Kirkpatrick, Ruth .
What is Pellaea?.
Cheilanthoid ferns are a fascinating complex with worldwide distribution in seasonally dry and rocky places. Morphological convergence associated with adaptation to xeric habitats has been blamed for the historic frustration associated with attempts to decipher natural evolutionary lineages within this group. Gastony and Rollo utilized DNA sequence data, presumably independent of adaptation to xeric habitats, in an effort to reassess the generic relationships of cheilanthoids. Results from their study provided new insights into relationships, but many generic circumscriptions were unresolved. Many critical taxa were not included in their analysis; for example, only 8 of approximately 40 species of Pellaea were examined. These results suggest the need for further sampling and the need to incorporate data from additional genes. Pellaea, as traditionally defined, is centered in the southwestern United States and Mexico with other species in South America, Asia, Africa, the Pacific Islands, and Australia. The relationships of Pellaea species with Argyrochosma, Astrolepis, Cheilanthes, and Notholaena are not clear. My study utilizes DNA sequences from a dense sampling within these five genera in order to assess the monophyly of Pellaea. Results based on 27 specimens representing 9 species (sparingly sampled in previous studies) support a monophyletic P. mucronata group (P. brachyptera, P. bridgesii, P. mucronata var. californica, P. mucronata var. mucronata, P. ternifolia, P. truncata, P. wrightiana, and P. ×glaciogena). Other groups traditionally included in Pellaea appear more remotely related. Several African taxa usually placed in Pellaea (sect. Holcochlaena) fall within a larger cheilanthoid clade. Platyloma (Australia) appears sister to Pellaea s.s. Ormopteris (Cassebeera) (South America) appears more closely related to Doryopteris (confirming results by Barbará). Preliminary data suggest that Astrolepis may be nested within a paraphyletic Pellaea.
1 - University of California, Berkeley, Integrative Biology, University and Jepson Herbaria, 1001 Valley Life Sciences Building, Berkeley, California, 94720-2465, USA
Presentation Type: Paper
Location: Superior B (Cliff Lodge)
Date: Monday, August 2nd, 2004
Time: 10:00 AM