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CHROMOSOME NUMBERS AND THEIR CYTOTAXONOMIC SIGNIFICANCE FOR NORTH AMERICAN ASTRAGALUS (FABACEAE)
Author(s) -
Spellenberg Richard
Publication year - 1976
Publication title -
taxon
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 81
eISSN - 1996-8175
pISSN - 0040-0262
DOI - 10.2307/1220528
Subject(s) - biology , ploidy , fabaceae , taxon , old world , botany , chromosome , panicum , evolutionary biology , zoology , genetics , gene
Summary This study presents 126 original reports of chromosome numbers for 101 taxa of North American Astragalus ; 46 are the first records for species. Chromosome numbers are now known from at least one count for slightly more than 40 % of the North American species; on a world wide basis about 80% of the species are still unknown from a single count. This study supports earlier work demonstrating the basic division between Old World species, including their close New World relatives (x = 8, euploidy common), and strictly New World lineages (x = 11, 12, 13, 14, 15, euploidy rare). Two euploids of New World relationship, A. layneae Greene and A. pictiformis Barneby, are added to the long known A. grayi Parry ex Wats.; all are 2n = 44. The number 2n = 30 is reported for the first time in New World species, being recorded for A. guatemalensis Hemsl., A. radicans Hornm., A. ervoides H. & A., A. parvus Hemsl., and A. diphacus Wats. All are Mexican species; some are considered primitive, others advanced. The chromosome number 2n = 22 is also reported for primitive species. It is proposed, therefore, that the New World species originated from a tetraploid of 2n = 32 or a hypotetraploid, evolutionary radiation in some lineages concommitant with descending aneuploidy, in other lineages with little or no change in number.