Phylogeny and classification of the tribe Lepisoreae (Polypodiaceae; pteridophyta) with the description of a new genus, Ellipinema gen. nov., segregated from Lepisorus.

Lepisoroid ferns (tribe Lepisoreae, Polypodiaceae) are arguably one of the most confusing fern groups in Polypodiaceae in terms of delimitation of genera largely because of their simple morphology. Previous molecular studies either had very small taxon sampling of the non-Lepisorus genera and did not well resolve the relationships among these genera, or had a relatively large sampling at species level but the critical species were missing or their relationships were not well resolved. A recent study resolved the newly sampled Lepisorus jakonensis as sister to the remaining genera in Lepisoreae excluding Paragramma, and the authors lumped all the six well recognized genera into Lepisorus. In the present study, to infer a phylogeny we used DNA sequences of five plastid markers (matK, rbcL, rbcL-atpB, rps4 &rps4-trnS, trnL &trnL-F) of 172 accessions representing ca. 44 species of non-Lepisorus genera and 54 accessions representing ca. 50 species of Lepisorus as ingroup, and 10 non-Lepisoreae accessions from the most closely related four genera (Leptochilus, Microsorum, Phymatosorus, and Goniophlebium) in Microsoroideae and one genus (Pyrrosia) in Platycerioideae. Our major results include: (1) All seven currently defined genera except Lepisorus in Lepisoreae are confirmed to be monophyletic; (2) The Lepisorus jakonensis clade is confirmed to be the second earliest diverged lineage in Lepisoreae; (3) Neolepisorus is resolved as sister to the rest in a clade containing all non-Lepisorus genera except Paragramma; (4) Lemmaphyllum is sister to a clade containing Lepidomicrosorium, Neocheiropteris, and Tricholepidium; and (5) Ellipinema gen. nov. is segregated from Lepisorus based on the phylogeny and morphology in order to stabilize the current usage of the existing six non-Lepisorus genera and species names in these genera. A key to all eight genera of Lepisoreae is provided.
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