Phytologia {August 1991) 71(2):122-127. TRANSFER OF ASTER KINGII TO TONESTUS {ASJERACEAE: ASTEREAE) Guy L. Nesom Department of Botany, University of Texas, Austin, Texas 78713 U.S.A. ABSTRACT Aster kingii is not acconunodated in Machaeranthera or Xylorhiza, the only genera outside oi Aster y/'ith. which it has been formally aligned. Studies have returned it to Aster, its original position, but it has not been accepted even there in recent taxonomic overviews. Placements alternative to Aster have not been suggested by previous workers. Al-though it is white rayed, the species is transferred here to the primarily yellow rayed genus Tonestus, where it is hypothesized to be most closely related to the rayless T. aberrans. The new combinations required are T. kingii (D.C. Eaton) Nesom and T. kingii var. barnebyana (Welsh & Goodrich) Nesom. KEYWORDS: Tonestus, Aster, Mac/iaerant/iera, Asteraceae, Aster-eae Aster kingii D.C. Eaton, a species restricted to the Wasatch and Canyon Mountains of central to north central Utah, has been unsettled in its system-atic placement in the last 35 years. It was accepted by earlier North American taxonomists within the bounds of the large and variable genus Aster L., but Cronquist & Keck (1957) excluded the species from Aster and placed it in their expanded version of Machaeranthera Nees (within sect. Xylorhiza [Nutt.) Cronq. k. Keck series Integrifoliae Cronq. &: Keck). These authors noted (p. 233) that "The monocephalous montane true perennial ^Aster^ kingii D.C. Eaton is suggestive of Xylorhiza glabriuscula, but the involucre is that of Machaeranthera, and the plant blooms in late summer like other Machaer-antherae." The species of Machaeranthera sect. Xylorhiza are now treated as the genus Xylorhiza Nutt., mostly following the monograph by Watson (1977). Aster kmgii, however, was noted by Watson (1978, p. 209) to be "phenologically, ecologically, morphologically, and chromosomally anomalous ..." within Xy-lorhiza, while he observed resemblances in various features between A. kingii 122
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