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A plastid phylogeny of the Old World fern genus Leptochilus (Polypodiaceae): Implications for cryptic speciation and progressive colonization from lower to higher latitudes

Zhang, Liang, Lu, Ngan Thi, Zhou, Xin-Mao, Chen, De-Kui, Knapp, Ralf, Zhou, Lin, Guo, Lei, Luong, Thien Tam, Sun, Hang, Gao, Xin-Fen, Zhang, Li-Bing
Molecular phylogenetics and evolution 2019
Colysis, DNA, Kontumia, Leptochilus, Microsorum, Pyrrosia, cryptic speciation, cryptic species, ferns and fern allies, genetic markers, latitude, monophyly, nucleotide sequences, Indonesia, Pacific Ocean Islands
The newly defined fern genus Leptochilus contains about 50 species occurring in subtropical to tropical Asia and adjacent Pacific islands. The circumscription and phylogeny of the genus have been ambiguous and its species had been included in various genera such as Colysis, Dendroglossa, Kontumia, Microsorum, and Paraleptochilus. Previous molecular studies sampled only 2–4 molecular markers and 2–16 accessions of Leptochilus. In the present study, DNA sequences of six plastid markers of 105 accessions representing ca. 40 species of Leptochilus, including types of Colysis, Kontumia, Leptochilus, and Paraleptochilus, 39 species of six non-Leptochilus genera of Microsoroideae, and one species of Pyrrosia, are used to infer a phylogeny. Our major results include: (1) Leptochilus is monophyletic and resolved as nested within the microsoroid ferns, but its relationships with other members of Microsoroideae are not well resolved; (2) Six well-supported major clades in Leptochilus are recognized, differing from one another in molecular, morphological, and geographical features; (3) Species related to L. macrophyllus representing earliest split in Leptochilus are identified; (4) The inclusion of Microsorum pteropus in Leptochilus is confirmed, whereas M. insigne is closely related to Leptochilus but not resolved as a member of the genus; (5) The species number of the genus is likely to double the most recent estimate following our study, and quite a few cryptic species should be recognized; and (6) A basal grade formed by three major clades is recovered and they are composed of species almost exclusively distributed at lower latitudes (the Malay Archipelago), whereas the shallow-level clades contain species distributed at mainly higher latitudes, suggesting that Leptochilus might have evolved at lower latitudes and progressively dispersed to and colonized higher latitudes.