Anemia is a genus of ferns in the family Anemiaceae, order Schizaeales, belonging to the class Polypodiopsida (leptosporangiate ferns). It is the sole genus in Anemiaceae under the Pteridophyte Phylogeny Group classification of 2016 (PPG I). Alternatively, some treatments place it as the only genus in the subfamily Anemioideae within a more broadly defined Schizaeaceae — the arrangement followed by Plants of the World Online.
The genus was first formally described by the Swedish botanist Olof Swartz in 1806, and the family Anemiaceae was erected by Johann Link in 1841. Under modern molecular classifications (PPG I), Anemia is circumscribed broadly to include genera formerly treated separately, such as Mohria and Colina.
A defining morphological feature of the genus is strongly dimorphic fronds: in fertile fronds, the two lowermost pinnae are dramatically modified into elongated, erect structures that bear the sporangia, giving the plants a superficial resemblance to flowering plants — hence the informal name "flowering ferns," though this epithet is more widely applied to the unrelated genus Osmunda. Chromosome numbers in the genus are based on x = 38, with documented counts of n = 38, 76, and 114, indicating both diploid and polyploid lineages.
GBIF records approximately 159 taxa within this genus. The genus reaches its greatest diversity in the Neotropics, particularly in Central and South America, with some species extending into North America, Africa, and Asia.
Etymology
The genus name Anemia derives from the Ancient Greek aneimon (ἀνείμων), meaning "without clothing" or "naked," referring to the exposed, unprotected sporangia borne on the modified fertile pinnae. This contrasts with ferns that carry their sporangia enclosed in protective indusia.
Distribution
Anemia is predominantly a Neotropical genus, with its center of diversity in Central and South America. Some species extend into southern North America (including Mexico and the southern United States), sub-Saharan Africa, and parts of Asia. The genus occupies tropical and subtropical regions, typically in rocky, open, or seasonally dry habitats.
Taxonomy Notes
Anemia was described by Olof Swartz in 1806 and is the sole genus in Anemiaceae (Link, 1841). The Pteridophyte Phylogeny Group (PPG I, 2016) places it in order Schizaeales and expands the genus to absorb Mohria and Colina. An alternative treatment retains a broadly defined Schizaeaceae and reduces Anemiaceae to the subfamily Anemioideae; this is the placement used by Plants of the World Online (as of 2019). Some sources continue to treat Schizaeaceae in the narrow sense, keeping Anemiaceae distinct.
