Gaga, a New Fern Genus Segregated from Cheilanthes (Pteridaceae)

Abstract

Ongoing molecular phylogenetic studies of cheilanthoid ferns confirm that the genus Cheilanthes (Pteridaceae) is polyphyletic. A monophyletic group of species within the hemionitid clade informally called the “C. marginata group“ is here shown to be distinct from its closest relatives (the genus Aspidotis) and phylogenetically distant from the type species of Cheilanthes. This group is here segregated from Cheilanthes as the newly described genus, Gaga. In this study, we use molecular data from four DNA regions (plastid: matK, rbcL, trnG-R; and nuclear: gapCp) together with spore data to circumscribe the morphological and geographical boundaries of the new genus and investigate reticulate evolution within the group. Gaga is distinguished from Aspidotis by its rounded to attenuate (vs. mucronate) segment apices, minutely bullate margins of mature leaves (vs. smooth at 40×), and less prominently lustrous and striate adaxial blade surfaces. The new genus is distinguished from Cheilanthes s. s. by its strongly differentiated, inframarginal pseudoindusia, the production of 64 small or 32 large spores (vs. 32 small or 16 large) per sporangium, and usually glabrous leaf blades. A total of nineteen species are recognized within Gaga; seventeen new combinations are made, and two new species, Gaga germanotta and Gaga monstraparva, are described.