A revision of the indusiate scaly tree ferns (Cyatheaceae, Cyathea subgen. Alsophila sect. Alsophila) in Madagascar, the Comoros and the Seychelles

Based on the examination of herbarium specimens including numerous recent collections and on observations of most species in situ, we herein present a revision of the indusiate scaly tree ferns (Cyathea sect. Alsophila) for Madagascar, the Comoros and the Seychelles. One endemic species occurs on the Seychelles and three taxa (one endemic) are found on the Comoros. For Madagascar, we describe 55 taxa (40 species and 15 varieties), 51 of which are endemic. Among these, 11 species and 12 varieties are new. The species newly described for Madagascar comprise C. basirotundata Rakotondr. & Janssen, C. conferta Janssen & Rakotondr., C. dilatata Rakotondr. & Janssen, C. emilei Janssen & Rakotondr., C. hebes Janssen & Rakotondr., C. lisiae Janssen & Rakotondr., C. longispina Janssen & Rakotondr., C. meridionalis Janssen & Rakotondr., C. obtecta Rakotondr. & Janssen, C. pseudobellisquamata Janssen & Rakotondr., and C. valdesquamata Janssen & Rakotondr. The newly described varieties are C. acutula (R.M.Tryon) Janssen & Rakotondr. var. deltoidea Janssen & Rakotondr., C. a. var. rufescens Janssen & Rakotondr., C. bellisquamata Bonap. var. ambrensis Janssen & Rakotondr., C. b. var. australis Janssen & Rakotondr., C. boivinii Mett. ex Kuhn var. andringitrensis Janssen & Rakotondr., C. b. var. bevolo Janssen & Rakotondr., C. b. var. parahildebrandtii Janssen & Rakotondr., C. decrescens Mett. ex Kuhn var. cristata Janssen & Rakotondr., C. d. var. manongarivensis Janssen & Rakotondr., C. emilei var. dauphinensis Janssen & Rakotondr., C. similis C.Chr. var. leptoderma Rakotondr. & Janssen, and C. s. var. montana Janssen & Rakotondr. The descriptions of previously recognized taxa have been completed and where necessary corrected. Especially such characters have been added, that can be observed only in situ, e.g. trunk morphology and measurements of the entire leaf. Descriptions are accompanied by plates with detailed illustrations and by distribution maps. We thoroughly reviewed the nomenclatural status and typification of all names. We provide determination keys down to the varietal level including all taxa of Cyatheaceae of the Madagascan region. Photographic documentation of the trunk and habit of most species will facilitate determination in the field. Finally, we briefly comment on the distribution of the tree fern diversity in the Madagascan rainforests.