Phlegmariurus is a large genus of lycophyte plants belonging to the family Lycopodiaceae and the order Lycopodiales. The genus comprises over 300 species and is recognized in the Pteridophyte Phylogeny Group classification of 2016 (PPG I), though some authorities prefer to treat these plants within a broadly defined Huperzia.
Within Lycopodiaceae, Phlegmariurus is placed in the subfamily Huperzioideae alongside the closely related genera Huperzia and Phylloglossum. A 2016 phylogenetic study using both molecular and morphological data supported a three-genus arrangement of the subfamily, with Phlegmariurus receiving the majority of species previously assigned to a broadly circumscribed Huperzia. The genera are nonetheless difficult to distinguish on morphological grounds alone, and some classifications continue to synonymize them.
Phlegmariurus species are characteristically epiphytic — growing on the surfaces of other plants rather than in soil — and together constitute the dominant epiphytic lycophyte lineage in the world's tropical regions. The genus is absent from temperate and arctic habitats, which are instead occupied by its relative Huperzia. The Flora of North America notes that Phlegmariurus lacks the complex gemma-bearing shoots and subterranean mycorrhizal gametophytes that characterize Huperzia.
The genus was first described in 1909 by Wilhelm Herter as the section Phlegmariurus of Lycopodium, and was elevated to generic rank by Josef Ludwig Holub in 1964. As of 2024, the Checklist of Ferns and Lycophytes of the World accepted over 300 species, plus one known hybrid, Phlegmariurus × koolauensis.
Distribution
Phlegmariurus has a worldwide tropical distribution, occurring across tropical regions of Africa, Asia, the Pacific, and the Americas. Unlike its relative Huperzia, which favours temperate, arctic, and alpine habitats, Phlegmariurus is largely absent from non-tropical zones and is not recorded from North Africa, the Arabian Peninsula, or Western Asia.
Ecology
Species of Phlegmariurus are predominantly epiphytic, attaching to the bark or branches of trees and shrubs in tropical forests rather than growing in soil. This habit distinguishes the genus from Huperzia, whose species are typically terrestrial or saxicolous (rock-dwelling). The gametophyte generation is mycorrhizal and subterranean in related lycophytes, though Phlegmariurus's own gametophytes are not fully described in broad sources.
Taxonomy Notes
Phlegmariurus was originally described by Wilhelm Herter in 1909 as a section of Lycopodium, then elevated to genus rank by Josef Ludwig Holub in 1964. The genus sits within subfamily Huperzioideae of Lycopodiaceae, and its recognition remains contested: PPG I (2016) accepts a three-genus arrangement (Huperzia, Phlegmariurus, Phylloglossum), while other classifications treat all three as a single broadly defined Huperzia. The two approaches produce similar phylogenetic results — both a one-genus and a three-genus division of the subfamily yield monophyletic taxa.
