CHROMOSOME NUMBER DETERMINATIONS IN ASTER L. (COMPOSITAE) WITH COMMENTS ON CYTOGEOGRAPHY, PHYLOGENY AND CHROMOSOME MORPHOLOGY

Abstract

Chromosome number determinations from 360 individuals of 73 species, varieties and hybrids of Aster (not including Virgulus Raf.) are reported for the first time. Most reports confirm one or more earlier ones for the taxa. Several first counts are included: A. curtisii T. & G., 2n = 32; A. drummondii Lindl. var. drummondii, 2n = 16; A. eulae Shinners, 2n = 48; A. infirmus Michx., 2n = 18; A. lateriflorus (L.) Britt., 2n = 64; A. meritus A. Nels., 2n = 36; A. parviceps (Burg.) Macken. & Bush, 2n = 32; A. pubentior Cronq., 2n = 18; and A. sagittifolius Wedem., 2n = 48. Counts of 2n = 18 for A. avitus Alex. and A. hemisphaericus Alex. and 2n = 36 for A. paludosus Ait. provide additional evidence that the base number of A. sect. Heleastrum is x = 9, not x = 5. Counts of 2n = 32 and 2n = 48 for A. curtisii support its placement with other x = 8 species in sect. Foliacei, but not with x = 9 species in sect. Spectabiles. The geographic distributions of cytotypes support the taxonomic delimitations A. puniceus L. and A. praealtus Poir. Diploids were found throughout the range of A. puniceus, but tetraploids were rare and found only in the southwestern portion of the range; ploidy level did not correlate with morphological variation. In A. praealtus the distribution of tetraploids and octoploids correlated with the allopatric varities praealtus and angustior Wieg. Satellite chromosome morphology was determined in species not studied before. Aster engelmannii, A. glaucodes, A. infirmus, A. modestus, A. oregonensis, A. pauciflorus and A. pubentior had subequal satellites and short arms, the “primitive” type in the genus. Aster meritus, A. radula and A. radulina had the “derived,” subg. Aster type, a very large satellite attached to a very short proximal portion of the short arm.