Generic Affinities of the Star-Scaled Cloak Ferns

Abstract

The star-scaled cloak ferns, including Notholaena sinuata and its allies, are a relatively small group of New World xerophytes whose generic affinities have been the source of considerable debate. The first member of this group was described in 1806 as Acrostichum sinuatum Lagasca ex Sw. Although the sporangia of the star-scaled cloak ferns follow the veins for a short distance, they are not truly acrostichoid and subsequent authors (e.g., Presl, 1836; Domin, 1913) assigned A. sinuatum and its relatives to the cheilanthoid-gymnogrammoid alliance now included in the family Adiantaceae. Many of the genera in this alliance are poorly defined and the star-scaled cloak ferns have historically been placed in three different genera: Gymnogramma, Notholaena, and Cheilanthes. Gymnogramma is now considered invalid for the reasons discussed by Underwood (1902), and most recent authors have assigned the sinuata complex to Notholaena (Tryon, 1956; Hevly, 1965; Lellinger, 1985). However, this generic placement has not been universally accepted, and there is a growing tendency to include the star-scaled cloak ferns in the aggregate genus Cheilanthes (Mickel, 1979; Mickel & Beitel, 1988; Tryon & Tryon, 1982). The dispute over the proper generic treatment of the sinuata complex led us to undertake a series of biosystematic analyses culminating in a taxonomic revision of the group (Benham, 1989). In this paper, we present the suite of characters that uniquely defines the star-scaled cloak ferns and discuss the rationale for recognizing this group as a separate genus, distinct from either Notholaena or Cheilanthes. MATERIALS AND METHODS