Abstract
Based on cytological analyses, phylogenetic analyses using chloroplast and nuclear genes, and morphological examination, Lepisorus tajimaensis T. Fujiw. (Polypodiaceae, Polypodiales) is described as a new allohexaploid species in the Japanese L. thunbergianus polyploid species complex. Our phylogenetic analyses demonstrated that L. tajimaensis originated through interspecific hybridization between L. nigripes and L. oligolepidus. The new species can be distinguished from L. nigripes by the broadly lanceolate rhizome scales (vs. narrowly lanceolate to lanceolate), lanceolate laminae (vs. linear to narrowly lanceolate), scales throughout the abaxial surface of the laminae (vs. scales mainly along costa on the proximal part of the abaxial surface of laminae), and larger sori (3–5 mm in diam.) (vs. 1–2.5 mm in diam.), and from L. oligolepidus by the brown rhizome scales with 3 or 4 rows of marginal transparentlumina (vs. dark brown rhizome scales with 1 or 2 rows of transparent marginal lumina), the light brown leaf scales (vs. dark brown), and sori being closer to the margin (vs. sori nearer costa). Additionally, sterile pentaploid hybrids resulting from backcrossing between L. tajimaensis and one of the parental species, L. nigripes is reported.
