A biosystematic revision of Bommeria

Bommeria is a genus of ferns found in xeric and seasonally dry mountainous regions of the southwestern United Slates.Mexico, and Central America.The genus was first described by Fournier (1876), who named it for the Belgian pteridologist Jean Edouard Bommer.Prior to the present study, the most complel work discu sing species relationships in Bommeria was that of Maxon (1913), who delimited the genus based on its characteristic pedate lamina and strigose indument and differentiated its four species primarily on variation in venation and leaf size.In 1942, based on the Chihuahuan collection: o\ [rving Knobloch, Maxon added another species to the genus but did not otherwise alter his concept of species boundaries.A more complete historical treatment of the taxonomy and generic affinities of Bommeria ha recently been presented elsewhere (Gastony & Haufler, 1976).The distribution of spores along the veins in Bommeria species commonly allies the genus with the >.m-mi< • lt.. Hemionitis L. and Gymnopteris Bernh.).Some morphological features of Bommeria species, including leaf margin sporangial distribution and reticulate spores ( .-Liiil« i !\ i : i tonv 1° si.) however, are usually associated with the "cheilanthoid" genera (e.g.. Doryopteris J. Sm. and Cheilanthes Sw.).These two suprageneric groups are not adequately separated from each other, and intergeneric distinctions within the groups are imprecise.Since Bommeria shares gymnogrammoid and cheilanthoid features, understanding species relationships in this genus may be valuable in recognizing evolutionary lines and in defining the natural limits of related genera.Live material of all previously recognized species of Bommeria was collected in the field.Sporophytes of these collections were subsequently cultured under greenhouse conditions, and their gametophytes were grown on agar in the laboratory.A series of reports based on work with these living plants and herbarium specimens has discussed chromosome counts and apomixis (Gastony & Haufler, 1976), antheridiogen and breeding systems (Haufler & Gastony, V \ i icture and ontogeny of spore walls (Haufler & Gastony, 1978b).and flavonoid constituents (Haufler & Giannasi, in prep.) in this genus.These papers have provided information relevant to understanding species relationships and evolution in Bommeria and have addressed some general aspects of apogamy, outcrossing, and spore wall structure in the ferns.The present paper focuses on description of gametophytic and sporophytic organs and examines taxonomically critical aspects of hybridization and foliar ontogeny.In addition, it synthesizes the data accumulated from the entire series of studies into a realistic taxonomic revision of the genus and clarifies the relationship of certain other genera to Bommeria.