Leptochilus is a genus of ferns in the family Polypodiaceae, placed within the subfamily Microsoroideae under the Pteridophyte Phylogeny Group classification of 2016 (PPG I). The genus belongs to the order Polypodiales, a large and diverse order of leptosporangiate ferns that encompasses the majority of living fern species.
A molecular phylogenetic study of subfamily Microsoroideae published in 2019 concluded that Leptochilus is monophyletic — meaning all members share a single common ancestor — and found it to be the sister group to Microsorum. Together, these two genera form one of the three principal clades within Microsoroideae.
The circumscription of Leptochilus has long been contentious. PPG I recognized approximately 10 species in the genus, while the Checklist of Ferns and Lycophytes of the World (as of February 2020) accepted 34 species and hybrids and explicitly flagged the species limits as "fairly controversial and fluctuating." This instability reflects the broader difficulty of delimiting genera within Polypodiaceae, a family that has seen substantial reclassification in the molecular era.
Species assigned to this genus are primarily distributed across tropical and subtropical Asia, with representatives recorded from South Asia, Southeast Asia, and East Asia.
Distribution
Leptochilus species are found primarily in tropical and subtropical regions of Asia, including South Asia, Southeast Asia, and East Asia, consistent with the broader distribution of subfamily Microsoroideae within Polypodiaceae.
Taxonomy Notes
Leptochilus has historically had unstable circumscription, with species counts ranging from about 10 (PPG I, 2016) to 34 species and hybrids (Checklist of Ferns and Lycophytes of the World, 2020). A 2019 molecular phylogenetic study confirmed the genus as monophyletic and sister to Microsorum within subfamily Microsoroideae of Polypodiaceae.
