Systematics of the Leptochilus macrophyllus complex (Polypodiaceae, Polypodiales)

Abstract Leptochilus is an Old World fern genus with uncertain species diversity. The Leptochilus macrophyllus complex exemplifies this uncertainty, as previous taxonomic treatments recognized it as a broadly circumscribed species with considerable morphological variation. Recent phylogenetic studies revealed multiple distinct lineages within L. macrophyllus, further suggesting the presence of potential cryptic species. In this study, we investigate the systematics of the L. macrophyllus complex using phylogenetic analyses based on five chloroplast markers, complemented by detailed morphological comparisons of sori arrangement, venation patterns, and laminae texture. We also reconstructed the historical biogeography of the complex, examining dispersal patterns that shaped its current distribution. Our findings support the classification of the L. macrophyllus complex into six distinct species, including three newly described species (Leptochilus nooteboomii C.T.Chen, C.W.Chen & Y.S.Chao sp. nov., Leptochilus papuasiaticus C.T.Chen, C.W.Chen & Y.S.Chao sp. nov., and Leptochilus punctiformis C.T.Chen, C.W.Chen & Y.S.Chao sp. nov.), two reinstated basionyms (Leptochilus polysorus (Brause) C.T.Chen, C.W.Chen & Y.S.Chao comb. nov. and Leptochilus regularis (Mett.) C.T.Chen, C.W.Chen & Y.S.Chao comb. nov.), and the recircumscribed L. macrophyllus. We provide detailed morphological descriptions and taxonomic notes for each species, along with a distribution map and an identification key. For names not treated in this study due to insufficient material, we offer insights based on existing data. This work advances the taxonomy of Leptochilus in Malesia and Papuasia by clarifying species boundaries within the L. macrophyllus complex and illuminating its evolutionary and biogeographical history.