Root Anatomy As Phylogenetic Evidence for Cheilanthoid Ferns (Pteridaceae)

Background and aims:To our hypothesis on the evolutionary relationships of Cheilanthoid ferns, based on molecular data and partially on morphological and reproductive data, we add here a study of root anatomy in the genera of the subfamily occurring in South America.M&M: Root characters were analyzed anatomically in 48 South American species representing the 12 genera of Cheilanthoideae occurring in South America. Techniques of plant histology were used for anatomical analysis and tissue characterization. Characters with possible diagnostic value were identified and mapped on a molecular phylogeny of Cheilanthoideae based on three plastidial markers (rbcL, trnL-F and rps4).Results: The character "type of root cortex" showed a distribution of states that fit to the major clades or genera in the phylogeny of the subfamily. The homogeneous cortex state was plesiomorphic for Cheilanthoideae, whereas the heterogeneous cortex state was acquired by some genera of the hemionitoid clade: Hemionitis and the genera of the Adiantopsis-Doryopteris clade (except Mineirella). In addition, we discuss the role of different tissues in the root mechanics of this group.Conclusions: The character "type of root cortex" could contribute to the characterization of genera and the generic assignment of confusing species in the classification of Cheilanthoideae. However, the complete resolution of the relationship of hemionitds clade in the global phylogeny of the subfamily is necessary