv Sci, 2021, 29(12): 1607-1619.

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URL: https://www.biodiversity-science.net/EN/10.17520/biods.2021273

https://www.biodiversity-science.net/EN/Y2021/V29/I12/1607

Figures/Tables 8

Table 1 Primers used in amplification and sequencing

分子标记 Marker	引物 Primer	正反向 Direction	序列 Sequence (5′-3′)	参考文献 Reference
26S	26S 60F	正向 Forward	TTTAAGCATATCACTAAGCGGAGG	Korall & Kenrick (2004)
26S	26S 380F	正向 Forward	CCGCGAGGGAAAGATGAAAAGGAC	Korall & Kenrick (2004)
26S	26S 1160R	反向 Reverse	CCAGTTCTGCTTACCAAAAATGGCCC	Korall & Kenrick (2004)
pgiC	SWPGIC-1666F	正向 Forward	VTTYGCTTTYTGGGAYTGGG	Weststrand & Korall (2016a)
pgiC	SWPGIC-2523R	反向 Reverse	GTCGTGGTTRCTSACAATCTC	Weststrand & Korall (2016a)
rbcL	rbcL-192F	正向 Forward	CACGTGGACTACCGTTTGGA	Shalimov et al (2019)
rbcL	rbcL-1324R	反向 Reverse	TACCCTCAAGAGCGGGATCA	Shalimov et al (2019)
psbA	psbA-169F	正向 Forward	CCRGTAGATATTGACGGTATTC	Shalimov et al (2019)
psbA	psbA-1026R	反向 Reverse	ATCTRGWGGGAAGTTGTGAGC	Shalimov et al (2019)
atpI	atpI-119F	正向 Forward	CYCAGGTTCATGGACAAGTAC	Shalimov et al (2019)
atpI	atpI-540R	反向 Reverse	GRGTATYGGGGTTGGTTG	Shalimov et al (2019)

Fig. 1 Maximum likelihood tree of the Selaginella delicatula group based on the nuclear dataset (26S nrDNA + pgiC). Maximum parsimony bootstrap values and Bayesian posterior probabilities are shown on the branches (ML/PP). A dash (-) indicates no support value.

Fig. 2 Maximum likelihood tree of the Selaginella delicatula group based on the chloroplast dataset (atpI + psbA + rbcL). Maximum parsimony bootstrap values and Bayesian posterior probabilities are shown on the branches (ML/PP). A dash (-) indicates no support value.

Fig. 3 Chloroplast rbcL gene haplotype network of the Selaginella delicatula group (A) and their distributions (B). CQ, Chongqing; FJ, Fujian; GD, Guangdong; GX, Guangxi; GZ, Guizhou; HB, Hubei; HK, Hong Kong; HN, Hainan; HuN, Hunan; SC, Sichuan; TW, Taiwan; XZ, Xizang; YN, Yunnan; MY, Myanmar; VT, Vietnam; ML, Malaysia.

Fig. 4 Strobili and sterile leaves of Selaginella delicatula group. (A-D) S. picata, Xizang, B. S. Li & S. Z. Cheng 02630 (PE); (E-H) S. wallichii, Yunnan, X. C. Zhang & S. Y. Dong 1421 (PE); (I-L) S. delicatula B, Hainan, S. Y. Dong 826 (PE); (M-P) S. delicatula A, Hunan, Y. H. Yan 7765 (PE). (A, E, I, M) Strobili, Scale bars = 1 mm; (B, F, J, N) Ventral leaves; (C, G, K, O) Dorsal leaves; (D, H, L, P) Axillary leaves. Scale bars = 0.2 mm.

Fig. 5 Specimens of Selaginella delicatula group. (A) S. delicatula A, Guizhou, X. C. Zhang et al. 6849 (PE); (B) S. delicatula B, Pisang Island near New Guinea, Gaudichaud 13 (Lectotype, G); (C) S. wallichii, Penang and Singapore, Dr. Wallich 128 (Isotype, E); (D) S. picta, India, Griffith sn (Syntype, K).

Fig. 6 Spores morphology of Selaginella delicatula group. (A-E) S. delicatula A (A-C Megaspores, D-E Microspores), Guizhou, X. C. Zhang et al. 6849 (PE); (F-K) S. delicatula B (F-I Megaspores, J-K Microspores), Hainan, X. C. Zhang 2867 (PE); (L-O) S. picta (L-M Megaspores, N-O Microspores), Yunnan, Z. Y. Li & R. Wei WR295 (PE); (P) S. wallichii (Megaspores), Guangxi, Shiwandashan Exped. 050 (PE); (Q-R) S. wallichii (Microspores), Guangxi, X. C. Zhang & Z. Y. Guo 7882 (PE).

Fig. 7 Principal components plots based on six morphological characters of the Selaginella delicatula group

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