Taxonomic Study of the Mexican Genus Hemiphylacus (Hyacinthaceae)

Abstract

The formerly monotypic Mexican genus Hemiphylacus, typified by H. latifolius, is reviewed. Hemiphylacus has characters intermediate between the families Hyacinthaceae and Funkiaceae. Four new species from central and southern Mexico are described: Hemiphylacus alatostylus (Guanajuato, Queretaro, and San Luis Potosi), H. hintoniorum (Nuevo Le6n), H. mahindae (Oaxaca and Puebla), and H. novogalicianus (Aguascalientes). Species differ from each other in inflorescence, flowers, and fruits. Hemiphylacus S. Watson is a genus restricted to desert scrub and oak forests of Mexico at the eastern and southern limits of the Chihuahuan Desert and in the Tehuacan Valley (Fig. 1). The genus has been considered monotypic since Sereno Watson described it in 1883 (e.g., McVaugh 1989). Although plants of Hemiphylacus are locally abundant, the distributions of its species are restricted. Therefore, the genus is not well represented in the different herbaria. The present study reviews the taxonomic history, generic relationships, and taxonomy of the five species of Hemiphylacus. When describing Hemiphylacus, Watson (1883) considered it to be intermediate between his concept of the Chlorogaleae (containing Chlorogalum Kunth, Hastingsia (Durand) S. Watson, and Schoenolirion Torr.), and the Anthericeae (Echeandia Ortega). Engler (1888) placed Hemiphylacus in the subtribe Chlorogalinae of the tribe Asphodeleae, near Chlorogalum and Schoenolirion. According to Hoover (1940), the large rhizomes of Hemiphylacus should place it way out of the bulbous Chlorogalum and Schoenolirion. Nevertheless, some single species of Schoenolirion can produce conspicuous vertical rhizomes as well as bulbs (Sherman and Becking 1991), whereas Chlorogalum bears bulbs and small rhizomes (as seen from herbarium specimens). Hutchinson (1934) considered Hemiphylacus within the tribe Asphodeleae of Liliaceae. However, he erroneously placed the genus near Paradisia Mazzuc. in the group of taxa with not spirally twisted after flowering, since the perianth segments of Hemiphylacus do twist after anthesis. Huber (1969) placed Hemiphylacus within the group of taxa bearing phytomelaniferous seeds and loculicidal capsules in the order Asparagales. He considered Hemiphylacus allied to Chlorogalum and Schoenolirion as part of the tribe Chlorogaleae of his Agapanthaceae. Dahlgren and Clifford (1982), included Hemiphylacus in their concept of the family Hyacinthaceae (Order Asparagales). However, because of the presence of rhizomes in Schoenolirion and the narrow bulb of Chlorogalum, Dahlgren and Clifford (1982) and Dahlgren et al. (1985) considered the Chlorogaleae a peripheral group of the Hyacinthaceae, or possibly a distinct family. GENERIC RELATIONSHIPS Hemiphylacus remains relatively unknown, largely because anatomical, embryological, and cytological data are missing. Therefore, the present discussion and analysis are based solely upon morphological features. Similarities of Hemiphylacus with some genera of Hyacinthaceae (Chlorogalum, Hastingsia, Schoenolirion) and Funkiaceae (Hesperocallis A. Gray and Leucocrinum Nutt.), place it in an intermediate situation. Several characters of Hemiphylacus are shared with the tribe Chlorogaleae (Hyacinthaceae), namely, a thyrse with naked inflorescence, persistent perianth twisting after anthesis, persistent style, and a slightly curved embryo. Hemiphylacus and Chlorogalum share a variable length of styles (two flower types varying in style size within the same species, Jernsted 1982), and a stipitate ovary. With Hastingsia, Hemiphylacus also shares a stipitate ovary. Hastingsia and