Abstract
Abstract: Adiantum is a Pantropical genus of ferns, monophyletic, and has about 225 species. It can be recognized by the indusia with veins, bearing sporangia directly on the underside of its reflexed tissue. About 110 species occur in the Neotropical region and 65 of them are reported to Brazil. Among them, 64 are native species and occur mainly in the Amazon Rainforest, Caatinga, Central Brazilian Savanna, and in the Brazilian Atlantic Rainforest. Among the species that occur in Brazil, 16 are endemic and they represent 25% of the total. This paper presents a key to identify the 63 native species of Adiantum in Brazil, excluding the hybrid one. Illustrations of some morphological features, as well as of all species are also presented to help in the process of identification.
Highlights
Presl and concluded that the group of A. poiretii Wikstr. is the most closely related and they can be separated morphologically by the shape of the indusium. This important result is strongly supported by the molecular data indicating that the species of A. poiretii group differ from the A. raddianum group by a unique deletion of 66 nucleotides, at positions 288–353 in the chlN gene alignment
Adiantum can be recognized by terete, blackish to castaneous stipes, rachises, and costae, and sporangia borne on the false indusium; characterized by scales borne at rhizome apices and stipe bases; laminae monomorphic, pinnate to more divided, sometimes forked or pedate; veins free or rarely anastomosing without included free veinlets; linear epidermal idioblasts present or not between the true veins; sori formed on the recurved laminar margins, on the veins, paraphyses absent (Prado et al 2017a)
Among those endemic species to Brazil, some have been recently described as Adiantum lindsaeoides, Figure 4C, Prado & Hirai (2013)
Summary
Adiantum L. is monophyletic, with ca. 225 species, and is the second biggest genus of the family Pteridaceae (PPG I 2016), behind only Pteris L. with 250 spp. Adiantum has been a target of several investigations, including molecular data to access the evolution of the group and its relationship, and some Brazilian species were sampled for these works. Is the most closely related and they can be separated morphologically by the shape of the indusium (reniform in A. raddianum group and oblong in the A. poiretii group). This important result is strongly supported by the molecular data indicating that the species of A. poiretii group differ from the A. raddianum group by a unique deletion of 66 nucleotides, at positions 288–353 in the chlN gene alignment
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