| The systematics of Aster subgenus Oxytripolium (Compositae) is discussed, including a reevaluation of the taxonomic position of species placed here in recent treatments of Aster. Data are derived from a variety of approaches, including cytology, flavonoid chemistry, hybridization experiments, and field observations. Subgenus Oxytripolium includes three species: A. potosinus, A. tenuifolius (with two varieties), and A. subulatus (with five, widely distributed, varieties). Hybridization experiments demonstrate that these species are not interfertile. Artificial hybrids have been produced between some pairs of A. subulatus varieties, as well as between the two varieties of A. tenuifolius. The anomalous species, Aster spinosus, is treated as Erigeron ortegae (with four varieties) on the basis of morphological and phytochemical similarity to other species of Erigeron. Aster intricatus is recognized as Leucosyris carnosa, consisting of two varieties. Aster pauciflorus is recognized as the sole member of Aster subg. Almutaster. Other species historically placed in subgenus Oxytripolium are variously relegated to synonymy under other species of the subgenus (A. bracei, A. hydrophilus, A. lemmonii, A. madrensis, A. squamatus); allied to other subgenera of Aster (A. leonis); or treated in other genera (A. lepidopodus, A. riparius). |
