Microsorum is a genus of tropical ferns belonging to the family Polypodiaceae, placed in the subfamily Microsoroideae under the Pteridophyte Phylogeny Group classification of 2016 (PPG I). The genus was described by the German botanist H.F. Link. Like most ferns, Microsorum species grow from rhizomes rather than true roots, and the genus is notable for including some lithophytic rheophytes — plants that grow on rocks in or near fast-flowing water.
Species of Microsorum are distributed across the Old World tropics, with a concentration in Africa, South and Southeast Asia, Australia, and the Pacific islands. The genus encompasses a morphologically diverse group of ferns; fronds range from simple and undivided to deeply pinnate, and plants may grow as epiphytes, lithophytes, or terrestrial herbs in humid, tropical habitats.
The taxonomic boundaries of Microsorum have been subject to revision. The related genus Phymatosorus is treated within Microsorum under PPG I (2016), though some checklists continue to recognise it separately. A 2019 molecular phylogenetic study of subfamily Microsoroideae placed Microsorum (as broadly circumscribed) as sister to Leptochilus, together forming one of the three principal clades of the subfamily. Several species previously assigned to Microsorum have been transferred to other genera, including Neolepisorus, Dendroconche, and Bosmania. The genus name is frequently misspelled as "Microsorium" or "Microsoreum" in horticultural literature.
Etymology
The genus name Microsorum was established by H.F. Link. It is frequently misspelled in the literature as Microsorium or Microsoreum, and plants sold under those variant spellings typically belong to this genus.
Distribution
Microsorum is a tropical genus distributed across the Old World, with species recorded in Africa, South and Southeast Asia, Australia, New Zealand, and the Pacific islands including Polynesia. Multiple species occur in Australia (M. australiense, M. grossum, M. irioides, M. maximum, M. punctatum, M. scolopendria) and across the Pacific.
Taxonomy Notes
Under the Pteridophyte Phylogeny Group classification of 2016 (PPG I), the genus Phymatosorus is subsumed within Microsorum and the genus is placed in the subfamily Microsoroideae of Polypodiaceae. As of early 2019, both the Checklist of Ferns and Lycophytes of the World and Plants of the World Online retained Phymatosorus as a separate genus. A 2019 molecular phylogenetic study found that Microsorum (broadly circumscribed) did not distinguish Phymatosorus and resolved the genus as sister to Leptochilus, together forming one of three main clades in Microsoroideae. Several species previously assigned to Microsorum have been transferred to Bosmania, Dendroconche, and Neolepisorus.
