Sphaeropteris Bernh., J. Bot. (Schrader) 1800

Lehnert, Marcus & Kessler, Michael, 2018, Prodromus of a fern flora for Bolivia. XX. Cyatheaceae, Phytotaxa 334 (2), pp. 118-134 : 131

Sphaeropteris Bernh., J. Bot. (Schrader) 1800 (2): 122, t. 1(1). 1801.

Sphaeropteris is a diverse genus of 103 species mostly restricted to Malesia and Australasia, among which several natural lineages ( Korall et al. 2006, 2007, Korall & Pryer 2014) may be recognized at subgeneric level ( Holttum 1963). These clades show some general ecological preferences and concomitant morphological adaptations. Plants of the Fourniera clade can establish in the dense understory and slowly grow with straight trunks into the canopy, where the crown becomes fertile. Plants of the Schizocaena + Sarcopholis clade are normally fertile in deep shade and have curved or decumbent trunks; some are generally trunkless. Sphaeropteris s.s. comprises the largest living tree ferns, with trunks up to 20 m tall. Plants usually establish in tree fall gaps and on the borders of landslides, apparently needing both full sun and constant soil moisture; their crowns are usually level with the canopy or surpass it as the forest closes in. In the Neotropics, only six species of the so-called Sphaeropteris horrida -group ( Tryon 1971) within the Sphaeropteris s.s. clade ( Korall & Pryer 2014) are present, occuring largely parapatrically from Mexico to southeastern Brazil; one species occurs in Bolivia.

The genus is morphologically united by conform petiole scales, i.e., a differentiated scale margin of smaller, differently oriented cells as in Alsophila and Cyathea is absent. Several Neotropical species of Cyathea with secondarily reduced scale margins had been erroneously treated under Sphaeropteris in the past ( Tryon 1970, Windisch 1977, 1978).