Chromosomes and Phyletic Position of Aster sonorae Gray (Asteraceae-sect. Oxytripolium)
1975; Southwestern Association of Naturalists; Volume: 19; Issue: 4 Linguagem: Inglês
10.2307/3670394
ISSN1943-6262
AutoresB. L. Turner, John D. Bacon, Thomas Wendt,
Tópico(s)Rangeland and Wildlife Management
ResumoAster sonorae, a lavender-rayed, annual taxon, previously thought to be synonymous with the white-rayed, perennial, A. riparius H.B.K., is shown to be a valid species of saline habitats of north central Mexico. Its morphology is problematic, suggesting a relationship with both sect. Oxytripolium of Aster and Machaeranthera. Meiotic complements from several populations show the chromo- some number to be n = 5, comprising one large pair, 2 medium, j-shaped pairs, and two small v-shaped pairs. The phyletic implications of these data with respect to both Aster and Machaeranthera are discussed. Aster sonorae Gray, a tap-rooted annual originally described from collections made by Charles Wright in southeastern Arizona and ad- jacent Mexico, has heretofore been known by relatively few collec- tions. Field work in north-central Mexico during the past year by Prof. M. C. Johnston, Mr. Fernando Chiang and Tom Wendt, in con- nection with Johnston's projected work on the flora of the Chi- huahuan Desert, has resulted in several collections of this taxon. Gray (1852) initially placed the species in the section Oxytripolium of Aster along with a newly described perennial species, A. blepharo- phyllus Gray. However, Gray (1884) subsequently reduced A. sono- rae to synonymy under A. riparius H.B.K., a perennial species col- lected by Humboldt near lacum Cueseo (which, according to infor- mation from Prof. Donald D. Brand, University of Texas, refers to Lago de Cuitzeo, near the modern Town of Cuitzeo in north- ern Michoacan). Apparently, Gray took the Humboldt collections to be sufficiently similar to the Wright collections to warrant this action, in spite of the fact that he was aware that A. riparius was reportedly perennial, had white rays and a somewhat subsquarrose involucre; A. sonorae, as noted by Gray in his original description, is annual, has decidedly blue rays and a very gradate involucral series, not at all squarrose. Gray stated that the original authors of A. riparius had probably (made) a mistake in their observations, but this does not explain why Gray (1884, p. 201) changed his own views as to the now
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